ARRT Image Acquisition and Evaluation 3 — Questions and Answers
Question 1: A grid with a ratio of 16:1 is most appropriate for which clinical scenario?
- Pediatric chest at low kVp
- Large body part requiring high kVp technique (Correct answer)
- Extremity imaging without scatter
- Fluoroscopic spot imaging
Correct answer: Large body part requiring high kVp technique
High-ratio grids (12:1 or 16:1) are used for large anatomical areas where significant scatter is produced, especially at higher kVp settings.
Question 2: Quantum mottle (noise) in digital radiography is primarily caused by which factor?
- Excessive mAs
- Too few X-ray photons reaching the detector (Correct answer)
- High kVp settings
- Large focal spot
Correct answer: Too few X-ray photons reaching the detector
Quantum mottle results from insufficient photon flux reaching the detector, producing a grainy, noisy appearance on the image.
Question 3: Which positioning error causes grid cutoff on a cross-table lateral projection?
- Angling the tube across the grid lines (Correct answer)
- Centering the beam off-axis laterally
- Using a grid with too low a ratio
- Excessive OID
Correct answer: Angling the tube across the grid lines
Angling the tube perpendicular to the grid lines (off-axis in the wrong direction) causes photons to be absorbed, resulting in grid cutoff.
Question 4: On a PA chest radiograph evaluated for proper exposure, which anatomical landmark is used to verify adequate penetration?
- Clear visualization of the carina
- Faint visibility of the thoracic spine through the cardiac shadow (Correct answer)
- Sharp lung markings in the periphery
- Even density bilaterally
Correct answer: Faint visibility of the thoracic spine through the cardiac shadow
Adequate penetration on a PA chest is confirmed when the thoracic vertebrae are faintly visible through the cardiac silhouette.
Question 5: A radiograph exhibits a wide latitude (long scale) of contrast. Which exposure factor most directly caused this?
- Low mAs
- High kVp (Correct answer)
- Short SID
- Small focal spot
Correct answer: High kVp
Higher kVp produces more penetrating, homogenous radiation that results in low contrast (long gray scale) across the image.
Question 6: Which CR/DR artifact appears as a bright or dark line running across the image parallel to the scan direction?
- Ghosting artifact
- Dead pixel cluster
- Detector lag artifact
- Dropout line artifact (Correct answer)
Correct answer: Dropout line artifact
A dropout line artifact occurs when a row or column of detector elements fails, creating a bright or dark line across the image.
Question 7: Which action best reduces magnification of a structure on a radiograph?
- Increase OID
- Decrease SID
- Decrease OID (Correct answer)
- Use a smaller focal spot
Correct answer: Decrease OID
Decreasing OID (object-to-image distance) brings the object closer to the receptor, reducing magnification.
ARRT Image Acquisition and Evaluation 3
A grid with a ratio of 16:1 is most appropriate for which clinical scenario?