ARRT Contrast Media 2 — Questions and Answers
Question 1: A patient with a serum creatinine of 1.8 mg/dL is scheduled for a contrast-enhanced CT. Which action is most appropriate?
- Proceed normally with standard iodinated contrast dose
- Notify the radiologist and consider pre-hydration protocols (Correct answer)
- Cancel the exam entirely without further evaluation
- Switch to gadolinium-based contrast agent
Correct answer: Notify the radiologist and consider pre-hydration protocols
Elevated creatinine indicates impaired renal function, requiring radiologist notification and consideration of pre-hydration or dose reduction to minimize contrast-induced nephropathy risk.
Question 2: Which type of iodinated contrast media is considered safest for patients at risk for contrast-induced nephropathy?
- High-osmolar ionic contrast
- Low-osmolar ionic contrast
- Iso-osmolar nonionic contrast (Correct answer)
- High-osmolar nonionic contrast
Correct answer: Iso-osmolar nonionic contrast
Iso-osmolar nonionic contrast (e.g., iodixanol) has the lowest nephrotoxic potential and is preferred for high-risk patients.
Question 3: During a CT pulmonary angiography, the technologist notices extravasation of contrast at the injection site. What is the first action?
- Continue the injection at a slower rate
- Stop the injection immediately and notify the radiologist (Correct answer)
- Increase the injection pressure to maintain flow
- Switch to a new injection site and restart the injection
Correct answer: Stop the injection immediately and notify the radiologist
Extravasation can cause tissue injury; the injection must be stopped immediately and the radiologist informed for proper management.
Question 4: Which oral contrast agent is most commonly used in CT of the abdomen and pelvis to opacify the bowel?
- Barium sulfate suspension or dilute water-soluble iodinated contrast (Correct answer)
- Gadolinium-based oral agent
- Manganese chloride solution
- Air alone as a negative contrast agent
Correct answer: Barium sulfate suspension or dilute water-soluble iodinated contrast
Barium sulfate or dilute iodinated contrast (e.g., dilute Gastrografin) are the standard oral agents used to opacify the GI tract in abdominal/pelvic CT.
Question 5: What is the primary purpose of the portal venous phase in a multiphasic liver CT protocol?
- To detect hypervascular lesions at peak arterial enhancement
- To evaluate the hepatic veins and biliary ducts exclusively
- To demonstrate maximum enhancement of the liver parenchyma for lesion detection (Correct answer)
- To assess the early arterial supply to renal tumors
Correct answer: To demonstrate maximum enhancement of the liver parenchyma for lesion detection
The portal venous phase (approximately 60–70 seconds post-injection) provides peak liver parenchymal enhancement, optimizing detection of hypovascular metastases.
Question 6: A patient taking metformin for type 2 diabetes is receiving IV iodinated contrast. Per ACR guidelines, when should metformin be withheld after contrast administration in a patient with normal renal function?
- It does not need to be withheld in patients with normal renal function (Correct answer)
- Withhold for 24 hours before and after the exam
- Withhold only if the patient has an allergic reaction
- Withhold for 72 hours regardless of renal function
Correct answer: It does not need to be withheld in patients with normal renal function
ACR guidelines state that patients with normal renal function (eGFR ≥ 30) receiving IV contrast do not need to withhold metformin.
Question 7: Which characteristic best describes a nonionic iodinated contrast medium compared to an ionic agent?
- Higher osmolality and greater ionization in solution
- Lower osmolality and does not dissociate into ions in solution (Correct answer)
- Identical osmolality but with ionic charge
- Lower iodine concentration per milliliter
Correct answer: Lower osmolality and does not dissociate into ions in solution
Nonionic contrast media remain intact molecules in solution, yielding lower osmolality and fewer adverse hemodynamic and chemotoxic effects than ionic agents.
ARRT Contrast Media 2
A patient with a serum creatinine of 1.8 mg/dL is scheduled for a contrast-enhanced CT.
Which action is most appropriate?