Fluoroscopy & Digital Fluoroscopy

Fluoroscopy system

FluoroscopyA type of radiographic studyProvides a dynamic imaging sourceAllows the observer to visualize motility of organsFilms provide a static imageContrast media is generally used in conjunction with fluoroscopyStatic images are obtained on a spot film

History Of FluoroscopyInvented in 1896 by Thomas EdisonOriginal phosphor was zinc-cadmium sulfideThe screen was placed above the patient, the image was observed by viewing the screenDark adaptation was necessary to view imagesThis type of fluoroscopy was adapted to mirror optics but only one person could view at a timeIn the 1950s, image intensification was developedIn the 1990s, digital fluoroscopy was developed and is widely used today

Conventional Fluoroscopy

Two types of Fluoroscopy are:under-couch tube designover-couch tube design Over-couch tube design offers a greater distance between tube and both patient and intensifier.This improves image quality by reducing geometric unsharpness and reduces radiation skin dose to the patient.Under-couch tube design provides direct fluoroscopy screen and there for allows operator to be close to the patient.

Illumination During FluoroscopyFluoroscopy is generally visualized in dimly lit roomsCapable of limited brightness levelsImage-intensified fluoroscopy is much brighter than conventional fluoroscopyIllumination levels are measured in lambertsII levels are about the same brightness as viewing radiographic films

FLUOROSCOPIC DATA AQUSITION-IMAGE INTENSIFIED SYSTEMX-RAY TUBEPATIENTIMAGE INTENSIFIEROUTPUT PHOSPHORCAMERA (Viewing system)MONITOR

Image Intensifier TubeReceives remnant radiationConverts it to light Increases the light intensitySimilar to x-ray tubeContains a vacuumMounted in a metal container to protect it

Viewing SystemsImage produced at output phosphor is much smaller, brighter imageCould be viewed directly off output phosphorMirror opticsFinally updated to a television monitorClosed circuit monitor system

Television CameraPlumbicon and vidicon are most often usedPlumbicon - Best for imaging moving organs, i.e., heartVidicon - Best for imaging stationary organsA typical vidicon is contained in a glass envelope with a vacuumInternal components:Electron gun CathodeElectrostatic gridsTarget assembly Anode

Television Camera Tube

Television Camera Tube - WorkingLight image from II is converted to electric signalVarying light intensity is received at target assemblyElectrons are emitted - number depends on light intensity received by the target assemblyThe electron gun supplies electrons to fill any deficiency

Television Camera Tube - WorkingThis causes a current to flowCauses a varying voltage across the tubeThis is the video signalThe video signal pulses are reassembled into a visible image by the image monitor

TV camera and video signalThis scanning electron beam moves across the surface of the TV camera tube in a series of lines. This is achieved by a series of external coils, which are placed on the outside of the camera tube. In a typical television system, the image is formed from a set of 625 lines. On the first pass the set of odd numbered lines are scanned followed by the even numbers. This type of image is called interlaced.The purpose of interlacing is to prevent flickering of the television image on the monitor, by increasing the apparent frequency of frames (50 half frames/second). In Europe, 25 frames are updated every second.

Different types of scanning

INTERLACED SCANNING PROGRESSIVESCANNING12 2 14 4 16 18 6 1 8201315171011 32119 5 7 9351816141210 8 6 4 279111315171625 lines in 40 msi.e. : 25 frames/s

Image or TV MonitorThe final component in the II systemConverts the varying voltage from the Vidicon into a visible imageElements of the TV MonitorCathode ray tubeElectron gunFocusing coilsControl grids

Television Monitor Tube

Image Monitor (Continued)Electron gun emits electron toward a fluorescent screen, (TV screen) of the monitorElectrons emitted are in synchronicity with the signal being emitted by vidicon

Coupling Of The Television Camera with Image IntensifierTwo methods:Fiber opticsCassette loaded spot films are necessaryLens couplingCineSpot film camera

Recording The Fluoroscopic ImageDynamic SystemsCine film systemsVideotape recordingStatic SystemsCassettesSpot film cameraVideo recordersDigital fluoroscopy

Cine Film SystemsUses a 16 - 35mm movie cameraImage quality is better with 35mmPatient dose is higher with 35mmPatient dose is higher with cine than regular fluoro - requires higher mACine camera is driven by an electronic synchronous motor

Videotape RecordingCan record image from TV monitorUses VHS in. or U-matic in recorderDoes not exhibit high resolutionCan provide instant playback of examinationDoes not provide additional dose to patient

CassettesHigh image quality High patient doseDelay of two seconds is required before cassette can be exposed Multiple images can be exposed on one cassetteProvides a familiar format, therefore, most popular

Spot Film CamerasAlso called millimeter and photospot camerasSimilar to movie cameras, but only expose one frameImage comes directly from output phosphorThis requires less heat loading, lower mA, shorter interruption of examUsed with a beam splitting mirrorAvailable in 70 and 105mm70 mm can expose up to 12 frames/sec

Video RecordersUses a magnetic diskUsually records single framesHas a playback mode

Viewing System Over allOutput screen image can be transferred to different optical displaying systems:

conventional TV Generating a full frame of 525 lines (in USA) 625 lines and 25 full frames/s up to 1000 lines (in Europe)interlaced mode is used to prevent flickeringcinema35 mm film format: from 25 to 150 images/sphotographyrolled film of 105 mm: max 6 images/sfilm of 100 mm x 100 mm

Digital (Computerized) FluoroscopyDeveloped in late 70sImages are taken directly from output phosphorA video camera and digital image processor are used to obtain imagesThe image is converted from analog to digitalA dynamic recording can be madeImage can be manipulated in many waysLess radiation is used

Digital Fluoroscopy Chain of Events

CCD SYSTEM ADVANTAGE OVER CAMERA SYSTEMLOW LEVEL OF ELECTRONIC NOISEHIGH SPATIAL RESOLUTIONNO LAG OR BLOOMINGNO MAINTENANCEUNLIMITED LIFEUNAFFECTED BY MAGNETIC FIELDLINEAR RESPONSELOWER DOSE

Mobile FluoroscopyCan provide both static and dynamic imagesUsually connected to a video diskCan do everything that a fixed unit canGenerally used in critical care areas and surgery

Mobile Fluoroscopy

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