Stability of α-[11C]methyl-l-tryptophan brain trapping in healthy male volunteers
- 75 Downloads
The purpose of this study was to assess the reproducibility in healthy volunteers of α-[11C]methyl-l-tryptophan (α[11C]MT) brain trapping imaging with positron emission tomography (PET), using volumes of interest (VOIs) and voxel-based image analysis.
Six right-handed healthy male volunteers (34.3±10.9 years) with a negative family history for psychiatric disorders were scanned twice in the resting condition, 22±17 days apart. An unbiased semiautomatic segmentation of the brain was used to define VOIs. The trapping constant K* (ml g−1 min−1) for α[11C]MT was calculated for the whole brain and seven brain regions using the graphical method for irreversible tracers. In addition, parametric maps of K* were obtained from dynamic scans using the same method. Comparison of test and retest K* functional images was performed using SPM99. Student’s paired t statistic was applied for comparisons of α[11C]MT brain trapping in a priori selected VOIs.
α[11C]MT brain trapping in VOIs showed a mean variability 2.6±1.8% (0.3–5%) for absolute and 1.5±2.1% (1.4–4.1%) for normalized K*. Intraclass correlations between test and retest conditions were 0.61±0.34 for absolute K* values and 0.73±0.20 for K* values normalized by global mean. SPM99 analysis using a height threshold of p=0.05 (two tailed) and an extent threshold of 100 voxels showed no significant differences between scans.
Rest measurements in healthy male volunteers of the trapping constant for α[11C]MT, using PET, appeared to be stable during an average interval of 3 weeks.
KeywordsPET α[11C]MT Brain trapping Serotonin synthesis Test–retest
This research was supported in part by grants from the NIH, CIHR, and FRSQ.
- 2.Frazer A, Hensler J. Serotonin. In: Siegel GJ, Agranoff BW, Albers RW, et al., eds. Basic neurochemistry, 5th edn. Vol. 3. New York: Raven Press; 1995Google Scholar
- 8.WHO. Declaration of Helsinki: recommendations guiding physicians in biomedical research involving human subjects. In: 18th World Medical Assembly. Helsinki: World Medical Association; 1964Google Scholar
- 10.First MB, Spitzer RL, Gibbon M, William JBW. Structured clinical interview for the DSM-IV-TR axis I disorders—patient edition (SCID-I/P, version 2.0). New York: Biometrics Research Department, New York State Psychiatric Institute; 1998Google Scholar
- 13.Diksic M, Tohyama Y, Takada A. Brain net unidirectional uptake of alpha-[14C]methyl-L-tryptophan (alpha-MTrp) and its correlation with regional serotonin synthesis, tryptophan incorporation into proteins, and permeability surface area products of tryptophan and alpha-MTrp. Neurochem Res 2000;25:1537–46CrossRefPubMedGoogle Scholar
- 24.Collins DL, Zijdenbos AP, Barré WFC, Evans AC. ANIMAL+INSECT: inproved cortical structure segmentation. In: Kuba A, Samal M, Todd-Pokropek A, eds. Proc. of the annual symposium on information processing in medical imaging. Vol. 1613. Springer, 1999;210–23Google Scholar
- 26.Zijdenbos A, Forghani R, Evans A. Automatic quantification of MS lesions in 3D MRI brain data sets: validation of INSECT. In: Proceedings of International Conference on Medical Image Computing and Computer-Assisted Intervention (MICCAI). Berlin Heidelberg New York: Springer; 1998Google Scholar
- 30.Shoaf SE, Carson R, Hommer D, Williams W, Higley JD, Schmall B, et al. Brain serotonin synthesis rates in rhesus monkeys determined by [11C]alpha-methyl-L-tryptophan and positron emission tomography compared to CSF 5-hydroxyindole-3-acetic acid concentrations. Neuropsychopharmacology 1998;19:345–53Google Scholar