SPEX Radiology and Imaging Flashcards

A 58-year-old patient undergoes a CT pulmonary angiography (CTPA). The radiologist notes a saddle embolus straddling the main pulmonary artery bifurcation with right heart strain. Which CT finding most specifically indicates hemodynamic compromise requiring urgent intervention rather than anticoagulation alone?

Answer: Reflux of contrast into the inferior vena cava and hepatic veins

Reflux of contrast into the IVC and hepatic veins on CTPA is the most specific indicator of severe right heart failure and elevated right atrial pressure, signifying hemodynamic compromise that often necessitates systemic thrombolysis or catheter-directed therapy. While the D-sign and RV/LV ratio > 0.9 indicate right heart strain, contrast reflux into the IVC and hepatic veins directly reflects markedly elevated right atrial pressure and predicts clinical deterioration requiring escalated intervention.

During interpretation of a gadolinium-enhanced MRI brain, a radiologist observes T1 hyperintensity in the globus pallidus and dentate nucleus without prior gadolinium administration. The patient has received 18 prior MRI exams over 8 years using linear ionic agents. Which mechanism best explains this finding?

Answer: Gadolinium chelate dechelation and tissue deposition of free Gd³⁺ ions

Repeated exposure to linear gadolinium-based contrast agents (GBCAs) — particularly linear ionic and linear non-ionic agents — results in dechelation (release of free Gd³⁺ from the chelate molecule) and subsequent deposition in brain tissue. Free Gd³⁺ has strong T1-shortening properties and preferentially accumulates in the dentate nucleus and globus pallidus. Macrocyclic agents (e.g., gadobutrol, gadoteridol) have far lower dechelation rates and are less associated with this finding.

A nuclear medicine physician reviews a bone scintigraphy study in a patient with known prostate cancer. The scan shows markedly increased uptake throughout nearly the entire skeleton with no apparent normal bone activity, and the kidneys are barely visualized. Which interpretation is most accurate?

Answer: Super scan due to diffuse osteoblastic metastatic disease with minimal renal excretion

A 'superscan' occurs when there is such widespread uptake in osteoblastic metastases throughout the skeleton that it consumes nearly all the Tc-99m MDP, leaving minimal free tracer for renal excretion — explaining the faint or absent kidney visualization. The scan appears diffusely and symmetrically bright rather than showing discrete lesions. This pattern is classically associated with diffuse osteoblastic metastases (prostate, breast cancer) and can be mistaken for a normal scan by the inexperienced reader. Key clues are absent or faint kidneys and lack of expected soft-tissue background activity.

A radiologist is evaluating a hepatic lesion on a multiphasic contrast-enhanced CT. The lesion shows arterial phase hyperenhancement followed by washout appearance and a capsule on portal venous phase. However, it also demonstrates marked T2 hypointensity on MRI. Which diagnosis is MOST likely given this combination of findings?

Answer: Sclerosed hemangioma with progressive fibrous replacement

Sclerosed (or sclerosing) hemangiomas are a diagnostic pitfall because they can mimic HCC by showing arterial hyperenhancement and apparent washout on CT. However, the key distinguishing feature is marked T2 hypointensity on MRI — classic hemangiomas are T2 hyperintense ('light bulb bright'), but sclerosed hemangiomas exhibit T2 hypointensity due to progressive fibrosis replacing the vascular spaces. This combination — arterial enhancement, CT washout appearance, and profound T2 hypointensity — should raise suspicion for a sclerosed hemangioma rather than HCC, particularly in non-cirrhotic patients.

In mammography interpretation using BI-RADS, a cluster of calcifications is identified with the following morphology: fine linear and fine linear branching (casting) calcifications in a segmental distribution. The patient has no prior history of breast cancer. Which management is most appropriate?

Answer: BI-RADS 5 — biopsy recommended, findings highly suggestive of malignancy

Fine linear and fine linear branching (casting) calcifications represent calcium deposited within the lumens of ducts involved by high-grade ductal carcinoma in situ (DCIS) — these are the highest-suspicion calcification morphology in the ACR BI-RADS lexicon. When combined with a segmental distribution (suggesting involvement of a duct and its branches supplying a segment of the breast), the findings are highly suggestive of malignancy (BI-RADS 5, ≥95% PPV). BI-RADS 5 mandates tissue sampling with the expectation that pathology will confirm malignancy.

A patient undergoes fluoroscopic esophagram with water-soluble contrast for suspected esophageal perforation after instrumentation. The study shows extravasation of contrast into the mediastinum. The attending radiologist recommends switching to barium for better mucosal detail. Which response is most appropriate?

Answer: Disagree — barium in the mediastinum causes severe granulomatous mediastinitis and should never be used if perforation is suspected

Barium is absolutely contraindicated when esophageal perforation is suspected or confirmed. Barium sulfate is biologically inert in the GI lumen but highly caustic when extravasated into mediastinal or pleural spaces, causing severe barium-induced granulomatous mediastinitis, pleuritis, and fibrosis that dramatically worsens prognosis — historically associated with near-universal mortality when combined with esophageal perforation. Water-soluble iodinated contrast (e.g., Gastrografin) is used instead despite lower mucosal detail. If mediastinal extravasation is already confirmed, CT is the next step; additional contrast administration through the perforation is not indicated.