[Quantification of brain perfusion SPECT with N-isopropyl-p-iodoamphetamine using noninvasive microsphere method: estimation of arterial input by dynamic imaging].

We have developed a noninvasive method to quantify brain perfusion SPECT with 123I-N-isopropyl-p-iodoamphetamine (IMP) using serial dynamic planar imaging of the initial transit phase. The method is based on the microsphere model, but does not require arterial sampling. Serial dynamic planar imaging was performed for 6 min after the bolus injection of IMP (167 MBq in 1.5 ml), followed by additional planar imaging at 20 min and SPECT scan thereafter. The total arterial input to the brain during the initial 5 min after injection was estimated by the injected dose, with the correction of the lung retention, divided by cardiac output (CO). CO was estimated from the initial transit of IMP in the right heart. Cardiac output index (COI), obtained from the integral of the first transit of IMP in the right heart divided by the injected dose, was calibrated by CO measured by Doppler ultrasonography. Regional cerebral blood flow (rCBF) obtained by this method in normal subjects was acceptable. However, the results may be influenced by the injection technique, and careful attention should be considered for clinical application of this method.