Abstract
Introduction: We have been using a method of paired FDG PET scans immediately prior to and following infusion with psychoactive compounds as a means of assessing regional effects of these drugs on brain metabolism. We wished to test the validity of this method by use of placebo (PBO) infusions. Results from this study can help us estimate the likelihood of observed differences between the scans occurring from chance or the imaging method. Methods: Five healthy males (mean age 26.2 yrs) underwent 18 fluoro-2-deoxy glucose PET scans immediately before (3 mCi) and after (5 mCi) a 30 minute infusion with PBO. Five templates (A-E) comprised of 62 regions of interest (ROIs) were applied to five matched transaxial planes from each pair of scans. Differences in the mean global, absolute and normalized regional metabolic rates between the pre- and post-scans (within subjects) were evaluated using paired t-tests, uncorrected for multiple comparisons. Results: Absolute Metabolic Rate: No difference was detected in the global metabolic rate between the two scans; of the 62 regions tested, only one, the Anterior Medial Frontal ROI in the D plane, showed a significant difference (increase). Normalized Metabolic Rate: Of the 62 regions tested, three were significantly different: right parietal occipital in the C plane (decrease), Anterior Medial Frontal in the D plane (increase), and the Right Primary Visual Cortex (increase). Discussion: The absence of any significant global difference between test and retest scans suggests that the method of correcting for residual activity is valid. The occurrence of significant differences in normalized metabolism in three ROIs indicates the possibility of systematic changes in regional brain activity during the procedure. However, in applying paired t-tests to sixty-two ROIs with a significance level of. 05, it is expected that three regions would appear to be significantly different on the basis of chance alone.
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Schmidt, M., Matochik, J., Kwako, L. et al. The Paired FDG Pet Scan Method: Validation Using Placebo Infusions. Neuropsychopharmacol 11, 282 (1994). https://doi.org/10.1038/sj.npp.1380202
Published:
Issue Date:
DOI: https://doi.org/10.1038/sj.npp.1380202