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32 Cards in this Set
- Front
- Back
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Conventional fluoroscopy |
Refers to the use of an image intensifier coupled to a video camera that converts the image from the output screen of the image intensifier into a video signal ( analog data). Signal sent to TV monitor where images are displayed at least at 30 frames per second |
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Closed circuit television chain |
A video camera is coupled by a coaxial cable to a Tv monitor to display the processed X-ray output image |
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Contrast ratio |
In an image intensifier tube, the ratio of the image brightness at the periphery to that at the center of the output screen |
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Digital fluoroscopy systems with flat panel detectors (FPDs) |
Replaced systems with image intensifier and video camera ( both tv camera tubes and CCD cameras)
- common place in Angiography |
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Digital subtraction angiography |
Process in which pre contrast angiography images are subtracted from post contrast images |
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Dynamic FPD |
detector capable of producing fluoroscopy images that can be displayed and viewed in real time |
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Energy subtraction |
digital subtraction of angiography images taken at different kVs |
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Frame rate |
from latent radiological images on the film created by X-ray photons |
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Gray-scale image manipulation |
Changes the contrast and brightness of an image displayed on the monitor in order to facilitate diagnostic interpretation |
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Host computer |
A minicomputer system capable of receiving dynamic digital data from the ADC and processing it for image display and storage |
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Image intensification |
Brightening of a fluoroscopic image through the use of an image intensifier |
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Image intensifier artifacts |
unwanted interference in an image, including image lag, vignetting(loss of brightness at the edges), pincushion distortion and S distortion |
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Image Intensifier based digital fluoroscopy |
system of fluoroscopy that consists of an X-ray tube and generator , image intensifier , video camera, ADC, DAC, computer and TV monitor |
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Last-image hold (LIH) |
an image processing technique that reduces radiation dose to the patient by allowing the X-ray beam to be turned on and off while retaining the previous image frame. |
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Magnification |
In conventional fluoroscopy , uses multi field image intensifiers to increase spatial resolution |
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Matrix size |
pixel matrices making up a digital image that vary according to the physical dimensions of the detector ; as matrix size increases for the same field of view the pixel sizes decrease and the image appears sharper |
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Pulsed fluoroscopy |
production of X-rys in short bursts or pulse by using a grid controlled Xray tube that reduces radiation dose to the patient as much as 90% compared to non pulsed fluoroscopy |
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Temporal framed averaging |
reduction of noise in an image by averaging frames collected overtime |
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Temporal subtraction |
digital subtraction of post-contrast images from pre contrast images over a time sequence |
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Video camera |
in conventional fluoroscopy , a video camera coupled to an image intensifier , which sends an analog signal to a TV monitor for image display |
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Electrostatic lens |
Seriesof electrodes that accelerate and focus photoelectrons from photocathode tooutput screen |
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Which is bigger Input screen or output screen? |
Diameterof output screen is about one-tenth the diameter of input screen |
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What is brightness gain? |
Increase in brightness at output screen due to small size of output screen |
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Opticalimage distributor |
Splitstotal light from output screen between video camera and photospot film camera |
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EXTINCTIONTIME |
THETIME REQUIRED FOR THE X-RAY TUBE TO BE SWITCHED ON |
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VideoCamera types |
Canbe either television camera tube or CCD camera |
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1980 |
CCDREPLACED THE CAMERA IN VIDEO SYSTEM |
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CCDSYSTEM ADVANTAGE OVER CAMERA SYSTEM |
HIGHDQE LOWLEVEL OF ELECTRONIC NOISE HIGHSPATIAL RESOLUTION NOLAG OR BLOOMING NOMAINTENANCE UNLIMITEDLIFE UNAFFECTEDBY MAGNETIC FIELD LINEARRESPONSE LOWERDOSE |
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Limitationsof image intensifier technology: |
Artifactsincluding vignetting, image lag, and pincushion and Sdistortions Lightand electron scattering within tube degrades the image contrast (veiling glare) Imagemagnification results in increased dose to patient |
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Typesof Dynamic FPDs |
Twotypes currently available:CsI a-Si TFT indirect digitaldetector a-SeTFT direct digital detector |
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EdgeEnhancement |
Unsharp masking operation Blurredimage of original image obtainedBlurredimage subtracted from original imageSubtractionprocess produces new image that is added to original image Producesfinal image, referred to as edge-enhanced image |
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DigitalSubtraction Angiography |
Twomethods TemporalsubtractionDigitalsubtraction of images in time EnergysubtractionSubtractionof images taken at different kVs Contrastmaterial is used in angiography Pre-contrastimages are digitally subtracted from post-contrast images during the procedure |
