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RAD 147
DR/Scatter
| Term | Definition |
|---|---|
| grid frequency | the number of lead lines per in or cm |
| compared to lover kVp exposures, using a higher kVp will result in a scattered photon with ___ energy | higher |
| grid ratio | height of the lead strips/distance between the strips |
| amorphous silicon | photodetector for indirect DR imaging |
| two major factors that affect the amount of scatter radiation produced and exiting the pt are: | volume of the tissue irradiated & kVp |
| PSP plates are read using: | helium neon laser |
| a grid should be used when imaging tissue that is greater than ___ thick | 10 cm |
| increasing collimation results in: (2) | smaller field size & higher contrast |
| aperture diaphragm | the simplest type of beam restricting devices, a flat piece of lead with a hole in it |
| the purpose of automatic collimation is to: | limit pt exposure |
| scintillator | a material that absorbs x-ray energy and emits visible light in response |
| at a higher kVp, ___ interactions occur overall | fewer |
| of those that occur at a higher kVp, a greater percentage are ____ interactions | compton |
| Benefits of compression devices include: lower patient dose, lower SNR, increased photoelectric absorption, reduced scatter production, increased scatter production | lower pt dose & reduced scatter production |
| Which of the following produces the greatest amount of scatter radiation exiting the patient? Low kVp and small field size. Low kVp and large field size. High kVp and small field size. High kVp and large field size. | high kVp & lg field size |
| linear grid | has lead strips that travel in one direction. |
| cesium iodide. | The scintillator for the indirect capture DR system that utilizes a CCD |
| barium fluorohalide | The type of phosphor found in the PSP plate for computed radiography |
| off-center cutoff | when the x-ray beam is not lined up with the center of the grid |
| Which of the following is (are) a result of grid usage? improved contrast, decreased receptor exposure, increased receptor exposure, reduced patient dose | improved contrast & decreased receptor exposure |
| Grids absorb scatter radiation because the scattered photons | travel at an angle to the transmitted photons. |
| histogram | a graphical representation of the amount of radiation that stuck the IR |
| focused grid | lead strips are angled to match the angle of divergence in the primary beam. |
| photomultiplier | The part of the reader that senses the light released from the PSP plate |
| A significant amount of collimation will have what effect on the amount of radiation reaching the IR | reduced |
| Variable-aperture | The most commonly used beam restriction device |
| To compensate for the reduction of radiation reaching the IR when a grid is used, ___________ is typically increased. | mAs |
| dynamic range/exposure latitude | The range of exposure intensities/values an IR system can accurately detect |
| contrast resolution | the ABILITY of the imaging system to distinguish between objects that attenuate the x-ray beam |
| bit depth | controls the contrast resolution |
| another word for noise | quantum mottle |
| what are the three forms of ionizing radiation? | thin high band of UV light, x-rays, gamma |
| what does lambda represent? | wavelength |
| FSS | the physical area where xrays are created |
| use grid when patient body part is ___ thick | >10 cm thick |
| as filtration increases, RE ___ | decreases, filtration up-quantity down-re down |
| AMA | active matrix array |
| digital imaging system dynamic range benefits | better contrast, more shades of grey, sensitive to low levels of radiation & can take high exposure levels, can use a lower mAs |
| film imaging system dynamic range | narrow, non linear |
| digital imaging system dynamic range | wide, linear |
| SIGNAL-to-NOISE RATIO | Describes strength of exposure to amount of noise present in an image, Need adequate signal to create quality images, High SNR: more signal than noise; better quality |
| CONTRAST-to-NOISE RATIO | Describes contrast resolution compared to amount of noise present in image, High CNR will allow better visualization of anatomic tissues |
Created by:
taetay5831