Diagnostic Imaging & Radiology Flashcards

A 45-year-old woman undergoes MRI of the liver. The lesion shows marked hypointensity on T1-weighted images, hyperintensity on T2-weighted images, and peripheral nodular enhancement on dynamic contrast study with centripetal fill-in on delayed phases. Which diagnosis does this pattern most specifically indicate?

Answer: Cavernous hemangioma

The described MRI pattern — peripheral nodular enhancement with progressive centripetal fill-in on delayed phases — is pathognomonic for cavernous hemangioma. This reflects the slow pooling of contrast in the large vascular spaces of the lesion. HCC shows arterial enhancement with washout; FNH has a central scar; metastases typically show ring enhancement without fill-in.

On a chest CT, a pulmonary nodule demonstrates a CT attenuation value of -80 HU. What is the most appropriate next step in management?

Answer: No further workup — this is almost certainly benign

A CT attenuation value of -80 HU is consistent with fat density, indicating a pulmonary hamartoma or lipoid lesion — both benign entities. Fat-containing pulmonary nodules are virtually always benign and require no further investigation. PET-CT would be inappropriate as hamartomas can show mild FDG uptake. Biopsy is unnecessary given the diagnostic attenuation value.

During fluoroscopic barium swallow, a 'bird-beak' tapering is identified at the gastroesophageal junction with failure of relaxation. Esophageal manometry confirms absent peristalsis. A 58-year-old patient presents with this finding for 6 months. Which additional imaging finding would most raise concern for pseudoachalasia rather than primary achalasia?

Answer: Asymmetric or rigid appearance of the GEJ on multiple projections

Pseudoachalasia is caused by an underlying malignancy (most commonly gastric cardia or distal esophageal cancer) mimicking achalasia. Radiologically, asymmetry or rigidity of the GEJ seen on multiple fluoroscopic projections suggests an infiltrating mass rather than the smooth, symmetric tapering of primary achalasia. Short symptom duration (< 1 year), older age at onset, and weight loss also raise suspicion. CT or endoscopy is mandatory when pseudoachalasia is suspected.

A radiologist reviews a mammogram and identifies a mass with spiculated margins, no calcifications, and a 'comet tail' retraction sign. The mass was not present on a mammogram 18 months ago. What is the ACR BI-RADS category and recommended action?

Answer: BI-RADS 5 — tissue sampling recommended

A new spiculated mass with comet-tail retraction (a sign of architectural distortion caused by fibrotic or malignant infiltration) carries a >95% likelihood of malignancy, qualifying as BI-RADS 5. BI-RADS 5 indicates findings that are highly suggestive of malignancy and mandates tissue diagnosis (biopsy). BI-RADS 4 covers intermediate probability; BI-RADS 3 applies to probably benign findings; a new spiculated mass does not meet either lower-category threshold.

A patient with known renal cell carcinoma undergoes bone scintigraphy. A solitary focus of increased tracer uptake is identified in the right 6th rib. Plain radiograph of the rib appears normal. What is the most appropriate next imaging step to characterize this lesion?

Answer: MRI of the thorax with STIR and post-contrast sequences

Renal cell carcinoma metastases are often lytic and highly vascular, and can be photopenic (cold spots) or show increased uptake on bone scan. When a plain radiograph is negative, MRI with STIR (highly sensitive for marrow edema/replacement) and post-contrast sequences is the gold standard for characterizing a solitary equivocal bone scan finding, particularly in an oncologic patient. CT with bone windows can miss early marrow infiltration before cortical destruction occurs. PET-CT is useful but MRI has superior soft-tissue and marrow sensitivity for solitary lesions.

On a non-contrast head CT, a hyperdense crescent-shaped collection is identified along the inner table of the skull, crossing the midline and compressing the superior sagittal sinus region. There is no midline shift. Which of the following is the most likely diagnosis?

Answer: Acute subdural hematoma with bilateral collection

Subdural hematomas (SDH) can be bilateral and, when symmetric, may show no midline shift despite significant blood volume. A crescent-shaped hyperdense collection that crosses sutures (unlike epidural hematomas, which are limited by dural attachments at sutures) and follows the inner table bilaterally is characteristic of acute bilateral SDH. The crossing of the midline via the falx region and involvement near the superior sagittal sinus suggests a bilateral collection compressing from both sides — hence no net shift. Epidural hematomas are biconvex and suture-limited; SAH fills cisterns and sulci.