FIG 1. CTA with targeted MIP was performed in a 48-year-old man with surgically confirmed pericallosal arterial aneurysm and hypoplasia of A1 segment.

A, Anteroposterior (AP) arteriogram of right carotid artery shows hypoplasia of A1 segment (arrow).

B, CTA with targeted MIP reveals extended coverage of CTA with double-detector technology. Complete arterial volume is shown by MIP, ranging from the atlas loop to the pericallosal artery. By drawing a freehand line on any selected projection of the volume, targeted MIPs can be created (C and D), avoiding superimposition of vessels.

C, Targeted MIP of anterior circulation clearly shows hypoplasia of A1 segment (long arrow) as well as aneurysm (short arrow).

D, Targeted MIP of posterior circulation shows normal vasculature.