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image quality test
| Question | Answer |
|---|---|
| what does the inverse square law state | the intensity of radiation is inversely related to the distance from the source squared |
| radiographic density | degree of blackening or opacity of an area in a radiograph due to the accumulation of black metallic silver following exposure and processing film |
| how much of a change in mAs is required for there to be a noticeable density change on a radiograph | 30% |
| brightness | measurement of the luminance of a monitor or soft copy calibrated in units of candela per square meter |
| what are the controlling factors of density/brightness of a radiograph | -mA -SID -post processing for CR/DR |
| what technical factor has a significant influence on density/brightness of a radiograph(15% change will half or double density) | kVp |
| what are the influencing factors of density brightness | -kVp(significant) -focal spot size -anode heel effect -SID/OID -Inverse Square Law -filtration -beam restriction -part -pathology -grids -film/screen combo -automatic processing |
| what is the reciprocity law | density on an image should remain unchanged as long as mAs is constant |
| radiographic contrast | visible density differences between any two selected areas of density levels within the radiograph |
| the display of contrast on an image is primarily determined by what during processing | default algorithm |
| bit depth | determines the number of shades of gray that can be visualized(2 to the nth) |
| what is the technical factor controls contrast | kVp |
| what are the factors that influence contrast | -subjec(size, shape, pathology, type of tissue -film -receptor(dynamic range and quantization) -scatter -grid -collimation -over/under exposed -mAs -SID -OID -filtration |
| what is recorded detail | sharpness of the structural lines as recorded in the photograph |
| what is spatial resolution | sharpness of structural edges recoreded in the image |
| what technical factors affect recorded detail/spatial resolution | -motion/time -OID -SID -focal spot siz -IR |
| what is visibility of detail | anything that affects contrast or density on an image |
| umbra | distinctly sharp area of a shadow |
| penumbra | imperfect, unsharp shadow surrounding the umbra |
| what are two types of distortion | -size -shape |
| what is size distortion | -magnification-deviation from true size(controlled by SID and OID) - |
| what is shape distortion | -deviation from true shape *controlled by angle of part or tube |
| what are the additive pathologies we discussed. | -ascites -atelectasis -cirrhosis -metastases -pleural effusion -pneumonia |
| what are the destructive pathologies we discussed | -bowel obstruction -emphysema -osteoporosis -pneumothorax |
| higher atomic # will give more _______ | density |
| what are the ways that cancer spreads | -blood -lymph -seeding |
| what is the log base formula used by the densitometer to measure density | log 10=Io incident light/ It transmitted light |
| what is the anode/heel effect | absorption of xrays in the heel of the target, resulting in reduced xray intensity to the anode side of the central axis. |
| what are the options for kVp without a grid vs. with a grid | *5:1=+8-10 *8:1=+13-15 *12:1=+20-25 *15:1=+30-40 |
| what is the kVp rule | a 15% change in kVp(about 10) requires you to double or half your mAs to maintain density |
| what can bit depth be limited by | dynamic range and quantization |
| quantization | bits per pixel |
| dynamic range | range of exposures possible by a detector |
Created by:
bigad1982
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