Radiography Exam ARRT Radiography 3 — Questions and Answers
Question 1: What is the primary purpose of using automatic exposure control (AEC) in radiography?
- To select the optimal kVp
- To terminate exposure when sufficient radiation reaches the detector (Correct answer)
- To reduce heat units on the anode
- To automatically collimate the beam
Correct answer: To terminate exposure when sufficient radiation reaches the detector
AEC detects radiation reaching the detector and terminates the exposure once a preset charge is reached, ensuring consistent image density.
Question 2: A radiograph of the lumbar spine appears too light (underexposed). Which single change will most effectively increase radiographic density?
- Increase SID by 10 cm
- Increase mAs by 50% (Correct answer)
- Decrease grid ratio
- Switch to a smaller focal spot
Correct answer: Increase mAs by 50%
mAs directly controls the quantity of x-ray photons produced; increasing mAs proportionally increases image density.
Question 3: Which projection of the sacroiliac joints places both joints equidistant from the image receptor?
- AP axial with 30° cephalad angle
- Posterior oblique (30° rotation) (Correct answer)
- Lateral decubitus
- AP with 15° caudal angle
Correct answer: Posterior oblique (30° rotation)
A 30° posterior oblique (LPO or RPO) rotation places one sacroiliac joint parallel to the image receptor for optimal visualization.
Question 4: Under ALARA principles, which of the following is a primary method to reduce patient dose in fluoroscopy?
- Using pulsed fluoroscopy (Correct answer)
- Increasing the kVp to maximum
- Using a larger field of view
- Increasing fluoroscopic frame rate
Correct answer: Using pulsed fluoroscopy
Pulsed fluoroscopy delivers x-rays in brief pulses rather than continuously, significantly reducing patient and operator dose.
Question 5: Which artifact appears as thin, sharp lines parallel to the long axis of the grid, caused by damage to grid strips?
- Moiré pattern
- Grid cutoff
- Grid lines (Correct answer)
- Pseudofocal cutoff
Correct answer: Grid lines
Damaged or improperly aligned grid strips cause grid lines to appear as parallel white lines on the radiographic image.
Question 6: The anatomical structure located at the level of T4-T5 that serves as a landmark for chest radiography is the:
- Carina
- Aortic arch (aortic knuckle) (Correct answer)
- Right hemidiaphragm
- Clavicular notch of the sternum
Correct answer: Aortic arch (aortic knuckle)
The aortic arch (aortic knuckle) is found at the T4-T5 level and is a key landmark on the PA chest radiograph.
Question 7: Which federal regulation requires that the x-ray beam be collimated to no larger than the size of the image receptor?
- NRC 10 CFR 20
- 21 CFR 1020.30–1020.33 (CDRH) (Correct answer)
- OSHA 29 CFR 1910
- NCRP Report 116
Correct answer: 21 CFR 1020.30–1020.33 (CDRH)
21 CFR Part 1020 (administered by the FDA/CDRH) sets federal performance standards for diagnostic x-ray equipment including beam limitation.
Radiography Exam ARRT Radiography 3
What is the primary purpose of using automatic exposure control (AEC) in radiography?