Assessment of cerebral hemodynamics before and after revascularization in patients with occlusive cerebrovascular disease by means of quantitative IMP-SPECT with double-injection protocol

The purpose of this study was to validate a double-injection (DI) method wi th N-isopropyl-[I-123]p-iodoamphetamine (IMP) to measure regional cerebral blood Row (rCBF) twice in a single session of dynamic SPECT and to elucidat e a possible role of this method to identify patients with occlusive diseas e of major cerebral arteries, who might benefit from cerebral revasculariza tion procedures (CR). Materials and Methods: Fourteen patients with occlusi on or severe stenosis of the internal carotid or middle cerebral artery wer e studied before and after CR to assess hemodynamic changes after revascula rization treatment. We quantitatively measured rCBF before and after acetaz olamide (ACZ) challenge along with cerebrovascular reserve capacity (CVR) w ith two injections of IMP in a single session of dynamic SPECT scans (DI me thod). The reliability and reproducibility of the DI method were validated by means of a simulation study and in eight patients who were examined with out ACZ challenge to measure baseline rCBF twice. Results: The analysis of simulated noisy data with realistic noise levels showed that the errors of the estimates for the first and the second rCBF and for the increase in rCB F were 2.6%, 8.1% and 10.4%, respectively. In the 8 patients examined by th e DI method to measure baseline rCBF twice, the mean and the SD of percenta ge differences between the two consecutive measurements in rCBF were -1.3% and 5.5%, respectively. Eight out of 14 patients with occlusive disease had at least one region with a CVR less than 10%. They showed a significant in crease in resting rCBF after CR, not only in the ipsilateral hemisphere (fr om 26.1 +/-6.4 to 33.4 +/-4.7) but also in the contralateral one (from 28.3 +/-7.0 to 34.7 +/-4.7) with a recovery of the ipsilateral CVR from 9.3 +/- 17.2 to 41.2 +/- 20.1%. The remaining six patients with good-moderate CVR did not show an increase in rCBF after CR (from 28.0 +/-2.7 to 28.3 +/-3.4) . The three of them with a moderate CVR (10-25%) before CR showed normaliza tion of CVR after CR. Conclusion: Patients with decreased rCBF and reduced CVR benefited from CR in terms of an increase in rCBF and recovery of CVR. The quantitative double-injection IMP-SPECT has the ability to identify tho se patients who may benefit from CR.