Shortened protocol in practical [11C]SA4503-PET studies for sigma1 receptor quantification.

In practical positron emission tomography (PET) diagnosis, a shortened protocol is preferred for patients with brain disorders. In this study, the applicability of a shortened protocol as an alternative to the 90-min PET scan with [(11)C]SA4503 for quantitative sigma(1) receptor measurement was investigated. Tissue time-activity curves of 288 regions of interest in the brain from 32 [(11)C]SA4503-PET scans of 16 healthy subjects prior to and following administration of a selective serotonin reuptake inhibitor (fluvoxamine or paroxetine) were applied to two algorithms of quantitative analysis; binding potential (BP) was derived from compartmental analysis based on nonlinear estimation, and total distribution volume (tDV) was derived from Logan plot analysis. As a result, although both BP and tDV tended to be underestimated by the shortened method, the estimates from the shortened protocol had good linear relationships with those of the full-length protocol. In conclusion, if approximately 10% differences in the estimated results are acceptable for a specific purpose, then a 60-min measurement protocol is capable of providing reliable results.