Critical cerebral blood flow thresholds studied by SPECT using xenon-133 and iodine-123 iodoamphetamine

Regional cerebral blood flow (rCBF) was assessed in patients with cerebrovascular diseases (CVD) by single photon emission computed tomography (SPECT) using 133Xe and N-isopropyl-p-[123I]iodoamphetamine ([123I]IMP). The purpose of this study was to determine the infarcted and symptomatic blood flow thresholds of cerebral cortex by SPECT. In the 133Xe inhalation method rCBF was calculated by employing the Celsis modification of the Kanno and Lassen algorithm. In the [123I]IMP SPECT quantitation was obtained by counting-rate ratio for the low flow lesion to the contralateral homologous region which was presumed to be normal (Lesion/Normal ratio, L/N ratio). The infarcted and symptomatic blood flow thresholds by 133Xe SPECT was 19-23 and 33-36 ml/100 g/min, respectively. While, those of L/N ratio in the [123I]IMP SPECT were 39-48 and 65-72%, respectively. There was a significant correlation between the ischemic degrees evaluated by 133Xe and [123I]IMP SPECT studies.