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