FIG 1. Angiogram and ACZ-challenged SPECT scans of patient 8, who had right internal carotid artery occlusion.

Left, Baseline and ACZ-challenged SPECT scans. Asymmetry index in right MCA territory of baseline scan is 0.78 (A/B) and of ACZ-challenged scan is 0.55 (A'/B'); therefore, regional reactivity index is 0.71 (0.55/0.78).

Right, Angiogram of right vertebral artery. Right MCA territory is perfused via the leptomeningeal artery from the right posterior cerebral artery (PCA). When the left PCA territory is in capillary phase, the right MCA territory is still in arteriole phase. Although the rACCT of left MCA territory is 3.9 s, that of right MCA territory is 8.8 s; therefore, the rACCT ratio is 2.3 (8.8/3.9).