Computed Tomography Test Computed Tomography (CT Brain) 5 — Questions and Answers
Question 1: On CT brain in a patient with suspected cerebral venous sinus thrombosis, the 'empty delta sign' is best seen:
- On post-contrast CT as a filling defect within the superior sagittal sinus (Correct answer)
- On non-contrast CT as hypodensity in the temporal lobe
- On bone windows as a skull base fracture
- On CT angiography as MCA occlusion
Correct answer: On post-contrast CT as a filling defect within the superior sagittal sinus
The empty delta sign appears after contrast as a triangular filling defect (clot) surrounded by enhancing collateral vessels within the superior sagittal sinus.
Question 2: Which artifact on CT brain appears as alternating bright and dark bands radiating from a high-density object such as a surgical clip?
- Streak artifact (Correct answer)
- Partial volume artifact
- Ring artifact
- Motion artifact
Correct answer: Streak artifact
Streak artifacts radiate from high-density objects like metal clips or dense bone due to photon starvation and polychromatic X-ray beam effects.
Question 3: A CT brain ordered for a 70-year-old with progressive cognitive decline shows diffuse enlargement of sulci and ventricles proportional to each other. This pattern most likely represents:
- Cerebral atrophy (ex vacuo ventriculomegaly) (Correct answer)
- Communicating hydrocephalus
- Obstructive hydrocephalus
- Bilateral subdural hygromas
Correct answer: Cerebral atrophy (ex vacuo ventriculomegaly)
Proportional enlargement of both sulci and ventricles reflects volume loss (atrophy), distinguishing it from hydrocephalus where ventricles enlarge disproportionately.
Question 4: The CT finding of 'cytotoxic edema' is characterized by:
- Hypodensity that respects vascular territory boundaries and involves both gray and white matter (Correct answer)
- Hypodensity confined to white matter that crosses vascular territories
- Hyperdensity within the cortex after contrast
- Enhancement along the cortical ribbon
Correct answer: Hypodensity that respects vascular territory boundaries and involves both gray and white matter
Cytotoxic edema from ischemia causes swelling of neurons and glia within a vascular territory, appearing as hypodensity involving both cortex and white matter.
Question 5: On CT brain, the normal attenuation of CSF within the ventricles approximates:
- 0–10 HU (Correct answer)
- 20–30 HU
- 35–45 HU
- 50–60 HU
Correct answer: 0–10 HU
CSF has nearly the same density as water and measures 0–10 HU on CT, appearing dark (hypodense) relative to brain parenchyma.
Question 6: A non-contrast CT brain in a neonate with seizures reveals periventricular calcifications. The most likely causative infection is:
- Cytomegalovirus (CMV) (Correct answer)
- Toxoplasma gondii
- Herpes simplex virus
- Rubella virus
Correct answer: Cytomegalovirus (CMV)
Congenital CMV classically produces periventricular calcifications on CT, along with microcephaly and cortical malformations.
Question 7: When performing a CT brain for evaluation of acute stroke, the primary reason to acquire a non-contrast series BEFORE contrast-enhanced sequences is:
- To detect acute hemorrhage, which is a contraindication to thrombolytic therapy (Correct answer)
- To assess the degree of atherosclerotic calcification
- To measure baseline Hounsfield units of the tumor
- To reduce radiation dose from overlapping sequences
Correct answer: To detect acute hemorrhage, which is a contraindication to thrombolytic therapy
Identifying acute hemorrhage on non-contrast CT is critical because thrombolytics (tPA) are absolutely contraindicated if hemorrhage is present.
Computed Tomography Test Computed Tomography (CT Brain) 5
On CT brain in a patient with suspected cerebral venous sinus thrombosis, the 'empty delta sign' is best seen: