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RAD231 - Unit 4

Display and artifacts

QuestionAnswer
What are the acceptable ways to divide the CR plate to make multiple exposures? Vertical split - 2 images; Horizontal split - 2 images: Quarter split - 4 images
Name the types of exposure artifacts. *Motion *patient artifacts *improper positioning/clipped anatomy *quantum mottle *double exposure (CR) *grid lines/cutoff *moire effect
What is DICOM? Digital Imaging and Communications in Medicine - international standard to transmit, store, retrieve, print, process, and display medical imaging information
What is HL7? Health Level 7 - a comprehensive framework and related standard for the exchange, integration, sharing and retrieval of electronic health information
What does SMPTE stand for? Society of Motion Picture and Television Engineers
What does AAPM stand for? American Association of Physicists in Medicine
What does NEMA stand for? National Electronics Manufacturer's Association
How is QC of electronic display devices performed? using a SMPTE or AAPM TG18-QC test pattern
What does a Display Test Pattern evaluate? First, clean the screen. *Geometric distortion *general image quality *Luminance *Spatial Resolution *Ambient Light
What is geometric distortion? involves verification all lines/borders in pattern are visible, straight and centered within active area of display device. No DISTORTION is present in viewing area
What is general image quality? involves evaluating overall appearance of pattern - look for dropped pixels (no brightness, appears as a dark space that doesn't change location w/diff images)
What is luminance? verification all 16 luminance patches are distinctly visible from adjacent patches
What is resolution? All letters and numbers are visible
What is ambient light and what is standard? measure illuminance in area where primary reading takes place and ensure it doesn't exceed 4.5foot candles/50lux
Are you able to visually identify a monitor test pattern? Papp p191-194
Describe procedure for QC displays? Papp p 187-188 a- max luminance (luminance response) ; e - luminance dependencies - viewing angle f - spatial/geometric distortion
What is maximum luminance ? (luminance dependencies) - relationship between display luminance and input values from standard display systems (test pattern)
What is luminance dependency? viewing angle between observer and center of display - no less than 80' for LED screen
What is spatial/geometric distortion in QC of displays? verify that pattern lines are recorded accurately - straight lines, perfect squares/circles
What is low contrast resolution of QC displays? verify contrast patterns are visible both in white and black squares; verify proper contrast balance available within image
What is spatial resolution ? Note any differences in visibility of test patterns between horizontal and vertical lines
What is grayscale uniformity? uniformly gray across entire display
What is display artifacts? verify no streaks, lines or dark/light patches; look for small black dots (dropped pixels)
What is display reflection? verify all light coming from display surface has been generated by display device only and no reflected light
Which display is best luminance (brightness)? Plasma; however, we will probably see LCD/CRTs due to cost
What is reject and repeat analysis program (RAP)? systematic process of cataloging rejected images and determine the nature of error to eliminate or minimize going forward. REJECT -
What are the advantages of RAP? increased department efficiency; decreased department cost; decrease patient dose (most important)
What is an artifact? any irregularity on an image that is not caused by proper shadowing of tissue by primary x-ray beam; undesirable optical density or blemish on radiograph
Why do CR artifacts require special attention ? b/c may be produced by CR system itself; users not using proper image techniques or selecting appropriate imaging protocols
Why is using a grid so important in CR? because the IP is very sensitive to scattered radiation
Why should a technologist be concerned about artifacts? artifacts can obscure important anatomy; picture looks bad; cannot be corrected by any image processing algorithm
List some Image Plate artifacts. Papp p 137-139 Phantom image artifact - not properly erased prior to exp; foreign objects - dirt/debris cause light colored specks; Phosphor wear - friction removes part of PSP crystal from IP
What are digital radiography artifacts? positioning errors; collimation errors; backscatter radiation; LUT selection/histogram
are you familiar with appropriate collimation when making more than one exposure on a CR plate? four symmetrical borders; can do three; must be symmetrical and even number of patterns (1,2,4) no more than 4 per plate
Describe exposure artifacts. *motion - involuntary/voluntary *patient artifacts - removable/not removable *improper positioning or anatomy *quantum mottle *double exposure (CR plates) *grid lines/cutoff (angel hair pasta) *Moire effect (Nyquist frequency)
Describe CR / DR artifacts *Heat Blur - CR *Improper image brightness (incorrect algorithm) *Electronic noise *Quantum mottle *Phantom image *Scatter *Dbl exposure *Foreign Objects *Dropped pixel *Halo artifacts
What is heat blur? occurs when plate gets too hot; considered operator error
What is Improper image brightness? incorrect algorithm
What is electronic noise?
Created by: Larobbins