FRCR Image Interpretation and Anatomy Flashcards

Which radiological feature differentiates a simple renal cyst from a complex cystic renal mass on CT?

Answer: Enhancing internal septations or nodules

Enhancing internal septations, nodularity, or thick walls (Bosniak categories III–IV) distinguish complex cystic masses requiring surgery from simple benign cysts (Bosniak I–II).

On a lateral knee radiograph, which line is used to assess patellar height (patellar height index)?

Answer: Insall-Salvati ratio (patellar tendon length to patellar length)

The Insall-Salvati ratio compares patellar tendon length to patellar length on a lateral radiograph; a ratio >1.2 indicates patella alta and <0.8 indicates patella baja.

What does the 'double bubble' sign on plain abdominal radiograph indicate in neonates?

Answer: Duodenal atresia

The double bubble sign — two air-fluid levels representing the stomach and dilated proximal duodenum — is pathognomonic of duodenal atresia, strongly associated with trisomy 21.

On liver MRI, which enhancement pattern is characteristic of a hepatocellular carcinoma (HCC)?

Answer: Arterial phase hyperenhancement with portal venous phase washout

HCC shows arterial hyperenhancement (due to neoangiogenesis) followed by washout in the portal venous and delayed phases — a pattern called 'arterial hyperenhancement and washout' (LI-RADS criteria).

Which vertebral level marks the bifurcation of the abdominal aorta into the common iliac arteries?

Answer: L4

The abdominal aorta bifurcates into the right and left common iliac arteries at the level of L4 (approximately at the level of the iliac crests).

What does the Hounsfield unit (HU) value of approximately −100 HU indicate on CT?

Answer: Fat tissue

Fat has a characteristic CT attenuation of approximately −50 to −150 HU, clearly distinguishing it from water (0 HU) and soft tissue (+20 to +80 HU).