Digital Projection Radiography

DIMOND III

Image Quality and Dose Management

For Digital Radiography

Final Report

H.P. Busch

Trier 2004

DIMOND III

Contract: FIGM-CT-2000-00061

Working Group: Brüderkrankenhaus Trier

Germany

Prof. Dr. H.P. Busch M.D. Chr. Decker Dipl. Ing

C. Schilz Dipl. Ing A. Jockenhöfer M.D. St. Busch cand.med. M. Anschütz MTRA

Lead Contractor: Prof. Dr. H.P. Busch

Contents: Chapter I Image Quality and 5 Dose Management for Digital Projection Radiography Chapter II Digital Projection Radiography: 11 Principles, Imaging and Application Chapter III Diagnostic Requirements 24 Chapter IV Referral Guidelines 52 (with the three level band for image quality) Chapter V Optimisation and Quality Assurance 66 Chapter VI Image Quality and Dose for 77 Digital Projection Radiography (H.P. Busch, S. Busch, Chr. Decker, C. Schilz) Chapter VII References 93

Annex 1: Final Report Annex 2: - Janalyser-CDRAD - Quality Testing for Digital Projection Radiography (C. Schilz) Annex 3: - Janalyser - Constancy Testing for Digital Projection Radiography (C. Schilz) Annex 4: CD1: Quality- and Dose- Management CD2/3/4: Digital Mammography (Examples) Annex 5: Acknowledgements

Chapter I

Image Quality and Dose Management for Digital Projection Radiography

In the field of projection radiography, conventional film/screen radiography is continuously being replaced by digital imaging methods (such as storage phosphor plates and flat detectors). Digital technology has many advantages, especially for imaging without automatic exposure control, such as bedside imaging. In recent years, costs have decreased significantly and a greater range of specific units has become available. The new technology is likely to lead to increased spatial resolution, decreased dose values, and a faster direct readout. Storage phosphor plates, for example, can be used with all existing projection radiography units. Flat detectors have excellent imaging capabilities and can achieve very high image quality, even at low doses. The immediate availability of images is another advantage of this technique. The increased cost of the new technology is compensated by increased patient throughput. Successful use of this technology in economic terms requires not only replacement of the previous imaging system, but adaptation of the workflow and patient management. Digital imaging differs significantly from film/screen radiography in that the digital detectors’ imaging capabilities are greater and the individual processes of image acquisition, image processing and image documentation are separated from one another. Choosing suitable technique parameters will often provide additional diagnostic information, whereas an unsuitable choice can have negative outcomes right down to misdiagnosis. Optimal use of digital methods in clinical practise requires optimisation and quality assurance of the acquisition, post-processing, and image documentation processes. Imaging methods have to solve diagnostic problems with sufficient quality and certainty. The full spectrum of imaging methods (from ultrasound to MRI and CT) has to be included in the discussion of suitable indications for projection radiography. It must also be taken into account that alterations to the spectrum of applications can change the value of a given imaging method from that of a final diagnostic tool to that of a screening method, or a starting point for further diagnosis. In recent years, film/screen radiography has been characterised by the search for optimal image quality, independent of the specific clinical problem. In striving for such image quality, no effort was made to minimise the dose value,

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other than ensuring it did not exceed a maximum level. The advantage of pursuing the strategy of attempting to attain the highest image quality is the fact that aside from specific diagnostic information, other useful and unexpected additional information can also be obtained. The use of digital imaging methods can also mean that dose values can be reduced over a broad range -- sometimes with decreases in image quality, and sometimes without. Dose and quality management now uses this potential along the guidelines of the ALARA principle (As Low As Reasonably Achievable) to implement the strategy of setting image quality and dose to fit the clinical situation (“quality as good as necessary, not as good as possible – dose value as low as possible”). A clear definition of indications for Digital Projection Radiography should be the starting point for image quality and dose management. The criteria and methods of evidence-based medicine should form the basis for the definition of guidelines. These guidelines must take into account the clinical situation and the risk to the patient. The aim is to avoid unnecessary, “routine” exposures as well as reduce the dose per image. Two publications can be considered a starting point for further discussion here, namely “Referral Guidelines for Imaging”, published by the European Commission (European Commission – Radiation protection 118 – ISBN 92-828-9452-5), and the Council Directive 97/43/ Euratom on protecting the health of individuals against the dangers of ionising radiation in relation to medical exposure. These directives include purpose and scope, definitions, justification, optimisation and responsibilities. The choice of specific imaging method and exposure parameters must be fixed against diagnostic image quality requirements. Examples of these requirements can be found in “European guidelines on quality criteria for diagnostic radiographic images” (European Commission – EUR 16260EN), the results of the European research project DIMOND II and the guidelines of the German Bundesärztekammer (German Federal Medical Association), for example. One parameter that can be varied over a broader range in digital radiography than in film/screen radiography is the exposure dose value. Past experience and research demonstrate that for flat detectors, the speed class of 800 is sufficient for nearly all indications. The dose value of the speed class 200 is no longer used. For many indications, speed class 1600 is suitable. The storage phosphor technique’s potential for dose reduction is significantly lower. Part of the DIMOND III project involved developing a three-level concept of image quality (high, medium, low) and dose management, which lead to certain dose values (for example, the speed classes 400, 800, and 1600) being assigned to certain quality levels, depending on the specific imaging method.

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Examples of the high, medium, and low quality classes for skeletal exposures are: High: Diagnosis of a fracture/fissure Medium: Control of the position of fractures Low: Control of complete metal explantation, adaptation of hip prostheses, metric measurements of the spine Indications for these three dose level bands have been defined corresponding to the European referral guidelines. Clinical problems have been assigned to quality levels in “extended” referral guidelines(Chapter IV). Afterwards the recommended image quality level was transferred to a choice of suitable parameters for the specific imaging method. One example resulting out of a comparative study (see chapter VI) is shown in the following diagram: Relation between image quality classes and dose for various on imaging methods (speed class) Image quality class High Medium Low Flat detector (400) Flat detector (800) Flat detector (1600) Stor.Phos. (200/400) Stor.Phos. (400) Stor.Phos. (800) Film/screen (200) Film/screen (400) Film/screen (800) There must be intensive debate on the strategies and methods for optimising and standardising image quality in the future. Although many individual studies (see references) describe interesting results, they are missing a methodical framework. This new concept consists of three steps: 1. Optimisation (use clinical criteria) 2. Objectivation (description with phantom exposures) 3. Standardisation (defined bandwidth of image quality) As a first approach, exposure parameters (focus size, voltage, grid, and so on) and projection can be chosen as for film/screen exposures. Future research projects on digital radiography will exhaust the existing potential for further optimisation.

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Past experience shows that optimal post-processing is not independent of the dose range. Therefore, optimisation strategies depend on the organ field, the clinical problem and the required image quality class. Optimisation must be carried out according to clinical criteria. Experience of many years shows that optimisation according to “physical test phantoms” is not possible. However, test phantom images (such as CDRAD2.0) are well suited for objectivation and standardisation of image quality. Standardisation of the various manufacturers’ post-processing algorithms and unit generations is not possible. Therefore, a “black box” model has to be taken as a starting point. A “black box” model can be described by the relation of the output function (image) to the input function (image). A strategy of quality management leads to necessary optimisation for each organ program with different units in reference centres. The results can then be objectivated by phantom exposures. The range of results, which correspond to a suitable image quality, is defined by these reference centres. It is also possible to determine the image quality of images produced by unknown equipment by evaluating phantom exposures under the same exposure conditions. A digital test pattern should be integrated into a corner of the raw images to demonstrate the influence of individual post-processing (in additional to standard post-processing). This test pattern should combine high and low contrast structures. The same kind of post-processing should be applied to both the whole image and the test pattern. The results of this individual post-processing can then be demonstrated on laser film or on a monitor. An important part of quality assurance is constancy testing, something that digital radiography offers new ways of performing. Image quality can be graded by digital parameters (e.g. signal/noise – see chapter V , annex3). A subjective visual evaluation is no longer necessary. The starting point for the evaluating the image quality of documentation on laser films or monitors should be a defined digital test pattern (e.g. SMPTE). Digital imaging units are often interlinked and offer new potential for central constancy testing using personal computers.

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The Future Aspects for “Digital Projection Radiography”

1. There will be an extensive replacement of conventional film/screen

radiography by digital radiographic systems in the near future. 2. Both storage phosphor plates and flat detectors are well suited to the

spectrum of digital projection radiography. Flat detectors have better imaging capabilities, storage phosphor systems lower costs.

3. The capabilities of digital imaging methods differ significantly from

film/screen radiography. This demands a new choice of parameters and regulations for equipment standards, as well as guidelines and recommendations for use.

4. Image quality and dose management strategies must be based on

European and international standards and guidelines. It is anticipated that national standards and guidelines will soon become obsolete.

5. Image quality and dose management strategies must take into account the

complete diagnostic chain, from the referral indication to the quality of diagnosis.

6. The application of the ALARA principle means that the image quality

should be as good as necessary, not as good as possible. That means that the dose value should be as low as possible and consistent with the clinical objective.

7. No significant differences exist between digital radiography and film/screen

radiography in terms of the definition of diagnostic image criteria. 8. Image optimisation must take place according to clinical criteria. However,

“physical” test phantoms are well suited to objective evaluation and standardisation of image quality.

9. Economically efficient application of new techniques (e.g. flat detectors)

not only requires the implementation of the new digital detector, but the adaptation of the workflow and patient management

10. The new technological capability that digital projection radiography

provides demands strategies for optimisation and standardisation. Discussion of keywords such as radiation protection, dose reduction, and image quality and dose management can be heard and this demands the definition of new paradigms.

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11. The development of new strategies of optimisation and standardisation is a challenge for the next years.

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Chapter II

Digital Projection Radiography - Principles, Imaging and Application -

The application of the digital image intensifier technique for projection radiography started at the beginning of the 1980s after the introduction of digital subtraction angiography (DSA) for fluoroscopic imaging units. This new technique was used primarily for examining the gastrointestinal tract, for myelograms, and for arthrographies. In the following years, the clear advantages of this technique (high image quality, low dose values, direct availability, easy handling) led to its nearly completely replacing film/screen technology for fluoroscopic units (1, 2). In the mid-1980s, the storage phosphor technique came into clinical application as a new imaging method for exposures at the wall stand, Bucky table and for bedside imaging. The very high technical requirements and financial costs, limited image quality and difficult handling without a reduction of examination time delayed the transfer into routine clinical use, which started to increase at the beginning of the 1990s. Today, storage phosphor radiography makes an important contribution to obtaining optimal imaging in all fields of projection radiography. In recent years, the progress of technology has allowed direct acquisition of the image information at the detector (flat detector technology). After first being successfully tested in manufacturers’ research laboratories, the new technology made the transition into clinical use (3, 4). From a radiologist’s point of view, the aim of further developing imaging systems is to improve diagnostic information while simultaneously decreasing dose value. Additionally, easy handling, high exposure frequency and a favourable cost-benefit ratio are also important.

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New or improved methods of digital projection radiography must fulfil the following criteria: 1. High image quality (spatial resolution, contrast detectability, dynamic range,

homogeneity) 2. Low dose value (high sensitivity for x-ray quanta) 3. Simple and fast handling 4. Integration into existing x-ray units and workflows 5. Integration into PACS/RIS-systems 6. Favourable cost/benefit relationship Principles of imaging systems for digital projection radiography

Film/screen imaging is a well-proven system for projection radiography. Its advantages include the high image quality, “simple” exposure technique and favourable cost benefit relationship. Its disadvantages are its limited dynamic range, difficulties in post-processing, relative high dose values, uncomfortable handling and limited availability of x-ray films. The exposed film is simultaneously a detector and a medium for archiving and demonstration, which makes it fundamentally different in principle to digital techniques, which require separate steps. The digital imaging chain consists of three independent steps: image acquisition, image processing and image display. The main differences between the specific digital projection radiography systems are in detector technology and signal processing. Optimising image processing and display on laser films or monitors is a problem common to all systems.

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In the following, five techniques are described: 1. Image intensifier (II) technique 2. Storage phosphor technique 3. Selenium drum technique 4. CCD (charged coupled device) technique 5. Flat detector technique

5.1. Direct conversion (selenium) 5.2. Indirect conversion (scintillator)

1. Digital image intensifier technique

The image intensifier (II) converts the latent absorption image of x-rays into a reduced size image at the II exit. The steps involved in this process are the entrance screen (Caesium iodine) and photocathode steps, which convert x-ray quanta first into light quanta and then into electrons. An electrical field leads these electrons to a screen at the exit of the II, upon which the electrons are converted into light again (1). A television camera records this screen over tandem optics. If the camera consists of a conventional television tube (e.g. Vidicon, Saticon) the information is transferred as an analogue signal to an analogue/digital converter. The image information is recorded directly by a semiconductor image detector (CCD), digitised, and transferred to a computer system. CCD detectors have a lower inertia compared to conventional television tubes and are both more tolerant against burn-out effects and have very homogenous imaging capabilities. While technical progresses in II technology have been only slowly forthcoming due to physical and financial limitations, there have been improvements in pulsed fluoroscopy and shuttering without radiation dose over the last few years, as well as the introduction of the matrix size 2048X2028 (5, 6, 7).

2. Storage phosphor radiography

Storage phosphor radiography involves exposing phosphor plates instead of x-ray films. Within the layers of the storage phosphor plate, electrons are elevated to a higher energy level by the absorption and deposition of energy by x-ray quanta. The way these electrons are distributed corresponds to the intensity distribution of the radiation. A laser beam scans the plates in a separate readout unit. During this process, electrons drop down to a basic level and emit light, which is registered by a photomultiplier. After analogue signals have been converted to digital values, a numerical intensity value is assigned to every point of the image. Homogenous light irradiation then erases the remaining image information off the plates.

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3. Digital radiography with the selenium drum technique

Here, the detector consists of a rotating drum covered with selenium. Selenium is a semiconductor which becomes conductive by absorbing x-ray radiation. The selenium layer of the drum is positively charged homogeneously before exposure. During the exposure, charges are equalised, that is, the positive charge is reduced. This creates a charge pattern on the surface that is proportional to the radiation pattern. The charge pattern is scanned during drum rotation and converted to digital image information (8).

4. Digital CCD technique

X-ray quanta is converted into light on a fluorescent entrance screen. The emitted light is then transferred to four CCD-cameras (9), which convert the optical image into digital information. A CCD detector uses the property of selenium to convert light into moveable charge carriers. The light image is stored as a charge image in a number of pixel-elements. After exposure, the “charge” image is read as a sequence of signals and, after conversion from analog to digital, is stored as digital information.

5.1. Flat detectors with direct conversion (selenium)

Flat detectors allow the direct conversion of x-ray quanta into charges (electrons). A voltage of 6 kV is passed through a 500 µm thick layer of selenium. A matrix of image elements (pixels) lies behind the layer. Every pixel contains an electrode for charge detection, a charge capacitor and a transistor. In the selenium layer, x-ray quanta are converted to charges, transferred to the electrode, and stored in the capacitor. If the element is selected, the charge is transferred to an analogue/digital converter. A digital image is then generated by line-by-line readout (10, 11, 12, 13).

5.2. Flat detector with indirect conversion (scintillator)

A glass plate is coated with a layer of amorphous silicon (thickness 500 µm). The structure is as a matrix of silicon photodiodes similar to the CCD detector. A switching transistor selected by a control line is connected to the element (pixel). A scintillator layer with caesium iodine is in front of the silicon elements. Within this layer the x-ray quanta are converted to light quanta. The needle-structured caesium iodine crystals focus the light quanta to the detector elements. The charge of the specific photodiode is read out and transferred to an analogue/digital converter (14, 15).

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Imaging capabilities of systems for digital projection radiography

The imaging capabilities of digital radiography are determined by the characteristics of detectors, signal processing (amplification, digitalisation), digital post-processing and documentation (16, 17, 18). The parameters characterising digital systems are: Spatial resolution Dynamic range Quantum efficiency (DQE) Modular transfer function (MTF)

Spatial resolution:

The parameter spatial resolution describes the detectability of small, high-contrast objects. Spatial resolution is usually demonstrated by a lead bar pattern and measured as linepairs per millimetre (lp/mm). Scattering inside the detector has a significant influence on resolution, similar to film/screen exposures. For analogue systems, the maximum resolution is determined by the evaluation of the image of the lead bar pattern. The cut-off resolution is defined as 4% of the maximal amplitude of the modulation transfer function (MTF). For digital systems, there exists an additional limitation by pixel size. The scanning formula means that for a pixel size of a, the maximal transfer frequency can be 1/2a. A pixel size of 0.25 mm, therefore, would lead to a cut-off frequency (Nyquist cut-off) of 2 lp/mm. If this limitation is exceeded by a lead bar pattern image, an aliasing pattern will result, with a reduction of image quality.

Dynamic range:

The dynamic range is determined by the dose range, which can be imaged without the effects of underexposure or overexposure. Digital systems have a linear correlation between dose value and signal amplitude. Conventional film/screen systems have only a narrow dynamic range for imaging that is characterized by the linear perform of s-shaped density curve. A large dynamic range is connected to a broad range for the exposure parameter dose (e.g. bedside imaging (reduction of the number of retakes!)). It allows simultaneous imaging of large absorption differences (e.g. bone/soft tissue: mediastinum/parenchyma of the lung) within only one exposure (reduction of dose value!).

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Detective quantum efficiency (DQE):

DQE describes the efficiency of x-ray quanta-to-signal conversion. The DQE depends on the dose value and the spatial resolution (object size) and is influenced by the quantum noise and the noise of the detector. An ideal detector has a DQE=100%. A high DQE is correlated with a high effective use of x-ray quanta. This results in a reduction of dose value without loss of image quality.

Modulation transfer function (MTF):

Imaging means demonstrating different sized objects with different attenuation of x-rays. A description of imaging of contrast and object size can be done using the modular transfer function. The MTF shows how the contrast of different sized objects are demonstrated by the image. The MTF should be high in the range of object size between 0 and 2 lp/mm, because this range contains the medically-relevant details. The MTF’s special parameters are cut-off resolution (resolution at 4% of the maximal amplitude) and specific modulation at fixed resolution (e.g. 60% for 1 lp/mm). The reference point is 100% for 0 lp/mm (that is, a homogenous background). Characteristic modulation underlines that the shape of the MTF is more important in the range of 0 – 2 lp/mm than the cut-off frequency because, again, this range frequently contains structures relevant to diagnosis.

Image quality:

The image quality at the end of the imaging chain (laser film, monitor) is determined by the parameters already described, with the addition of digital post-processing. Post-processing can lead to increased image quality and additional diagnostic information. Image processing should result in improved detail contrast, edge enhancement, reduction of dynamic range and noise (19). Digital Image Intensifier Technique

The diameter of the entrance surface is between 15 cm and 40 cm. With a matrix size of 1024X1024 (or 2048X2048), the pixel size is between 0.15(0.07)mm and 0.4(0.2)mm. The II entrance dose for a diameter of 17cm is about 2,2 µGy, comparable to film/screen speed class 400, and for a 40cm entrance screen the dose is about 0.4 µGy. The dynamic range (1:100) is larger than for film/screen (1:30). The DQE is 60% (70kV). Alongside single exposures, image intensifier technology can also be used for fluoroscopy. Fluoroscopy should guarantee sufficient image quality for controlling catheter

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position, projections and vessels. The II entrance dose for fluoroscopy is 0.02 µGy/sec (3 pulses/sec, II 27cm) and 0.17 µGy/sec (continuous beam, II 27 cm). Pulsed fluoroscopy, image integration (recursive filtering) and collimation without radiation is the major potential of dose reduction. Digital storage phosphor radiography

In storage phosphor radiography, pixel size and spatial resolution depend on the entrance size. A format of 35X43cm (matrix 1769x2140) has a pixel size of 0.2 mm and a cut off resolution of 2.5 lp/mm, whereas a format of 18x24cm (1770x2370) results a pixel size of 0.1 mm and a cut-off frequency of 5.0 lp/mm. The dynamic range is 1:40000 and the quantum efficiency 25% (70 kV, 0 lp/mm). This means that, in comparison to film/screen radiography for storage phosphor radiography, no significant reduce of dose value is possible. The large dynamic range, the high contrast amplification and a limited spatial resolution are characteristic of storage phosphor radiography. The method of post-processing also has significant role in attaining high image quality of storage phosphor radiography (19, 20). Digital radiography with the selenium drum technique

The selenium drum technique is used in dedicated systems for the lung. (Philips: Thoravision). For an image format of 35x43 cm (matrix: 2166x2448), the pixel size is 0.2mm and the corresponding cut-off frequency 2.5 lp/mm. The dynamic range is higher than 1:10.000. The DQE of 60% (60 kV) points to the possibility of dose reduction from that of film/screen (DQE 20%). Digital CCD technique

The number of pixels of a CCD camera is 1024x1280. The sum of 4 CCD targets is therefore 4096x5120 for an entrance field of 34 x 43 cm. The pixel size is 169 µm and the cut-off resolution 3 lp/mm. CCD systems have a dynamic range of about 1:4000 and a DQE of 40%. Decreased signal-to-noise ratio is attributed to the transfer of light from the scintillator surface to the CCD detector. Flat detector with direct conversion (selenium)

For a detector area of 35x43 cm (matrix 2560x3072), the pixel size is 0.139 mm and the cut-off resolution 3.6 lp/mm. The DQE is 43% (70kV, 0 lp/mm) and the dynamic range >1:10.000.

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Flat detector with indirect conversion (scintillator)

Flat detectors manufactured by Trixel (a joint venture by Thomson, Siemens, and Philips) have a detector area of 43x43 cm (matrix 3120x3120). The pixel size is 0.143 mm and the cut-off resolution 3.5 lp/mm. The dynamic range is >1:10.000 and the DQE 60% (70kV, 0 lp/mm). The readout time is 1.25 sec. The General Electric silicon detector has a pixel size of 0.2 mm (cut-off resolution 2.5mm) and a DQE of 80% (70 kV, 0 lp/mm). The first successful fluoroscopy applications for silicon detectors are now been described. With an entrance field of 20cm, (Matrix 1024x1024) the pixel size is 0.2mm. The detector has an image frequency of 25 images/second in continuous mode. For medium and high dose levels, image quality is considered to be higher in comparison to II radiography. For low dose values, however, there is lower signal-to-noise ratio when compared to II radiography.

Clinical applications of digital projection radiography

Today, image intensifier, storage phosphor and selenium drum radiography all play an important role in projection radiography as it is used every day. The advantages of digital imaging techniques are: 1. Large dynamic range (no retakes, imaging of great differences of

attenuation) 2. High contrast detectability 3. The potential for dose reduction 4. Increased image quality through post-processing 5. Immediate availability of image information 6. Integration into PACS/RIS systems (storage, transfer, availability) The digital image intensifier technique

The digital imaging technique has completely replaced film/screen radiography for fluoroscopic units. This is because the digital technique has several advantages over film/screen radiography, despite the lower detail resolution when compared to film/screen radiography (21). The future is likely to bring only limited innovation because of the boundaries of physics and financial resources. The increase of matrix size from 1024 to 2048 is advantageous, but it is difficult to prove this in every-day clinical use.

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There are similar problems associated with the increase in matrix size from 2000 to 4000 for storage phosphor radiography (22). Increasing the matrix size makes sense only if it results in increased diagnostic information. The image quality of state-of-the-art II units should be considered to be sufficient because of its being able to be applied to all existing clinical situations. Further innovation is likely to focus on reducing the dose (pulsed fluoroscopy, collimation without radiation) and improving handling rather than improving the image quality itself. Because the digital image intensifier technique can already be integrated into PACS systems, there is no strong need for new detectors in fluoroscopic units when compared to projection radiography as a whole. But the first applications of flat detectors for single exposures and fluoroscopy show promising results. Flat detector fluoroscopy’s potential of improving image quality is greater than its potential to reduce dose. The signal-to-noise ratio is still lower in the low dose range in comparison to II units (23). It is, however, likely that image intensifiers will be replaced by this flat detector technique in the future. Storage phosphor technique

As can be read in current literature (24, 25) and the results of a consensus conference (26), the storage phosphor technique can be applied to all clinical situations requiring projection radiography. One excellent field of application is bedside imaging without automatic exposure control. The large dynamic range guaranties a constantly high image quality. However, early expectations for a significant reduction of dose value (in comparison to film/screen) didn’t hold. The necessary dose level is between the speed class 200 and 400. Handling of the storage phosphor technique is disadvantageous, because exposed cassettes have to be brought to a central reading unit and erased cassettes have to be carried back to the exposure room. Storage phosphor radiography is the only method for bedside imaging because all other detector techniques are restricted to a fixed examination room. Currently, the only way to conduct horizontal beam imaging at Bucky tables is the storage phosphor technique. An alternative to this would be C-arm units, which are not marketed by all manufacturers. A flat detector which can be read out like a mobile cassette is expected in the near future. However, innovation to the detective material of storage phosphor plates (with needle configuration) and a faster readout by detection of the information line by line could result in improved image quality and handling. First attempts to read out the plate just at the exposure unit could lead to competition with flat detectors (that is, in terms of cost).

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Selenium drum technique

Clinical studies have shown that, based on the better imaging capabilities of selenium detectors, the selenium drum technique is more favourable for lung units than the storage phosphor technique (22). The literature describes the ways in which doses can be reduced. One disadvantage of the selenium drum technique is that the units for selenium technique can be used only for thoracic imaging in an upright position, requiring a high frequency of these examinations. It is assumed that flat detectors for Bucky tables and wall stands will play a greater role in the future and will probably replace the selenium drum technique. CCD technology

Until now, only a limited number of reports of clinical results for this technology have been published. Based on its imaging capabilities, CCD technology probably produces similar image quality to storage phosphor radiography for the same dose value. A significant reduction of dose cannot be expected because of the limited DQE. CCD technology does, however, have the advantageous of no cassettes having to be carried. Flat detector technique

Flat detectors with amorphous selenium have the advantage of a direct conversion of x-ray quanta to electrical charge. This can lead to very high image quality. Selenium flat detectors offer the potential for high image quality and/or significant dose reduction. Flat detectors with scintillators demonstrated higher image quality and a lower dose level compared to film/screen and storage phosphor radiography (27, 28, 29, 30).

Digital radiography - a new challenge

The new potential of digital projection radiography can be discussed from the standpoint of a single stand-alone unit without integration into a digital system or from the standpoint of a necessary component for PACS (picture archiving and communication system) systems. For the near future, the view from a stand alone unit will remain more common. The option of integration into a fully digital system, with its many advantages (transfer, archiving, post-processing) is an important aspect of this new digital technique. X-ray units for projection

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radiography are part of radiologists’ tools; image quality thus has to fulfil the diagnostic demands – not more and not less. An increase of image quality beyond these clinical demands is useless as it costs money and also requires higher doses. New discussion of the quality of new imaging methods must be based on the 100 years of experience with film/screen radiography, 25 years of experience with digital image intensifier radiography and 20 years of experience with storage phosphor radiography that the industry has. A suitable spectrum of indications has been discussed in a large number of publications and a consensus conference. Image quality is defined by physical measurements (spatial resolution, MTF, DQE, homogeneity) and clinical studies comparing different methods. Initial results of the new flat detector systems demonstrate the potential to increase image quality and to decrease dose values. It cannot be foreseen whether this will be connected to a broadening of the spectrum of referral indications. There is a close correlation between dose and image quality. The commonly known image quality and radiation protection requirements are leading to new strategies for dose reduction. One way of achieving this could be a higher image quality with the same dose; another way the same image quality with a lower dose value. In the past, the focus has been more on image quality; today, however, dose reduction, easy handling and a favourable cost/benefit relation are important decision criteria. Better image quality is only useful if it has consequences on the outcome of therapy and follow-up and reduces the number of additional examinations. Discussion of the financial aspects is difficult in light of the high purchase and service costs and the need for specific IT infrastructure. The costs for a flat detector system are three times as high as a film/screen Bucky table with wall stand. For a stand alone unit, the potential of cost reduction lies in time and personnel costs (increase of throughput, reduction of personnel costs) and in a reduction of film costs (smaller film size, no retakes, lower number of films). The reduction of patient risk cannot, however, be calculated in terms of economics. The cost/benefit relation of a PACS system is also very difficult to calculate and largely depends on the requirements placed on the examinations themselves, the system and personnel. Further clinical experience must now show whether this new potential will lead to a new examination workflow and to a new spectrum of referral indications. Higher costs demand an intensive discussion of cost/benefit relation. The physical imaging capabilities of flat detectors point to the possibility of a successful introduction into every-day clinical world in the near future.

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[6] Vetter S, Faulkner K, Strecker EP, Busch HP (1998) Dose reduction and image quality in pulsed fluoroscopy. Radiation Protection Dosimetry. 80: 299 – 301

[7] Busch HP, Hoffmann HG, Kruppert H, Mörsdorf M(1997). Digitale BV-Radiography – Eine Methode hat sich durchgesetzt. Electromedica 65: 62 – 64

[8] Neitzel U (1993). Selenium: a new image detector for digital chest radiography. Medica Mundi 38: 89 – 93

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performance of a direct digital radiographic detector using selenium and a thin film transistor array. In: Lemke HU(ed) Computer assisted Radiology. Elesevier: 41 – 46

[11] Lee DL, Cheung LK, Jeromin LS (1995). A new digital detector for projection radiography. SPIE 2432: 237 – 249

[12] Shaber GS, Maidment ADA, Bell J, Jeromin LS, Lee DL, Powell GF (1997) Full field digital projection radiography system: Principles and image evaluaten. In: Lemke HU (ed) Computer assisted radiology and surgery. Elsevier: 1 – 7

[13] Yaffee MJ, Rowlands JA (1997) X-ray detectors for digital projection radiography. Phys Med Biol: 1 - 39

[14] Chaussat Ch, Chabbal J, Ducourant Th, Spinnler V, Vieux G, Neyret R (1998) New CsJ/a-Si X-ray flat panel detector provides superior detectivity and immediate direct digital output for General Radiography systems. SPIE 3336: 45 – 56

[15] Neitzel U(1999) Integrated digital radiography with a flat –panel sensor. Medical Imaging Technology 17,2: 123-129

[16] Neitzel U (1998) Grundlagen der digitalen Bildgebung. In Ewen K(Hrsg) Moderne Bildgebung. Georg Thieme: 71 – 76

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[17] Neitzel U(1998) Systeme für die digitale Bildgebung. In: Ewen K (Hrsg) Moderne Bildgebung. Georg Thieme: 127 – 135

[18] Kamm KF (1998) Grundlagen der Röntgenabbildung. In: Ewen E (Hrsg) Moderne Bildgebung. Georg Thieme: 45 – 60

[19] Prokop M, Schaefer-Prokop CM(1997) Digital image processing. Eur Radiol 7(Suppl3): 73 – 82

[20] Vuysteke P, Schoeters E (1994) Multiscale image contrast amplification (MUSICA). SPIE 2167: 551 – 560

[21] Lehmann KJ, Busch HP, Georgi M (1992) Digitale Bildverstärker Radiographie – welche Aufnahmedosis für welche Fragestellung? Akt Radiol 2:11 – 15

[22] Schaefer-Prokop CM, Prokop M (1996) Digitale Radiographie des Thorax – der Selendetektor im Vergleich zu anderen Abbildungssystemen. Kontraste: 14 – 22

[23] Bruijns TJC, Alving PL, Bury R, Cowen AR, Jung N, Luijendijk HA, Meulenbrugge HJ, Stouten HJ (1998) Technical and clinical results of an experimental FLat Dynamic (digital) X-ray image Detector (FDXD) system with real-time corrections. SPIE 3336: 33 – 44

[24] Busch HP (1997) Digital radiography for clinical application. Eur Radiol 7 (Suppl 3): 66 – 72

[25] Leitlinien der Bundesärztekammer zur Qualitätssicherung in der Röntgendiagnostik (1995) Deutsche Ärzteblatt 92, 49: 1691 – 1703

[26] Busch HP, Klose KJ, Braunschweig R, Neugebauer E (1999) Digitale Radiographie – Ergebnisse einer Anwendungsumfrage und einer Konsensuskonferenz. Akt.Radiol. 7: 56 – 63

[27] Hamers S, Freyschmidt J (1998) Digital radiography with an electronic flat-panel detector: First clinical experience in skeletal diagnostics. Medica Mundi 42,3: 2 – 6

[28] Reiff KJ (1999) Flat panel detectors – closing the (digital) gap in Chest and skeletal radiology. European Journal of Radiology (in press)

[29] Strotzer M, Gmeinwieser J, Völk M, Fründ R, Feuerbach S (1999) Digitale Flachbilddetektortechnik basierend auf Cäsiumjodid und amorphem Silizium: Experimentelle Untersuchungen und erste klinische Ergebnisse. Fortschr Röntgenstr 170: 66 – 72

[30] Strotzer M, Gmeinwieser J, Völk M, Fründ R, Seitz J, Manke C, Albricht H, Feuerbach S (1998) Clinical application of a flat-panel X-ray detector, based on amorphous silicon technology: image quality and potential for radiation dose reduction in skeletal radiography. Amer J Roentgenol 171: 23 – 27

This article was translated from a publication in German language: H.P.Busch: Digitale Projektionsradiographie - Technische Grundlagen, Abbildungseigenschaften und Anwendungsmöglichkeiten. Radiologe 1999 – 39: 710 – 724.

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Chapter III

Diagnostic Requirements for Digital Projection Radiography

Based on: 1. European Guidelines on Quality Criteria

for Diagnostic images (EC) 2. Diagnostic Requirements for

Digital Radiographic Procedures (DIMOND II ) 3. Leitlinien der Bundesärztekammer zur

Qualitätssicherung in der Röntgendiagnostik – Qualitätskriterien röntgendiagnostischer Untersuchungen (the German Federal Medical Association's Quality Assurance Guidelines for Radiological Diagnostics: Quality criteria for radiological examinations)

24

Content: 1) Chest/lungs and heart PA projection, wall stand 2) Chest/lungs and heart Lateral projection, wall stand 3) Chest/lungs and heart AP projection, bedside 4) Cervical spine AP projection, grid table or vertical stand 5) Cervical spine Lateral projection, grid table or vertical stand 6) Thoracic spine AP projection, grid table or vertical stand 7) Thoracic spine Lateral projection, grid table or vertical stand 8) Lumbar spine AP projection, grid table or vertical stand 9) Lumbar spine Lateral projection, grid table or vertical stand 10) Pelvis AP projection, grid table or vertical stand 11) Skull AP projection, grid table or vertical stand 12) Skull Various projections, grid table or vertical stand 13) Extremity I Various projections, grid table or vertical stand

Hip Thigh

14) Extremities II Various projections, grid table or vertical stand Shoulder Upper arm Ribs Sternum Knee joint Lower leg

15) Extremities III Various projections, grid table or vertical stand Elbow Forearm Ankle Tarsus

16) Extremities IV Various projections, grid table or vertical stand Hand Fingers Foot Toes

17) Abdomen AP projection, grid table or vertical stand

25

Chest/lungs and heart - PA projection, wall stand

Image criteria

Performed at full inspiration (as assessed by the position of the ribs above the diaphragm - either 6 anteriorly or 10 posteriorly) and with suspended respiration Symmetrical imaging of the thorax, as shown by the central position of a spinous process between the medical ends of the clavicles Medical border of the scapulae to be outside the lung fields Visualisation of the whole lung including the costophrenic angles Clear visualisation of the lung structure and vascular pattern throughout the lung fields including the retrocardiac area Clear delineation of vertebral disc spaces

Suggested radiographic technique

Radiographic device: Vertical stand with moving grid Nominal focal spot value: ≤ 1.3 mm Total filtration: ≥ 3.0 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 180 cm (140-200) Radiographic voltage: 125 kV Automatic exposure control: Both lateral chambers Exposure time: < 20 ms Imaging technique: Flat detector, storage phosphor radiography

26

Chest/Lungs and Heart - lateral projection, wall stand

Image criteria

Performed at full inspiration and with suspended respiration Arms should be raised clear of the thorax Superimposition of the posterior lung borders Visualisation of the trachea Visualisation of costophrenic angles Visually sharp reproduction of the posterior border of the heart, aortic arch, mediastinum, diaphragm, sternum and thoracic spine


Radiographic device: Vertical stand with moving grid Nominal focal spot value: ≤ 1.3 mm Total filtration; ≥ 3.0 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 180 cm (140-200) Radiographic voltage: 125 kV Automatic exposure control: Central chamber Exposure time: < 40 ms Imaging technique: Flat detector, storage phosphor radiography

27

Chest/ Lungs and Heart - AP projection, bedside

Image criteria

Imaging of the whole rib cage above the diaphragm and both hemidiaphragms at full inspiration (if possible) The mediastinum should be sufficiently penetrated to visualize trachea and major bronchi. Visualisation of venous catheters, draining catheters… including the tip Visually sharp reproduction of the vascular pattern


Radiographic device: Mobile unit Nominal focal spot value: ≤ 1.3 mm Total filtration: ≥ 2.5 mm Al Anti-scatter grid: r = 10; 60/cm FFD: 100 cm Radiographic voltage: >100 kV Automatic exposure control: No Exposure time: < 40 ms Alternative Anti-scatter grid: No FFD: 100 cm Radiographic voltage: 80 - 90 kV Imaging technique: Storage phosphor radiography

28

Cervical Spine - AP projection

Image criteria

Complete imaging of the cervical spine, including the upper cervical spine and the 7th vertebra, if necessary with additional spotfilm Visually sharp imaging, as a single line, of the upper and lower-plate surface in the centred beam area Visualisation of the intervertebral joints and the spinous processes Visually sharp imaging of the cortical and trabecular structures


Radiographic device: Grid table or vertical stand with moving grid Nominal focal spot value: ≤ 1.3 mm Total filtration: ≥ 3.0 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 115 cm (100-150) Radiographic voltage: 65-75 kV Automatic exposure control: Central chamber Exposure time: < 100 ms Imaging technique: Flat detector, storage phosphor radiography

29

Cervical Spine - lateral projection

Image criteria

Complete imaging of the cervical spine, including the upper cervical spine and the 7th vertebra Visually sharp imaging, as a single line, of the upper and lower-plate surface in the centred beam area Visualisation of the intervertebral spaces, intervertebral joints and spinous processes Visualisation of the soft tissues, particularly the retrotracheal space Visually sharp imaging of the cortical and trabecular structures



30

Thoracic Spine - AP projection

Image criteria

Complete imaging of the thoracic spine, including Th1 Visually sharp imaging, as a single line, of the upper and lower-plate surface in the centred beam area Visually sharp imaging of the pedicle, spinous processes and costovertebral joints


Radiographic device: Table or vertical stand with moving grid Nominal focal spot value: ≤ 1.3 mm Total filtration: ≥ 3.0 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 115 cm (100-150) Radiographic voltage: 75-85 kV Automatic exposure control: Central chamber Exposure time: < 200 ms Imaging technique: Flat detector, storage phosphor radiography

31

Thoracic Spine - lateral projection

Image criteria

Complete imaging of the thoracic spine from T2 down to the thoracolumbar junction Visually sharp imaging, as a single line, of the upper and lower-plate surface in the centred beam area Visualisation of the intervertebral spaces and intervertebral joints in the centred beam area Visually sharp imaging of the cortical and trabecular structures



32

Lumbar Spine - AP projection

Image criteria

Complete visualisation of the lumbar spine and sacrum Visually sharp imaging, as a single line, of the upper and lower-plate surfaces in the centred beam area Visualisation of the intervertebral spaces in the centred beam area Visually sharp imaging of the pedicles, transverse processes, spinous processes and intervertebral joints Visualisation of the sacroiliac joints Visually sharp imaging of the cortical and trabecular structures



33

Lumbar Spine - lateral projection

Image criteria

Complete visualisation of the lumbar spine and lumbosacral junction Visually sharp imaging, as a single line, of the upper and lower-plate surface in the centred beam area Visualisation of intervertebral spaces, intervertebral joints and spinous processes Visually sharp imaging of the cortical and trabecular structures



34

Pelvis - PA projection

Image criteria

Symmetrical imaging of both sides of the pelvis Visually sharp imaging of the necks of the femora – should not be distorted by foreshortening or rotation Visually sharp imaging of the pubic and ischial rami and the sacroiliac joints Visually sharp imaging of the cortial and trabecular structures including the trochanters Visually sharp imaging of the sacrum and its intervertebral foramina



35

Skull - PA projection

Image criteria

Symmetrical reproduction of the skull, particularly cranial vault, orbits and petrous bones Projection of the apex of the petrous temporal bone into the centre of the orbits Visually sharp reproduction of the frontal sinus, ethmoid cells and apex of the petrous temporal bones and the internal auditory canals Visually sharp reproduction of the outer and inner lamina of the cranial vault


Radiographic device: Grid table or vertical stand with moving grid Nominal focal spot value: 0,6 mm Total filtration: ≥ 2,5 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 115 cm (100-150) Radiographic voltage: 70-85 kV Automatic exposure control: Central chamber Exposure time: < 100 ms Imaging technique: Flat detector, storage phosphor radiography

36

Skull - lateral projection

Image criteria

Visually sharp reproduction of the outer and inner lamina of the cranial vault, the floor of the sella, and the apex of the petrous temporal bone Superimposition respectively of the contours of the frontal cranial fossa, the lesser wing of the sphenoid bone, the clinoid processes and the external auditory canals Visually sharp reproduction of the vascular channels, the vertex of the skull and the trabecular structure of the cranium Superimposition of the mandibular angles and ascending rami


Radiographic device: Grid table or vertical stand with moving grid Nominal focal spot value: 0,6 mm Total filtration: ≥ 2,5 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 115 cm (100-150) Radiographic voltage: 70-85 kV Automatic exposure control: Central chamber Exposure time: < 100 ms Imaging technique: Flat detector, storage phosphor radiography

37

Extremities I - Various projections, grid table or vertical stand

Hips

Thighs

Image criteria

Visualisation of typical structures of compacta and spongiosa Imaging of the joints in typical projections Visually sharp reproduction of the cortical joint surface


Radiographic device: Grid table or vertical stand with moving grid Nominal focal spot value: ≤ 1,3 mm Total filtration: ≥ 2,5 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 115 cm (100-150) Radiographic voltage: 70-80 kV Automatic exposure control: Central chamber Exposure time: < 200 ms Imaging technique: Flat detector, storage phosphor radiography

38

Extremities II - Various projections, grid table or vertical stand

Shoulder

Upper arm

Ribs

Sternum

Knee joint

Lower leg

Image criteria



Radiographic device: Grid table or vertical stand with moving grid Nominal focal spot value: ≤ 1,3 mm Total filtration: ≥ 2,5 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 115 cm (100-150) Radiographic voltage: 60-75 kV Automatic exposure control: Central chamber Exposure time: < 100 ms Imaging technique: Flat detector, storage phosphor radiography

39

Extremities III - Various projections, grid table or vertical stand

Elbow

Forearm

Ankle

Tarsus

Image criteria



Radiographic device: Grid table Nominal focal spot value: ≤ 1,3 mm Total filtration: ≥ 2,5 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 105 cm (100-150) Radiographic voltage: 50-60 kV Automatic exposure control: Off Imaging technique: Flat detector, storage phosphor radiography

40

Extremities IV - Various projections, grid table or vertical stand

Hands

Fingers

Feet

Toes

Image criteria



Radiographic device: Table Nominal focal spot value: ≤ 1,3 mm Total filtration: ≥ 2,5 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 105 cm (100-150) Radiographic voltage: 45-55 kV Automatic exposure control: Off Imaging technique: Flat detector, storage phosphor radiography

41

Abdomen - PA projections, grid table or vertical stand

Image criteria

Reproduction of the area of the whole abdomen from the diaphragm to the base of the bladder Reproduction of the kidney outlines Visualisation of the psoas outlines Visually sharp reproduction of the bones


Radiographic device: Grid table Nominal focal spot value: ≤ 1,3 mm Total filtration: ≥ 1,3 mm Al Anti-scatter grid: r = 10; 40/cm FFD: 115 cm (100-150) Radiographic voltage: 75-90 kV Automatic exposure control: Chamber selected – central or lateral Exposure time: < 200 ms Imaging technique: Flat detector, storage phosphor radiography

42

Guidelines and user-defined recommendations for the

selection of imaging parameters Based on: Recommendations of the EU(EU) German Guidelines (RiLiBÄ) Krankenhaus der Barmherzigen Brüder Trier (BKT-Trier) University Hospital, Innsbruck (Innsbruck) Athens Hospital (Athens) San Carlos Hospital, Madrid (San Carlos/Madrid) Limerick Hospital, Ireland (Limerick)

43

44

45

46

47

48

49

50

51

Chapter IV

Referral Guidelines with the Three Level Band for Image Quality

In recent years, film/screen radiography has been characterised by the search for optimal image quality, independent of the specific clinical problem. The only restricting parameter was the dose value, which could not exceed a maximum value. The advantage of pursuing a strategy of trying to obtain the highest level of image quality is the fact that a range of unexpected, yet complementary diagnostic information can be obtained, over and above the information normally obtained at a lower dose. By implementing digital imaging methods, however, doses can be reduced over a broad range – which sometimes does decrease image quality, but often does not. Dose and quality management realises this new potential using the ALARA principle (As Low As Reasonably Achievable), adapting image quality and dose to fit the clinical situation (“quality as good as necessary, not as good as possible – dose value as low as possible”). Quality and dose management should start with establishing a clear definition of indications for Digital Projection Radiography. These guidelines should be based on the criteria and methods of evidence-based medicine, taking into account the clinical situation and the risk for to the patient. The aim is to avoid unnecessary, routine exposures as well as to reduce the dose per image. Two documents can be considered a starting point here, namely “Referral Guidelines for Imaging”, published by the European Commission (European Commission – Radiation protection 118 – ISBN 92-828-9452-5). and the Council Directive 97/43/ Euratom on health protection of individuals against dangers of ionizing radiation in relation to medical exposure. The latter publication includes sections on purpose and scope, definitions, justification, optimisation and responsibilities. One parameter that can be varied over a broader range in digital radiography than in film/screen radiography is the exposure dose value. Past experience and research demonstrate that for flat detectors, the speed class of 800 is sufficient for nearly all indications. The dose value of the speed class 200 is no longer used. For many indications speed class, 1600 is suitable. The storage phosphor technique’s potential for dose reduction is significantly lower. Part of the DIMOND III project involved developing a three-level concept of image quality (high, medium, low) for quality and dose management. Certain dose values (for example, the speed classes 400, 800, and 1600) have been assigned to certain quality levels, depending on the specific imaging method.

52

One example resulting out of a comparative study (see chapter VI) is shown in the following diagram: Image Quality classes ( ) Speed class

High Medium Low

Flat detector (400) Flat detector (800) Flat detector (1600)

Storage Phosphor (200/400)

Storage Phosphor (400)

Storage Phosphor (800)

Film (200) Film (400) Film (800)

There must be intensive discussion on the strategies and methods for optimising and standardising image quality in the future. Although many individual studies (see references) describe interesting results, they are missing a methodical framework.

53

Examples of quality classes high, medium and low: Referral Guidelines for Imaging: European Commission – Radiation protection 118 – ISBN 92-828-9452-5 The column “Quality Class” has been added as a result of the DIMOND III project

INVESTIGATION {DOSE}

XR Plain radiography one or more films CXR Chest radiograph

Class Typical effective Dose (mSv) Examples

0 0 US, MRI I <1 CXR, limb XR, pelvis XR

II 1–5 IVU, lumbar spine XR, NM (e.g. skeletal scintigram), CT head & neck

III 5–10 CT chest and abdomen, NM (e.g. cardiac) IV >10 Some NM studies (e.g. PET)

QUALITY CLASS

H High M Middle L Low

RECOMMENDATION {GRADE}

(A) Randomised controlled trials (RCTs), metaanalyses, systematic reviews; or (B) Robust experimental or observational studies; or (C) Other evidence where the advice relies on expert opinion and has the

endorsement of respected authorities.

54

QUALITY - DOSE

- LEVEL CLINICAL PROBLEM

INVESTI-GATION {DOSE}

Trier

Athen

Madrid

Dublin

RECOM-MEN-

DATION {GRADE}

COMMENT

A. Head

Orbits Metallic FB (before MRI) XR orbits (I) H H H H Indicated (B)

Especially for those who have worked with metallic materials, power tools, etc. Some centres use CT. (see Trauma Section K for acute injury).

Headache: chronic XR skull, sinus C spine (I) M M M M Not indicated

routinely (B) Radiography of little use in the absence of focal signs/symptoms. See A13 below.

Pituitary and juxta-sellar problems SXR (I) . M H H M Not indicated

routinely (C) Patients who require investigation need MRI or CT

Hydrocephalus XR L L L L Indicated (C) XR can demonstrate whole valve system.

Sinus disease Sinus XR (I) M M M-H M Not indicated routinely (B)

Thickened mucosa is a non-specific finding and may occur in asymptomatic patients.

Dementia and memory disorders, first onset psychosis

SXR (I) M M L-M M Not indicated routinely (B)

Consider investigation if clinical course unusual or in younger patient.

Orbits Metallic FB (before MRI) XR orbits (I) H H H H Indicated (B)

Especially for those who have worked with metallic materials, power tools, etc. Some centres use CT. (see Trauma Section K for acute injury).

Visual disturbances SXR (I) M M M M Not indicated routinely (C)

Plain XRs rarely contributory. Specialists may require CT or MRI.

Epilepsy (adult) SXR (I) M M M M Not indicated routinely (B)

Evaluation requires specialist expertise. Late onset seizures should normally be investigated but imaging may be unnecessary if clearly alcohol-related.

B. Neck (for the spine see Sections C [The spine] and K [Trauma]) Soft tissues

Temporo-mandibular joint dysfunction XR (I) M H M-H M

Specialised investigation (B)

Radiographs will demonstrate bony abnormalities, but are normal in great majority, as problems are usually related to articular disk dysfunction.

C. The spine General (for trauma see Section K)

Congenital disorders XR (I) L L L L Specialised investigation (C)

e.g. Full-length standing radiograph for scoliosis. See Section M for back pain (M10).

Cervical spine

Possible atlanto-axial subluxation XR (I) M M M-H M Indicated (C)

A single lateral cervical spine XR with the patient in subluxation supervised comfortable flexion should reveal any significant subluxation in patients with rheumatoid arthritis, Down’s Syndrome, etc. MRI (flexion/extension) shows effect on cord when XR positive or neurological signs present.

55

Neck pain, brachalgia, degenerative change XR (I) M M M M Not indicated

routinely (B)

Degenerative changes begin in early middle-age and are often unrelated to symptoms which are usually due to disk/ligamentous changes undetectable on plain XR. MRI increasingly being used, especially when brachalgia is present.

Thoracic spine

Pain without trauma: degenerative disease XR (I) M M M M

Not indicated routinely (B) onwards.

Degenerative changes are invariable from middle-age. Examination rarely useful in the absence of neurological signs or pointers to metastases or infection. Consider more urgent referral in elderly patients with sudden pain to show osteoporotic collapse or other forms of bone destruction. Consider NM for possible metastatic lesions.

Lumbar spine

Chronic back pain with no pointers to infection or neoplasm

XR (II) M M M M Not indicated routinely (C)

Degenerative changes are common and non-specific. Main value in younger patients (e.g. younger than 20, spondylolisthesis, ankylosing spondylitis, etc.) or in older patients e.g. >55.

Acute back pain: disk herniation; sciatica with no adverse features (see above).

XR (II) M M M M Not indicated routinely (C)

Acute back pain is usually due to conditions which cannot be diagnosed on plain XR (osteoporotic collapse an exception). ‘Normal’ plain XRs may be falsely reassuring. Demonstration of disk herniation requires MRI or CT and should be considered immediately after failed conservative management.

D. Musculoskeletal system

Osteomyelitis XR (I) + NM (II) or MRI (0) M H M M Indicated (B)

The 2–3 phase skeletal scintigram is more sensitive than XR. However, findings are not specific and further specialised NM with alternative agents may be needed. Fat-suppressed MRI is becoming regarded as the optimal investigation.

Primary bone tumour XR (I) H H H H Indicated (B) XR may characterise the lesion.

Known primary tumour. Skeletal metastases

Skeletal survey (II) H H H H Not indicated routinely (C)

Bone pain XR (I) M M M M Indicated (B) Local view of symptomatic areas only.

Myeloma Skeletal survey (II) M M M M Indicated (C)

For staging and identifying lesions which may benefit from radiotherapy. Survey can be very limited for follow-up.

Metabolic bone disease Skeletal survey (II) H H H H Not indicated

routinely (C)

Biochemical tests usually suffice. If needed, this should be limited (e.g. hands, CXR, pelvis and lateral lumbar spine). Bone densitometry may be needed. (see D9).

Osteomalacia XR (0) H H H H Indicated (B) Localised XR to establish cause of local pain or equivocal lesion on NM.

Pain — osteoporotic collapse

XR (II) lateral thoracic and lumbar spine

M M M M Indicated (B)

Lateral views will demonstrate compression fractures. NM or MRI more useful in distinguishing between recent and old fractures and can help exclude pathological fractures. Bone densitometry (dual energy XR absorptiometry (DEXA) or quantitative CT) provides objective measurements of bone mineral content; can also be used for metabolic bone disease (see D7, D8).

Arthropathy, presentation XR (I) affected joint H H H H Indicated (C) May be helpful to determine cause although

erosions are a relatively late feature.

56

XR (I) hands/feet H H H H Indicated (C) In patients with suspected rheumatoid arthritis,

XR feet may show erosions even when symptomatic hand(s) appear normal.

XR (II) multiple joint(s) H H H H Not indicated

routinely (C)

Arthropathy, follow-up XR (I) M M M M Not indicated routinely (C)

XRs needed by specialists to assist management decisions.

Painful shoulder joint XR (I) M M M M Not indicated routinely (C)

Degenerative changes in the acromio-clavicular joints and rotator cuff are common. Earlier XR if soft tissue calcification is expected.

Painful prosthesis XR (I) + NM (II) M M M-H M Indicated (B) A normal NM study excludes most late complications. Further specialised NM studies can help distinguish loosening from infection.

SI joint lesion XR SI joints (II) H H H H Indicated (B) May help in investigation of sero-negative arthropathy. SI joints usually adequately demonstrated on AP lumbar spine.

Hip pain: full movement XR pelvis (I) M M M M Not indicated routinely (C)

XR only if symptoms and signs persist or complex history (e.g. chance of avascular necrosis, see D20)

Hip pain: limited movement XR pelvis (I) M M M M Not indicated

routinely (C)

Symptoms often transient. XR if hip replacement might be considered or symptoms persist. PET may be helpful, if XR, MRI standard NM all normal.

Hip pain: avascular necrosis XR Pelvis (I) M H M M Indicated (B) Abnormal in established disease.

Knee pain: without locking or restriction in movement

XR (I) M M M M Not indicated routinely (C)

Symptoms frequently arise from soft tissues and these will not be demonstrated on XR. OA changes common. XRs needed when considering surgery.

Knee pain: with locking, restricted movement or effusion (loose body)

XR (I) M M M M Indicated (C) To identify radio-opaque loose bodies.

Hallux valgus XR (I) L L L L Specialised investigation (C)

For assessment before surgery.

Plantar fasciitis — calcaneal spur XR (I) M M M-H M Not indicated

routinely (B)

Plantar spurs are common incidental findings. The cause of the pain is seldom detectable on XR. US, NM and MRI are more sensitive in showing inflammatory change but the majority of patients can be managed without imaging.

E. Cardiovascular system

Central chest pain myocardial infarction CXR (I) M M M M Indicated (B)

CXR must not delay admission to a specialised unit. CXR can assess heart size, pulmonary oedema, etc. and can exclude other causes. Department film preferable. Subsequent imaging involves specialised investigations (NM, coronary angiography, etc.) and depend on local policy. NM offers myocardial perfusion and ventriculography data. Increasing E1 interest in MRI.

Chest pain: aortic dissection: acute CXR (I) M M M M Indicated (B) Mainly to exclude other causes; rarely diagnostic.

Pericarditis — pericardial effusion CXR (I) M M M M Indicated (B) May be normal; effusion volume/effect not

determined.

Suspected valvular cardiac disease

CXR (I) and cardiac US (0) M M M M Indicated (B) Used for initial assessment and when there is a

change in the clinical picture.

57

Follow-up of patients with heart disease or hypertension

CXR (I) M M M M Not indicated routinely (B)

Only if signs or symptoms have changed, when comparison with the CXR obtained at presentation may be helpful.

F. Thoracic system

Non-specific chest pain CXR (I) M M M M Not indicated routinely (C)

Conditions such as Tietze’s disease show no abnormality on CXR. Main purpose is reassurance.

Chest trauma CXR (I) M M M-H M Not indicated routinely (C)

Showing a rib fracture after minor trauma does not alter management (see Trauma Section K).

Pre-employment or screening medicals CXR (I) M M M M Not indicated

Not justified except in a few high-risk categories (e.g. at risk immigrants with no recent CXR). Some have to be done for occupational (e.g. divers) or emigration purposes (UK category 2).

Pre-operative CXR (I) M M M M Not indicated routinely (B)

Exception before cardio-pilmonary surgery, likely admission to ITU, suspected malignancy or possible TB. Anaesthetists may also request CXRs for smokers, dyspnoeic patients, those with known cardiac disease and the very elderly. Many patients with cardio respiratory disease have recent CXR available; a repeat CXR is then not usually needed.

Upper respiratory-tract infection CXR (I) M M M M Not indicated

routinely (C)

Chronic obstructive airways disease or asthma; follow-up

CXR (I) M M M M Not indicated routinely (B) Only if signs or symptoms have changed.

Pneumonia adults: follow-up CXR (I) L L M L Indicated (A)

To confirm clearing, etc. Pointless to re-examine at less than 10-day intervals as clearing can be slow (especially in the elderly).

Pleural effusion CXR (I) M M M M Indicated (B) Small effusion can be missed, especially on a fronta CXR.l

Haemoptysis CXR (I) M H M M Indicated (B) PA plus lateral view.

ITU/HDU patient CXR (I) M M M M Indicated (B)

A CXR is most helpful when there has been a change in symptoms or insertion or removal of a device. The value of the routine daily CXR is being increasingly questioned.

G. Gastrointestinal system Gastrointestinal tract

Oesophageal perforation CXR (I) M M M M Indicated (B) CXR may be sufficient, unless localisation for surgical repair is planned.

Acute GI bleeding: haematemesis AXR (II) L L L L Not indicated

routinely (B) Of no value.

Acute abdominal pain- perforation- obstruction

CXR (I) (erect) and AXR (II) L M M L Indicated (B)

Decubitus AXR to show free air if CXR supine. Supine AXR usually sufficient to establish diagnosis and point to an anatomical level of obstruction.

Inflammatory bowel disease of colon AXR (II) L M M-H L Indicated (B) Often sufficient for evaluation.

General abdominal problems

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Acute abdomen pain; (warranting hospital admission and surgical consideration)

AXR (II) plus erect CXR (I) L M M L Indicated (B)

Local policy will determine strategy. Supine AXR (for gas pattern, etc.) is usually sufficient. Erect AXR not indicated routinely. Increasing use of CT as a ‘catch- all’ investigation here. US widely used as a preliminary survey.

Palpable mass AXR (II) L L M L Not indicated routinely (C)

Constipation AXR (II) L L L L Not indicated routinely (C)

Many normal adults show extensive faecal material; although this may be related to prolonged transit time it is impossible to assess significance on AXR alone. But AXR can help certain specialists (e.g. geriatricians) in refractory cases.

Biliary disease, (e.g. gallstones) AXR (II) M M M M Not indicated

routinely (C) Plain XRs only show about 10 % of gallstones.

Pancreatitis: acute AXR (II) M M M M Not indicated routinely (C)

Unless diagnosis in doubt; then AXR needed to exclude other causes of acute abdomen pain (see G19). Some patients presenting with acute pancreatitis have underlying chronic pancreatitis which may cause calcification evident on AXR.

Pancreatitis: chronic AXR (II) M M M M Indicated (B) To show calcification.

H. Urological, adrenal and genito-urinary systems

Hypertension (without evidence of renal disease)

IVU (II) M M M M Not indicated routinely (A)

IVU is insensitive for renal artery stenosis. See H3.

Renal colic, loin pain IVU (II) or US (0) and AXR (II) or CT (III)


Imaging should be performed as an emergency xamination whilst the pain is present, as radiological signs disappear rapidly after passage of a stone. Delayed films (up to 24 hrs) may be needed to show the site of obstruction. A plain AXR on its own is of little value. Both CT and US are increasingly being used, especially in those with contraindications to contrast medium.

Renal mass AXR (II) + IVU (II) M M M M Not indicated routinely (C)

CT or MRI preferable for further evaluation. NM may be needed to determine relative function.

Prostatism IVU (II) M M M M Not indicated routinely (B)

US can also assess upper tract and bladder volumes before and after voiding, preferably with flow rates. It can also show bladder calculi.

Urinary retention IVU (II) L L L L Not indicated routinely (C)

US for diagnostics of upper urinary tract (after catheterisation and relief of bladder distension), particularly if urea levels remain raised.

I. Obstetrics and gynaecology NB: Transvaginal (TV) US equipment should be available in all departments performing pelvic US

Lost IUCD AXR (II) M M ? M Not indicated routinely (C) Unless IUCD is not seen in uterus on US.

Suspected cephalopelvic disproportion XR (II) Pelvimetry L L L L Not indicated

routinely (B)

The need for pelvimetry is increasingly being questioned. Local policy should be determined in agreement with obstetricians. Furthermore MRI or CT should be used wherever possible. MRI is best as it avoids x-irradiation. CT generally offers a lower dose than standard XR pelvimetry.

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K. Trauma Head: general Head: low risk of intracranial injury

• Fully orientated • No amnesia • No neurological defects • No serious scalp laceration • No haematoma

SXR (I) M M M M Not indicated routinely (C)

These patients are usually sent home with head injury instructions into the care of a responsible adult. They may be admitted to hospital if no such adult is available.

Head: medium-risk of intracranial injury • Loss of consciousness or amnesia • Violent mechanisms of injury • Scalp bruise, swelling or laceration down to bone or > 5 cm • Neurological symptoms or signs (including headache, vomiting twice or more, return visit) • Inadequate history or examination (epilepsy/alcohol/child/etc.) • Child below 5 yrs: suspected NAI, tense fontanelle, fall of more than 60 cm or on to hard surface

CT (II) or M M M M Indicated (B)

CT is increasingly being used first and ONLY to exclude cranial injury. If no fracture is seen, patients will usually be sent home with head injury instructions into the care of a responsible adult. If no responsible adult is available or if a fracture is present, the patient will usually be admitted. See Section M (M13) for non-accidental injury in children. MRI of the brain is the preferred investigation for intracranial injuries in NAI, but SXR may still be needed to exclude fractures missed on CT.

Head: very high risk of intracranial injury

Nasal trauma SXR (I) XR facial bones (I), XR nasal bones (I)

H H H H Not indicated routinely (B)

Unless requested by a specialist. Poor correlation between radiological findings and presence of external deformity. Management of the bruised nose will depend on local policy: usually follow-up at an ENT or maxillo-facial clinic will determine the need for XR.

Orbital trauma: blunt injury

XR facial bones (I) H H H H Indicated (B)

Especially in those where ‘blow-out’ injury possible MRI or low dose CT may eventually be required by specialists, especially when XRs or clinical signs equivocal.

Orbital trauma: penetrating injury XR orbits (I) M M H M Indicated (C)

When: (1) Radio-opaque intra-ocular FB is a possibility (see A16). (2) Investigation requested by ophthalmologist. (3) Suspicion of damage to orbital walls.

Middle third facial injury XR facial bones (I) M M M M Indicated (B)

But patient cooperation essential. Advisable to delay XR in uncooperative patients. In children, XR often unhelpful.

Mandibular trauma XR Mandible (I) or orthopantomo-gram (OPG) (I)

M M M M Indicated (C) For non-traumatic TMJ problems see B11.

Cervical spine

Conscious patient with head and/or face injury only

XR C spine (I) M M M M Not indicated routinely (B)

In those who meet all of the following criteria: (1) Fully conscious (2) Not intoxicated (3) No abnormal neurological findings. (4) No neck pain or tenderness.

Unconscious head injury (see K3/4) XR C spine (I) H H H H Indicated (B)

Must be of good quality to allow accurate evaluation. But radiography may be very difficult in severely traumatised patient and must avoid manipulation (see K11 also K12).

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Neck injury: with pain XR C spine (I) H H H H Indicated (B)

Cervical spine XRs can be very difficult to evaluate. Radiography also difficult 1. Must show C7/T1. 2. Should show odontoid peg (not always possible at time of initial study) 3. May need special views, CT or MRI especially when XR equivocal or complex lesions.

Neck injury: with neurological deficit XR (I) H H H H Indicated (B) For orthopaedic assessment.

Neck injury: with pain but XR initially normal; suspected ligamentous injury

XR C spine; flexion and extension (I)

M M M M Specialised investigation (B)

Views taken in flexion and extension (consider fluoroscopy) as achieved by the patient with no assistance and under medical supervision. MRI may be helpful here.

Thoracic and lumbar spine

Trauma: no pain, no neurological deficit XR (II) M M M M Not indicated

routinely (B)

Physical examination is reliable in this region. If the patient is awake, alert and asymptomatic, the probability of injury is low.

Trauma: with pain, no neurological deficit or patient not able to be evaluated

XR painful area (II) M M M M Indicated (B)

A low threshold to XR when there is pain/tenderness, after a significant fall, if a high impact RTA or other spinal fracture present or it is not possible to clinically evaluate the patient. Increasing use of CT and MRI here.

Trauma: with neurological deficit - pain XR (II) M M M-H M Indicated (B)

Pelvis and sacrum

Fall with inability to bear weight

XR pelvis (I) plus lateral XR hip (I) M M M M Indicated (C)

Physical examination may be unreliable. Check for femoral neck fractures, which may not show on initial XR, even with good lateral views. In selected cases NM or MRI or CT can be useful when XR normal or equivocal.

Urethral bleeding and pelvic injury

Retrograde urethrogram (II) M M M M Indicated (C)

To show urethral integrity, leak, rupture. Consider cystogram if urethra normal and suspicion of bladder leak.

Trauma to coccyx or coccydynia XR coccyx (I) M M M M Not indicated

routinely (C) Normal appearances often misleading and findings do not alter management.

Upper limb

Shoulder injury XR shoulder (I) M M M M Indicated (B)

Some dislocations present subtle findings. As a minimum, orthogonal views are required. US, MRI and CT arthrography all have a role in soft tissue injury.

Elbow injury XR elbow (I) M M M M Indicated (B) Indicated in cases of effusion with no obvious fracture’ (see also Section M). Increasing use of CT and MRI here.

Wrist injury XR wrist (I) NM (II) or MRI (0) M M M M

Indicated (B) Specialised investigation (B)

Scaphoid fractures can be invisible at presentation. Most centres repeat XR at 10–14 days if there are strong clinical signs and initial XR negative. Some departments use CT, NM or MRI to exclude fracture earlier than this. Increasing use of MRI as the only examination.

Lower limb

Knee injury (fall/blunt trauma) XR knee (I) M M M M Not indicated

routinely (B)

Especially where physical signs of injury are minimal. Inability to bear weight or pronounced bony tenderness, particularly at patella and head of fibula, merit radiography. CT/MRI may be needed where further information is required (see D23).

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Ankle injury XR ankle (I) M M M M Not indicated routinely (B)

Features which justify XR include age ( elderly patients), malleolar tenderness, marked soft tissue swelling and inability to bear weight.

Foot injury XR foot (I) M M M M Not indicated routinely (B)

Not indicated unless there is true bony tenderness. Even then the demonstration of a fracture rarely influences management. Only rarely are XRs of foot and ankle indicated together; both will not be done togetherwithout good reason. Clinical abnormalities are usually confined to either foot or ankle.

Stress fracture XR (I) M M M M Indicated (B) Although often unrewarding.

NM (II) or MRI (0) M M M M Indicated (B) Provides a means of early detection as well as visual account of the biomechanical properties of the bone. Some centres use US here.

Foreign Body (FB)

Soft tissue injury: FB (metal, glass, painted wood)

XR (I) H H H H Indicated (B)

All glass is radio-opaque; some paint is radio-opaque. Radiography and interpretation may be difficult; remove blood-stained dressings first. Consider US, especially in areas where radiography difficult.

Soft tissue injury: FB (plastic, wood) XR (I) M M M-H M Not indicated

routinely (B) Plastic is not radio-opaque, wood is rarely radio-opaque.

Swallowed FB suspected in pharyngeal or upper oesophageal region

XR soft tissues of neck (I) M M M M Indicated (C)

After direct examination of oropharynx (where most FBs lodge), and if FB likely to be opaque. Differentiation from calcified cartilage can be difficult. Most fish bones invisible on XR. Maintain a low threshold for laryngoscopy or endoscopy, especially if pain persists after 24 hours (see K33). NB: for possible inhaled FB in children see Section M (M23).

Swallowed FB: smooth and small (e.g. coin) CXR (I) M M M M Indicated (B)

The minority of swallowed FBs will be radio-opaque. In children a single, slightly over-exposed, frontal CXR including neck should suffice. In adults, a lateral CXR may be needed in addition if frontal CXR negative. Majority of FBs that impact, do so at crico pharyngeus. If the FB has not passed (say within 6 days), AXR may be useful for localisation.

Sharp or potentially poisonous swallowed FB: (e.g. battery)

AXR (II) M M M M Indicated (B)

Most swallowed foreign bodies that pass the oesophagus eventually pass through the remainder of the gastrointestinal tract without complication. But location of batteries is important as leakage can be dangerous.

Swallowed FB: large object (e.g. dentures) CXR (I) M M M M Indicated (B)

Dentures vary in radio-opacity; most plastic dentures are radiolucent. AXR may be needed if CXR negative, as may barium swallow or endoscopy. Lat CXR may be helpful.

Chest

Chest trauma: minor CXR (I) M M M M Not indicated routinely (B)

The demonstration of a rib fracture does not alter management.

Chest trauma: moderate CXR (I) M M M M Indicated (B)

Frontal CXR for pneumothorax, fluid or lung contusion. A normal CXR does not exclude aortic injury and arteriography/CT/MRI should be considered.

Stab injury CXR (I) M M M M Indicated (C) PA and/or other views to show pneumothorax, lung damage or fluid. US useful for pleural and pericardial fluid.

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Sternal fracture XR lateral M M M M Indicated (C) Indicated (C) In addition to CXR. Think of thoracic spinal and sternum (I) aortic injuries too.

Abdomen (including Supine kidney). Blunt or stab injury

AXR (II) + erect CXR (I) M M M M Indicated (B)

US valuable for detecting haematoma and possible injury to some organs, e.g. spleen, liver. CT may be needed (see K40–K42).

Major trauma

Major trauma — general screen on unconscious or confused patient

C-spine XR (I), CXR (I), pelvis XR (I),


Stabilise patient’s condition as a priority. Perform only the minimum XRs necessary at initial assessment. C-spine XR can wait as long as spine and cord suitably protected, but CT C-spine may be combined with CT head. Pelvic fractures often associated with major blood loss. See Head Injury K1–K4.

Major trauma — abdomen/pelvis

CXR (I), Pelvis XR (I) M M M M Indicated (B)

Pneumothorax must be excluded. Pelvic fractures which increase pelvic volume often associated with major blood loss.

Major trauma – chest CXR (I) M M M M Indicated (B) Allows immediate management (e.g. pneumothorax).

CT Chest (III) M M M M Indicated (B) Especially useful to exclude mediastinal haemorrhage. Low threshold for proceeding to arteriography.

L. Cancer

Lung Diagnosis CXR PA and Lat

(I) M M M M Indicated (B) But can be normal, particularly with central tumours.

Bladder Staging IVU (II) M M M M Indicated (B) To assess kidneys and ureters for further

urothelial tumours.

Musculoskeletal tumours Diagnosis XR (I) + M M M M Indicated (B)

Imaging and histology complementary. Best before biopsy: See Musculoskeletal Section D. NM needed to ensure that lesion is solitary.

M. Paediatrics Minimise x-irradiation in children, especially those with long term problems (for head injury in children see Trauma Section K)

CNS Abnormal head appearance — hydrocephalus — odd sutures

SXR (I) M M M M Specialised investigation (C)

US indicated where anterior fontanelle is open. Where sutures are closed/closing. MRI indicated for older children. (CT may be appropriate if MRI not available).

Epilepsy SXR (I) M M M M Not indicated routinely (B) Poor yield.

Hydrocephalus —shunt malfunction (see A10) XR (I) M M M M Indicated (B) XR should include whole valve system.

Headaches SXR (I) M M M M Not indicated routinely (B)

If persistent or associated with clinical signs refer for specialised investigations.

Sinusitis see also A13 Sinus XR (I) M M M M Not indicated

routinely (B)

Not indicated before 5 years as the sinuses are poorly developed; mucosal thickening can be a normal finding in children. A single under-tilted OM view may be more appropriate than the standard OM view depending on the child’s age.

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Neck and spine — For trauma see Section K

Torticollis without trauma XR (I) L L L L Not indicated

Deformity is usually due to spasm with no significant bone changes. If persistent, further imaging (e.g. CT) may be indicated following consultation.

Back or neck pain XR (I) L L L L Indicated (B) Back pain is uncommon in children without an apparent cause. Follow-up is needed if infection is suspected.

Spina bifida occulta XR (I) L L L L Not indicated routinely (B)

A common variation and not in itself significant (even in enuresis). However, neurological signs would require investigation.

Hairy patch, sacral dimple XR (I) L L L L Not indicated routinely (B) May be helpful in older children.

Musculoskeletal

Non accidental injury — child abuse (for head injury see Section K)

XR (I) of affected parts M M M M Indicated (B)

Local policies will apply; close clinical/radiological liaison essential. Skeletal survey for those under two injury see Section K) years after clinical consultation. May occasionally be required in the older child. CT/MRI of brain may be needed, even in the absence of cranial apparent injury.

Limb injury: opposite side for comparison XR (I) M M L-M M Not indicated

routinely (B) Seek radiological advice.

Short stature, growth failure

XR (I) for bone age M M M M

Indicated at appropriate intervals (B)

2–18 yrs: left (or non-dominant) hand/wrist only. Premature infants and neonates: knee (specialised investigation). May need to be supplemented with a skeletal survey and MRI for hypothalamus and pituitary fossa (specialised investigations).

Limp XR pelvis (I) M M M M Indicated (C)

Gonad protection is used routinely unless shields will obscure area of clinical suspicion. If slipped epiphyses is likely, lateral XRs of both hips are needed.l

Focal bone pain XR (I) M M M M Indicated (B) XR may be normal initially. US can be helpful particularly in osteomyelitis.

Osgood–Schlatter’s disease XR knee (I) M M M M Not indicated

routinely (C)

Although bony radiological changes are visible in Osgood–Schlatter’s disease these overlap with normal appearances. Associated soft tissue swelling should be assessed clinically rather than radiographically.

Cardiothoracic

Acute chest infection CXR (I) M M M M Not indicated routinely (B)

Initial and follow-up films are indicated in the presence of persisting clinical signs or symptoms or in the severely ill child. Consider the need for CXR in fever of unknown origin. Children may have pneumonia without clinical signs.

Recurrent productive cough CXR (I) M M M M Not indicated

routinely (C)

Children with recurrent chest infection tend to have normal CXRs (apart from bronchial wall thickening). Routine follow-up CXR not indicated unless collapse present on initial CXR. Suspected cystic fibrosis requires specialist referral.

Inhaled FB (suspected) (see Section K) CXR (I) M M M M Indicated (B)

History of inhalation often not clear. Bronchoscopy is indicated, even in the presence of a normal CXR. NM/CT may be helpful to show subtle air trapping. Wide variation in local policy about expiratory films, fluoroscopy, CT and NM (ventilation scintigraphy).

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Wheeze CXR (I) M M M M Not indicated routinely (B)

Children with asthma usually have normal CXR apart from bronchial wall thickening. Sudden unexplained wheeze CXR indicated, may be due to inhaled FB (above).

Acute stridor XR neck (I) M M M M Not indicated routinely (B)

Epiglottitis is a clinical diagnosis, but consider FB (above).

Heart murmur CXR (I) M M M M Not indicated routinely (C)

Specialist referral may be needed; cardiac US often may be indicated.

Gastrointestinal — see also Section G for more general abdominal problems

Intussusception AXR (II) M M M M Indicated (C)

Local policies require close paediatric, radiological and surgical liaison. Where expertise is available, both US and contrast enema (air or barium) can confirm diagnosis and guide reduction.

Swallowed FBs (see Section K) AXR (II) M M M M Not indicated

routinely (C)

Except for sharp or potentially poisonous FBs, e.g. batteries. See Section K. If there is doubt whether the FB has passed, an AXR after 6 days may be indicated.

Minor trauma to abdomen AXR (II) M M M M Not indicated routinely (C)

US may be used as initial investigation but CT is more specific, particularly in visceral trauma. XRs may show bone injury in severe trauma. The principles for the investigation of major trauma in children similar to those in adults (see Major Trauma, K40–K42).

Constipation AXR (II) M M M M Not indicated routinely (C)

Many normal children show extensive faecal material; impossible to assess significance of radiological signs. But AXR can help specialists in refractory cases.

Uroradiology Continuous wetting IVU (II) L L L L Indicated Both examinations may be needed to evaluate

duplex system with ectopic ureter. GLOSSARY

TABLE Classification of the typical effective doses of ionising radiation from common imaging procedures

Class Typical effective Dose (mSv) Examples

0 0 US, MRI I <1 CXR, limb XR, pelvis XR

II* 1–5 IVU, lumbar spine XR, NM (e.g. skeletal scintigram), CT head & neck

III 5–10 CT chest and abdomen, NM (e.g. cardiac) IV >10 Some NM studies (e.g. PET)

* The average annual background dose in most parts of Europe falls in Band II.

Quality Dose Level L Low M Middle H high

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Chapter V

Optimisation and Quality Assurance for Digital Radiography

Diagnostic quality is determined by the justification for the examination itself (evidence based medicine), the optimal choice of imaging parameters, the quality of the imaging chain, the results being displayed optimally on monitors, and the quality of the diagnostic evaluation by experienced radiologists. Quality assurance has to guarantee a constant high quality of the overall imaging and diagnostic procedure. An important part of this procedure is the quality of the imaging equipment. There are a number of published discussions on strategies and methods for optimisation and standardization of image quality (see references). Many of these studies describe interesting results, but lack a methodical framework. The new concept can be considered in terms of four steps: 1. Optimisation (use clinical criteria) 2. Objectivation (“thumbprint” — description with phantom exposures) 3. Standardisation (defined bandwidth of image quality) 4. Quality assurance (Constancy testing) Past experience shows that optimal post-processing is not independent of the dose range. Therefore, optimisation strategies depends on the organ field, the clinical problem and the demanded image quality (dose) class. Any optimisation has to be done by clinical criteria. Several years of experience in this field has shown that optimisation by “physical test phantoms” only is not possible (although test phantom images such as CDRAD 2.0 are well suited to objectivation (“thumbprints”) and standardisation of image quality). A QA protocol has been developed for different digital detectors that uses the new potential of numerical and quantitative evaluation of image quality that digital technology provides (such as signal/noise relation). The protocol is based on the German standards for constancy testing, DIN 6868-58 and DIN 6868-13, but also includes digital evaluation of additional parameters.

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Optimisation Strategies

Any optimisation strategy should be designed with consideration to the diagnostic requirements of a given clinical situation. The referral guidelines mentioned in chapter IV are an excellent starting point for developing such optimisation strategies. The ideal clinical practice strategy should, in the first instance, lead to a reduction in the number of patients referred for investigation and, therefore, to a reduction in radiation exposure to patients. Additionally, the choice of imaging method must be made on the basis of evidence-based medicine. When developing clinical pathways for digital projection radiography as a diagnostic tool, the goal is to meet the requirements of the referring physician – which means choosing an imaging method and adjusting technique parameters to fit the given clinical task with the lowest risk to both patient and staff. After deciding which imaging method to use, the next issue is deciding the correct image quality. This, again, depends simply on the clinical application; on the “question” that has to be answered. Evaluating a fracture without dislocation, for example, requires high image quality, establishing the position of a fracture requires medium image quality, and locating a metal object requires a low image quality. Depending on the imaging method, three dose levels (or speed classes, if referring to conventional films/screens) can be assigned (e.g. speed class 400, 800, 1600). This represents the amendment of conventional radiography referral guidelines for use in digital radiography by adding an additional parameter: the image quality class (low, medium or high) when using digital radiography. According to this definition, imaging parameters, including post-processing, have to be optimised to reach the necessary quality with lowest dose. This can be achieved only by clinical studies, not test phantom exposures. In this sense, new optimisation strategies have to be defined for digital radiography. It is important that optimisation includes post-processing, the results of which depends on the different detectors in use and their exposure/dose parameters. One example of an optimising strategy is shown in fig. 1.

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Selection of the Organprogram (e.g. Spine lat)

Selection of the Exposure parameters

Film/Screen exposures of20 Patients (Reference point)

Digital Exposures of 20 patientswithout technical problems

Image quality okfor at least 16 Patients?

Documentation

End

Discussion of theParameter setting

yes no

Optimisation

Phantom exposuresFilm/Screen +digital

Image Quality ok?no

Exposures of 3 patients(small, normal, thick)

Image Quality ok?no

yes

Optimisation

yes

Fig 1: Optimisation of image quality (post-processing default values) Imaging chains that include post-processing and documentation require a tool to both describe and then standardise the chain. The post-processing methods used depend on the manufacturer of the equipment. User-defined default post-processing and individual post-processing are only partly known. Consequently, we have to handle the issue of post-processing using the “black box” model.

Imagepost-processing

““Black box”Black box”Input Output

Test image(CDRAD)

Monitor

Characterisation of the imaging procedure

Fig.2: The “Black box” model

This "black box” can be described in terms of the relation between an input function and an output function. A useful input function would be a digital test

68

pattern, placed like a trojan horse within a digital image. The output function can then be analysed in a numerical way. A more practical approach would be to perform an exposure of a test phantom with typical organ parameters in order to study the image quality on dedicated display monitors or on laser films via a viewing box. A good example of this phantom is the CRRAD 2.0 phantom (Artinis Medical Systems B.V.). Several of the squares (see below) contain a number of cylindrical objects each, each of different diameters and depths. These have to be detected by human observers. Exposures with different dose values and scattering material can indicate that the system being used has low contrast detectability. Using this phantom enables one to study the whole imaging chain. Phantom measurements cannot optimise the imaging chain, but can assess the imaging chain for quality control, standardization and comparison purposes.

Fig. 3: The CDRAD 2.0 phantom The CDRAD Phantom is a good tool for evaluating the imaging characteristics of digital radiographic systems, including computed radiographic imaging taken using storage phosphor systems or flat detector systems. One of the principle concerns in using digital radiography is the potential reduction in detail, which can have an adverse affect on diagnosis. Resolution (bar phantom) test objects, which are used to evaluate conventional x-ray imaging systems, are generally not appropriate for evaluating digital systems. The CDRAD Phantom allows reliable evaluation of the detail information, with the main disadvantage being that evaluation is time-consuming and observer-dependant. Therefore, we developed a program that automatically evaluates detail information (see annex 2). We first checked the sensitivity (correctly detected hole patterns) of the evaluation, looked for for alterations caused by post-processing parameters and the reproducibility of the results.

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Fig. 4 shows the sensitivity (detected holes) and the standard deviation of 10 exposures in a group depending on the dose (mAs). Detected by the automatic detection program.

77kV / 6,3mAs

77kV / 28mAs

77kV / 63mAs

0

20

40

60

80

100

120

140

0 1 2 3 4

Fig. 4: Sensitivity(correct detected holes) of CDRAD images depending on the dose. Standard deviation of 10 exposures in a group.

Fig. 5 demonstrates the influence of different post-processing on the evaluation of the CDRAD images.

Multi-Frequency B alance (77kV /12,5m As)

0

10

20

30

40

50

60

70

80

90

100

A B C D E F G H

Multi-F requency B alance C urves

Sesi

tivity

I

Fig. 5: Influence of different post-processing parameters on CDRAD evaluation

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To characterise the exposure conditions and the post-processing, a “thumbprint” of the unit for a special organ program is necessary. Without automatic post-processing optimisation, different local parts of an organ exposure can be simulated by CDRAD Phantom exposures, each using different dose values (fig. 6). Fig. 7 demonstrates examples of thumbprints of different organ programs. Results from different reference centres are also useful in developing guidelines by which images and post-processing can be standardised - but this is a job for a future program.

Signal

Dose

Thumbprint of a unit Fixed mode

Without automatic optimisation by post-processing

Fig. 6: Thumbprint of a unit

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Hand ap.

0

1020

30

40

5060

70

8090

100

0 2 4 6 8 10 12 14mAs

%

Abdomen

0

10

2030

40

50

60

7080

90

100

0 5 10 15 20 25 30 35 40mAs

%

BWS ap.

0

10

2030

40

50

60

7080

90

100

0 10 20 30 40 50 60 70mAs

%

BWS lat.

0

10

2030

40

50

60

7080

90

100

0 10 20 30 40 50 60 7mAs

%

0

Image quality thumbprint

Dose value

Sensitivity

Fig. 7: Image quality thumbprint of different organ programs (hand a.p., abdomen,

spine a.p., spine lat) Individual post-processing can either increase or decrease image quality. To demonstrate the influence of post-processing on individual images, it is helpful to integrate a fixed digital test pattern, a form of trojan horse, into the raw image. This digital test object could, for example, simulate a lead bar pattern and contrast detail phantom and have similar post-processing applied to this pattern and the whole image. Evaluation of this pattern on image display monitors or hard copy films will give in impression of the influence of post-processing on image quality. Quality control

Quality control can be performed by phantom exposures that assess the whole imaging chain. Qualitative evaluation can be obtained at the level of digital stored images, monitors or film documentation. This can be achieved by subjective assessment of image quality displayed on dedicated monitors or films (for example, spatial resolution or contrast detectability) or by direct evaluation of the digital images using computer QA programs (for example, signal/noise).

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Quality AssuranceConstancy testing

SMPTETestpattern

Flat detector

CR CR CR CR

Laserimager

Test images

Fig. 8: Central system for quality assurance and constancy testing Digital radiography imaging chains can be divided into two parts: imaging acquisition and documentation on monitors and laser films. The image quality of test phantom exposures(DIN 6868-58) can be evaluated by digital parameters such as signal/noise ratio, dynamic range or homogeneity. These parameters can be assessed by directly analysing the digital image. Image documentation testing can be performed through the use of digital test patterns, such as the SMPTE test. These can be evaluated either on a monitor or on laser film. The data should be stored and displayed as curves to demonstrate the results over a given period of time. Fig. 9: Test phantom DIN 6868-58 SMPTE test In conclusion, digital projection radiography does offer new possibilities for dose and quality management and quality control. The goal is optimal adaptation of image quality to the diagnostic task, with a reduction of risk to

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patients and staff through lowered dose levels. Constancy testing should keep the image quality constantly high by giving relative measurement values with reference to the acceptance test at the beginning. Follow ups and trends, for example, are of great interest to constancy testing. QA measurements: Phantom: Test phantom DIN 6868-58 Exposure parameters: 70 kV, small focus, with grid, focus detector distance 100 cm Field size equal to phantom size Filtration: 25 mm Al With automatic exposure control/ Without automatic exposure control (fixed mode) Evaluation: Parameters: homogeneity signal/noise high contrast (lead bar pattern) low contrast dynamic range The exposures has been evaluated by an automatic program (see annex 3). An example of the results is shown in fig. 9. The quality of monitor and laser film images has been described by the SMPTE phantom images.

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Automaticevaluation of test images

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Chapter VI

Image Quality and Dose for Digital Projection Radiography

S. Busch, Chr. Decker, C. Schilz, H.P. Busch Abstract : Purpose: Comparison of the imaging capabilities of storage phosphor (computed) radiography and flat detector systems with conventional film/screen radiography to find new strategies for image quality and dose management, i.e. optimising image quality and dose depending on the imaging method and clinical situation. Material and methods: Images of a CDRAD-phantom, hand-phantom, abdomen-phantom and lung-phantom were processed using different digital systems (Flat detector: DigitalDiagnost (Philips); Storage phosphor: ADC-70 (Agfa), ADC-Solo (Agfa), FCRXG1 (Fuji)) and a conventional film/screen system (Ortho Regular/HT1000G (Agfa)) with different exposure voltages (50kV, 73 kV, 109 kV) and different speed classes (200, 400, 800, 1600). The processed images where then evaluated. Results: The evaluation of CDRAD images demonstrated that the flat detector system delivered the highest contrast detectability, followed by the FCRXG1, the ADC-Solo, and the ADC70 systems. Comparison of organ-phantom images showed that the flat detector system in particular demonstrated excellent image quality at low speed classes in comparison to film/screen and storage phosphor systems. Conclusions: Flat detector systems demonstrated the highest potential to produce high image quality with low dose. Storage phosphor systems showed an increase of image quality depending on the system generation, but limited possibilities to lower dose significantly.

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Introduction

In recent years, the range of digital image information available to radiologists has been growing rapidly. This has been fuelled to a large extent by the improvements to workflow brought by fast image transfer, safe storage and images being much more easily accessible in digital form. Despite the dramatic progress in the fields of CT and MRI, projection radiography of the lung, skeletal and gastrointestinal tracts still form the largest areas of routine clinical radiology use. The development of storage phosphor plates and introduction of flat detectors has, however, significantly enlarged and improved the spectrum of digital methods for projection radiography (1). The milestones of reached by these new imaging methods include the significant increase of image quality and the new potential for dose reduction (2, 3, 4). Over a several years, there have been a number of national and international efforts to increase the diagnostic value and to minimise side effects of imaging with x-rays (Council directive 97/45 Euratom). The ALARA principle (dose As Low As Resonably Achievable) means that imaging has to be done with sufficient image quality, yet a low-as-possible dose value. This prerequires optimised technical equipment and sufficient knowledge of its imaging capabilities for certain dose values. This publication evaluates the relation between image quality and dose for different generations of storage phosphor and flat detector units in comparison to film/screen units. The results can serve as a basis on which to develop new strategies for optimal use of these methods (5).

Material and method:

Image quality was evaluated by images from four digital projection radiography units and one film/screen unit. Film/screen: Ortho Regular/HT1000G (AGFA) (speed class 400) Storage phosphor: ADC-70 (Agfa) ADC-Solo (Agfa) FCRXG1 (Fuji) Fat detector: DigitalDiagnost(Philips)

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Images of 4 phantoms were evaluated: 1. CDRAD 2.0 phantom 2. Hand phantom 3. Abdomen phantom 4. Thorax phantom Imaging capabilities can be demonstrated by a CDRAD 2.0 phantom. The phantom consists of a 1cm perspex plate, which is divided into 225 squares with cylindrical holes. The diameter decreases in the direction of the vertical axis logarithmically from 0.3 - 8.0 mm. The columns represent the depth in a logarithmic row from 0.3 - 8.0 mm. Each square has a specific drill pattern.

Fig. 1: CDRAD 2.0 phantom The hand, abdomen and thorax phantoms consist of organ parts embedded in perspex.

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Exposure conditions

Storage phosphor plates and film/screens were exposed at a Bucky table (Philips: Bucky Diagnost), flat detector images at a dedicated unit (Philips: DigitalDiagnost). The process started with a film/screen image at speed class 400. Orientated to this fixed mAs value for the speed class 400 of film/screen, exposures of the other phantoms were taken for speed classes 200, 400, 800, 1600. For thorax exposures, the dose values were limited to speed 200, 400 and 800 because of the limitation of switch time of the generator. Sequences of exposures had been taken with the described phantoms for 50 kV, 73 kV and 109 kV. Standard post-processing was run for 50 kV using the parameters of the hand program, for 73 kV using the organ program “abdomen”, and for 109 kV with the organ program “thorax”. Exposures of the CDRAD phantom with 50 kV (hand parameters) had 3 cm of perspex as additional scatter material; exposures with 73 kV (abdomen parameters) had 14 cm perspex, and exposures with 109 kV (thorax parameters) had 10 cm perspex. Holes of small diameter should be imaged in a direction nearly parallel to the central beam by asymmetric (decentralised) positioning (19). The grey values of the documentation on laser image films were normalised to a reference density of 1.2 +/- 0.2.

Evaluation of CDRAD exposures

Four observers evaluated the CDRAD images without knowledge of the exposure parameters and the exposure method. After the results were input into a computer, a processing program tested the surrounding squares and graded a square as correctly detected if the correct drill pattern was found and the correct pattern was identified in at least two of any four squares immediately surrounding that square. A mean value of these results was then taken. It was demonstrated in diagrams for each phantom and exposure sequence (50 kV, 73 kV, 109 kV). A standardisation of their individual evaluation of a common film/screen exposure (speed 400) was then performed, before the mean value was calculated. For the calculation of the relative detectability, the number of correctly detected squares was evaluated in relation to the absolute number of squares. Contrast detectability was evaluated by looking at the drill depth up to which a pattern with constant diameter was found correctly. The shape of the diagrams were difficult to compare. Therefore, the areas under the curves (sum of drill depths) were evaluated. To take in account the different parts of the curve, the results were shown for two ranges of diameters (diameter 0.5 – 2.0 and diameter 2.5 – 8 mm). The lower the sum of the drill

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depths is, the more the contrast detectability of the different imaging methods improves.

Evaluation of the hand, abdomen and thorax phantom exposures

Hand, abdomen and thorax phantom exposures were evaluated by eight radiologists. The attention of the observers was focused only on a selection of special areas by blackening out the remaining regions.

Fig. 2a: Hand phantom with Fig. 2b: Abdomen phantom with windowing for evaluation windowing for evaluation

Fig. 2c: Thorax phantom with windowing for evaluation Fig. 2: Image of the organ phantoms

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Image quality was graded into the quality classes (high, medium, low). The film/screen exposure was classified as medium quality. The exposure conditions and imaging method were unknown to the observers. Averaging had been done by classifying the image quality to the class to which it was graded most frequently.

Results:

Fig. 3 shows a boxplot diagram of the relative detectability for 50 kV with speed classes 200, 400, 800 and 1600. Lines above and below show the maximum and minimum values. The line within the box demonstrates the median and divides it into a second and third quartile. The straight line gives the value of film/screen images with speed class 400.

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Fig. 3: Boxplot diagram of relative detectability (400 speed class of film/screen (50%)) DiDi: DigitalDiagnost - Philips (flat detector) FCR XG1: FUJI (storage phosphor) Solo: AGFA (storage phosphor) ADC-70: AGFA (storage phosphor) The following figures show the mean values of the CDRAD evaluation for 50 kV (Fig. 4), 73 kV (Fig. 5) and 109 kV (Fig. 6).

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Hand, abdomen and thorax phantom exposures

The following tables show the results of the evaluation of hand, abdomen and thorax exposures (Table 1, 2, 3). Image quality Unit High Digital Diagnost 200 400 800 FCR XG1 200 400 ADC-Solo 200 Medium Digital Diagnost 1600 FCR XG1 800 1600 ADC-Solo 400 800 ADC-70 200 Film/Slide 400 Low ADC-Solo 1600 ADC-70 400 800 1600 Tab. 1: Evaluation of hand images (50 kV) depending on the speed classes 200 (6mAs) / 400 (3mAs) / 800 (1,5mAs) / 1600 (0,8mAs)

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Image quality Unit High Digital Diagnost 200 400 800 Medium Digital Diagnost 1600 FCR XG1 200 400 ADC-Solo 200 400 ADC-70 200 400 Film/Slide 400 Low FCR XG1 800 1600 ADC-Solo 800 1600 ADC-70 800 1600 Tab. 2 : Evaluation of abdomen images (73kV) dependant on the speed class 200 (25mAs) / 400 (12mAs) / 800 (6mAs) / 1600 (3mAs) Image quality Unit High Digital Diagnost 200 FCR XG1 200 Medium Digital Diagnost 400 800 FCR XG1 400 800 Film/Slide 400 Low ADC-70 200 400 800 Tab. 3: Evaluation of thorax images (109 kV) depending on the speed class 200 (1.8mAs) / 400 (0.9mAs) / 800 (0.5mAs)

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Discussion:

The goal of this study is to optimise digital imaging by assessing the imaging capabilities of different methods and systems, depending on the dose level. Therefore, a comparison between different digital systems and a film/screen system was performed. Exposures were taken using four different phantoms (CDRAD phantom, hand phantom, abdomen phantom and thorax phantom). Comparisons of the imaging capabilities of digital systems have already been conducted using CDRAD phantoms (6, 7, 8, 9). This study involved exposures being taken with the CDRAD phantom at 50 kV, 73 kV and 109 kV. CDRAD images were then evaluated by four observers. To take into account the individual detection and grading levels, the individual results were standardised in relation to the grading of a defined film/screen exposure (speed class 400). The boxplots clearly show that this standardisation leads to a clear separation of the results of the specific systems. The evaluation of relative detectability for exposures with 50 kV shows that image quality of the flat detector was graded highest by all observers. Next in line were the units FCRXG 1, ADC-Solo and ADC- 70. There was no overlap in the results of the specific systems. The relative detectability of the specific systems in relation to dose shows that flat detectors with speed class 800 demonstrate the same detectability as the storage phosphor system ADC 70 with speed class 200. This result means that, at the same image quality, the flat detector system allows a dose reduction of 75%. It should be noted, however, that the ADC-70 system is six years old and therefore no longer the latest generation of storage phosphor systems. The results of state of the art systems shows that development of technology over this period has led to a significant increase in image quality. In terms of contrast detectability of the exposure series 50 kV, the first part of the curve (diameter 0.6-2.0mm) demonstrates the superiority of the flat detector for all speed classes. The storage phosphor systems FCRXG1, ADC-Solo and ADC-70 show a lower quality. The second part of the curve (diameter 2.5 – 8.0) demonstrates the the same sort of superiority of the flat detector with the exception of the 400 speed value. For CDRAD exposures with 73kV and 109 kV, the flat detector system is at the top of the row for all speed classes, followed by the storage phosphor systems FCRXG1, ADC-Solo and ADC-70. Neitzel (6), Geijer (7) and Peer (9) used the same CDRAD phantom for their studies of imaging capabilities of different digital imaging systems. Our results prove the statements of these publications – that flat detector systems demonstrates a higher image quality in comparison to film/screen systems with a significant lower dose value. This study additionally shows that the image

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quality of storage phosphor systems is dependent on the age (generation) of the system. The ADC-70, the oldest system, had the worst results. The FCRXG1, as a representative of the new generation systems, is even equivalent to the flat detector in some cases. A comparison of flat detector system and film/screen showed that a similar quality had been reached with significantly lower dose. Anatomical phantoms (hand, abdomen, thorax) were also evaluated to give the relation to clinical image aspects. Imaging method and exposure parameters (such as dose) were not known by the observers. Only parts of the whole image were evaluated by the observers, in order for them to concentrate on the same regions. The overall result of all observers was classified into the quality classes “high”, “medium” and “low”. Exposures of the hand were taken at the voltage of 50 kV. Observers graded the total quality of flat detector images highest, followed by FCRXG1, ADC-Solo and ADC 70. DigitalDiagnost, FCRXG1 and ADC solo were graded as producing “high” image quality. DigitalDiagnost and FCRXG1 provided the highest dose reduction (up to 75%). Film/screen images were graded as “medium”. The ADC 70 needed double the dose to produce similar image quality. DigitalDiagnost and FCRXG1 required only 25% of the dose compared to film/screen. This potential for dose reduction has also been described by other authors mentioned in the references (2, 3, 4, 10, 11, 12). For exposures of the abdomen with a voltage of 73 kV the flat detector (speed class 200, 400, and 800) had been graded to the quality class “high”. Film/screen images with speed 400 were in the “medium” class. The flat detector image with speed 1600 was also graded to this class. In this case, a dose reduction of 75% was possible – without loss of quality. But in comparison to film/screen, there is storage phosphor systems at speed 200 are of no improvement. Doubling the dose also gives no additional image information. In the quality class “low”, storage phosphor images (FCRXG1, ADC-Solo, ADC-70) with speed classes 800 and 1600 were allocated. Overall, the results of the abdomen exposures demonstrated the high potential for dose reduction for the flat detector. This would also confirm what has been stated by various publications (11, 13). For the comparison of lung exposures; the DigitalDiagnost, the FCRXG1, the ADC 70 and the film/screen system were available. The results show that flat detector images were graded similar to FCRXG1 images. Imaging methods in both the quality classes “high” and “medium” had the same speed class. The ADC 70 images were graded lower in all speed classes. These advantageous imaging capabilities of digital systems for the thorax had been described already by some authors (14, 15, 16, 17, 18, 19). The results show that there is a significant gap in image quality between the flat detector system, the storage phosphor system, and the film/screen system.

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The flat detector demonstrated the highest potential for dose reduction for each of the evaluated phantom images. It was also shown that the gap in image quality between state of the art storage phosphor systems and flat detector systems has narrowed. The ADC 70, the oldest unit, produced the lowest quality. In comparison to film/screen radiography, digital systems produce high image quality with low dose values. Increased doses lead directly to significant increases in quality. Whether this is always connected to an increase of diagnostic information has to be decided for the specific case. The broad range of possible dose values gives radiologists the ability to adapt image quality and dose to the clinical situation – a strategy that has the potential to lower the radiation dose significantly.

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References: 1. Busch HP. Digitale Projektionsradiographie: Technische Grundlagen,

Abbildungseigenschaften und Anwendungsmöglichkeiten. Radiologe 1999; 39: 710-724

2. Reissberg S, Hoeschen C, Kästner A, Theus U, Fiedler R, Krause U, Döhring W. Erste klinische Erfahrung mit einem großformatigen Flächendetektorsystem bei Aufnahmen des peripheren Skelettsystems Fortschr. Röntgenstr 2001; 173: 1048-1052

3. Heyne JP, Merbold H, Sehner J, Neumann R, Adler R, Freesmeyer M, Kaiser WA. Reduktion der Strahlendosis mittels Speicherfolienradiographie am Handskelett. Fortschr. Röntgenstr 2000; 172: 386-390

4. Hamers S, Freyschmidt J, Neitzel U. Digital Radiography with a large-scale electronic flat-panel detector vs. screen-film radiography: observer preference in clinical skeletal diagnostics. Eur Radiol 2001; 11: 1753-1759

5. Busch HP, Bosmans H, Faulkner K, Peer R, Vano E, Busch S. Dose management with new digital imaging technique. European Radiology 2002; B-0561/Scientific paper

6. Neitzel U, Böhm A, Maack I. Comparison of low- contrast detail detectability with five different conventional and digital radiographic imaging systems. SPIE Medical Imaging 2000; 3981: 31

7. Geijer H, Beckman KW, Andersson T, Persliden J. Image quality vs. radiation dose for a flat- panel amorphous silicon detector: a phantom study. Eur Radiol 2001; 11: 1704-1709

8. Harrell G, Chotas MS, Carl E, Ravin MD. Digital Chest Radiography with a Solid-state Flat-Panel X-ray Detector: Contrast –Detail Evaluation with Processed Images Printed on Film Hard Copy. Radiology 2001; 218: 679-682

9. Peer S, Neitzel U, Giacomuzzi S M, Peer R, Gassner E, Steingruber I, Jaschke W. Comparison of low- contrast detail perception on storage phosphor radiographs and digital flat- panel detector images. IEEE 2001; 20-3: 239-242

10. Ludwig K, Lenzen H, Kamm KF, Link M, Diederich S, Wormanns D, Heindel W. Performance of a flat-panel detector in detecting artificial bone lesions: Comparison with conventional screen-film and storage- phosphor radiography. Radiology 2002; 222:453-459

11. Okamura T, Tanaka S, Koyama K, Norihumi N, Daikokuya H, Matsuoka T, Kishimoto K, Hatagawa M, Kudoh H, Yamada R. Clinical evaluation of digital radiography based on an large-area cesium iodide-amorphous silicon flat- panel detector compared with screen-film radiography for skeletal system and abdomen. Eur Radiol 2002; 12: 1741-1747

12. Strotzer M, Völk M, Wild T, Landenberg P, Feuerbach S. Simulated bone erosions in a hand phantom: detection with conventional screen- film technology vs. caesium iodide- amorphous silicon flat- panel detector Radiology 2000; 215: 512-515

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13. Persliden J, Beckman KW, Geijer H, Andersson T. Dose-image optimisation in digital radiography with a direct digital detector: an example applied to pelvic examinations. Eur Radiol 2002; 12: 1584-1588

14. Floyd CE, Warp RJ, Dobbins JT, Chotas HG, Baydush AH, Vargas-Voracek R, Ravin CE. Imaging characteristics of an amorphous silicon flat- panel detector for digital chest radiography. Radiology 2001; 218: 683-688

15. Hennigs S P, Garmer M, Jaeger HJ, Classen R, Jacobs A, Gissler HM, Christmann A, Mathias K. Digital chest radiography with a large-area flat panel silicon X-ray detector: clinical comparison with conventional radiography. Eur Radiol 2001; 11: 1688-1696

16. Kim TS, Im JG, Lee HJ, Lee YJ, Kim SH, Kim S. Detection of Pulmonary Edema in Pigs: storage Phosphor versus Amorphous Selenium-based Flat –Panel-Detector Radiography. Radiology 2002; 223: 695-701

17. Schaefer-Prokop C, Eisenhuber E, Fuchsjäger M, Puig S, Prokop M. Aktuelle Entwicklung auf dem Gebiet der digitalen ThoraxradiographieRadiologe 2001; 41:230-239

18. Aufrichtig R. Comparison of low contrast detectability between a digital amorphous silicon and a screen-film based imaging system for thoracic radiography. Medical Physics 1999; 26-7: 1349-1358

19. Hermann KA, Bonel H, Stäbler A, Kulinna C, Glaser C, Holzknecht N, Geiger B, Schätzel M, Reiser MF. Chest imaging with flat-panel detector at low and standard doses: comparison with storage phosphor technology in normal patients. Eur. Radiol 2002; 12: 385-390

This article was translated from a publication in German language: S. Busch, Chr. Decker,C. Schilz, H.P. Busch: Bildqualität und Dosis in der Digitalen Projektionsradiographie. Fortschr.Röntgenstr. 175, 32 – 37

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Chapter VII

Digital Radiography – Quality Criteria References

1999 Busch, H.P., Lehmann, K.J., Freund, M.C., Georgi (1991), “Digitale Projektionsradiographie” (Digital Projection Radiography), Röntgenpraxis 44: 329-335 Busch, H.P., Lehmann, K.J., Freund, M.C., Georgi, M. (1992), “Digitale Projektionsradiographie: Klinische Anwendungsmöglichkeiten” (Digital Projection Radiography: Clinical application), Röntgenpraxis 45: 35-43 Lehmann, K.J., Busch, H.P., Georgi, M. (1992), “Digitale Bildverstärker Radiographie – welche Aufnahmedosis für welche Fragestellung (Digital Image Intensifier Radiography – What dose for what diagnostic question?)”, Akt Radiol 2: 11-15 Neitzel, U. (1993), “Selenium: a new image detector for digital chest radiography”, Medica Mundi 38: 89-93 Vuysteke, P., Schoeters, E. (1994), “Multiscale image contrast amplification (MUSICA)”, SPIE 2167: 551-560 Lee, D.L., Cheung, L.K., Jeromin, L.S. (1995), “A new digital detector for projection radiography”, SPIE 2432: 237-249 “Leitlinien der Bundesärztekammer zur Qualitätssicherung in der Röntgendiagnostik”, (1995), Deutsche Ärzteblatt 92, 49: 1691-1703 Lee, D.L., Cheung, L.K., Jeromin, L.S., Palecki, E. (1996), “Imaging performance of a direct digital radiographic detector using selenium and a thin film transistor array”, In: Lemke HU (ed), “Computer assisted Radiology”, Elesevier: 41-46 Schaefer-Prokop, C.M., Prokop, M. (1996), “Digitale Radiographie des Thorax – der Selendetektor im Vergleich zu anderen Abbildungssystemen”, Kontraste: 14-22

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Busch, H.P., Hoffmann, H.G., Kruppert, H., Mörsdorf, M. (1997), “Digitale BV-Radiography – Eine Methode hat sich durchgesetzt” (Digital II-Radiography – A method has prevailed),.Electromedica 65: 62-64 Busch, H.P. (1997), “Digital radiography for clinical application”, Eur Radiol 7 (Suppl 3): 66-72 Prokop, M., Schaefer-Prokop, C.M. (1997), “Digital image processing”, Eur Radiol 7 (Suppl 3): 73-82 Shaber, G.S., Maidment, A.D.A., Bell, J., Jeromin, L.S., Lee, D.L., Powell, G.F. (1997), “Full field digital projection radiography system: Principles and image evaluation”, In: Lemke HU (ed), “Computer assisted radiology and surgery”, Elsevier: 1-7 Tapiovaara, M.J., “Efficiency of low-contrast detail detectability in fluoroscopic imaging”, MEDICAL PHYSICS (1997) 24, 5, 655-64 Yaffe, M.J., Rowlands, J.A., “X-ray detectors for digital radiography”, PHYSICS IN MEDICINE AND BIOLOGY (1997) 42, 1, 1-39 Bruijns, T.J.C., Alving, P.L., Bury, R., Cowen, A.R., Jung, N., Luijendijk, H.A., Meulenbrugge, H.J., Stouten, H.J. (1998), “Technical and clinical results of an experimental Flat Dynamic (digital) X-ray image Detector (FDXD) system with real-time corrections”, SPIE 3336: 33-44 Busch, H.P., Jaschke, W., “Adaptation of the Quality Criteria Concept to digital radiography”, Rad. Prot Dosimetry, 80 (1998) 1-3, 61-63 Chaussat C., Chabbal, J., Ducourant, T., Spinnler, V., Vieux, G., Neyret, R., “New CsI / a-Si x17 X-ray flat panel detector provides superior detectivity and immediate direct digital output for General Radiography systems”, SPIE Medical Imaging (1998) 3336 Hamers, S., Freyschmidt, J. (1998), “Digital radiography with an electronic flat-panel detector: First clinical experience in skeletal diagnostics”, Medica Mundi 42,3: 2-6 Kamm, K.F. (1998), “Grundlagen der Röntgenabbildung” (Principles of x-ray imaging), In: Ewen E (Hrsg), “Moderne Bildgebung”, Georg Thieme: 45-60 Neitzel, U. (1998), “Grundlagen der digitalen Bildgebung (Principles of x-ray imaging)”, In Ewen, K. (Hrsg), “Moderne Bildgebung”, Georg Thieme: 71-76 Neitzel, U. (1998), “Systeme für die digitale Bildgebung (Systems for digital imaging)”, In: Ewen K (Hrsg), “Moderne Bildgebung”, Georg Thieme: 127-135

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Strotzer, M., Gmeinwieser, J., Völk, M., Fründ, R., Seitz, J.; Manke, C., Albrich, H., Feuerbach, S., “Clinical application of a flat-panel X-ray detector based on amorphous silicon technology: image quality and potential for radiation dose reduction in skeletal radiography”, AJR. AMERICAN JOURNAL OF ROENTGENOLOGY (1998), 171; 23-27 Vetter, S., Heckmann, H., Strecker, E.P., Busch, H.P., Kamm, K.F., Allmendinger, H. (1998), “Klinische Aspekte zu Bildqualität und Dosis bei gittergesteuerter gepulster Durchleuchtung”, Akt.Radiol. 8: 191-195 Vetter, S., Faulkner, K., Strecker, E.P., Busch, H.P. (1998), “Dose reduction and image quality in pulsed fluoroscopy”, Radiation Protection Dosimetry, 80: 299-301 Aufrichtig, R., “Comparison of low contrast detectability between a digital amorphous silicon and a screen-film based imaging system for thoracic radiography”, MEDICAL PHYSICS (1999), 26, 7, 1349-58 Busch, H.P., Klose, K.J., Braunschweig, R., Neugebauer, E. (1999), “Digitale Radiographie – Ergebnisse einer Anwendungsumfrage und einer Konsensuskonferenz” (Digital radiography – results of a user survey and a consensus conference), Akt.Radiol. 7: 56-63 Busch, H.P., “Digitale Projektionsradiographie: Technische Grundlagen, Abbildungseigenschaften und Anwendungsmöglichkeiten” (Digital Radiography: Basics, imaging and application), Radiologe (1999), 39: 710-724 Chotas, H.G., Dobbins, J.T., Ravin, C.E. (1999), “Principles of digital radiography with large-area, electronically readout detectors: A review of the basics”, Radiology 210: 595-599 Frija, G. (1999), “Flat Panel Sensors: Questions and Answers”, Medical Imaging Technology, Vol 17, 2: 99-104 Neitzel, U. (1999), “Integrated digital radiography with a flat-panel sensor”, Medical Imaging Technology, 17, 2: 123-129 Strotzer, M., Gmeinwieser, J., Völk, M., Fründ, R., Feuerbach, S. “Digitale Flachbilddetektortechnik basierend auf Cäsiumjodid und amorphem Silizium: Experimentelle Untersuchungen und erste klinische Ergebnisse”, Fortschr Röntgenstr 170 (1999): 66-72

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Reiff, K.J. “Flat panel detectors – closing the (digital) gap in chest and skeletal radiology”, European Journal of Radiology (1999) Vano, E., Fernandez, J.M., Gracia, A., Guibelalde, E., Gonzalez, L., “Routine quality control in digital versus analog radiography”, Physica Medica Vol XV (1999), 319-321

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2000 Aufrichtig, R., Xue, P., “Dose efficiency and low-contrast detectability of an amorphous silicon x-ray detector for digital radiography”, Physics in Medicine and Biology; 45 (2000) 9, 2653-69 Heyne, J.P., H. Merbold, J. Sehner, R. Neumann, R. Adler, M. Freesmeyer, W. A. Kaiser: “Reduktion der Strahlendosis mittels Speicherfolienradiographie am Handphantom/ Reduction of radiation dosage by using digital luminescence radiography on a hand phantom”, Fortschr Röntgenstr (2000) 172, 4, 386-90 Ludwig, K., Link, T. M., Fiebich, M., Renger, B., Diederich, S., Oelerich, M., Lenzen, H., Heindel, W., “Selenium-based digital radiography in the detection of bone lesions: preliminary experience with experimentally created defects”, RADIOLOGY (2000) 216, 1, 220-224 Neitzel, U., Böhm, A., Maack, I., “Comparison of low-contrast detail detectability with five different conventional and digital radiographic imaging systems”, SPIE Medical Imaging (2000) 3981-31 Strotzer, M., Völk, M., Wild, T., Landenberg, P., Feuerbach, S., “Simulated bone erosions in a hand phantom: detection with conventional screen-film technology versus cesium iodide-amorphous silicon flat-panel detector”, RADIOLOGY (2000) 215, 2, 512-515 Vlk, M., Strotzer, M., Holzknecht, N., Manke, C., Lenhart, M., Gmeinwieser, J., Link, J., Reiser, M., Feuerbach, S., “Digital radiography of the skeleton using a large-area detector based on amorphous silicon technology: image quality and potential for dose reduction in comparison with screen-film radiography”, Clinical radiology, 55 (2000) 8, 615-21

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2001 Nuclear Associates Diagnostic Radiology and Radiation Therapy Catalog, “CDRAD contrast detail digital/conventional radiography phantom”, Scientific program RSNA 2001 Chotas, H.G., Ravin, C.E., “Digital Chest Radiography with a Solid-state Flat-Panel X-ray Detector : Contrast-Detail Evaluation with Processed Images Printed on Film Hard Copy”, Radiology 201; 218: 679-682 Floyd, C.E., Warp, R.J., Dobbins, J. T. Dobbins, H. G. Chotas, A. H. Baydush, R. Vargas-Voracek, C. E. Ravin: “Imaging characteristics of an amorphous silicon flat-panel detector for digital chest radiography”, RADIOLOGY (2001) 218, 3, 683-688 Geijer, H., Beckman, K.-W., Andersson, T., Persliden, J., “Image quality vs. radiation dose for a flat-panel amorphous silicon detector: a phantom study”, Eur. Radiol. (2001) 11, 1704-1709 Hammers, S., Freyschmidt, J., Neizel, U., “Digital radiography with a large-scale electronic flat-panel detector vs. screen-film radiography: observer preference in clinical skeletal diagnostics”, Eur. Radiol. (2001) 11, 1753-1759 Harrell, G., Chotas, M.S., Carl, E., Ravin, M.D, “Digital Chest Radiography with a Solid-state Flat-Panel X-ray Detector: Contrast-Detail Evaluation with Processed Images Printed on Film Hard Copy”, Radiology 2001; 218: 679-682 Hennis, S.P., Garmer, M., Jaeger, H.J., Classen, R., Jacobs, A., Gissler, H.M., Christmann, A., Mathias, K., “Digital chest radiography with a large-area flat panel silicon X-ray detector: clinical comparison with conventional radiography”, Eur. Radiol. (2001) 11: 1688-1696 Jessen, K.A., “The quality criteria concept: an introduction and overview”. Radiat Prot Dosimetry, 94 (201) 1-2, 29-32 Marshall, N.W., “Optimisation of dose per image in digital imaging.” Radiat Prot Dosimetry, 94 (201) 1-2, 83-7 Peer, S., Neitzel, U., Giacomuzzi, S.M., Peer, R., Gassner, E., Steingruber, I., Jaschke, W. “Comparison of low-contrast detail perception on storage phosphor radiographs and digital flat panel detector images”, IEEE TRANSACTIONS ON MEDICAL IMAGING (2001) 20; 3; 239-42 Peer. S., Peer, R., Giacomuzzi, S.M., Jaschke, W., “Comparative reject analysis in conventional film-screen and digital storage phosphor radiography”. Radiat Prot Dosimetry, 94 (201) 1-2, 69-71

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Reissberg, S., Hoschen, C., Kästner, A., Theus, U., Fiedler, R., Krause, U., Dühring, W., “Erste klinische Erfahrung mit einem großformatigen Flächendetektorsystem bei Aufnahmen des peripheren Skelettsystems (First clinical experience with a flat panel detector for imaging the peripheral skeleton)”, Fortschr Röntgenstr (2001) 173, 1048-1052 Schaefer-Prokop, C., Eisenhuber, E., Fuchsjäger, M., Puig, S., Prokop, M., “Aktuelle Entwicklung auf dem Gebiet der digitalen Thoraxradiographie (Current developments in the field of thoracic imaging)”, Radiologe 2001; 41: 230-239

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2002 Busch, H.P., Bosmans, H., Faulkner, K., Peer, R., Vano, E., Busch, S., “Dose management with new digital imaging techniques”, European Radiology Association § Congress; 2002 ,SS 1013: Digital radiography/Digital mammography Hermann, K.A., Bonel, H., Stäbler, A., Kulinna, C., Glaser, C., Holzknecht, N., Geiger, B., Schätzel, M., Reiser, M.F., “Chest imaging with flat-panel detector at low and standard doses: comparison with storage phosphor technology in normal patients”, Eur. Radiol 2002; 12: 385-390 Ludwig, K., Lenzen, H., Kamm, K.F., Link, M., Diederich, S., Wormanns, D., Heindel, W., “Performance of a flat-panel detector in detecting artificial bone lesions: Comparison with conventional screen-film and storage-phosphor radiography”, Radiology 2002; 222: 453-459 Kim, T.S., Im, J.G., Lee, H.J., Lee, Y.J., Kim, S.H., Kim, S., “Detection of Pulmonary Edema in Pigs: Storage Phosphor Versus Amorphous Selenium-based Flat-Panel-Detector Radiography”, Radiology 2002; 223: 695-701 Okamura, T., Tanaka, S., Koyama, K., Norihumi, N., Daikokuya, H., Matsuoka, T., Kishimoto, K., Hatagawa, M., Kudoh, H., Yamada, R., “Clinical evaluation of digital radiography based on an large-area cesium iodide-amorphous silicon flat- panel detector compared with screen-film radiography for skeletal system and abdomen”, Eur Radiol 2002; 12: 1741-1747 Persliden, J., Beckman K.W., Geijer H., Andersson T., “Dose-image optimisation in digital radiography with a direct digital detector: an example applied to pelvic examinations”, Eur Radiol 2002; 12: 1584-1588 Strotzer, M., “Digital radiography with flat-panel detectors: the missing link”, Eur Radiol (202) 12: 1603-1604

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2003 Busch, H.P., Busch, S., Decker, C., Schilz, C., “Bildqualität und Dosis in der Digitalen Projektionsradiographie” (Image quality and exposure dose in Digital Projection Radiography), Fortschr. Röntgenstr. 2003; 175, 32 – 37 Busch, H.P., “Qualitäts- und Dosismanagement in der Digitalen Projektionsradiographie” (Dose and Quality Management in Digital Radiography), Fortschr. Röntgenstr 203; 175; 17 - 19 Dobbins, J.T., Samei, E., Chotas, H.G., Warp, R.J., Baydush, A.H., Floyd, C.E., Ravin, C.E., “Chest Radiography: Optimization of X-ray Spectrum for Cesium Iodine-Amorphous Silicon Flat-Panel Detector”, Radiology 203; 226: 221-230 Eisenhuber, E., Stadler, A., Prokop, M., Fuchsjäger, M., Weber, M., Schaefer-Prokop, C., “Detection of Monitoring Materials on Bedside Chest Radiographs with the Most Recent Generation of Storage Phosphor Plates: Dose Increase Does Not Improve Detection Performance”, Radiology 203; 227: 216-221 Ludwig, K., Schülke, Ch., Diedrich, S., Wormanns, D., Lenzen, H., Bernhardt, Th.M., Brinckmann, P., Heindel, W., “Detection of Subtle undisplaced Rib Fractures in a Porcine Model: Radiation Dose Requirement – Digital Flat-Panel versus Screen Film and Storage Phosphor Systems”, Radiology 203; 227: 163-168 Rapp-Bernhardt, U., Roehl, F.W., Gibbs, R.C., Schmidl, H., Krause, U.W., Bernhardt, T.M., “Flat-Panel X-ray Detector Based on Amorphous Silicon versus Asymmetric Screen Film System: Phantom Study of Dose Reduction and Depiction of Simulated Findings”, Radiology 203; 227: 484-492

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Annex1:

DIMOND III (Contract: FIGM-CT-2000-00061)

Final Report 1st October 2003

Lead contractor:

Workpackage 1

Leading partner:

WP 1.2: Identification of the three image quality bands

technology WP 2.2: QA protocol for digital detectors and new imaging devices WP 6.7: Circulation of mammography images between centres

Clinical Quality Criteria

WP 1.4: Report on clinical quality criteria for new digital

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DIMOND III

Research Issues in Diagnostic Radiology 1st October 2003

Clinical Quality Criteria (Lead contractor H.P. Busch)

WP 1.1 – 1.10

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Workpackage 1: Clinical Quality Criteria

Lead contractor: H.P. Busch, Trier

WP 1.1: Publication of equipment requirements for specific interventional procedures Lead partner: H. Zoetelief, Delft

WP 1.2: Identification of three image quality bands

Lead partner: H.P. Busch, Trier WP 1.3: Protocols for optimisation of post-processing

and display conditions Lead partner: H. Bosmans, Leuven

WP 1.4: Report on clinical quality criteria for new

digital technology Lead partner: H.P. Busch, Trier

WP 1.5: Publication, compendium document

Lead partner: K. Faulkner, Newcastle WP 1.6: Quality criteria for fluoroscopic guided

interventional procedures Lead partner: W. Jaschke, Innsbruck

WP 1.7: Experimental verification of the theoretical

model linking physical measurements to clinical indices Lead partner: J. Malone, Dublin

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WP 1.8. Pilot study on equipment requirements for fluoroscopic guided interventional radiology Lead partner: H. Zoetelief, Delft

WP 1.9: Pilot study into the optimisation of viewing

conditions and display settings Lead partner: J. Kotre, Newcastle

WP 1.10: Pilot study of quality criteria for new detectors

Lead partner: W. Jaschke, Innsbruck

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DIMOND III


Lead partner: Brüderkrankenhaus Trier, Germany, partner 3 The new techniques of digital radiography, such as computed radiography and flat panel radiography, offer new potential for dose reduction. In order to adapt dose and image quality to diagnostic requirements, we developed the model of three image quality bands and discussed this extensively at the DIMOND III meeting in Trier. In WP 1.2, imaging capabilities were determined by different phantoms to define these three image quality bands using the results of both the CDRAD phantom and different organ phantoms, for example the abdomen, lung, hand and pelvis. Images of different dose (speed) classes (200, 400, 800, 1600) were evaluated or graded by different observers and assigned to either the “high”, “medium” or “low” image class. This forms the base of our description of the three image quality bands. One of the main focuses of WP 1.2 was last year’s development of a computer program to automatically evaluate CDRAD images by pattern recognition. This was a breakthrough because of the significant decrease in workload it has brought and the objectivity it gives to CDRAD image evaluation. We tested the program intensively and determined its sensitivity and performance. This program is now available to all DIMOND III partners. Starting with the “Referral guidelines for imaging” (Radiation Protection 118), we asked DIMOND partners to define the necessary image quality for all diagnostic questions. We received responses from four centres. We then modified our proposal based on these results and distributed them to all DIMOND partners prior to the Trier meeting in October 2002. As a result of the discussion that took place at this meeting, we cancelled the trial that had been planned for February 2003. These results have now been outlined. This should be the starting point of a broad discussion within the European community of radiology and radiation protection.

1. Review of existing literature and clinical experience

A summary of the existing literature for digital radiography was sent to all DIMOND partners in December 2001. This list has now been updated to coincide with the release of the final report.

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2. Definition of three image quality bands for digital radiography

Based on the results of phantom measurements taken with the CDRAD phantom, we defined the three bands for different storage phosphor systems and a flat detector system. The results were presented as part of a refresher course at the German Röntgenkongress (radiography conference) 2003. These results were then discussed extensively during the DIMOND meeting in Trier with specific reference to digital images. A full set of clinical images of the image quality band is now available to all DIMOND partners for the purpose of training and education.

3. Definition of three quality bands by clinical criteria

The three quality bands were defined by clinical criteria based on the European Commission’s Referral Guidelines for Imaging (European Communities, 2001 ISBN 92-828-9454-1). A subgroup was created by taking the applications for which projection radiography examinations are recommended and graded the image quality into the levels high, medium, low. We sent this “new” version of the referral guidelines to the DIMOND partners for discussion.

4. Testing the model (partners)

5. Workshop with physicists and radiologists

At the Trier meeting, there was intensive discussion of the three quality bands. The discussion resulted in a specific modification of the description for the final report. The trial that had been proposed for February 2003 was therefore cancelled.

6. Recommendations for the three image quality bands (with examples)

We worked out the recommendations for the final DIMOND III report. A full set of clinical images is now available to all DIMOND III partners for training and education proposes.

Summary:

WP 1.2 achieved what it set out to do at the beginning. We convinced our partners to take the CDRAD 2.0 as a standard phantom for evaluating image quality in the project and intensively discussed the results of criteria for the three image quality bands and their application to clinical problems.

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List of deliverables


1. Review existing literature and clinical experience (Yes) 2. Define three image quality bands for digital radiography (Yes) 3. Define the three quality bands by clinical criteria (Yes) 4. Test this model (discussion, trial use by DIMOND partners) (Yes) 5. Meet with physicists and radiologists (Trier meeting)(Yes) 6. Make recommendations for the three image quality bands (with examples)

(Yes)

WP 1.2 was finished on time and met its goals.

Partners: Haughton Institute, Ireland (Prof. Dr. Jim Malone) Department of Radiology, Leuven (Dr. Hilde Bosmans) Department of Radiology, Innsbruck (Prof. Dr. W. Jaschke) Medical Physics Department, Newcastle(Dr. CJ Kotre) Department of Radiology, Karlsruhe (Dr. S. Vetter) Linked projects: 1.4 Lead partner: BKT Trier 1.6 Lead partner: Radiology Innsbruck 1.10 Lead partner: Radiology Innsbruck 4.1 Lead partner: Radiology Karlsruhe 5.1 Lead partner: Azienda Ospedaliera Udine 6.1 Lead partner: Radiology Innsbruck

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WP 1.4: Report on clinical quality criteria for new digital technology

Lead partner: Brüderkrankenhaus Trier, Germany, partner 3 The main goal of this workpackage was to adapt quality criteria to further digital imaging procedures involved in the DIMOND II project. The recommended diagnostic requirements for digital projection radiography are based on the European Guidelines on Quality Criteria for Diagnostic images (EC), the diagnostic requirements for digital radiographic procedures (DIMOND II) and the guidelines published by the Bundesärztekammer (German Federal Medical Association) for quality assurance in radiological examinations. We sent these recommendations to all partners for further examination. Additionally, we asked the partners to send us technical parameters of their exposures. Using this material, we prepared a contribution to a book on European guidelines on quality criteria for diagnostic digital radiographic images, similar to what already existed for conventional film/screen radiography.

1. Adaptation of quality criteria for new digital technology

Compared to what we had originally planned, the list of examinations covered by this workpackage was enlarged to include all indications for projection radiography (all of which were also included in the report on clinical quality criteria). We limited the report on new digital technologies to storage phosphor and flat panel technology. As discussed with the partners and the coordinator at the Vienna meeting in 2002, we did not extend this report to fluoroscopic procedures because of the possible overlap with WP 4. The quality criteria of fluoroscopic procedures will be dealt with there. Post-processing of digital images has a great impact on quality criteria. Therefore, before beginning with the optimization of post-processing, a description of the “black box” post-processing model was needed. In addition to the work planned for WP 1.4, we worked out possible ways of describing the quality of post-processing and developed strategies for optimization. This was discussed extensively at the Trier workshop in October 2002. We will present the results of this at the final DIMOND meeting and in the final DIMOND report.

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2. Trial (WP 1.4 partners)

3. Final workshop with clinical partners

Because we extensively discussed the results at the DIMOND Trier meeting in various working groups and modified the description, we were able to cancel the proposed trial and final workshop.

4. Development of draft for “European Guidelines on quality criteria for Digital Radiographic images”

This draft was finished and will be presented at the final meeting and in the final report in 2004. Summary: WP 1.4 is now finished. After intensive discussion with the DIMOND partners, we are now preparing the draft for the final meeting. A full set of clinical examples is now available for all DIMOND partners.


List of deliverables:

1. Adapt quality criteria for new digital technology (Yes) 2. Trial at Trier meeting (partners of DIMOND III) (Yes) 3. Final workshop with clinical partners (at Trier meeting) (Yes) 4. Contribution to the draft version of “European Guidelines on Quality

Criteria for Digital Projection Radiography” (Yes)

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WP 2.2: QA protocol for digital detectors and new imaging devices

Lead partner: Brüderkrankenhaus Trier, Germany, partner 3 We developed a QA protocol for different digital detectors. This protocol uses the new capability of numerical and quantitative evaluation of image quality (e.g. signal/noise). The protocol is based on the German standards for constancy testing DIN 6868-58 and DIN 6868-13, but includes digital evaluation of additional parameters. We tested this protocol with a flat detector system (Philips DigitalDiagnost) and a storage phosphor system (Philips Compano). We have also sent the protocol to the DIMOND partners for evaluation before summarising our experience.

1. Development of a QA protocol for digital detectors and new imaging devices

In WP 2.2, we developed a new QA protocol for flat detectors. We sent this protocol to all DIMOND partners for evaluation. This protocol intentionally featured a larger number of parameters than was necessary so that it would choose only the important and useful parameters. After discussion with our partners and a year’s experience working with the protocol, we suggested a final version. This was discussed, among other places, at the Trier DIMOND meeting in October 2002. Different partners’ suggestions have now been integrated. We also expanded the application to work with storage phosphor radiography. The protocol for fluoroscopic procedures will be dealt with in WP 4.

2. Trial (partners)

3. Meeting to summarise trial results

Trial results were extensively discussed in different working groups at the DIMOND Trier meeting and comments integrated. We were therefore able to cancel the proposed trial and final workshop. We also developed a program to automatically recognise patterns in test phantom exposures in order to evaluate the images automatically using PCs.

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Summary:

WP 2.2 is now finished. Over the course of the workpackage, we developed a new procedure for constancy testing based on the new capabilities of digital imaging. We then tested this procedure over a long period and discussed the results intensively with our colleagues and DIMOND partners. In addition, we developed a new computer program to automatically evaluate the test images. This program is now available to all DIMOND partners via the internet.


Deliverables:

1. Develop a QA protocol for digital detectors and new image devices (Yes). 2. Discussion/feedback from the partners (Yes) 3. Meet to discuss and summarise results (Trier meeting) (Yes) 4. Contribution to the draft of European guidelines (Yes)

Partners:

Haughton Institute, Dublin( Prof. Jim Malone) Department of Radiology, Madrid ( Prof. E. Vano) Department of Radiology, Leuven (Dr. H. Bosmans) Department of Radiology, Innsbruck (Prof. W. Jaschke) Department of Radiology, Karlsruhe (Dr. S. Vetter)

Linked projects:

1.2. Lead partner: BKT Trier 1.5. Lead partner: Newcastle City Health Trust 1.6. Lead partner: Radiology Innsbruck 1.10. Lead partner: Radiology Innsbruck 4.1. Lead partner: Radiology Karlsruhe 6.1. Lead Partner: Radiology Innsbruck

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WP 6.7: Circulation of mammographic images between centres

1. Preparation

Circulation of mammography images will coincide with the final report in 2004. This set of images contains both clinical and test images and was put together from images received from our DIMOND partners in Innsbruck and Madrid.

2. Circulation of mammography images

The mammography images were discussed at the Trier meeting in October 2002. We will send the image folder for further discussion and evaluation along with the final report.

Summary:

WP 6.7 was not totally successful. If we can obtain more images over the next few months, we will integrate them into the image file for the final workshop.


However, we were not totally satisfied because of the limited input.

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Annex 2:

JAnalyser-CDRAD

Quality Testing of Digital Projection Radiography

C. SCHILZ

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“Contrast-Detail CDRAD phantom” (Designer’s description: Nuclear Associates / USA)

Introduction

Most definitions of image quality in radiology are based on characterizing the physical properties of the image chain. However, medical diagnosis is not made on the basis of the image alone. The observer’s perception of the image is crucial to the result. This perception can be tested using so-called Contrast-Detail (CD) phantoms. These CD phantoms make it possible to quantify both detail and contrast, as observed by the radiologist. The CDRAD phantom can be used within the entire range of diagnostic imaging systems, such as fluoroscopy and digital subtraction angiography.

Construction

The CDRAD phantom consists of a Plexiglas tablet with cylindrical holes of exact diameter and depth (tolerances: 0.02 mm). Together with additional Plexiglas tablets, which are used to simulate the dimensions of the patient, the radiographic image of the phantom gives information about the imaging performance of the whole system.

This image shows 225 squares, 15 rows and 15 columns. In each square, either one or two spots are present, these being the images of the holes. The first three rows show only one spot, while the other rows have two identical spots – one in the middle and one in a randomly chosen corner. The optical densities of the spots are higher compared to the uniform background. Due to the (exponentially) increasing depth of the holes in a horizontal direction, the image shows 15

columns of spots with increasing contrast. In the vertical direction, the diameter of the holes increases in stages, exponentially from 0.3 to 8.0 mm. For the image, this means 15 rows of spots with increasing spatial resolution.

Evaluation

To evaluate the phantom image, the observer indicates the location of the second spot in each square. Correct indication proves that a the observer really does see contrasts. At the transition from visible to invisible, it is difficult

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to decide in which corner the second spot is located, and the response equals pure chance. The line connecting the central spots with smallest visible diameter and contrast is called the contrast-detail (CD) curve. In order to compare the imaging performance of different systems, phantom images are made under identical conditions and evaluated by the same observer and at the same time. The better system will produce an image in which smaller contrasts and details are visible. This results in a shift of the CD curve to the lower left part of the image

Why is computer-based evaluation of CDRAD phantoms useful?

The aim of the program JAnalyser-CDRAD to provide computer-based evaluation of CDRAD phantoms. There are some good reasons for evaluating the examination by computer. Manual evaluation: - Depends on the observer - Is very time-consuming - Will train the observer (the results change), which means that

- The observer learns to “read” the examination - The observer learns the sequence of the holes

Computer-based evaluation: - Is independent of the observer (depends only on the algorithm used) - Is faster - Produces results that are reproducible It is, thus, useful to have a computer-based evaluation of the CDRAD PHANTOM.

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How does the program work?

The 15x15 grid of spot-containing squares is surrounded by a thin metallic grid, which is easily visible during the examination. Using various methods of digital image processing (edge enhancement, skeletation, outline pursuit the grid is selected and the adjustment of the phantom is determined. If the grid is completely shown, any turn of the phantom can be recognized (although due to the divergence of the x-rays, dertermining the position of the grid is not simple).

The position and angle of the 225 squares are now established. We now try to determine the position of the spots based on the original picture information. There are a number of tested methods for determining the position of the spots: Hough transformation (for cycles) Mask contrast procedure Standardized cross correlation

The result is compared with the CDRAD phantom. If the position of the spots is determined correctly, then the square is considered as recognized (“1”). If the position is not correctly determined, then the square is considered as not recognized (“0”). The results for all 225 fields are then submitted for a plausibility check, because the evaluation is prone to error. The plausibility check minimizes the influence of: Fields that are correctly recognised by chance Fields that are not recognized fields (but should have been)

This check involves comparing the results for each square with the results for each surrounding square. The figures displayed by the programme represent square recognition results after the plausibility check.

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Procedures for evaluating the position of the spots

Hough transformation

Original image After edge extraction After hough transformation A filter is applied to extract the outline of the spots (edge extraction) from the original picture. Hough transformation is then applied to these outlines, dependent on the diameters of the spots. This hough transformation transmits the outer edge of the circle to the centre of the circle. The positions of the centres are determined by a search for the two maximum values . In squares with one spot: - If the maximum value is in the centre of the square, the square is

recognized (“1”) In squares with two spots: - If one of the two maximum values is in the centre and the other in a corner

of the square, the square is provisionally recognized. Tests are then carried out to establish whether the spot is in the correct corner. If it is, then the square is considered as recognized.

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Annex 3:

JAnalyser

Constancy Testing of Digital Projection Radiography

C. SCHILZ

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General information

The computer program JAnalyser allows automatic evaluation of constancy tests using stored digital radiography images. For this, phantom exposures need to be made in accordance with DIN6868-12 (Fig1) and constancy tests must have constant exposure parameter values. Once taken, the digital image has to be transferred without additional image processing, or otherwise image processing parameters should be kept constant. Constancy test evaluation is computer based, with high contrast, low contrast, homogeneity, the square wave response function of the lead bar pattern and the light field/xray-field are all measured. The evaluation conforms to the German DIN standards: DIN 6868-12 DIN 6868-58

Company: Pehamed Company: Pehamed Company Wellhöfer Fig.1: Different images of supported phantoms. The program searches the representative marks in the image (A to D)

D A B

C D

After these marks have been found, the program calculates the characteristic values for high contrast, low contrast, homogeneity, the square Wave Response Function” of the lead bar pattern and the light field/xrayfield. The entire program structure is a Client/Server solution. On the server there is a data base (mySQL) for sampling and storage of determined data. Communication between server and client is made by an JDBC interface. The client program is written in Java, therefore it can be used in each operating system environment (Windows, Linux, Sun etc.). For the execution the Java Runtime Environment in version 1.4.0 or newer is needed. For mySQL the usual data base interfaces (JDBC; ODBC...) exist, so the collected data can be evaluated by other statistic tools (e.g. Microsoft Excel/pivot tables).

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Constancy Testing for digital x-ray units

The characterisation of imaging systems is based on communication theory. According to this theory, x-ray devices can be considered in terms of “black boxes". The black box has a defined transmission characteristic and noise characteristic. The output signal can be determined from the input signal, if the characteristic of the “Black box" is known. Even if the manufacturers keep the characteristics of their systems secret, tests can be developed using this communications theory. The aim of constancy tests is not to establish system characteristics of the black box with absolute values, but to establish the follow up of routine performance of an x-ray unit .

Demands on an imaging system

An imaging system should represent differences in absorption without distortion as a two-dimensional picture. It should have the following conditions:

1. Linearity The input signal changes by the factor α, then the output signal changes with the same factor α. The intensity value from the sum of the single intensities is devoted to two objects which are superpositioned in the object level (absolute detected values, without calibration or adjustment by exposure index) Logarithmically linearity The input signal changes by a factor α, then the output signal changes with the factor “log α”

2. Local or shift invariance The position of the object, whether central or peripheral, has no influence on the image. If the object is shifted, than the position of the object within the image is shifted in the same way.

3. Time invariance Images made under comparable conditions but at different times should be identical.

X-ray systems fulfil only the first two of these criteria, while constancy tests are based on time invariance.

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The first criteria is restricted through - A partial lack of logarithmic linear/linear characteristics - Change of measured values by post-processing (which is not

influenced by the user) The second criteria is restricted through

- Inhomogeneous radiation (heel effect, parameter of examination) - Different local sensitivity of the detector

These first two demands are system-dependent and cannot not be ignored. For constancy tests, the restriction is not importanted if

1. The conditions of examination are constant 2. The measured variables are comparable to those measured during the

acceptance test Constancy tests for digital systems can be execuded under the same system characteristics as as conventional (film/screen) constancy tests. Measurements of these characteristics must be adapted to the requirements and conditions of digital radiography.

Measured system characteristics

The image below shows a test phantom for digital radiography (according to DIN 6868-12).

Fig.2: Image of a test phantom for digital radiography

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This phantom allows all relevant data to be assessed:

- Dynamic range, - Detail detectability, - Spatial resolution - Homogeneity - Light field / x-ray field

The measurement of the parameters must be adapted to the requirements and conditions of digital radiography. The measurement of the variables can be done by hand or by computer.

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Dynamic range

In conventional radiography, optical density depends on dose. The dynamic range of an examination depends on the dose and the film-screen combination selected (as well as whether a film is over-exposed, correctly-exposed, or under-exposed). The constancy of an analogue x-ray device can be established if constant dose values produce the same optical density. The relationship between dose and optical density is logarithmically linear. For digital x-ray devices, dynamic range can be adapted using post-processing techniques. Images will show the same brightness independent of the dose (see fig. 3). There is no relation between printed grey value / optical density and dose.

81kV S200

81kV S400

81kV S800

81kV S1600

Fig.3: Digital images with different dose values (speed class 200, 40, 80, 1600) Nearly all digital x-ray systems have a logarithmically linear relation between dose and detected value. For constancy tests of digital x-ray systems, a measured value should be used, which is unchanged or linearly changed during post-processing. The high contrast is measured in the seven fields shown above, with the different mean values describing the dynamic range. In logarithmic linear systems, the noise is defined by the standard deviation. If post-processing is linear, the standard deviation within homogeneous ranges is linearly dependent on the dose and the gradient of the post-processing curve. The post-processing parameters must be kept constant for the constancy test so the standard deviation depends only on the dose. The "average value" (signal) and the "standard deviation" (noise) are calculated (automatically) for different levels of the grey values. If the quality of the x-ray system changes, the measured “average values” and “standard deviation” change too. For the interpretation of the change further measured variables are necessary (e.g. the area dose product or surface dose)

What JAnalyser does

The high contrast is measured in the seven fields shown above. The following values are determined in the shown ROIs:

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Mean value of the ROIs - Standard deviation of the mean value - Minimum grey value - Maximum grey value - Contrast of the ROIs to the surrounding area - Contrast of the ROIs to the surrounding area divided with the noise

(standard deviation) - Area of the ROIs

Detail detectability

Objects can be detected in relation to the contrast of the surrounding area. However, the next four pictures show that contrast is not the only criterion for detectability. The four images have the same tube voltage (81 kV) but different dose classes (S200, S400, S800, S1600). All images have the same contrast. You can see that, in addition to the contrast, noise is also important to the detectability of objects. The higher the noise gets, the more difficult it is to recognize the objects.

81kV S200

81kV S400

81kV S800

81kV S1600

This regularity can be used during constancy testing. In the low contrast area, the "contrast" and the relationship between the object's contrast and noise of the objects can be determined (automatically). If the quality of an x-ray system (and thus the detail detectability) decreases, then the contrast/noise ratio decreases too.

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What JAnalyser does

Contrast measurement can be taken putting by the mean value (MeanObj) of a ROI (HC) of the same form and size above (Meanup) and below (Meandown). The contrast has been calculated using the formula:

2)( downup

Objx

MeanMeanMeanHCContrast

−−=

Calculation of "contrast / noise" divided the contrast to the standard deviation ( Objϑ ) of the regarded ROI (HC).

x

xHC

HCObj

downupObj

x

MeanMeanMean

NHCContrast

ϑ2)(−

−=

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Homogeneity

The demand “local or shift invariance” on x-ray systems is restricted by:

- Inhomogeneous radiation (heel effect, parameters of examination) - Different local sensitivity of the detector

The influence of these effect should be able to be kept as small as possible by:

- Using the maximum film-focal distance, thereby minimising the heel effect

- Calibrating the detector (depending on the x-ray system) With increasing work time of an x-ray unit:

- The emitted dose distribution of the x-ray tube can change - The local sensitivity of the detector can change

To determine this change, homogeneity should be measured during the constancy test. For the description of homogeneity, the absolute or relative difference between the minimum an maximum grey value can be accepted.

What JAnalyser does

The homogeneity is measured in the fields marked with "hori" and "vert" (see image below). Horizontal homogeneity: For noise reduction, vertical grey values are averaged. After that, the minimum (gmin) and maximum (gmax) grey value is determined and the homogeneity can be calculated. The results of the calculation are presented in the table “measurement”. In addition, the minimum and the maximum grey values are registered and saved in the data base. The following formula is used to calculate homogeneity (hom):

inxgg −= maxhom Vertical homogeneity is measured in the same way.

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Spatial resolution / square wave response function

If a sinusoidal distribution of intensity in the object level is represented by an imaging system, then the distribution of intensity of the image has the same spatial frequency as that of the object.

However, the amplitudes of intensity distribution in the image with increasing spatial frequency are reduced by the optical transfer errors of the system. The reduced amplitudes of the image express the loss of resolution. The influence of the amplitude of a sinusoidal distribution is called modulation. The modulation transfer function (MTF) describes the relationship between the modulation (Mod(u))at the frequency u and the modulation (Mod(0)) at the frequency 0.

)/0()()(mmLpMod

uModuMTF =

The production of a sinus wave raster is very complex and expensive. For this reason, constancy tests are made using a lead bar pattern. With lead bar patterns, the square wave response function (SWRF) is measurable. This function stands in close relationship to the MTF. In order to state the constancy, the SWRF measurement and the relative comparison to the accepting test are sufficient.

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For an exact determination of the MTF/SWRF, single images of lead bar pattern are insufficient. Particularly at high spatial frequency, the number of based measuring points becomes too small. The SWRF measurement is more precise than the determination of the last visible linepair in analogue radiography. In the SWRF, the last visible linepair corresponds with the range, in which the curve leads to zero. Changes to the characteristic of systems should be able to be recognised earlier using the measurement of the SWRF than by determining the last visible linepair.

What JAnalyser does

The square wave response function is determined within the lead bar (0.6-5.0 lp/mm). The program itself automatically finds the object borders of the line pairs of lines.

direction, in which the mean value of the intensitivty values is build

ROI

Direction, in which the profile of intensity is build

grid group in y-direction

After that, the program calculates the mean value for each row and searches the three maxima and two minima (or two maxima and

three minima).

Fig. 11: Lead-bar pattern

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Fig. 12: mean values of the rows The linepair is recognized and the program finds exactly three maxima (max1 until max3) and two minima (min1 until min2). If this is impossible, the SWRF(lp(n)) is set to 0. (= > line pair cannot be recognized). The modulation and the SWRF are calculated using the following formula.

))6.0(())(())((

3))(())(())(())((

...))((

...))((

))((min2

))((max))((max))((

321

3

2

121

1

lpModnlpModnlpSWRF

nlpModnlpModnlpModnlpMod

nlpModnlpMod

nlpnlpnlpnlpMod

=

++=

==

−+

=

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Light field / X-ray field

Measurement of the difference between the light field and the X-ray-field. (This is only possible/useful if the exposure of the phantom has been made conforming to DIN6868-12)

d

b

a

c

The relative difference is calculated using the following formula:

.__

_

_

distafilmfocusffdffddc

ffavert

ffdba

ffahori

=

+=

+=

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Annex 4: CD1: Quality and Dose Management for Digital Radiography

WP 6.7 – Circulation of Mammography Images Between Centres CD2 : Image Quality Evaluation “Digital Mammography CD2” Prof. Dr. E. Vano (Madrid / Spain) CD3 : Image Quality Evaluation “Digital Mammography CD3” Prof. Dr. E. Vano (Madrid / Spain) CD4 : Image Quality Evaluation “Digital Mammography CD4” Prof. Dr. W. Jaschke (Innsbruck / Austria)

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CD Einlegeblatt 1

134

CD Einlegeblatt 2

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Annex 5: Acknowledgements

Those involved in the DIMOND projects (DIMOND I, II, and III) can look back on 13 successful years of cooperation. This European study has made a significant contribution to the development of digital radiography as a new examination technique. Our goal was to achieve optimal image quality (and with it, better diagnostic information) under minimal radiation doses and to standardize digital radiography techniques all over Europe. Now that DIMOND III has come to and end, I would like to express my thanks to all of the European research groups involved for both the collaboration and the interesting dialogue that came out of it. In particular, I would like to thank the projects' founding members, Dr. Keith Faulkner and Prof. Dr. Jim Malone, who directed and coordinated the projects DIMOND I-III with dedication and enthusiasm. Our collaboration over the last 13 years has turned into great friendship – a wonderful example of how Europeans can grow closer on a scientific and a social level. Besides the scientific research, DIMOND will surely be remembered by all by their experiences at the various events that took place over the course of the project. The DIMOND project would not have been possible without the support of the European Union, and I would also like to take this opportunity to thank them for their support and patronage, particularly Dr. Schibilla for her extraordinary efforts in the early years. Thanks are also due to the Krankenhaus der Bamherzigen Brüder hospital in Trier for their support during the project – in particular for their understanding of the numerous compromises and allowances made for DIMOND.

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Special thanks go to the DIMOND team at the radiology department at the Krankenhaus der Barmherzigen Brüder hospital here in Trier for their work and dedication: Christian Decker Clemens Schilz Anke Jockenhöfer Stephanie Busch Marion Anschütz as well as the rest of the staff at the radiology department, whose extra workload has now paid off. Lastly, I would like to thank my wife Hildegard and my children Stephanie and Thomas for their support and understanding throughout DIMOND, not least for the large amount of travel I have done over the course of the projects. I, for one, would be happy to see such successful collaboration between European research groups continue in the future in the area of digital radiography. Trier, 11 January 2004 Prof. Dr. H.P. Busch

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Digital Projection Radiography