Regional distribution of N-isopropyl-p-(I-123)iodoamphetamine in cerebrovascular disease compared with regional cerebral blood flow and oxygen metabolism

N-isopropyl-p-(I-123)iodoamphetamine (IMP) has been introduced for the assessment of regional cerebral blood flow (RCBF) by single photon emission computed tomography (SPECT). Although some preliminary studies in animals have revealed a good correlation between the distribution of IMP and RCBF, it has not been validated in diseased states in humans. The purpose of this study is to compare the regional distribution of IMP measured by SPECT WITH RCBF and oxygen metabolism measured by positron emission tomography (PET). Twenty patients with cerebrovascular disease were studied. Following the intravenous IMP (3 mCi), SPECT was performed using a rotating gamma camera. PET study was carried out by continuous inhalation of 0-15 labeled gases to measure RCBF, oxygen extraction fraction (OEF) and oxygen utilization (CMR02). PET study and X-ray CT scan were performed on the same day, and SPECT with IMP was studied within a few days. In chronic cerebrovascular disease, the distribution of IMP was well correlated with RCBF. However, in two cases with cerebral infarction in the subacute stage, the discrepancy between IMP distribution and RCBF were observed. In these cases, relatively increased RCBF was demonstrated in the infarcted area where CMR02 was markedly depressed, and the distribution of IMP was more similar to that of CMR02. These results suggest that although SPECT with IMP is a valuable diagnostic tool for the assessment of cerebrovascular disease, IMP distribution may not be determined only by RCBF