Diagnostic Imaging Interpretation Flashcards

A 58-year-old patient presents with a solitary pulmonary nodule on CT. The nodule measures 12 mm, has a spiculated margin, and demonstrates a CT attenuation value of -40 HU. Which characteristic is MOST consistent with a benign hamartoma rather than malignancy?

Answer: Fat attenuation (-40 HU) within the lesion

Fat attenuation (negative HU values, typically between -40 and -120 HU) within a pulmonary nodule is a hallmark feature of pulmonary hamartoma, a benign lesion. Hamartomas are composed of cartilage, fat, connective tissue, and epithelium. Spiculated margins and size >10 mm are features more suggestive of malignancy, while absence of calcification is non-specific.

On MRI of the brain, a 34-year-old patient with relapsing-remitting multiple sclerosis shows a lesion that appears hypointense on T1-weighted imaging and hyperintense on T2/FLAIR. The T1 hypointense lesion in this context is best described as:

Answer: A chronic 'black hole' reflecting irreversible axonal loss

Chronic T1 hypointense lesions in MS, often called 'black holes,' represent areas of severe tissue destruction with irreversible axonal loss and gliosis. Acute plaques may transiently appear T1 hypointense due to edema but typically normalize. In contrast, persistent T1 hypointensity indicates permanent damage. This differs from acute enhancing plaques or cortical lesions which have distinct imaging profiles.

A radiograph of the wrist in a 25-year-old athlete reveals a fracture of the proximal pole of the scaphoid. Which vascular anatomy principle makes this fracture MOST prone to avascular necrosis?

Answer: The scaphoid's blood supply enters distally and travels retrograde to the proximal pole

The scaphoid receives its primary blood supply through branches of the radial artery that enter the bone at its distal dorsal ridge and travel retrograde (distally to proximally) through intraosseous vessels. A proximal pole fracture thus interrupts this retrograde flow, leaving the proximal fragment with no remaining vascular supply, resulting in a high rate of avascular necrosis. Waist fractures also carry risk but not as severely as proximal pole fractures.

Ultrasound of the liver reveals a 3 cm lesion with posterior acoustic enhancement and uniform anechoic internal echogenicity. Contrast-enhanced CT shows peripheral nodular enhancement in the arterial phase that fills in centripetally on delayed imaging. This enhancement pattern is MOST characteristic of:

Answer: Cavernous hemangioma with progressive centripetal fill-in

Cavernous hemangiomas classically demonstrate peripheral nodular enhancement in the arterial phase with progressive centripetal fill-in on delayed images, reflecting slow blood pooling in large vascular spaces. On ultrasound, they appear uniformly hyperechoic (in fatty livers) or anechoic with posterior acoustic enhancement. HCC shows arterial enhancement with venous phase washout. FNH has a central scar and spoke-wheel pattern. Adenoma shows heterogeneous enhancement, often with fat or hemorrhage.

On a chest radiograph, a 67-year-old patient with heart failure demonstrates Kerley B lines. Which of the following CORRECTLY describes the anatomic substrate and location of Kerley B lines?

Answer: Interlobular septal thickening in the lung periphery, perpendicular to the pleural surface

Kerley B lines represent edematous interlobular septa. They appear as short (1–2 cm), horizontal, non-branching lines at the lung periphery (typically costophrenic angles), oriented perpendicular to the pleural surface. They arise when pulmonary venous pressure exceeds ~18 mmHg, causing fluid to accumulate within the connective tissue septa separating secondary pulmonary lobules. Kerley A lines are longer, central, and radiate from the hila.

A 45-year-old woman undergoes 18F-FDG PET/CT for staging of suspected malignancy. The scan reveals intense FDG uptake in the uterus. Which physiologic or technical factor is MOST likely to represent a false-positive finding in this region?

Answer: Physiologic endometrial uptake during the menstrual or periovulatory phase of the cycle

Physiologic FDG uptake in the uterus is well documented and varies with the menstrual cycle. During menstruation and at periovulation, the endometrium can show intense, diffuse FDG uptake that mimics malignancy. This is the most common cause of false-positive uterine FDG uptake. While leiomyomas and inflammatory conditions can occasionally show uptake, they are less common causes compared to cyclic physiologic variation. Correlating scan timing with the menstrual cycle is essential to avoid misinterpretation.