Term
| what is the primary controlling factor for contrast |
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Definition
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Term
| which of the two types of contrast exhibit wide exposure latitude? |
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Definition
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Term
| what influences image receptor (film) contrast |
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Definition
| characteristics of the film and processing |
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Term
| what determines subject contrast |
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Definition
| size, shape, and attenuating charateristics of the material being irradiated |
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Term
| how does tighter collimation affect contrast? |
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Definition
| tighter collimation reduces the number of photons available, thus reducing the amount of scatter and increasing contrast (shortens the scale of contrast) |
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Term
| what change in kVp is needed to make a visible change in contrast |
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Definition
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Term
| when making contrast changes on a radiograph, what changes in kVp should be made |
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Definition
| changes should be made in increments of 8 or 15% |
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Term
| what is the controlling factor for density? |
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Definition
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Term
| what factors secondarily influence density |
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Definition
| kVp, distance, beam restriction, anatomic part, grid, film/screen combination, processing, anode heel effect |
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Term
| what effect does SID have on density |
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Definition
| as SID increases, density decreases |
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Term
| what percent change in mAs makes a visible difference in density |
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Definition
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Term
| how does beam restriction affect density |
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Definition
| it reduces the amount of scatter radiation and therefore reduces the overall density of the image |
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Term
| how does tissue thickness affect density |
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Definition
| there is an inverse relationship; as tissue thickness, average atomic number, and/or tissue density increases, radiographic density decreases. |
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Term
| which formula should be used to maintain density when making distance changes |
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Definition
the density maintenance formula
mAs1/mAs2 = D1 squared/D2 squared |
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Term
| how does film processing affect density |
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Definition
density increases as developer temperature, immersion time or replenishment rates increase
contaminated developer will decrease density |
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Term
| what are the two factors that control size distortion (magnification) |
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Definition
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Term
| how does SID affect size distortion |
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Definition
| as SID increases, size distortion decreases |
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|
Term
| how does OID affect size distortion |
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Definition
| as OID increases, size distortion increases |
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Term
| what factor causes foreshortning of an object |
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Definition
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Term
| what factors cause elongation of the radiographic image |
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Definition
| misalignment of the tube or film |
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Term
| how does OID (object-to image receptor distance) affect recorded detail |
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Definition
| recorded detail improves as OID decreases |
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|
Term
| how does SID (source-to-image-receptor distance) affect recorded detail |
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Definition
as SID increases, recorded detail increases. as SID decreases, recorded detail decreases.
shorter SIDs cause an increase in magnification, thus causing a decrease in recorded detail. |
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Term
| how does focal spot size affect recorded detail |
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Definition
| there is an increase in recorded detail as focal spot size decreases |
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Term
| how does target angle affect effective focal spot size |
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Definition
| the smaller the target, the smaller the effective focal spot size |
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|
Term
| how many inches must the SID be increased to compensate for each increase of 1 inch in OID |
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Definition
| an increase of 7 inches of SID is required for every 1 inch of OID |
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|
Term
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Definition
| the invisible image induced in the silver halide crystals |
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|
Term
| where should radiographic film be stored |
|
Definition
| in a cool, dry place (not in excess of 68 degrees F) between 40 and 60% |
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|
Term
| how should radiographic film be stored? |
|
Definition
| on edge, rather than lying flat |
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|
Term
| what causes static artifacts |
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Definition
| static electricity caused by low humidity |
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|
Term
| what causes small white spots on a radiograph |
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Definition
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|
Term
| how will dust and scratches on an intensifying screen appear on a finished radiograph |
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Definition
| there will be little or no density in those areas |
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|
Term
| film should be stored at what humidity |
|
Definition
between 40% and 60%
above 60% reduces contrast and increases fog
under 40% and static results |
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Term
| what factor determines whether aan artifact is a minus-density artifact or a plus density artifact |
|
Definition
whether the artifact was caused before or after exposure
(if it was before exposure a minus density usually results, after exposure a plus density artifact) |
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|
Term
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Definition
| it is the emulsions ability to record a long range of densities from black to white (long scale contrast) |
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|
Term
| what factors cause film fog |
|
Definition
| outdated film, excessive safelight exposure, excessive processor temperature. |
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|
Term
| which type of safelight is safe with green sensitive film emulsion |
|
Definition
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|
Term
| which type of safelight should be used with blue sensitive film |
|
Definition
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|
Term
| what is the proper safelight distance from the working area in a darkroom |
|
Definition
| 3-4 feet from feed trays or loading counters |
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|
Term
| what kind of artifact results from dirty or warped rollers |
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Definition
| dirty or warped rollers can cause emulsion pick off and gelatin buildup, which results in sludge deposits on films. |
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|
Term
| what causes chemical fog on radiographic film |
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Definition
| improper or inadequate processing chemistry (the chemical fog is called a diachroic stain) |
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|
Term
| what causes guide shoe marks on a film |
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Definition
| sprung or improperly positioned guide shoes (guide shoe lines run the same direction as the film) |
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|
Term
| what is the cause of PI lines on a film |
|
Definition
| dirt or chmical stain on a roller causes PI lines (the lines occur 3.1416 inches apart because a roller is 1 inch in diameter) |
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|
Term
| what determines film resolution |
|
Definition
| the size of the silver halide crystals |
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|
Term
| what type of relationship exists between film resolution and crystal size |
|
Definition
| inverse-the smaller the crystals the higher the resolution, the larger the crystals the lower the resolution |
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|
Term
| how should laser film be handled in the dark room |
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Definition
| since laser film is sensitive to all light most has to be handled in total darkness |
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|
Term
| as a general rule when should a grid be used |
|
Definition
| when body part thickness exceeds 10 cm and tissue density is primarily soft tissue and bone; kVp above 60 |
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|
Term
|
Definition
| the ratio of the height of the lead strips to the distance between them |
|
|
Term
|
Definition
| the number of grid strips or grid lines per inch or per cm |
|
|
Term
| what is the average grid frequency |
|
Definition
| 85-103 lines per inch (22 to 41 lines per cm) |
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|
Term
| what is the disadvantage of parallel grids |
|
Definition
| grid cutoff occurs at short distances (they function best at long distances) |
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|
Term
| what is the major disadvantage of a crosshatch grid |
|
Definition
| they require accurate alignment of the CR and do not allow for angulation |
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|
Term
| what are the limitations of the focused grid |
|
Definition
| their use is limited to a specific SID range |
|
|
Term
| define the term grid focusing distance |
|
Definition
| distance from the lead strips of a focused grid to the point where they converge |
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|
Term
| which grids have higher contrast improvement factor |
|
Definition
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|
Term
| what is meant by selectivity of a grid |
|
Definition
| grids that absorb a greater percentage of scatter than primary radiation are described as having a greater degree of selectivity |
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|
Term
| what factor primarily influences the selectivity of a grid |
|
Definition
| lead content (the more lead, the more effective clean up of scatter) |
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|
Term
| when do grid lines appear on a radiograph |
|
Definition
| when the lead strips attenuate the primary beam are imaged on the radiograph |
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