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RSC1101FINAL2
Chapter 11 and 13 kahoot
| Question | Answer |
|---|---|
| AEC devices work by measuring: | exit radiation |
| What exposure system operates by ionizing air that creates an electrical charge? | ionization chamber |
| During the operation of the AEC device, the time of exposure is ____(directly, inversely) related to the intensity of exit radiation. | directly |
| What are 3 important factors to consider when using AEC devices? | 1. detector selection 2. centering part to detector 3. backup mAs |
| Increasing the pt thickness while using an AEC device would result in: | increased exposure time |
| Primary goal of exposure technique charts? | consistency in image quality |
| What exposure technique system uses a fixed mAs regardless of pt thickness? | variable kVp |
| What is the most important when using a technique chart? | accurately measure pt |
| An advantage of the variable kVp technique chart is that it | makes smaller technique changes possible |
| Which 2 considerations may require a decrease in mAs? | soft tissue exam and pediatric pt |
| Which 3 considerations may require an increase in mAs? | 1. contrast medium 2. bariatric pt 3. tissue edema |
| Which AEC device uses light paddles, coated with a fluorescent material to convert light to electricity? | phototimers |
| (T/F): A PMT is the only device used by a phototimer to convert light energy into electricity. | False- also uses photodiode |
| A hollow cell that contains air and is connected to the timer circuit via an electrical wire. | ionization chamber |
| Detectors positioned behind the IR so that radiation must exit the IR before it is measured by the detectors. | exit type device |
| (T/F): Ionization chambers are exit-type devices. | False- phototimers are exit-type |
| 3 other terms for AEC detectors? | 1. sensors 2. chambers 3. cells |
| Displays actual amount of mAs used for the image: | mAs readout |
| (T/F): AEC controls only the quantity of radiation reaching the IR and therefore has no effect on contrast. | True |
| A low kVp requires ___ exposure time to reach the predetermined amount of exposure. | more |
| Increasing mA ___ exposure time to reach the predetermined amount of exposure. | decreases |
| (T/F): The minimum response time with most modern AEC systems is 1 ms. | True |
| The maximum length of time the XR exposure continues when using an AEC system: | backup time |
| (T/F): The backup time should be set at 150-200% of the expected exposure time. | True |
| Tool that allows the RT to adjust the amount of preset radiation detection values: | exposure adjustment |
| (T/F): The density control numbers change exposure time by some predetermined amount or increment expressed as a percentage. | True |
| (T/F): The size of the detectors within an AEC system can be adjusted by the RT. | False |
| (T/F): Accurate centering of the AOI over the detectors is critical to ensure proper exposure to the IR. | True |
| If the AOI is thicker due to pt size, the exposure time will ___ to reach the preset exposure. | lengthen |
| An XR field size that is collimated too closely will ___ exposure time, resulting in ___. | increase; overexposure |
| (T/F): Different types of IRs can be interchanged easily once an AEC device is calibrated. | False |
| A pre-programmed set of exposure factors displayed and selected for use on the control panel: | anatomically programmed technique |
| Manual exposure techniques should be used for what 4 factors? | 1. pediatric pts 2. anatomic parts that do not adequately cover the detectors 3. pathology 4. contrast media |
| Reproducibility of exposures and selected detector should result in mR readings within ___. | 5% |
| Pixel brightness levels for areas within the displayed image should be within ___. | 30% |
| Pre-established guidelines used by the RT to select standardized manual or AEC exposure factors for each exam: | exposure technique charts |
| 3 variables on a technique chart? | 1. kVp 2. mAs 3. grid |
| Devices that measure part thickness: | calipers |
| Based on the concept that kVp can be increased as the anatomic part size increases: | variable kVp-fixed mAs |
| The baseline kVp is increased by ___ for every ___ cm increase in thickness when using variable kVp-fixed mAs charts. | 2; 1 cm |
| Concept of selecting an optimal kVp that is required for the exam and adjusting the mAs for variations in thickness: | fixed kVp-variable mAs |
| kVp that is high enough to ensure penetration of the part but not too high to diminish subject contrast: | optimal kVp |
| For fixed kVp-variable mAs charts, for every ___ cm change in part thickness, mAs should be adjusted by a factor of ___. | 4-5 cm; 2 |
| The concept that different parts of the same size can be radiographed by use of the same exposure factors: | comparative anatomy |
| Exposure techniques may need to be ___ for pts who appear thin and frail. | decreased |
| (T/F): Pediatric imaging requires long exposure times. | False |
| (T/F): Fiberglass casts require an increase in exposure factors, whereas plaster casts do not. | False |
| Conditions that increase the absorption characteristics of the part, making the part more difficult to penetrate: | additive diseases |
| When imaging pathologic conditions, which exposure factor is routinely adjusted? | kVp |
| Destructive diseases require a(n) ___ in kVp. | decrease |
| Positive contrast media appear ___ on a RG image and require a(n) ___ in exposure factors. | white; increase |
| A bowel obstruction is considered a(n) ___ disease. | destructive disease |
| A pleural effusion is considered a(n) ___ disease. | additive |
| What type of relationship does mAs have with the exposure reaching the IR? | direct |
| What describes the relationship between mA and exposure time to maintain exposure to the IR? | inverse |
| Increasing the mAs has ___ effect on brightness displayed in digital imaging. | no |
| given the anatomic part is adequately penetrated, changing the kVp will affect: | both Compton scattering and subject contrast |
| Which of the following factors do not affect spatial resolution? | grid |
| The amount of remnant radiation will decrease when increasing ___. | tissue thickness |
| What factor affects the amount of radiation and scatter reaching the IR, magnification, and spatial resolution? | OID |
| How is the primary beam affected when increasing the tube filtration? | increase in the proportion of higher energy XRs |
| What happens when the tube alignment is not parallel with the object and IR? | shape distortion |
| 3 primary exposure factors: | 1. mA 2. kVp 3. exposure time |
| (T/F): Changing the kVp affects the quantity and the quality of the beam. | True |
| A high kVp results in ___ variation in XR intensities exiting the pt | less |
| SOD can be determined by: | SID - OID |
| For every ___ of part thickness, the RT should adjust the mAs by a factor of 2 | 4-5 cm |
| The radiographic grid is located: | between the pt and the IR |
| Increased quantum noise is seen in a digital image with: | mAs that is excessively lower than needed |
| Increasing part thickness ___ radiographic contrast. | decreases |
| Magnification is affected by what 2 factors? | SID and OID |
| Increasing tube filtration results in an XRB with | higher energy and fewer photons |
| What effect will increasing SID have on spatial resolution? | increased spatial resolution |
| How much change in kVp will change the radiation exposure to the IR by a factor of 2? | 15% |
| (T/F): When choosing a grid for an exam, the grid with the highest grid ratio will improve contrast and decrease pt dose. | False- high ratio grid will increase pt dose |
| During selection of the focal spot size, the RT is really determining the: | actual size of filament used |
| What quality factor is not affected by a change in SID? | contrast |
| Decreasing collimation results in ___ scatter, ___ patient exposure, and ___ image contrast. | more; more; less |
| With all factors remaining the same, a pt with which body habitus requires the highest exposure factors? | hypersthenic |
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