Quantitative evaluation of regional cerebral perfusion pressure by means of PET: A study in normal volunteers

Objectives Reduction of cerebral perfusion pressure (CPP) causes hemodynamic infarction in patients with steno-occlusive carotid artery disease. The ratio of cerebral blood flow (CBF) to cerebral blood volume (CBV) is positively correlated with systemic arterial blood pressure and a marker of CPP (Schuman P, et al., Brain, 1998). We investigated regional CPP distribution in normal volunteers by PET.

Methods We studied 12 normal volunteers (6 males and 6 females, mean age: 50.3 years, SD=3.4). Vascular and morphological normality of the brain was examined by cranial MR. CBF was quantitatively measured by H215O bolus injection (Herscovich et al, JNM, 1983). CBV was measured by C15O inhalation (Martin et al, J Cereb Blood Flow Metab, 1987). During the study, systemic blood pressure, arterial partial pressure of CO2, and hematocrit were monitored. By means of SPM2 software (the Wellcome Department of Cognitive Neurology), the CBF images were anatomically normalized to PET template. The set of converting parameter was applied to normalize CBV images. Regions of interest were set on various brain structures.

Results The CBF/CBV (min-1) was highest in lentiform nucleus (27.8) among brain structures followed by thalamus (26.7), caudate nucleus (25.2, cerebellum (22.1), and midbrain (21.8). The CBF/CBV in cerebral cortex ranged from 19.9 (frontal cortex) to 15.3 (parietal cortex). The CBF/CBV in cerebral deep white matter was lowest (12.0). The CBF/CBV was not accurately estimated in brain regions adjacent to large venous and sinus.

Conclusions The present study indicated that the CPP is not uniform among brain structures. Low CPP in deep white matter may be correlated with high incidence of hemodynamic infarction in this region in patients with steno-occlusive arterial disease.

Research Support Global COE project, Japa