FIG 4. Grade 2 stenosis overestimated with spiral CT angiography.

A, Oblique DSA image shows grade 2 stenosis in the left internal carotid artery.

B, Elliptic centric contrast-enhanced MR angiogram shows the same findings.

C and D, Spiral CT angiograms show type 4 calcification. In this case, the stenosis was overestimated (grade 3) because of the difficulty in separating calcium from the contrast material.