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mAs controls what?
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Review-Image A and E
Image acquisition and evaluation review
| Question | Answer |
|---|---|
| Density (brightness) | amount of blackness on a given area of a radiograph |
| mAs controls what? | quantity of xrays produced |
| kVp controls what? | the energy or quality of xrays produced |
| Contrast | differences in adjacent densities on the radiographic image |
| density may be defined as: | darkness on a radiograph |
| the radiographic image is formed by: | exit rays striking the image receptor |
| the primary controlling factors of density are: | mAs and window level |
| How do you describe the relationship between mAs and density? | density is directly proportional to mAs |
| the number of electrons boiled off the cathode and consequently the number of xrays produced are controlled by: | mAs |
| the law stating that any combinations of mA and time that produce the same mAs value will produce the same radiographic density is the: | reciprocity law |
| the active portion of a CR IP is: | PSP |
| the primary controlling factors of contrast are: | kVp and window width |
| the relationship between kVp and density may be described as: | direct, although not proportional |
| the 15% rule states that: | density may be halved be decreasing kVp by 15% |
| what governs the relationship between SID and density? | inverse square law |
| if SID is doubled, what may be said about radiographic density? | density is reduced to one-fourth |
| if SID is reduced by one-half, what must done to mAs to maintain a constant density? | reduce mAs to one-fourth its original value |
| What can cause poor recorded detail? | Long OID, Large focal spot, patient motion, magnification |
| in digital fluoroscopy, what equipment should be used to view the image? | high-resolution monitor capable of displaying millions of pixels |
| a primary advantage to digital fluoroscopy is: | postprocessing manipulation of the image |
| which of the following describes the relationship between radiographic density and the use of grids? | grids reduce density unless mAs is increased to compensate |
| the use of filtration: | has little effect on density because xrays removed from beam are not image producing rays |
| as beam restriction increase: | density decrease |
| the variation of xray intensity along the longitudinal axis of the xray beam describes: | anode heel effect |
| the thicker part of anatomy should be placed under which aspect of the xray tube? | cathode |
| the function of contrast is to: | make detail visible |
| a radiograph with few gray tones, primarily exhibiting black and white, would be described as having what type of contrast? | high contrast, short scale |
| poorer recorded detail may be caused by which of the following factors? | pixel pitch wide |
| high kVp produces which of the following? | low contrast, long scale, many gray tones |
| low kVp produces which of the following? | high contrast, short scale, few gray tones |
| more uniform penetration of anatomical structures occurs when what level of kVp is used? | high |
| differential absorption of the xray beam is a function of: | photoelectric interaction |
| What effect does beam restriction have on contrast? | increase contrast because of reduction in the number of compton interactions that occur |
| the adjustment in technical factors required when using beam restriction is: | increase mAs to compensate for the number of rays removed from the primary beam |
| what effect does the use of radiographic grids have on contrast? | increase contrast |
| as the amount of beam filtration is increased: | contrast decreases |
| the portion of contrast that is caused by variations in the anatomy or is secondary to pathological changes is called: | subject contrast |
| recorded detail is: | geometric representation of the part being radiographed |
| better recorded detail may be caused by what? | long SID, short OID, small focal spot |
| optimal recorded detail may be created using what? | narrow pixel pitch |
| elongation and foreshortening are examples of: | shape distortion |
| magnification is caused by: | short SID, long OID |
| distortion that occurs when the xray beam is angled against the long axis of a part is: | foreshortening |
| distortion that occurs when the xray beam is angled along the long axis of a part is: | elongation |
| the actual patient dose as measured by a meter embedded in the collimator is: | dose area product (DAP) |
| quality assurance and maintenance of CR cassettes includes cleaning and inspecting the plates at least: | every 3 months |
| quality assurance and maintenance of CR cassettes includes erasing plates at least: | daily |
| quality assurance of digital imaging requires the uniformity of processing codes to ensure: | image appearance consistency |
| a software function that evens the brightness displayed in the image called: | smoothing |
| beam part receptor alignment latitude describes: | the latitude of collimation that still allows the software to detect collimated edges |
| exposure technique in digital imaging may be adjusted by: | increasing kVp |
| digital imaging is more sensitive to: | scatter and background radiation |
| inappropriate collimation causes: | histogram analysis error |
| an artificial increase in display contrast at an edge of the image is: | edge enhancement |
| as speed class increases: | the likelihood of noise increases |
| smoothing software may result in: | loss of fine detail |
| excessive processing of the digital image may: | degrade visibility of anatomy |
| a high SNR provides an image with: | higher spatial resolution |
| quantum noise limits ability to see: | detail |
| grid ratio is defined as: | the ratio of the height of the lead strips over the distance between the lead strips |
| grid frequency is defined as: | the amount of lead in the grid (expressed as the # of lead strips per inch) |
| a grid with lead strips and aluminum interspacers that are angled to coincide with the divergence of the xray beam is called a: | focused grid |
| the range of SIDs that may be used with a focused grid is called: | grid radius |
| the best scatter cleanup is achieved with the use of: | crosshatch grids |
| grid cutoff may be described as: | decreased density on a radiograph as a result of absorption of image forming rays |
| use of the air gap technique: | works because scatter radiation travels in divergent paths and misses the IR as a result of increased OID |
| materials that make flat panel detectors possible are: | amorphous silicon |
| Which of the following maintains image brightness over a wide range of exposures? | automatic rescaling |
| the available gray scale of an imaging system is determined by: | bit depth |
| the smallest exposure change able to be captured by a detector is called: | contrast resolution |
| an indicator of the dose level needed to acquire an optimal image is: | dose area product |
| the useful image acquisition area of an image receptor is: | detector size |
| the smallest resolvable area in a digital imaging device is: | detector element |
| what allows more anatomical structures to be captured during an exposure? | dynamic range |
| the range of receptor exposures that provides a quality image is called: | exposure latitude |
| which of the following is a graphical representation of pixel values? | histogram |
| undesirable fluctuations in brightness are called: | image noise |
| the number of pixels making up the digital image is the: | matrix size |
| the expression of image quality provided by a detector is called: | modulation transfer function (MTF) |
| which of the following terms describes the highest spatial frequency that can be recorded by a digital detector? | nyquist frequency |
| what converts light into a charge? | photodiode |
| the smallest area represented in a digital image is the: | pixel |
| the number of pixels/mm in an image is called: | pixel density |
| the space from the center of a pixel to the center of the adjacent pixel is called: | pixel pitch |
| the process of assigning a value to each pixel to represent a gray tone is called: | quantization |
| a material that absorbs xray energy and emits part of that energy as visible light is called: | scintillator |
| bit depth is equal to: | 2n (n equals the # of bits) |
| receptor exposure | the amount of radiation striking the image receptor |
| 30% rule | to see a difference in density, the mAs must change at least 30% |
| filtration effect on contrast? | increase filtration=lower contrast |
| collimation effect on contrast? | increase collimation=increase contrast |
| units of spatial resolution? | lines pairs per millimeter (lp/mm) |
| what technical factors should be used for wet plaster casts? | increase 15 kVp |
| what technical factors should be used for dry plaster casts? | increase 10 kVp |
| what technical factors should be used for fiberglass cast? | increase 5 kVp |
| what technical factors should be used for iodinated contrast? | not over 70 kVp |
| what technical factors should be used for barium contrast? | not over 100 kVp |
| whats the order of film development? | developer, fixer, wash, dry |
| where do most processor problems with film occur? | developer |
| what temperature should the developer be? | +/- 2 degrees of 95 F/ 35 C |
| the faster the speed of the screen? | the greater the density |
| where is the micro switch located that controls replenishment | near the entrance roller |
| collimation effect on density? | increase collimation=decrease in density |
| how high is the safelight over the processor | 36" |
| does mAs go up or down for a higher grid ratio? | mAs goes up |
| mAs effect on density? | increase mAs=increase density |
| kVp effect on density? | increase kVp=increase density |
| SID effect on density? | increase SID=decrease density |
| grid ratio effect on density? | increase grid ratio=decrease density |
| filitration effect on density? | increase filitration=decrease density |
| anode heel effect on density? | increase anode heel effect=decrease density |
| patient factors effect on density? | increase factors=decrease density |
| kVp effect on contrast? | increase kvp=decrease contrast |
| OID effect on contrast? | increase OID=increase contrast |
| grid ratio effect on contrast? | increase grid ratio=increase contrast |
| patient factors on contrast? | increase factors=decrease contrast |
Created by:
Chrslarsen
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