ARRT Scan Protocols 2 — Questions and Answers
Question 1: When performing a CT pulmonary angiography (CTPA), which scan direction is preferred?
- Caudal to cranial (Correct answer)
- Cranial to caudal
- Bidirectional
- Either direction equally
Correct answer: Caudal to cranial
Caudal-to-cranial scanning in CTPA ensures the densest contrast bolus reaches the pulmonary arteries during image acquisition.
Question 2: A CT enterography protocol differs from a standard abdominal CT primarily in which way?
- Use of oral contrast to distend the small bowel (Correct answer)
- Higher tube current for better resolution
- Intravenous contrast is not used
- Scanning only the large intestine
Correct answer: Use of oral contrast to distend the small bowel
CT enterography uses large volumes of neutral oral contrast (e.g., VoLumen) to distend and visualize the small bowel mucosa.
Question 3: Which scan phase best demonstrates hepatic metastases that are hypervascular?
- Non-contrast phase
- Hepatic arterial phase (Correct answer)
- Portal venous phase
- Delayed phase
Correct answer: Hepatic arterial phase
Hypervascular metastases enhance avidly during the hepatic arterial phase when liver parenchyma enhancement is low, maximizing lesion-to-liver contrast.
Question 4: For a CT-guided biopsy protocol, which parameter is typically reduced to minimize patient dose during the procedure?
- Slice thickness
- Tube voltage (kVp)
- Tube current (mA) (Correct answer)
- Gantry rotation speed
Correct answer: Tube current (mA)
Fluoroscopic CT guidance uses low-mA (fluoroCT) settings to reduce cumulative dose while maintaining adequate image quality for needle visualization.
Question 5: A standard high-resolution CT (HRCT) chest protocol uses which reconstruction approach to evaluate interstitial lung disease?
- Thick slices with soft tissue kernel
- Thin slices with high-frequency (sharp) kernel (Correct answer)
- Thick slices with bone kernel
- Thin slices with soft tissue kernel
Correct answer: Thin slices with high-frequency (sharp) kernel
HRCT uses thin slices (≤1.5 mm) with a high-spatial-frequency kernel to maximize edge detail of lung parenchyma and airways.
Question 6: In a renal stone protocol CT, intravenous contrast is typically:
- Administered in a split-bolus technique
- Not administered (Correct answer)
- Administered before scanning only
- Administered after scanning only
Correct answer: Not administered
Non-contrast CT is the gold standard for detecting urolithiasis because stones are visible without IV contrast and contrast can obscure small calculi.
Question 7: Which of the following best describes a 'dual-phase' liver CT protocol?
- Non-contrast and delayed phases only
- Arterial and portal venous phases (Correct answer)
- Portal venous and delayed phases only
- Non-contrast and arterial phases only
Correct answer: Arterial and portal venous phases
A dual-phase liver protocol acquires images in both the hepatic arterial phase and the portal venous phase to characterize liver lesions.
ARRT Scan Protocols 2
When performing a CT pulmonary angiography (CTPA), which scan direction is preferred?