Cerebral hemodynamics in patients with chronic obstructive carotid disease by rCBF, rCBV, and rCBV/rCBF ratio using SPECT

To evaluate cerebral hemodynamics, 21 patients with chronic occlusion or severe stenosis of the internal carotid or middle cerebral artery with normal or only lacunar infarction on x-ray CT were studied using single photon emission computed tomography (SPECT). We measured rCBV with ^99mTc erythrocytes after rCBF with ¹³³Xe, and calculated rCBV/rCBF. rCBF and rCBV of the 25 affected hemispheres were classified as (a) patients with normal rCBF →type I (n = 7) and type II (n = 3)←; (b) patients with decreased rCBF →type III (n = 6) and type IV (n = 9)←. These two groups then could be subdivided according to findings of rCBV, normal, and increased blood volumes. rCBV/rCBF increased as the cerebral perfusion pressure dropped from type I to type III. In type IV, other situations but cerebral autoregulation could be assumed. rCBV/rCBF signifies vascular mean transit time. Type III (high rCBV/rCBF) assumed as the increased OEF, misery perfusion as reported in PET. We propose rCBF, rCBV and rCBV/rCBF using SPECT can be an index for cerebral circulatory reserve.