Table 2.

Vessel Selectivity Measurements

Note.—Data are means ± standard deviations. Selectivity was measured as the ratio of signal in vessel segments in hemispheres contralateral and ipsilateral to selective labeling in the ICA. ROI values were averaged across subjects. A high degree of selectivity is shown: All ratios are significantly different from a value of 1 (P < .001), where a value of 1 represents nonselectivity. ACA = anterior cerebral artery, ECA = external carotid artery. Subscripts a, b, and c indicate relative distance along the artery from the COW, with a being the closest.