Radiography Exam Risk Assessment & Management 2 — Questions and Answers

Question 1: A patient is scheduled for a contrast-enhanced CT but reports a serum creatinine of 1.8 mg/dL. This finding primarily raises concern for:

Iodine allergy
Contrast-induced nephropathy (CIN) (Correct answer)
Pulmonary embolism risk
Thyroid storm

Correct answer: Contrast-induced nephropathy (CIN)

An elevated serum creatinine indicates reduced renal function, increasing the risk of contrast-induced nephropathy (CIN). The radiologist must evaluate the risk-benefit ratio and may order hydration protocols or consider alternatives.

Iodinated contrast media are nephrotoxic and can worsen existing renal insufficiency, potentially leading to contrast-induced nephropathy (CIN) — an acute decline in renal function within 48–72 hours of contrast exposure. Risk factors include: baseline creatinine >1.5 mg/dL, eGFR <60 mL/min/1.73m², diabetes, dehydration, heart failure, and NSAID use. Management includes: hydration (IV normal saline), use of iso-osmolar or low-osmolar contrast, minimizing contrast volume, and holding nephrotoxic medications. The ACR recommends eGFR measurement before contrast administration in at-risk patients.

Question 2: Which of the following best describes the radiation risk concept of 'stochastic effects'?

Effects with a threshold dose below which no harm occurs
Probabilistic effects (cancer/genetic mutations) whose probability increases with dose but severity does not (Correct answer)
Deterministic effects that worsen at higher doses
Acute radiation syndrome effects seen at very high doses

Correct answer: Probabilistic effects (cancer/genetic mutations) whose probability increases with dose but severity does not

Stochastic effects (cancer and heritable genetic mutations) have no dose threshold — even small doses carry a probability of occurrence. The probability increases with dose but the severity of the effect (if it occurs) is independent of dose.

The linear no-threshold (LNT) model assumes stochastic radiation risks increase linearly with dose from zero. Stochastic effects include radiation-induced cancer (somatic stochastic) and heritable mutations (genetic stochastic). In contrast, deterministic effects (e.g., cataract, skin erythema) have a threshold dose below which they do not occur, and their severity increases above the threshold. Diagnostic radiology doses (typically 0.01–20 mSv) are in the stochastic risk range — the goal is to minimize dose while maintaining diagnostic adequacy (ALARA).

Question 3: A patient's medical history reveals they are taking metformin for type 2 diabetes. What is the primary concern when iodinated contrast is planned?

Hypertensive crisis from contrast interaction with metformin
Risk of lactic acidosis if contrast-induced nephropathy develops (Correct answer)
Anaphylactic reaction caused by metformin
Blood glucose instability during the procedure

Correct answer: Risk of lactic acidosis if contrast-induced nephropathy develops

Metformin is associated with lactic acidosis — a rare but life-threatening complication — if excreted renally and renal function deteriorates (e.g., due to CIN). Standard protocol is to hold metformin at the time of contrast administration and for 48 hours afterward.

Metformin is renally cleared. If contrast-induced nephropathy reduces kidney function, metformin can accumulate, increasing the risk of lactic acidosis. The ACR Manual on Contrast Media recommends: for patients with eGFR ≥30 mL/min with no acute kidney injury risk, metformin can be continued; for eGFR <30 or high CIN risk, metformin should be held at the time of contrast administration and for 48 hours post-procedure. Renal function is rechecked before restarting metformin. This protocol applies to both IV and intra-arterial iodinated contrast.

Question 4: The 10-day rule for radiographic examination of the abdomen and pelvis in women of childbearing age is designed to:

Ensure menstrual cycle synchrony with imaging
Minimize the chance of irradiating an early unrecognized pregnancy (Correct answer)
Improve image quality by scheduling around hormonal cycles
Comply with insurance pre-authorization requirements

Correct answer: Minimize the chance of irradiating an early unrecognized pregnancy

The 10-day rule (now largely superseded by ALARA principles) historically recommended scheduling abdominal/pelvic X-rays in the first 10 days after menstruation, when pregnancy is unlikely. Modern practice uses pregnancy screening questions instead.

The 10-day rule was proposed by ICRP in 1970 to limit the chance of exposing an unrecognized early pregnancy. It is largely been replaced by a 'ask before every exam' approach: verbally asking women of reproductive age if they could be pregnant before any exam involving pelvic irradiation. Current NCRP and ACR guidance recommends: (1) ask about pregnancy status before abdominal/pelvic exams; (2) use ALARA regardless; (3) for emergencies where delay would harm the patient, proceed with documentation. The clinical benefit usually outweighs the radiation risk in diagnostic imaging.

Question 5: Which of the following is a major risk factor for developing a venous thromboembolism (VTE) in patients undergoing lengthy radiologic procedures?

Premedication with corticosteroids
Prolonged immobility during the procedure (Correct answer)
Use of non-ionic contrast media
Excessive exposure to ionizing radiation

Correct answer: Prolonged immobility during the procedure

Prolonged immobility is a major risk factor for VTE (deep vein thrombosis and pulmonary embolism) because venous stasis promotes clot formation. Long interventional radiology procedures require VTE risk assessment and prophylaxis planning.

The Virchow triad of VTE risk factors includes: venous stasis (immobility), endothelial injury, and hypercoagulability. In radiology, patients undergoing lengthy procedures (interventional radiology, extended MRI studies, prolonged fluoroscopy) face VTE risk from immobility. Additional risk factors include: cancer, prior VTE, obesity, age >60, and post-surgical status. Prophylaxis includes: leg exercises, pneumatic compression devices, and pharmacologic prophylaxis (heparin) when indicated. Radiographers should be aware of procedure duration and report concerning symptoms (leg pain, swelling, dyspnea).

Question 6: Which imaging modality is considered safest for imaging a pregnant patient when the clinical question requires cross-sectional imaging?

CT with contrast
MRI without gadolinium contrast (Correct answer)
Nuclear medicine bone scan
CT without contrast

Correct answer: MRI without gadolinium contrast

MRI without gadolinium contrast is the preferred cross-sectional imaging modality in pregnancy because it does not use ionizing radiation. Gadolinium crosses the placenta and is avoided in the first trimester; CT and nuclear medicine involve ionizing radiation.

MRI uses radiofrequency waves and magnetic fields — no ionizing radiation — making it the safest cross-sectional option for pregnant patients. The ACR guidelines recommend: MRI can be used at any gestational stage when clinically necessary; gadolinium should be avoided unless the potential benefit justifies the risk (gadolinium crosses the placenta and is retained in amniotic fluid). CT involves ionizing radiation and is reserved for urgent indications where MRI is unavailable or inadequate. Fetal radiation dose from CT abdomen/pelvis is 10–50 mGy — well below the threshold for deterministic effects (100–200 mGy) but not zero risk.

Radiography Exam Risk Assessment & Management 2

A patient is scheduled for a contrast-enhanced CT but reports a serum creatinine of 1.8 mg/dL.
This finding primarily raises concern for: