Radiology MCQs with answers: free practice for FCPS, FRCR and EDiR

Q1. A radiology resident is preparing for the physics portion of the board exam and is reviewing the physical decay mechanisms, half-lives, and primary gamma photopeaks of diagnostic radiopharmaceuticals. One radiopharmaceutical decays exclusively via electron capture with a physical half-life of 73 hours, emitting characteristic low-energy mercury X-rays in the range of 69 to 83 keV, as well as minor gamma photons at 135 and 167 keV. Which radiopharmaceutical possesses these specific decay and energy properties?

Answer E. Thallium-201 (Tl-201) decays via electron capture with a physical half-life of ~73 hours (~3.0 days). Its primary diagnostic imaging photons are NOT gamma rays, but rather characteristic Mercury X-rays (K-shell fluorescent X-rays) generated during atomic rearrangement, spanning 69 to 83 keV (accounting for ~85% of detected events), with minor gamma peaks at 135 and 167 keV. In contrast: Tc-99m has a 6-hour half-life and 140 keV gamma peak; In-111 decays by electron capture (67h) with dual photopeaks at 171 and 245 keV; Ga-67 decays by electron capture (78h) with four photopeaks (93, 185, 300, 393 keV); and F-18 decays by positron emission (110 min), yielding dual 511 keV annihilation photons.

Q2. A 3-month-old female infant is brought to the emergency department with lethargy and poor feeding. A skeletal survey is performed. Radiographs demonstrate a classic metaphyseal lesion (corner fracture) of the proximal tibia, bilateral posterior rib fractures adjacent to the costovertebral junctions in subacute healing with callus, and an undisplaced fracture of the scapular acromion. There is no generalized demineralization, cortical thinning, or wormian bones. Which fracture identified in this patient has the highest diagnostic specificity for physical child abuse (non-accidental trauma)?

Answer B. In pediatric non-accidental trauma (NAT), skeletal fractures are categorized by diagnostic specificity: (1) High Specificity: Classic Metaphyseal Lesions (CMLs; corner/buckethandle fractures), posterior rib fractures (from violent thoracic squeezing), scapular fractures, spinous process fractures, and sternal fractures; (2) Moderate Specificity: Multiple bilateral fractures, fractures of different ages, epiphyseal separations, and vertebral body compression fractures; (3) Common / Low Specificity: Clavicular fractures (common in birth trauma/falls), long-bone diaphyseal fractures, and linear parietal skull fractures. CMLs result from violent acceleration-deceleration shearing through the primary spongiosa and are virtually pathognomonic for abuse in non-ambulatory infants.

Q3. A 52-year-old male with severe acute necrotizing pancreatitis develops acute left flank fullness. Abdominal CT demonstrates an extensive fluid collection dissecting into the retroperitoneum. The collection is located posterior to the posterior parietal peritoneum, anterior to the anterior renal fascia (Gerota fascia), and medial to the lateroconal fascia, directly surrounding the pancreatic tail and the descending colon. The perinephric fat and kidney are completely uninvolved. Within which specific anatomical retroperitoneal space is this fluid collection confined?

Answer A. The retroperitoneum is divided into three distinct fascial compartments: (1) Anterior Pararenal Space: bounded anteriorly by the posterior parietal peritoneum, posteriorly by the anterior renal fascia (Gerota fascia), and laterally by the lateroconal fascia. It contains the pancreas, ascending/descending colon, and the second through fourth portions of the duodenum. Fluid collections from pancreatitis or colon perforation preferentially decompress into this space; (2) Perirenal (Perinephric) Space: bounded by Gerota fascia anteriorly and Zuckerkandl fascia posteriorly, containing the kidney, adrenal gland, proximal ureter, and perinephric fat; (3) Posterior Pararenal Space: bounded anteriorly by posterior renal fascia (Zuckerkandl) and posteriorly by transversalis fascia, containing only fat without viscera.

Q4. A premature male infant born at 26 weeks of gestation undergoes routine screening transfontanellar cranial ultrasound on day 4 of life. Parasagittal and coronal ultrasound images through the anterior fontanelle reveal echogenic material filling the caudothalamic groove bilaterally. The echogenic hemorrhage extends into the lateral ventricles, with marked distension and dilatation of the lateral ventricles (ventricular index > 97th percentile). There is no parenchymal echogenicity in the periventricular white matter. According to the Papile/Volpe classification, what grade of germinal matrix hemorrhage is present?

Answer C. Germinal matrix hemorrhage (GMH) is classified by the Papile grading system on cranial ultrasound: (1) Grade I: Hemorrhage confined strictly to the subependymal germinal matrix (at the caudothalamic groove) without intraventricular rupture; (2) Grade II: Intraventricular hemorrhage filling < 50% of the lateral ventricle WITHOUT ventricular dilatation; (3) Grade III: Intraventricular hemorrhage WITH acute lateral ventricular dilatation/distension (> 50% ventricular lumen fill); (4) Grade IV: Intraventricular hemorrhage with Periventricular Venous Hemorrhagic Infarction (PVHI; secondary to deep medullary venous thrombosis causing parenchymal hemorrhagic necrosis). Because there is intraventricular hemorrhage with significant ventricular dilatation and absent parenchymal involvement, this is definitively Grade III.

Q5. An interventional radiology fellow is preparing for a diagnostic visceral angiogram. The attending physician quizzes the fellow on basic vascular access hardware, French sizing, and wire compatibility. The access plan involves placing a 5-French vascular sheath in the common femoral artery using the standard modified Seldinger technique. Which of the following statements regarding vascular hardware dimensions and sheath sizing is correct?

Answer B. In vascular and interventional radiology, hardware sizing rules are critical. The French (Fr) catheter scale measures circumference in millimeters, where 1 French = 1/3 mm (0.33 mm). For standard diagnostic and therapeutic CATHETERS, the stated French size refers to the OUTER DIAMETER (e.g., a 5-Fr catheter has an outer diameter of 5 * 0.33 = 1.67 mm). However, for VASCULAR INTRODUCER SHEATHS, the stated French size refers to the INNER DIAMETER (the maximum catheter size that can pass through its lumen). Therefore, a 5-French vascular sheath has an inner lumen that accepts a 5-Fr catheter, but because of its wall thickness, the SHEATH'S OUTER DIAMETER is approximately 1.5 to 2 French sizes larger (i.e., 6.5 to 7 French, or ~2.2 mm).

Q6. A 54-year-old female presents with acute left-sided pulsatile tinnitus. Digital subtraction angiography (DSA) and CT angiography demonstrate a small 4 mm saccular aneurysm arising from the horizontal segment of the internal carotid artery as it traverses within the carotid canal of the petrous temporal bone, giving rise to tiny caroticotympanic branches. According to the Bouthillier classification, which numerical segment of the internal carotid artery is involved?

Answer B. The Bouthillier classification standardizes the seven segments of the internal carotid artery (ICA) in antegrade sequence: (1) C1: Cervical segment (from bifurcation to carotid canal entrance; zero normal branches); (2) C2: Petrous segment (within the carotid canal of the temporal bone, vertical then horizontal genu; gives off caroticotympanic and vidian arteries); (3) C3: Lacerum segment (short segment above foramen lacerum); (4) C4: Cavernous segment (within cavernous sinus, surrounded by venous blood; gives off meningohypophyseal trunk and inferolateral trunk); (5) C5: Clinoid segment (wedge-shaped segment between proximal and distal dural rings); (6) C6: Ophthalmic segment (intradural; gives off ophthalmic and superior hypophyseal arteries); (7) C7: Communicating segment (terminates in ACA/MCA bifurcation; gives off PCom and anterior choroidal arteries). The petrous segment within the carotid canal is C2.