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RD5.1-4 | Core Image Interpretation Skills — Practice Quiz
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A medical officer reports cardiomegaly on a portable supine AP chest film of a ventilated adult because the cardiothoracic ratio (CTR) measures 0.58. Before accepting this diagnosis, which single principle most directly invalidates the measurement on this film?
Correct. The CTR < 0.5 rule applies only to a PA erect radiograph. On any AP, supine or portable film the heart-to-film distance is greater, magnifying the cardiac shadow, so an apparently raised CTR cannot be used to diagnose an enlarged heart.
Always confirm the projection before calling cardiomegaly. CTR < 0.5 is a PA-erect rule; on AP/supine/portable films the heart is magnified.
Re-read the rule. The CTR < 0.5 threshold is projection-dependent and valid only on a PA erect film. Portable AP/supine films magnify the heart and make CTR unreliable for diagnosing cardiomegaly.
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A frontal chest radiograph of a 3-week-old neonate shows a well-defined, sail-shaped soft-tissue opacity in the right upper mediastinum with a smooth, slightly wavy lateral border continuous with the cardiac silhouette. The infant is asymptomatic. What is the most likely explanation?
Correct. The thymus is a normal, prominent structure in neonates and infants. The triangular 'sail sign' (classically on the right) and a wavy border indented by the ribs are normal appearances, not pathology.
The neonatal/infant thymus is normal and prominent; the triangular thymic sail sign is a recognised normal appearance, not pathology.
This is the normal neonatal thymus. The triangular 'sail sign' with a smooth wavy border in an asymptomatic neonate is a normal appearance and should not be mistaken for consolidation or a mass.
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On the knee radiograph of a healthy 6-year-old, a lucent line is seen crossing the distal femur transversely near its end, with a separate ossified fragment beyond it. There is no soft-tissue swelling and the child is asymptomatic. What does this lucent line most likely represent?
Correct. In children the growth plate (physis) appears as a normal lucent line between the metaphysis and the separately ossifying epiphysis. In an asymptomatic child with no soft-tissue swelling this is normal development, not a fracture.
Paediatric growth plates and epiphyses are normal and must not be mistaken for fractures; correlate with a known anatomical site, symmetry and absence of soft-tissue swelling.
This is the normal physis (growth plate) and adjacent epiphysis. A paediatric growth plate is a smooth, regular transverse lucency at a typical site with no soft-tissue swelling — do not call it a fracture.
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A clinician requests 'an X-ray for age' on a person whose documentary age is disputed. The radiologist reports skeletal maturity from the left hand and wrist. Which statement best reflects the correct interpretation of the result?
Correct. Skeletal (bone) age is a measure of maturity, not calendar age. It may lag (constitutional delay, hypothyroidism, chronic illness) or lead (precocious puberty) chronological age, so the output must be an age RANGE with a stated margin.
Bone age is maturity, not calendar age; report a RANGE with a margin and select sex- and population-appropriate reference standards.
Bone age ≠ chronological age. Skeletal maturity can lag or lead calendar age, and standards are sex- and population-specific, so age is always reported as a RANGE with a margin — never a single precise year.
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For estimating skeletal age in a child using a left hand-wrist radiograph, which pairing of reference standard to its method is correct?
Correct. The Greulich-Pyle method matches the hand-wrist film against atlas reference images, while the Tanner-Whitehouse method scores the maturity of individual bones and sums the scores; both use the left hand and wrist.
Hand-wrist bone-age methods: Greulich-Pyle atlas matching vs Tanner-Whitehouse bone-by-bone scoring — select the method to suit the subject's age band.
Greulich-Pyle = atlas matching of the hand-wrist film; Tanner-Whitehouse = bone-by-bone scoring summed to a maturity score. Both use the left hand and wrist, not dental or pelvic landmarks.
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A patient with sudden severe abdominal pain has an ERECT chest radiograph showing a thin crescent of lucency between the right hemidiaphragm and the liver. The supine abdominal film taken earlier looked unremarkable. What is the finding and the key reason it was missed on the first film?
Correct. Free intraperitoneal gas (pneumoperitoneum) rises to the highest point and is seen as a crescent under the diaphragm on an erect/horizontal-beam film. A supine film does not allow the air to rise there, so it can hide the sign — a negative supine film does NOT exclude free air.
Pneumoperitoneum = free air under the diaphragm on an erect CXR (Rigler sign on AXR). Confirm an erect/horizontal-beam projection before excluding free air.
This is pneumoperitoneum — free air under the diaphragm on an erect CXR. Projection is the master variable: free air only rises under the diaphragm on an erect (horizontal-beam) film, so a supine film can hide it.
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A skeletal radiograph shows a lucent line through a long bone. Which combination of features most reliably indicates an ACUTE fracture rather than an old/chronic one?
Correct. An acute fracture shows a sharp, non-corticated (no sclerotic rim) lucent line, usually with adjacent soft-tissue swelling. A chronic/old fracture or non-union develops a corticated, sclerotic margin and lacks acute soft-tissue swelling.
Acute fracture: sharp non-corticated lucent line + soft-tissue swelling; chronic/old: sclerotic, corticated margin without acute swelling.
Acute = sharp, non-corticated lucent line + soft-tissue swelling. Sclerotic/corticated margins, bridging callus and absent swelling indicate an OLD/chronic fracture, not an acute one.
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On a portable AP chest film of a ventilated adult, you trace the endotracheal tube and find its tip lying just at the level of the carina with the neck in a neutral position. What is the correct interpretation and immediate action?
Correct. The ET tube tip should sit ~3-5 cm above the carina in a neutral neck. A tip at the carina is too low and risks slipping into the right main bronchus (endobronchial intubation), so the tube should be withdrawn. Remember the tip moves DOWN with neck flexion and UP with extension.
ET tube tip target ~3-5 cm above the carina (neutral neck); the tip moves down with flexion, up with extension. CVC tip target = cavoatrial junction/lower SVC.
Judge the ET tube against the carina: the target tip is ~3-5 cm above the carina in a neutral neck. A tip at the carina is too low (risk of endobronchial intubation) and should be withdrawn. The cavoatrial junction is the CVC target, not the ET tube.
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