What is the difference between a CT angiography and a conventional CT scan for stroke evaluation?

• A. CTA uses non-contrast imaging; conventional CT uses arterial-phase contrast.
• B. CTA visualizes brain parenchyma only; conventional CT shows vessels.
• C. CTA visualizes cerebral vessels with arterial-phase contrast; conventional CT is non-contrast primarily for hemorrhage.
• D. CTA is slower and uses no contrast; conventional CT uses contrast.

Answer: (C)

In evaluating stroke, the key difference is that CT angiography images the brain's blood vessels by injecting contrast and timing the scan to the arterial phase, so you can directly see vessel patency, occlusions, or collateral flow. A conventional CT scan, performed without contrast, is mainly used to detect hemorrhage and to give a general view of the brain tissue.

This is why the statement that CT angiography visualizes cerebral vessels with arterial-phase contrast while conventional CT is non-contrast and focused on hemorrhage is the best description. CTA's contrast-enhanced arterial phase highlights the vessels, whereas non-contrast CT relies on density differences to identify bleeding and structural abnormalities, not vessels.