FIG 2. Mean asymmetry indices (±SD) for rCBV, CBFi, and MTT from MR studies performed in five patients before, 1 week after, and 1 month after bypass surgery. Bars represent the mean values of each of the three variables calculated in all patients: a indicates significantly lower values on the affected side than on the contralateral side (P = .0001); b indicates postoperative asymmetry indices significantly higher than the preoperative values (P < .05)