Measurement of time-to-peak parameter by use of a new standardization method in patients with stenotic or occlusive disease of the carotid artery

BACKGROUND AND PURPOSE: A quantitative, easily obtained measure of cerebral hemodynamics would be valuable in planning surgical or interventional ther apy for patients with stenotic or occlusive disease of the carotid artery. We evaluated the recently introduced standardized time-to-peak variable (st dTTP), obtained with dynamic susceptibility contrast-enhanced MR (DSC-MR) i maging, in different states of stenotic/occlusive carotid artery disease. METHODS: We examined 24 patients with unilateral, high-grade stenosis (85%- 95%) of one internal carotid artery (ICA) and 10 patients with stenosis (85 %-95%) of one TCA and occlusion of the contralateral ICA. Mean stdTTP was e valuated in the central vascular territories of the anterior, middle, and p osterior cerebral arteries and the anterior and posterior border zones and compared with the mean stdTTP values from 36 cerebral hemispheres without h emodynamic impairment. RESULTS: Patients showed no significant prolongation of stdTTP in the centr al vascular territories compared with the reference group, whereas signific ant prolongations of stdTTP were measured in the anterior and posterior bor der zones in patients with ICA disease (ANOVA, P < .05) and were most promi nent in higher grades of carotid disease. Hemispheres with hemodynamic impa irment always showed a stdTTP > 3.5 s in the border zones. CONCLUSION: The StdTTP quantitatively describes the hemodynamic impairment in cerebral hemispheres supplied hy a stenosed or occluded ICA. An stdTTP v alue of > 3.5 s, as has been postulated, seems to point out hemodynamic imp airment.