Reliability of a non-invasive [11C]-raclopride scan to measure D2- dopamine receptors

[11C]-raclopride scans are currently the most common method for in vivo imaging of D2 dopamine receptors using PET. The present study was performed to assess the reliability of a single-scan, noninvasive method for determination of the D2 receptor binding potential, that obviates the use of an arterial puncture. Twelve healthy control subjects underwent two [11C]-raclopride PET scans each, 1-42 days apart using a GEMS-Scanditronix PC2048-15B scanner. The scans were then analyzed using striatal regions of interest determined with the assistance of a co-registered MRI scan. D2 receptor binding potential, which reflects Bmax/Kd or k3/k4, was calculated using a three compartment model with the cerebellum as a reference tissue. The D2 binding potential was then compared between Scan1 and Scan2 for each of the twelve subjects using an automated algorithm. Results show that the technique is highly reliable with an average difference between Scan 1 and Scan 2 of <1% and a standard deviation of 6%. The difference between the results of the two scans was independent of the duration between them. The reliability of this method is the same as that reported with techniques using arterial input sampling. We conclude therefore, that this single-scan, non-invasive technique is a reliable method to assess the availability of D2 receptors and lends itself well to most clinical research questions. Applications of this method to the study of the relationship between plasma levels and D2 occupancy will be presented. The Authors acknowledge the support of NARSAD and the MRC of Canada for this work.