ARRT Contrast Media 3 — Questions and Answers
Question 1: What physiologic mechanism underlies contrast-induced nephropathy (CIN)?
- Immune-mediated glomerulonephritis triggered by iodine
- Renal medullary ischemia and direct tubular cell toxicity from contrast (Correct answer)
- Obstructive uropathy from contrast precipitation in the collecting ducts
- Systemic vasodilation leading to prerenal azotemia
Correct answer: Renal medullary ischemia and direct tubular cell toxicity from contrast
CIN results from renal medullary vasoconstriction causing ischemia combined with direct cytotoxic effects of contrast on tubular epithelial cells.
Question 2: A 55-year-old patient develops generalized urticaria approximately 5 minutes after IV contrast injection. This reaction is best classified as:
- A physiologic reaction due to contrast osmolality
- A mild acute allergic-like (anaphylactoid) reaction (Correct answer)
- A severe anaphylactic reaction requiring epinephrine
- A delayed hypersensitivity reaction
Correct answer: A mild acute allergic-like (anaphylactoid) reaction
Generalized urticaria without systemic involvement (no bronchospasm or hypotension) represents a mild acute allergic-like reaction, typically treated with antihistamines.
Question 3: For a CT abdomen/pelvis with IV contrast, what is the typical scan delay after contrast injection to capture the nephrographic phase of the kidneys?
- 10–15 seconds
- 25–35 seconds
- 80–120 seconds (Correct answer)
- 3–5 minutes
Correct answer: 80–120 seconds
The nephrographic phase occurs approximately 80–120 seconds post-injection, when the renal cortex and medulla enhance uniformly, optimizing detection of renal masses.
Question 4: Which patient condition is an absolute contraindication to intravascular iodinated contrast media administration?
- History of mild contrast allergy treated with antihistamines
- Previous severe anaphylactic reaction to iodinated contrast without premedication (Correct answer)
- Serum creatinine of 1.2 mg/dL
- Age over 70 years
Correct answer: Previous severe anaphylactic reaction to iodinated contrast without premedication
A prior severe anaphylactic contrast reaction is a contraindication unless the patient is premedicated and the benefit outweighs the risk; the radiologist must be involved.
Question 5: What is the recommended IV injection rate range for a CT angiography of the aorta using a power injector?
- 0.5–1.0 mL/sec
- 1.0–2.0 mL/sec
- 3.0–6.0 mL/sec (Correct answer)
- 8.0–10.0 mL/sec
Correct answer: 3.0–6.0 mL/sec
CTA of the aorta typically requires injection rates of 3–6 mL/sec to achieve sufficient intravascular iodine concentration for diagnostic arterial enhancement.
Question 6: A delayed adverse reaction to iodinated contrast media most commonly occurs within what timeframe after injection?
- Within 1 minute
- 1–60 minutes
- 1 hour to 1 week (Correct answer)
- More than 2 weeks
Correct answer: 1 hour to 1 week
Delayed adverse reactions, often skin reactions such as rash or urticaria, typically occur between 1 hour and 1 week after contrast administration.
Question 7: When using bolus tracking for a contrast-enhanced CT aorta study, where is the region of interest (ROI) typically placed to trigger scanning?
- Pulmonary artery
- Left ventricle
- Descending aorta at the level of the diaphragm or ascending aorta (Correct answer)
- Inferior vena cava
Correct answer: Descending aorta at the level of the diaphragm or ascending aorta
For aortic CTA, the ROI for bolus tracking is placed in the aorta (ascending or at the diaphragm level) to trigger acquisition when contrast reaches the threshold HU.
ARRT Contrast Media 3
What physiologic mechanism underlies contrast-induced nephropathy (CIN)?