Statistical mapping analysis of serotonin synthesis images generated in healthy volunteers using positron-emission tomography and alpha-[C-11]methyl-L-tryptophan

Objectives: To assess the suitability of analyzing functional images of bra in serotonin (5-HT) synthesis with statistical parametric mapping (SPM), an d to investigate further possible sex-related regional differences. Design: Prospective study. Participants: Six healthy men and 5 healthy women. Inte rvention: Participants' brains were scanned with positron-emission tomograp hy (PET) after intravenous injection of alpha-[C-11]methyl-L-tryptophan (al pha-[C-11]MTrp). Outcome measures: Tissue radioactivity images were convert ed into functional images using the Patlak plot approach, and analyzed with 2 methods for global normalization in the SPM program: proportional scalin g and analysis of covariance (ANCOVA). Results: The data structure suggests that PET alpha-[C-11]MTrp data meet the criteria for analysis with SPM, an d that the proportional scaling method is more appropriate than the ANCOVA method for normalization. Regional differences in 5-HT synthesis were ident ified between men and women, and the significance of these findings was sup ported by region of interest (ROI) analyses. Conclusion: SPM analyses of PE T alpha-[C-11]MTrp data may be of value for identifying regional difference s in brain 5-HT synthesis between groups, and in investigating the effects of psychotropic drugs. Since we found regional differences between male and female subjects, men and women should not be grouped for data analysis in PET alpha-[C-11]MTrp studies.