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Unit 4 Homework
Terms in this set (34)
What makes singe-phase AC so inefficient when compared to DC is:
a. Single-phase AC voltage does not drop from peak to 0 twice per cycle
b. Single-phase AC voltage displays 0% voltage ripple
c. Single-phase AC voltage does not fluctuate
d. Single-phase AC voltage drops from peak to 0 twice per cycle
The alignment of the bucky center mark and the light field central ray should be within _______ of the SID.
When shielding accessories such as aprons and thyroid shields demonstrate cracks, tears, or holes under fluoroscopy, these accessories should be:
2 and 3
Identify the methods of timer measurement with three-phase and high-frequency equipment.
1. Spinning top test
2. Measurement of solid arc pattern produced by a synchronous top test
2 and 3
While using AEC to image a hyperstenic patient's lateral lumbar spine the backup timer terminates the exposure at 600 mAs and the IR is underexposed. Using AEC and to avoid setting off the backup timer again during the repeat image the technologist could:
1. Adjust the kVp lower
2. Adjust the kVp higher
3. Use a higher mA
1, 2, and 3
If there is incomplete erasure of a previous image on a CR imaging plate:
1. Ghost images are possible
2. Non-uniformity is possible
3. A repeat may be necessary after the next image is taken with this CR imaging plate
Misalignment between the collimator light field and the radiation field must not exceed _______ of the SID per exposure.
1 and 2
An AEC unit can operate on which of the following principles?
1. A photomultiplier tube receives light from a fluorescent screen
2. An ionization chamber is charged by x-ray photons
3. A fluorescent screen and ionization chamber working in tandem
If while using the center AEC cell for a lateral knee radiograph, a part of the cell is exposed to primary radiation due to the anatomic part not being positioned properly over the center cell.
a. The knee will be off-center but correctly exposed
b. The knee will be overexposed
c. The knee will be underexposed
Exposure timer accuracy is evaluated annually and should be within _______ of the indicated time on the console for exposure times greater than 10 ms.
1, 2, 3, and 4
The Society of Motion Picture and Television Engineers (SMPTE) created the SMPTE pattern that is used to evaluate a digital monitor's:
1. Spatial resolution
3. Optical density/brightness
KVp measurements can be made with filtered ion chambers, filtered diodes, voltage diodes, and oscilloscopes. The measured kVp for an exposure should be within _______ of the indicated kVp on the console.
Used to measure digital monitor luminance
A tool used for the measurement of focal spot size include the
a. Pinhole camera
b. Star pattern
c. Slit camera
d. All of these are correct
1, 2, and 3
Given 60 Hz current and an exposure time of .10 seconds, a spinning top test produces a solid arc pattern. This solid arc pattern is consistent with a
1. Three-phase six-pulse generator
2. Three-phase twelve-pulse generator
3. High-frequency generator
The modern AEC configuration relies on the ionization chamber being placed
a. Inside the IR
b. In front of the IR (radiation interacts with the ionization chamber first)
c. Behind the IR (radiation interacts with the IR first)
d. At the level of the collimator assembly
The voltage waveform that most closely resembles DC is created by which generator type?
If while using the AEC an AP projection of a patient's hip appears underexposed and a surgical prosthesis is visible. For the repeat exposure the technologist can
a. Lower the kVp for a correctly exposed image
b. Adjust the density control setting to -3
c. Raise the kVp for a correctly exposed image
d. Adjust the density control setting to +3
A spinning top test produces 5 more pulses than was expected. These extra pulses represent a malfunctioning timer and are consistent with IR __________________.
Of the x-ray generators listed below, select the one that would generate the lowest exposure to the IR if the kVp/mAs was kept exactly the same for each generator exposure.
a. Single-phase, half-wave rectified
c. Three-phase, twelve-pulse
d. Single-phase, full-wave rectified
AEC backup timer
Is a separate timer used as a safety measure to end the exposure if the AEC fails to do so
Half value layer
Measuring a general purpose radiographic unit's filtration requires the measurement of the x-ray beam's:
The voltage ripple associated with a three-phase, twelve-pulse rectified generator is
If while imaging a patient for a PA chest projection using AEC the technologist selects the center cell instead of the two side cells. Describe the amount of exposure to the air filled lungs.
a. The radiation exposure will be too low for the air filled lungs
b. The radiation exposure will be optimal for the air filled lungs
c. The radiation exposure will be appropriate for the air filled lungs
d. The radiation exposure will be too high for the air filled lungs
1 and 3
While imaging a 100 year old, 80 pound patient for a lateral chest using AEC, two consecutive images are overexposed. The technologist decides the MRT is too slow and she can alleviate this issue on the next repeat image using AEC by
1. Lowering the mA station
2. Increasing kVp
3. Decreasing kVp
A device used to ensure reproducible radiographs, regardless of tissue-density variations is the:
Exposure linearity and exposure reproducibility should be evaluated how often?
When DC is graphed while in the on phase, the voltage ripple displayed is:
Of the x-ray generators listed below, select the one that would generate the highest average photon energy per exposure if the kVp/mAs were kept exactly the same for each generator exposure.
a. Three-phase, twelve-pulse
c. Single-phase, full-wave rectified
d. Single-phase, half-wave rectified
1 and 2
The AEC minimum response time (MRT) may be defined as the quickest exposure time that an x-ray generator will allow. Exposure times that are less than the MRT may occur when
1. Using a high mA station
2. Imaging small body parts
3. Imaging large body parts
A technologist images an AP lumbar spine using AEC. He neglects to select the center AEC cell and leaves the two side cells energized from the previous exam done in this room. The resulting image will most likely demonstrate
a. A properly exposed lumbar spine
b. An underexposed lumbar spine
c. An overexposed lumbar spine
It would be longer
A technologist using AEC equipment makes an image of a lateral lumbar spine with wide open collimation and no lead strip behind the patient's back. The same technologist using the same AEC equipment makes the same lateral lumber spine image on the same patient but this time he/she collimates appropriately and uses a lead strip behind the patient's back. How would the second image's exposure time differ from the first image's exposure time?
would be longer
Using AEC, a technologist images a patient's L5/S1 joint space using a 10x12 IR with wide open collimation and the image is diagnostic. The same exam is repeated with all factors remaining the same except the technologist collimates closely to decrease scatter production. The exposure time for the second image:
It's essential function is to Terminate the x-ray exposure once the IR is exposed correctly
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