SPEX SPEX Radiology and Imaging 5 — Questions and Answers
Question 1: A patient with a pacemaker is referred for cardiac MRI. Which factor is most important in determining whether the scan can proceed safely?
- Whether the device is labeled MR-Conditional and the scan is performed per manufacturer conditions (Correct answer)
- The patient's symptom severity and the urgency of the clinical question
- The field strength of the scanner alone, since 1.5T is always safe for all pacemakers
- The age of the pacemaker, since devices implanted after 2010 are universally MR-safe
Correct answer: Whether the device is labeled MR-Conditional and the scan is performed per manufacturer conditions
MR-Conditional labeling with adherence to specific conditions (field strength, SAR limits, programming) is the regulatory and safety standard for pacemaker MRI.
Question 2: On a Tc-99m bone scan, a 'superscan' pattern is characterized by:
- Diffusely increased skeletal uptake with absent or faint renal activity (Correct answer)
- Multiple discrete hot spots corresponding to known metastatic sites
- Focal cold defects replacing normal marrow activity
- Unilateral increased uptake confined to one limb
Correct answer: Diffusely increased skeletal uptake with absent or faint renal activity
A superscan reflects diffuse bony metastatic disease (or metabolic bone disease) with such avid skeletal uptake that the kidneys appear faint or absent.
Question 3: Which CT window and level settings are most appropriate for evaluating lung parenchyma?
- Window width ~1500 HU, window level ~-600 HU (Correct answer)
- Window width ~400 HU, window level ~40 HU
- Window width ~80 HU, window level ~35 HU
- Window width ~2000 HU, window level ~300 HU
Correct answer: Window width ~1500 HU, window level ~-600 HU
Lung windows use a wide window (~1500 HU) centered at approximately -600 HU to display the full range of attenuation from air to soft tissue within the lungs.
Question 4: A patient develops sudden onset of urticaria, bronchospasm, and hypotension 5 minutes after IV iodinated contrast administration. The most appropriate immediate treatment is:
- Intramuscular epinephrine 0.3 mg (1:1000) and IV fluid resuscitation (Correct answer)
- IV diphenhydramine 50 mg alone
- Oral prednisone 60 mg and observation for 30 minutes
- IV methylprednisolone 125 mg followed by H2-blocker
Correct answer: Intramuscular epinephrine 0.3 mg (1:1000) and IV fluid resuscitation
Anaphylactic shock requires immediate IM epinephrine as the first-line treatment; antihistamines and corticosteroids are adjuncts, not primary therapy.
Question 5: The ALARA principle in radiation protection stands for:
- As Low As Reasonably Achievable (Correct answer)
- Appropriate Limit After Radiographic Assessment
- Allowable Level for Acute Radiation Absorption
- Average Limit for Annual Radiation Activity
Correct answer: As Low As Reasonably Achievable
ALARA (As Low As Reasonably Achievable) is the guiding principle that radiation exposure should be minimized as much as practical while still achieving the diagnostic or therapeutic goal.
Question 6: Which finding on hepatic ultrasound is most characteristic of hepatic steatosis (fatty liver)?
- Diffusely increased hepatic echogenicity compared to the renal cortex with posterior attenuation (Correct answer)
- Multiple discrete anechoic cysts scattered throughout the parenchyma
- A heterogeneous mass with peripheral nodular enhancement on Doppler
- Decreased echogenicity with loss of the normal hepatic vascular architecture
Correct answer: Diffusely increased hepatic echogenicity compared to the renal cortex with posterior attenuation
Fatty infiltration causes increased hepatic echogenicity relative to the kidney and posterior beam attenuation due to increased fat content.
Question 7: On CT pulmonary angiography (CTPA), which finding is most diagnostic of acute pulmonary embolism?
- A filling defect within a contrast-enhanced pulmonary artery that is partially or completely outlined by contrast (Correct answer)
- Ground-glass opacity in a peripheral distribution
- Wedge-shaped pleural-based consolidation without vessel involvement
- Cardiomegaly with bilateral pleural effusions
Correct answer: A filling defect within a contrast-enhanced pulmonary artery that is partially or completely outlined by contrast
The direct sign of PE on CTPA is an intraluminal filling defect — a clot seen as a low-attenuation structure surrounded by high-attenuation contrast within the pulmonary artery.
SPEX SPEX Radiology and Imaging 5
A patient with a pacemaker is referred for cardiac MRI.
Which factor is most important in determining whether the scan can proceed safely?