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Levels on CTA source images for the measurement of the Hounsfield units at a specific artery and venous structure
| Level | Artery | Venous structure |
|---|---|---|
| Neck | Common carotid artery (proximal to bifurcation) | Internal jugular vein |
| Circle of Willis | Proximal M1 segment of the middle cerebral artery | Confluence of sinuses |
| High convexity | Distal A2 segment of the anterior cerebral artery | Superior sagittal sinus |
