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Stability of α-[11C]methyl-l-tryptophan brain trapping in healthy male volunteers

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Abstract

Purpose

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.

Methods

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.

Results

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.

Conclusion

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.

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Acknowledgements

This research was supported in part by grants from the NIH, CIHR, and FRSQ.

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Authors and Affiliations

  1. Department of Neurology and Neurosurgery, McGill University, Montreal, QC, H3A 1A1, Canada

    Pedro Rosa-Neto, Mirko Diksic, Marco Leyton, Shadreck Mzengeza & Chawki Benkelfat

  2. Department of Psychiatry, McGill University, Montreal, Canada

    Pedro Rosa-Neto, Marco Leyton & Chawki Benkelfat

Authors
  1. Pedro Rosa-Neto
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  2. Mirko Diksic
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  3. Marco Leyton
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  4. Shadreck Mzengeza
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  5. Chawki Benkelfat
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Correspondence to Chawki Benkelfat.

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Rosa-Neto, P., Diksic, M., Leyton, M. et al. Stability of α-[11C]methyl-l-tryptophan brain trapping in healthy male volunteers. Eur J Nucl Med Mol Imaging 32, 1199–1204 (2005). https://doi.org/10.1007/s00259-005-1829-5

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  • DOI: https://doi.org/10.1007/s00259-005-1829-5

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