craniofacial imaging-Recent advances

GOOD MORNING

By Dr Tony Pious

RECENT ADVANCES IN CRANIOFACIAL

IMAGING

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Clinical examination

Radiological examination

Ortho radio diagnosis

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“EXAMINATION WITHOUT RADIOGRAPHSDETECTS ONLY TIP OF ICEBERG.”

5There are 2 essential truths which characterize the

orthodontic profession -

First - Changes in technique are inevitable, with new materials and new technology. Change is a natural consequence.

Secondly - The fundamental truth is that the biology does not change.


clinician is to apply his skills the boundaries of these

The real task for the and his techniques within biologic limits.

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Comprehensive Diagnosis

Case

History

Study cast Analysis

Clinical Examination

Functional Analysis

Roentgeno- Cephalometric

Analysis

Radiographic Analysis

Photographic Analysis

History Nothing materializes as if by magic overnight. Even Roentgen’s discovery depended upon the development and

application of three converging thoughts ;

Movement of the electrons in a conductor.

Phenomena by which materials exert attractive or repulsive forces on other materials.

Complete absence of air.

ELECTRICITY

VACUUM MAGNETISM

Discovery of X-Rays While experimenting and searching

for the invisible light rays on a low pressure Crookes tube, to his surprise a fluorescence screen covered with Barium Platino cyanide started to glow brightly. The screen was on a table some distance away.

Wilhem Conrad RoentgenNovember 8th 1895

While investigating he accidentally placed his hand between the tube and the fluorescent screen, to be surprised by seeing a faint image of the bones of his hand on the screen.

Tracing back the rays to their source, he found out that the rays were produced, whenever and wherever the cathode rays encountered matter.

His curuosity dint end here.., He proceeded to make 1st radiograph of human body; he

placed his wife’s hand and exposed it for 15 minutes.

Anna Bertha

http://www.xray.hmc.psu.edu/rci/ss1/img0009.JPG

He termed these rays as “ X- Rays ’’ after the mathematical symbol for the unknown – X, the American way.

These rays were ultimately called as Roentgen Rays.

Early pioneers of oral radiology:Otto Walkhoff, Germany Took first dental radiograph in1896. He placed a photographic glass plate in his mouth for 25

minutes to expose to X-Ray beam and obtained the image of crowns of maxillary and mandibular teeth.

William Morton and Kells - Made the first dental radiographs in America.

Later… An autopowered X-Ray was used

by physicians at the turn of the century.

The early X-Ray machine was small enough to be portable, and its tube could be operated on a car battery.

Wires leading through a bedroom window.

which radiograph to Prescribe ?

According to AOO for a orthodontic treatment a minimum of lateral cephalogram, opg and 3

anterior IOPAs are essential.

Pt presents with

orthodontic problem

Is the Pt a candidate for orthodontic

Rx

Obtain lateral Cephalogram

Evaluate the pt

individual radiographi

c needs

Is the Pt heavily

restored or exhibits PDL

problems

Obtain OPG, Ant IOPAs

Obtain complete mouth survey

(IOPAs & bitewing)

AJODO -1992

Does the Pt have a

severe facial asymmetry

Does Pt have

significant TMJ signs & symptoms

If growing, growth

modulation or subjecting for surgery

Diagnose and treat

the patient

Obtain TMJ tomograms

Obtain hand wrist

radiograph

Obtain PA Cephalogram

“An unobstructed or complete view of a region in every direction”Is based on the principle of the reciprocal movement of an X-Ray source and an image receptor around a central point or plane called image layer.

PANORAMIC IMAGING

It is a technique for producing a single tomographic image of the facial structures that include, both the maxillary and mandibular dental arches and their supporting structures.

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The 4 Diagnostic regions in OPG

Dentoalveolar region

Maxillary regionMandibular region

TMJ, including retromaxillary region

INTERPRETING:

1) Condylar process and temperomandibular joint2) Coronoid process3) Ramus4) Body and angle

A) The Mandible


The maxilla can be divided into different major sites for examination:1) Cortical boundary of the maxilla, including the posterior border and the alveolar

ridge2) Pterygomaxillary fissure3) Maxillary sinuses, Zygomatic complex, including inferior and lateral orbital rims,

zygomatic process of maxilla.

THE MIDFACIAL REGION:

1) Nasal cavity and conchae2) Temperomandibular joint

The maxillary sinuses are well visualized on panoramic images.

The borders are entirely outlined with cortical bone, roughly symmetric, and comparable in radiographic density. The borders should be present and intact.

1) Palatoglossal air space2) Nasopharyngeal air space3) Glossopharyngeal air space

SOFT TISSUES:

The tongue arching across the film under the hard palate lip markings The nasal septum, Ear lobes, Nose, and Nasolabial folds.

DENTITION:

1. Teeth number, position and anatomy should be evaluated. 2. Tooth germ positions.3. Atypical sequence of eruption.4. Ectopic tooth germs.5. Over retained primary teeth.6. Supernumerary teeth.

7. Pathological root formation.8. Root resorption.10. Bone loss, bony pockets.11. Third molars – orientation, configuration of roots

and its relationship to the surrounding structures. 12. Endodontic obturations, crowns, and other fixed

restorations, should be noted.

Advantages Broad coverage of the

facial bones and teeth.

Low patient radiation dose.

Patient education and case presentation.

Ability to be used in patients unable to open their mouths.

Fine anatomic detail is not possible.Proximal surfaces of the premolars also typically overlap.Magnification and distortion.Overlapping of the structures in midline such as the cervical spine.

Disadvantages

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Lateral Cephalogram


Although the cephalometric radiograph in standard lateral projection was introduced into orthodontics during 1930s, the method has become routine in recent years.

Today cephalometric analysis has firmly taken place in dentofacial diagnostic procedures.

uses1. Assessement of the facial

skeleton2. Relationship of the jaw

bases3. Relationship of the axial

inclination of incisors4. Assessment of the soft

tissue morphology5. Growth pattern and

direction6. Localization of the

malocclusion7. Treatment possibilities and

limitations.

Cephalometrics is used in three major areas:

Morphological Analysis: By evaluating the sagittal and vertical relations of dentition, facial skeleton and soft tissue profile.

Growth Analysis: By taking two or more cephalograms at different time intervals and comparing the changes.

Treatment Analysis: By evaluating alterations during and after therapy.

Tongue Position:

Root: It is usually flat in cases of mouth breathing. In all other cases slight contact of the tongue usually occurs with soft palate.

Dorsum: Is high in Class II malocclusion and in deepbite cases.

Tip: Is retracted in cases of Class II div 1 malocclusions. In openbite, tip is forward.

The changes in the position of the tongue relate closely to the different types of malocclusion.

In Class III the tongue is flat and

lies downward and forward.

And With Class II tongue is

backward.

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POSTERIOR ANTERIOR VIEW

The X-Ray passes in a posterior anterior direction through the

skull.

A cassette is positioned vertically in a holding device.

Frontal view is particularly important in cases of dentoalveolar & facial asymmetry, crossbites and functional mandibular displacements.

Uses

To detect developmental abnormalities like facial asymmetries.

Used to examine the skull for presence of disease, trauma, developmental

abnormalities.

Used to detect progressive change in the mediolateral dimensions of the skull.

It offers good visualization of facial structures including frontal, ethmoidal

sinus, nasal fossa and orbits.

Both the dental midline and skeletal midline is not matching in rest and occlusion.

LATEROGNATHY

Here at rest dental midline is matching but in occlusion there is shift of the mandible.

LATEROCLUSION

At rest At occlusion

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Suhana Tabasum 7/F

Tmj Views Transcranial Projection

Transpharyngeal Projection Transorbital Projection

a) Transcranial Projection:

Film placement: The cassette is placed flat

against the patient’s ear & centered over the TMJ of interest, parallel to the sagittal plane.

Diagnostic information:

Transcranial projection is useful for identifying gross osseous changes on the lateral aspect of the joint only.

We can see the position of the head of the condyle within the fossa, the shape of the glenoid fossa & articular eminence.

Closed mouth

Open mouth

b) Transpharyngeal

Film Placement: The cassette is placed flat

against the patient's ear and is centered to the external auditory meatus parallel to the sagittal plane.

Open mouth position.

Structures Shown: Sagittal view of the

medial pole of the condylar head and neck, usually taken in the open mouth position.

This view is effective for visualizing erosive changes of the condyle.

Film Position: The film is positioned behind

the patient's head at an angle of 45° to the sagittal plane & perpendicular to the X-ray beam.

Position of Patient: The patient head is bend 100

down so that canthomeatal line is horizontal.

Here patient mouth is opened maximally to avoid superimposition of the articular eminence.

c) Transorbital (Zimmer Projection):

Diagnostic information:

The entire mediolateral dimension of the articular eminence, condylar head & condylar neck is visible, so is particularly useful for visualizing condylar neck fractures.

Limitations of the 2D images

1. A conventional headfilm is a 2D representation of a 3D object.

2. Cephalometric analyses are based on the assumption of a perfect superimposition of the right and left sides about the mid sagittal plane.

3. A significant amount of external error, known as radiographic projection error, is associated with image acquisition.

a) Magnification

b) Distortion

c) Patient positioning

4. In cephalometry, errors are most likely in locating the landmarks due to the lack of well defined outlines, hard edges and shadows.

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Change is the only CONSTANT.

In orthodontics there are many ADVANCES taken place, especially in the area of Craniofacial Imaging.

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DIGITAL IMAGING

“Imaging beyond imagination”

1. In terms of spatial distribution of the picture elements.

2. In terms of different shades of grays of each of the pixels.

The term digital refers to the numeric format of the image content.

ImagesConventional

ANALOG PROCESS

Contemporary

DIGITAL PROCESS

What is an Analog image ? An analog image, such as a radiographic film, has

virtually an infinite number of elements, with each element represented by a continuous gray scale.

What is a digital image ? A digital image is a matrix of square pieces, or picture

elements (pixels), that form a mosaic pattern from which the original image can be reconstructed for visual display.

Characteristics of digital images A digital image is composed

of picture elements (pixels) that are arranged in a 2‑dimensional rectangular grid.

A pixel is the smallest element of a digitized image. Radiographic images generally use gray color with an intensity value between 8 bits (0 to 256 shades of gray).

Image resolution refers to the degree of sharpness of the image. Resolution is determined by the number of pixels per given length of an image (pixels/mm), the number of gray levels per pixel (bits).

i.e., the resolution of the image improves as the number of pixels increases.

PRINCIPLE OF DIGITAL IMAGING

Normal X-ray Digital X-raySilver halide grains in x-ray films perceived as different shades of gray by the human eye due to varying densities

Silver halide grains are replaced by small light- sensitive electronic sensors which produce an electric signal depending on the voltage recorded by the sensor.

CONVENTIONAL(ANALOG)

DIGITAL

CEPHALOGRAM

CONVENTIONAL DIGITAL

OPG

IOPA

INDIRECT DIRECT

a) Scanner

b) Photostimulable Phosphor plate (PSP)

a) Charged Coupled Device (CCD)

b) Complementary metal oxide semiconductor (CMOS)

c) Charge injection device. (CID)

METHODS OF IMAGE ACQUISITION

Equipment -

• X-ray source • Intraoral sensor • Computer It is used to digitize, process

and store information received from the sensor within 5 – 10 sec and display image on computer screen.

Radiovisiography

Image enhancement:1. Adjusted image is an improved version of

the original one. 2. Most image enhancement operations are

applied to make the image visibility more appealing.

3. This can be enhanced by increasing contrast, optimizing brightness.

4. Brightness & contrast5. Color6. Digital subtraction radiography

Color: Most digital systems currently provide opportunities for

color conversion of gray scale images also called pseudo-color.

Neither diagnostically nor educationally useful.

1. About 50% - 70% less radiation than conventional radiography

2. Immediate picture

3. Image improvable with image processing

4. Elimination of darkroom, film, and chemical processing

5. Reduce cost of daily maintenances

6. Easy to share by digital networking

7. Easy to store.

8. Easy for client education.

BENEFITS OF DIGITAL RADIOGRAPHY

1) Expensive.

2) Spare parts are expensive.

3) System, network, and database safety and security.

4) Potential training needs.

5) Cross infection.

DRAWBACKS OF DIGITAL RADIOGRAPHY

Computers With Tiny Carbon Tubes On Silicon Chips

It includes use of extremely tiny carbon 'nanotubes' instead of copper conductors to interconnect parts within integrated circuits (ICs).

One advantage of using carbon nanotube within integrated circuits is that these interconnects have the ability to conduct very high currents, more than a million amperes of current.

Digital subtraction radiography:

Subtraction in digital radiography is another image enhancement method.

When 2 images of the same area in the mouth are registered and the image intensities of the corresponding pixels are subtracted, a uniform difference image is produced.

The 1st image can be subtracted from the 2nd one to identify changes that may have occurred during a certain time period.

If there is a changes seen between pre and follow up examination, these changes show up as loss or gain of hard tissues.

In order for subtraction radiography to be diagnostically useful, it is imperative that the both the radiographs taken at different intervals must be reproducible.

BUT IT IS VIRTUALLY IMPOSSIBLE. Some form of mechanical standardization if done, it

may reduce the reliance on image processing and will generally produce better results.

Ortho radio diagnosis 71

XERORADIOGRAPHY

The word xeros – DRY

It is a technique of making dry radiographs by a totally photoelectric process, using metal plates coated with a semiconductor, such as selenium.

Special features-1. Prononced edge enhancement. 2. High contrast.3. A choice of positive & negative displays.4. Good detail.5. Does not require silver halide crystal containing films, hence no

dark room processing.6. Reduced patient exposure.

In this technique instead of conventional film, selenium coated photoreceptor plate with uniformly distributed electrostatic charge is used as the image receptor.

The charged plate is held in a light-tight cassette in a plastic bag and is exposed to x- ray.

The X-rays beam is left as a charged pattern on the plate.

Selenium plate

Selenium plate

++ ++ + + +

X-Ray exposure

Charged pattern on the plate

Selenium plate

Lines of forces++ ++ + + +

++++++++++++++++

Selenium plate

Toner distribution of charges

uses1. Mammography. 2. Sialography.3. Height of the alveolar crest is better visualized.4. Periodontal and periapical assessment. 5. Caries seen more readily.6. Tmj tomography.


DIGI CEPH

The graphical information contained within the cephalogram is transformed into numbers (digits) that the computer can store, retrieve and manipulate.

3 possible approaches may be used to perform a cephalometric analysis -

Digitization

1 • Manual tracing

2• COMPUTER AIDED ANALYSIS• Computer aided- landmarks are

located manually & digitized into a computer system, then the computer completes the analysis

3• COMPLETELY AUTOMATED. • Cephalogram is scanned into the

computer first, computer automatically locates landmark and performs ceph analysis.

Two methods – 1) DIGITIZING TABLET – it is a peripheral computer device that has 2

parts, tablet (writing surface) & stylus. Data input can be 2 modes - POINT AND

STREAM MODE.

2) DIRECTLY ON THE SCREEN - Here the image is fed directly into the

computer, and the mouse is clicked to identify the landmark points.Once digitization is complete, any analysis

can be performed in seconds


Spatial spectroscopy – Image pixels that are in regions of high intensity gradient

are identified as edges, & these edges are assumed to be object boundries:

it involves 4 steps – 1) Remove noise2) label pixels according to edginess3) Connect pixels and label edges 4) Find landmarks based on position or relationship to a

labeled edge.

3• COMPLETELY AUTOMATED• Cephalogram is scanned into the

computer first, computer automatically locates landmark and performs ceph analysis.

Signal to noise ratio • The useful signal for any imaging system

needs to be compared with backround noise.

• In analog film – backround noise is comparable to the base density and fog.

• Signal noise ratio improves with increased radiation dose for all systems.

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CAT SCAN

Introduced in medicine in early 70’s – Godfrey Hounsfield.

Tomography means an image of layer of tissue, and a computer is necessary to generate the pictures; hence the name – COMPUTED TOMOGRAPHY

Computerized axial tomographyComputerized tomographic scanningAxial tomographyComputerized trans-axial Tomography

Equipment - Scanner (movable X ray table + gantry) - Computer system - Display console

An image of a layer within the body is produced while the images of the structures above and below that layer are made invisible by blurring.

PRINCIPLE

Remnant radiation of this beam is detected by scintillation crystal.

Analog signal is then fed into computer

Digitized and analysed by mathematical algorithm

Data is reconstructed as an axial tomographic image.

AXIAL

SAGITTAL

CORONAL

To acquire a volume of data, 2 scanning modes are possible-

1) SEQUENTIAL – the table with the patient is positioned and the attenuation data are acquired. Then the table is moved to a next position, and a new acquisition is made.

2) SPIRAL – the table moves from the initial position to the end position while the X-Ray attenuation data are acquired.

Single slice CT – From an X-Ray source, a fan beam X-Ray is emitted through the imaged object towards a single array of detectors.

Multiple slice CT – Multiple slices can be produced using adjacent detector arrays.

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Shoba rani 21yr / F


OPG

Occlusal View

Conventional radiography has the following short comings,

1. Difficulty in assessing position (buccal/palatal)

2. Difficulty in assessing level and extent of resorption of adjacent teeth

CT scan was advised

Can determine the exact position of an impacted tooth.

Clear serial sections may be taken at graduated depth.

This technique allows the elimination of superimposition of other structures.

Position for axial section Position for coronal section

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AXIAL

Ortho radio diagnosisRight left

Right left

Right left

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CORONAL

Ortho radio diagnosisRight leftRight left

Advantages It completely eliminates

the superimpositions of images of structures outside the area of interest.

High contrast resolution - it can differentiate b/w the tissues of less then 1%.

Geometric accuracy. Tissue Characterization. Digital image processing.

Expensive Radiation dose.

Disadvantage

Limitations of CT Scan

However, even though the images are obtained at different planes, the analysis by the orthodontist is still limited. The images are seen as 2 dimensional on film and computer screen.

3D CT The CT images can be manipulated to undergo a three-

dimensional reconstruction of the image by a procedure called INTERPOLATION.

The original voxel - rectangular units, should be dimensionally altered into multiple cuboidal voxels.

Creation of these new cuboidal voxels allows the image to be reconstructed in any plane without loss of resolution.

The final image can be fed through a computer aided design system and viewed on a computer screen.

Steps :-

1. Image which is obtained consists of individual pixels along with the face of the volume called VOXEL .

2. Cuboid voxels can be created from the original rectangular voxel by INTERPOLATION.

THIS ALLOWS THE FORMATION OF MULTIPLANAR AND 3D IMAGES.


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Magnetic Resonance Imaging

MECHANISM OF MRI

The theory of MRI is based on the magnetic properties of an atom.

Atomic nuclei spin about their axis much as the earth spins about its axis.

In nuclei in which protons and neutrons are evenly paired, the spin of each nucleon cancels that of another, producing a net spin of zero.

Where as the nucleus of the element hydrogen contains a single, unpaired proton and therefore acts as a magnetic field.

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N

SN

S

N

S

N

S

N SN

S N

S

N

SN

S

To produce an MR image, the patient is placed inside a large magnet, which induces a relatively strong external magnetic field.

This causes the nuclei of many atoms in the body, including hydrogen, to align themselves with the magnetic field.

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N

S

N

S

N

S

N

S

N

S

Externally applied magnetic field

Higher energy state

Lower energy state

Energy in the form of an electromagnetic wave in the radiofrequency range from an antenna coil is directed to tissue.

Those protons that have a larger frequency matching that of the electromagnetic wave absorb energy and shift or rotate away from the direction induced by the magnet.

After removing the application of an radiofrequency signal, 2 events occur simultaneously-

1) The radiation of energy is released from the body.

T1 relaxation time 2) Return of the nuclei to their original state.

T2 relaxation time This energy is detected by the sensors and used to

construct the MR image by computer.

When images are displayed, intense signals show as white and weak ones as Black and intermediate as shades of gray.

Cortical bone and teeth with low presence of hydrogen are poorly imaged and appear black.

Indications Assessing diseases of the TMJ Cleft lip and palate Tonsillitis and adenoiditis Cysts and infections Tumors

Contraindications Patients with cardiac pacemakers. Patients with cerebral metallic aneurysm clips. Stainless steel and other metals produce artifacts.

Advantages Magnetic forces - does not produce any biological side

effects. Non invasive technique and can be used in most patients.

Short comings Inability to identify ligament tears or perforations Cannot be used in patients suffering from claustrophobia.

The limiting factor in the use of MRI in Orthodontics

Apart from economic cost, the functional modality of MRI depends on the presence of large numbers of hydrogen nuclei in the tissues being imaged.

Because hard tissues such as bone, enamel and dentin contain few if any free hydrogen nuclei, the use of this diagnostic tool is restricted in orthodontics to the visualization of the cartilaginous components of temperomandibular joint.


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3- D CEPHALOGRAM3- D CEPHALOGRAM3- D CEPHALOGRAM


For 3D imaging, 3D CT imaging is needed to volumetrically measure the patient’s anatomy.

However for cephalometric analysis, the availability of 2D lateral and frontal is beneficial to indicate landmarks accurately and repeatably in a 3D scene.

To avoid extra radiation dose, and to achieve this geometric relationship, lateral and frontal cepahlograms are computed from the CT data.

In this way an unlimited number of virtual X-Ray images of the skull can be computed.

To compute an virtual image, a bundle of parallel rays are cast through the CT volume.

The orientation of the virtual X-Ray image plane is perpendicular to the bundle of rays. Therefore, this X-Ray image can be added to the 3D scene as a textured rectangle.

Virtual cephalogram computed from the CT volume

Pre op -, mandibular asymmetry with chin deviated to Rt. ( Early loss of right condylar process )

Pre op 3D surface hard tissue representation

Linked frontal & lateral virtual ceph

Right Left

Virtual planning of a reverse L – osteotomy in the right ramus was planned.

Planning for reconstruction of right condylar process & placement of unilateral distractor & osteotomy of coronoid process

Post distraction – 1 week after distractor removal

Lengthening of the vertical ramus and improvement in chin projection, and increase in Anterior and Posterior facial height.

SUPERIMPOSITION

Pre op Post distraction

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Teleradiography


Electronic transmission of radiologic images from one location to another for the purpose of interpretation, consultation or both.

Teleradiology system allow direct digital or digitized film images to be transmitted to distant locations, where they can be viewed and downloaded to hard copy for reading and interpretation.

Transmission of images requires that the image files be in a digital format.

TRANSMISSION OF IMAGES

Digital images may be saved in a variety of file formats.

Commonly used are -

TIFF – tagged image format file.

WAN- wide area network.

IP - Internet protocol.

JPEG – joint photographic expert group.

Recent – DICOM. (Digital imaging and communication in medicine)

Transmission and receiving console system

Staff monitoring the transmission system.

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RAPID PROTOTYPING (RPT)

Prototype; Derived from Latin - "first form"

Rapid Prototyping is a method in which the part is created by a layer-additive process.

By using a specialized software a 3-D CAD model is obtained.

Then the RP machine constructs the part layer by layer until a solid replica of the CAD model is generated.

Rapid prototyping takes virtual designs (from CAD model), which transforms them into cross sections, and then create each cross section in physical space, one after the next until the model is finished.

It is a WYSIWYG process where the virtual model and the physical model correspond almost identically.

WYSIWYG acronym for What You See Is What You Get.

Techniques in Rapid Prototyping

131

Most commercially available RP machines use one of six techniques.

They are:1. Stereolithography (STL) 2. Laminated object manufacture (LOM) 3. Selective laser sintering (SLS) 4. Fused deposition modeling (FDM) 5. Solid ground curing (SGC) 6. 3-D ink jet printing

Basic steps in Prototyping1. CAD model creation

2. Conversion to STL format

3. Slice the STL format

4. Layer by layer construction

5. Clean & finish

Pre treatment – elevation in palatal mucosa

Image from STL file after elimination of all the tissues and structures

Findings from prototype models Crown of canine was tipped toward the palate Was 2.1mm away from the root of maxillary right

lateral incisor Root apex was over the apex of maxillary right

first premolar The model was used as an aid during surgical

exposure.

Advantages Diagnosis & treatment

planning

Communication with patients

Surgical access made easier

Disadvantages Exposure to CT

radiation Conventional

radiographs still required for records

The COST

Digigraph Equipment - Computer system Video camera with light source Sonic digitizing probe with receptor

microphones and Patient seat with a head holder.

With digigraph, any point can be located in 3 planes of space.

Head holder More comfortable Ear rods and forehead clamp.

Attached video monitor Images, text, numerical data can be displayed, stored, modified using a light pen or computer keyboard

Digitizing handpiece with removable, sterilizable tips Landmark location is recorded in 3 dimensional coordinates (x,y,z)

The time it takes the sound to reach each of the microphones determines the landmark location.

Digitization

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4 microphones are arranged strategically above the Pt’s head. A sound emitting probe is placed on various landmarks directly on the Patient’s head.

Each landmark is recorded by emitting a sound. The computer calculates the exact position of landmark

in 3D by analyzing the sound arriving at each microphone.


With the Pt in position, lateral and frontal cephalometric points are easily digitized.


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Cone Beam Computerized TomographyCBCT / CBVT

The 2 principle differences that distinguishes CBCT from traditional CT are –

1) The type of imaging source detector complex.

2) Method of data acquisition.

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• X-Ray source is a high output rotating anode generator.

• Uses a fan shape X-Ray beam.

• Image sensors used solid state detectors arranged in a 360 degree array around patient.

• In contrast to CT it uses a low energy fixed anode tube similar to that used for OPG machines.

• Uses a cone shaped X-Ray beam.

• The image sensors used are special image intensifier & solid state sensor.

CBCT uses 1 rotation sweep of the patient. Image data can be collected for a complete maxillofacial volume or limited area of interest.

Scan times vary from 10 – 90 sec. Dose is also reduced.

Possible Fields of View Include(A) 3 Inches, (B) 6 Inches, (C) 9 Inches, And (D) 12 Inches.

• Extended FOV scanning incorporating the craniofacial

region is difficult to incorporate into cone-beam design

because of the high cost of large-area detectors.

• The expansion of scan volume height has been accomplished

by one unit (iCAT Extended Field of View model) by the

software addition of two rotational scans to produce a single

volume with a 22-cm height.

IMAGE DISPLAY

• The availability of CBCT technology provides the dental

clinician with a great choice of image display formats.

• The volumetric data set is a compilation of all available

voxels and, for most CBCT devices, it is presented to the

clinician on screen as secondary reconstructed images in

three orthogonal planes (axial, sagittal, and coronal),

usually at a thickness defaulted to the native resolution

STANDARD DISPLAY MODES OF CBCT VOLUMETRIC DATA. (A) VOLUMETRIC 3D REPRESENTATION OF HARD TISSUE SHOWING THE THREE ORTHOGONAL PLANES IN RELATION TO THE RECONSTRUCTED VOLUMETRIC DATA SET; EACH ORTHOGONAL PLANE HAS MULTIPLE THIN-SLICE SECTIONS IN EACH PLANE. (B) REPRESENTATIVE AXIAL IMAGE. (C) REPRESENTATIVE SAGITTAL IMAGE, AND (D) REPRESENTATIVE CORONAL IMAGE

Types of CBCT machines

Available CBCT Imaging Systems – Worldwide Unit Model(s) Manufacturer/Distributor

Accuitomo 3D Accuitomo - XYZ Slice View

Tomograph/Veraviewpacs 3D

J. Morita, Japan

AUS: Henry Schein Halas

Galileos Galileos Sirona Dental Systems, Germany AUS:

Sirona Dental Systems

Hitachi CB MercuRay / CB Throne Hitachi Medical Systems, Japan AUS:

Unknown

iCAT i-CAT* / Platinum Imaging Sciences Int'l, USA AUS: Body Logic

Australia

ILUMA Ultra Cone Beam CT Scanner MTEC Imaging, USA/Kodak

AUS: Currently unavailable

KaVo 3D exam

* Announced at IDS 2007

KaVo, Germany

AUS: Currently unavailable

Newtom

3G / NewTom VG/5G

QR, Inc. Verona, Italy AUS: Inline Systems

Picasso Series Trio / Pro / Master E-Woo Technology, Korea AUS: Integradent

PreXion 3D TeraRecon Inc., USA AUD: Currently

unavailable

Promax 3D Planmeca OY, Helsinki, Finland AUS: Henry

Schein Halas

Scanora 3D CBCT Soredex , Helsinki, Finland AUS: Currently

unavailable

SkyView 3D Panoramic Imager My-Ray Dental Imaging, Italy AUS: Currently

unavailable 1

FOV 8 cm x 8 cm FOV 16 cm x 4 cm FOV 16 cm x 6 cm upper jaw TMJ

FOV 16 cm x 6 cm lower jaw

FOV 16 cm x 8 cm FOV 16 cm x 10 cm

FOV 16 cm x 11 cm FOV 16 cm x 13 cm FOV 23 cm x 17 cm

3D Facial photo

• Planmeca ProFace® is an exclusive 3D facial photo system

available for all of Planmeca 3D X-ray units.

• This integrated system produces a realistic 3D facial photo and

CBCT image in a single imaging session.

• can also take a separate 3D face photo without exposing your

patient to any radiation.

Create a 2D photo series automatically

Pre and post-operative comparisons Measure distances and relationships between boneand soft tissue

Superimpose images for comparison Deviate images for instant viewing of changes

Impacted Canines

• In the past, orthodontists have used the tube shift technique to compare two periapical

radiographs taken at different beam angles to determine the facial/lingual position of the

impacted canine.

• This same lingual, opposite buccal rule is helpful in determining whether the impacted

canine is labial or lingual to the incisor roots; however, the degree of displacement is

difficult to determine

• These 3D images are beneficial in determining the proximity of adjacent incisor and

premolar roots.

• Which can be invaluable in determining the ease of uncovering and bonding and the vector

of force that should be used to move the tooth into the arch with a lesser chance of adjacent

root resorption

Root Resorption

• Most root resorption involved in orthodontic treatment can be readily

viewed on periapical radiographs.

• However, resorption that occurs on the facial or lingual side of the

tooth is difficult to ascertain and quantify with this 2D view.

• CBCT scanning allows for better viewing of resorption on either of

these surfaces.

• Removal of the deciduous canine adjacent to the impacted permanent

canine has been shown to be effective if accomplished early.

Fractured Root

Orthodontic Temporary Anchorage Device Placement

• CBCT images allow more accurate and dependable views of the interradicular relationships

than panoramic radiographs.

• These images allow not only more successful placement but also better treatment planning of

where these TADs should be placed so that proper force vectors can be used during

orthodontic treatment.

• CBCT data can be used to construct placement guides for positioning mini-implants between

the roots of adjacent teeth in anatomically difficult sites.

• The quality of the bone in the proposed placement sites can be evaluated before insertion of

the mini-implants.

• Quantifying the thickness of the palatal bone can aid in determining the size and location of

any TADs that may be treatment planned for the palate.

Asymmetry Evaluation

• It can be difficult to evaluate the bony asymmetry of orthodontic patients using

cephalometric and panoramic radiographs.

• Direct measurements can be made of these structures with CBCT imaging by

comparing the right and left sides.

• Software companies are adding the ability to extract (segment) the mandible or maxilla

from the CBCT image and evaluate the bone independent of the other structures.

• In addition, the unilateral nature of posterior cross bites can be diagnosed more

specifically.

• A determination of an asymmetric maxilla or mandible can be accomplished more

easily by viewing and measuring the bones in 3D.

TMJ Degenerative Changes• Conventional tomography has been used extensively for the evaluation of TMJ hard

tissues; however, technique sensitivity and the length of the examinations made it a

less attractive diagnostic tool for the dental practitioner.

• CBCT images of the TMJ have been shown to provide greater reliability and

accuracy than tomographic or panoramic views in detecting condylar erosions.

• With temporomandibular dysfunction continuing to be a haunting pathology in some

orthodontic cases, it is important to view the anatomy of these patients’ joints

carefully before, during, and after orthodontic treatment.

• Current software solutions allow the visualization of TMJ osseous elements isolated

(segmented) from other surrounding structures.

Soft Tissue

• Frontal photographs are used to judge symmetry, but without numerous

views from different angles, it is difficult to gain a good feel of facial

symmetry.

• Using the soft tissue data gathered in the CBCT scan, it is possible to rotate

and tilt the head in an infinite number of positions to evaluate symmetry of

the soft tissue.

• It is difficult to gain a good view of the nose with some CBCT machines

because this area is at the edge of the image package.

• Recently, various companies have offered photographic imaging packages

to coordinate with the CBCT data, using multiple camera locations.

Airway• Using lateral cephalometric radiographs, the orthodontist may

evaluate the airway in a 2D manner.

• Many studies have been accomplished and various analyses

established in this way.

• All this evaluation, however, is limited by the fact that we are

looking at a flat projection seen in a sagittal or coronal plane.

• A 3D view of the airway can be readily available with CBCT

imaging.

CBCT airway view displaying the volume of the airway and sinuses. The most constricted region has been located and the minimum axial area calculated

ADVANTAGES

• Ray sum or ray casting• Multiplanar reformation• Interactive display modes unique to

maxillofacial imaging• Reduced patient radiation dose compared to

conventional CT• Image accuracy• Beam limitation• Rapid scan time

DISADVANTAGES

1. It is definitely more expensive than classic two-dimensional

radiologic investigations.

2. The dose of ionising radiation generated is greater than in a

pantomography investigation.

3. Any movement artefacts affect the whole data set and the

whole image rather than just one part.

4. It provides limited resolution of deeper (inner) soft tissues, and

MRI and classic CT are better for soft-tissue imaging.

5. It has low contrast range (dependent on the type of x-ray

detector).

6. It has increased noise from scattered radiation and

concomitant loss of

contrast resolution.

LIMITATIONS

• Noise and contrast • Image noise• Poor soft tissue contrast

CONCLUSION Orthodontic imaging has come a long way since the

“PLASTER ERA” during the times of E.H Angle and Calvin case when plaster was recording medium for dentition as well as facial form.

With advent of impression material, radiographic and photographic film – the orthodontic patient evolved into “FILM ERA”. Despite their limitations, these methods have served orthodontists well as research tools, diagnostic aids and medico-legal records.

We are now in “DIGITAL ERA” in which digital technologies are being used to resolve previous limitations.

Continuing evolution in orthodontic imaging and treatment of patients is such that these techniques will be key to future orthodontic practice.

REFERENCES 1) Oral radiology principle & interpretation.

White and Pharoah – 5th edition.2) Craniofacial imaging, 2nd chapter.

Graber Vanarsdall & Vig – 4th edition.3) 3D Cephalometry.

Swennen, Schutyser & Hausamen.4) Color atlas of Radiology. - Klaus and H.F.

Wolf. 5) Radiographic cephalometry –

Alexander Jacobson. 1st and 2nd edition. 6) Basics of radiography & radiology –

Eric whaites.7) Color atlas, orthodontic diagnosis –

T.Rakosi, Irmtrud jonas & T.M.Graber.

7) Current status and feature needs in craniofacial imaging – orthodontic craniofacial research -2003.

8) Digital imaging in dentistry -DCNA 2000.9) An algorithm for ordering Pre treatment

orthodontic radiographs – AJODO 1992. 10) Rapid prototyping as a tool for diagnosis

& treatment planning - AJODO 2006.11)Automatic computerized radiographic

identification of ceph landmarks. AJODO-1998.

12) Reliability of digital cephalometric landmark identification – SEMI IN ORTHOD 2005.

THANK YOU

Health & Medicine

craniofacial imaging-Recent advances