Quantitative measurement of cerebral blood flow by the microsphere model with super-early 123I-IMP brain SPECT

Cerebral blood flow (CBF) was quantitatively measured in 6 healthy young volunteers based on ''super-early'' acquisition of N-isopropyl-p-(123I) iodoamphetamine (IMP) brain SPECT obtained 4-6 min after IMP injection with a three-head rotating gamma camera and the microsphere (MS) model. The ratio of radioactivity (count/pixel/min) in the conventional early SPECT image (taken 25-55 min after IMP injection) to that in the ''super-early'' image for each brain region negatively correlated with regional CBF value obtained with the ''super-early'' MS method. This indicates that wash-out of IMP from the regions with higher CBF is faster than that from the regions with lower CBF and that CBF values are underestimated with the conventional MS method in regions with higher CBF. Regional CBF was quantitatively measured with the ''super-early'' MS method and the ARG method, a recently developed method based on two-compartment model. The mean cortical CBF was 52.5±7.0 (ml/100 g/min, mean±SD) with the ''super-early'' MS method and 47.5±3.3 with the ARG method. The CBF values obtained with the ''super-early'' MS method agreed with those previously reported with positron emission tomography. Since the MS method is theoretically the simplest model, the ''super-early'' MS method can be applied various disorders of the central nervous system where the behavior of IMP is not fully understood. (author)