Computed Tomography Test CT Anatomy and Clinical Applications 1 — Questions and Answers
Question 1: What CT finding is pathognomonic (diagnostic) for acute epidural hematoma?
- Biconvex (lens-shaped) hyperdense collection adjacent to the inner table of the skull (Correct answer)
- Crescent-shaped hyperdense collection spanning the brain surface
- Diffuse brain swelling with effacement of sulci
- Ring-enhancing lesion with surrounding edema
Correct answer: Biconvex (lens-shaped) hyperdense collection adjacent to the inner table of the skull
An acute epidural hematoma appears biconvex because it is limited by dural attachments at suture lines, and it is hyperdense (bright) due to fresh clotted blood.
Question 2: On non-contrast CT of the head, acute intraparenchymal hemorrhage typically appears as:
- Hyperdense (bright white) relative to adjacent brain parenchyma (Correct answer)
- Hypodense (dark) relative to brain
- Isodense to brain
- Ring-enhancing
Correct answer: Hyperdense (bright white) relative to adjacent brain parenchyma
Acute blood is hyperdense on NCCT due to the high protein content of clotted hemoglobin (55–75 HU), making it easily distinguishable from normal brain (~35 HU).
Question 3: In CT of the chest, the 'ground-glass opacity' (GGO) pattern is best described as:
- Hazy increased attenuation that does not obscure underlying vessels (Correct answer)
- Complete white-out of the lung with no visible vessels
- Air-filled cysts throughout the lung
- Thickening of bronchial walls only
Correct answer: Hazy increased attenuation that does not obscure underlying vessels
GGO is a non-specific finding of partial air space filling or interstitial thickening where the lung appears hazy but underlying vascular structures remain visible.
Question 4: What CT sign in the chest is used to identify a pulmonary embolism on CTPA?
- Filling defect (hypodense clot) within a pulmonary artery on contrast-enhanced images (Correct answer)
- Hyperdense pulmonary artery on non-contrast CT
- Consolidation with air bronchograms
- Pleural effusion only
Correct answer: Filling defect (hypodense clot) within a pulmonary artery on contrast-enhanced images
A PE appears as a hypodense (dark) filling defect within the opacified (bright) pulmonary artery lumen on CTPA, representing non-enhancing thrombus.
Question 5: Which CT finding best characterizes a simple hepatic cyst?
- Well-defined, water-density (0–10 HU), non-enhancing lesion with imperceptible walls (Correct answer)
- Solid lesion with arterial enhancement
- Lesion with internal septations and thick walls
- Calcified lesion with mass effect
Correct answer: Well-defined, water-density (0–10 HU), non-enhancing lesion with imperceptible walls
Simple hepatic cysts are fluid-filled with near-water attenuation, sharply defined margins, no internal complexity, and no enhancement after contrast administration.
Question 6: On CT of the abdomen, the normal appendix should have a maximum diameter of:
- Less than 6 mm (Correct answer)
- Less than 1 cm
- Less than 2 cm
- Size is not diagnostically relevant
Correct answer: Less than 6 mm
A normal appendix is typically less than 6 mm in outer wall diameter; a distended appendix ≥6 mm with periappendiceal inflammation is diagnostic criteria for acute appendicitis.
Computed Tomography Test CT Anatomy and Clinical Applications 1
What CT finding is pathognomonic (diagnostic) for acute epidural hematoma?