Abstract
1693
Objectives: Automated VOI placement, if validated, could improve our overall research efficiency and objectivity using PET. We compared regional binding potential (BP) values between automated and manual VOI placement approaches using PET scans of [11C]carfentanil and [11C]Methyl-naltrindole, mu- and delta-opioid receptor ligands, respectively. Methods: Forty-five subjects (age range: 25 – 60) were studied with PET following bolus injections of [11C]carfentanil and [11C]naltrindole on a baseline condition and following alcohol withdrawal and naltrexone induction (four scans per subject design). A standard VOI template was defined manually on one standard MRI for putamen, caudate nucleus, and occipital cortex. The MRI was spatially normalized using SPM2 to transfer VOIs to PET spaces, for MRI-to-PET coregistration. According to preliminary studies, one very high quality SPGR MRI was used as a standard and gray plus white matter masks were used on spatial normalization to improve agreements of automated VOIs on individual's MRI. Time-activity curves (TACs) were obtained by applying VOIs to dynamic PET frames. Regional binding potential (BP) values were obtained by tissue reference approaches (RTGA, Logan et al., 1996; MRTM2, Ichise et al., 2003), with occipital cortex as the reference region. Results: Regional BP values of two VOI approaches displayed excellent correlation for the RTGA (y (automatic) = 1.03 x (manual) + 0.008; r2=.994) and MRTM2 (y = 1.02 x + 0.008; r2=.971). The correlations were not significantly better than the correlation between the two tissue reference approaches using manually defined VOIs (MRTM2 = 0.96 RTGA + 0.055; r2=.0.955). Conclusions: This study established the feasibility of using an automated VOI placement approach for PET studies of the mu- and delta-opioid receptor ligands. Future directions will include fine tuning of spatial normalization of standard VOIs, such that the approach can be applied to a wide range of receptor/transporter ligands of various distributions in the brain.
Research Support (if any): R01-AA11872, R01-AA12303, R01-AA11855, R03-AA13723
- Society of Nuclear Medicine, Inc.