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electronic sys
electronic systems
| Question | Answer |
|---|---|
| DR console | exam list screen (worklist)- patient data |
| DICOM header | make sure correct pt. information bar coding and HIPAA compliance |
| LUT | look up table which is the grayscale rendered image that comes up. default gradient curve or code applied to the data set of your image determining the initial display. can be adjusted by changing window width or range after initial processing. |
| contrast | black white gray scale |
| patient histogram | selects projection. organ function -DR tag-CR- must match with bar code on cassette when scanned by bar code reader before processing in IRD (image reader device/dry processor) |
| histogram | data set, in a graphical form, of the pixel value vs. the prevalence number of those values in the image |
| horizontal axis | pixel exposure mR (milliroengten)- exposures in the air |
| vertical axis | incidence of those values # pixels/exposure |
| histogram cont. | identifies all densities on IP a graph that displays signal value series of peaks and valleys pattern varies for body part |
| automatic re-scaling | auto-ranging or normalization software that adjusts gray scale to values of interest (VOI)in histogram. provides density/brightness at a prescribed level over large range of exposures. must check expo index to assure no over expo to pt. ALARA |
| VOI | values of interest |
| histogram analysis | collimation is very inportant. if device cannot find collimation edges it will include all exposure on the histogram. histogram used is compared to body part histogram stored in computer |
| image acquisition errors | exposure field recognition. inappropriate collimation margins or beam alignment. histogram analysis and rescaling errors. wrong histogram or collimation use auto rescaling will not work |
| beam part alignment latitude | software must detect collimated edges for proper histogram analysis. histogram and rescaling errors can result in repeats |
| proper reading | requires proper centering and proper collimation. |
| fields need to be | centered to plate segment and there needs to be clean collimation margins between fields and between edge of field and plates edge |
| noise | graininess (quantum mottle)caused by low mas. contrast is also lost |
| S:N Ratio | signal- patient information noise- graininess or salt n pepper appearance you want a high S:N = C:N (contrast to noise) |
| fourier transformation | mathematical method to convert data,permits reconstruction of portions of data when other portions and there relationships are known. used to demonstrate diff attenuation coefficients (LAC/MAC) |
| inverse fourier transformation | allows for inverting of an image |
| LAC | linear attenuation coefficient |
| MAC | mass attenuation coefficient, depends on state of matter |
| smoothing or low pass filtering | software function to reduce the appearance of noise but causes loss of fine detail |
| edge enhancement or high pass filtering | artificial increase in contrast at the edge of structures |
| DV | diamond view (DR) |
| equalization | software function that evens out density on anatomy of different thicknesses |
| stitching | software that allows RT to place images together if too long for IR (scoliosis) |
| shuttering/masking | automatic or manual black border, black mask, collimation. minimizes eye fatigue. must be applied outside beam restricted border |
| pixel shifting (linear translation) | computer shifts pixel values. overcomes patient motion as avoids misregistration |
| grid | accessory device made up of radiopaque lead alternating strips of radiolucent material |
| when are grids used and what is the function? | used when more than 60 kvp is used or part is greater than 10 cm thick. grid cleans up and reduces scatter; scatter looks grey |
| grid artifact | aliasing moire-parallel motion of grid is equal to the frequency of the scanning of the grid by the electronic imaging system |
| aliasing or moire patterns are caused by what? | low frequency grids |
| window level | controls brightness/ direct relationship |
| window width | controls gray scale/ inverse relationship gray scale expansion or compression |
| EXI | exposure index indicator |
| critique | image accuracy |
| plate/ flat panel detector maintenance | cleaning/charging |
| reject analysis | continously evaluates/looks to see if images are consistantly over or under exposed. |
| system malfunctions | dead pixels (maintenance) readout problems (maintenance) printer distortion (laser) |
Created by:
eckoultd1972
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