@article {Bishu60P, author = {S. Bishu and K. Schmidt and T. Burlin and M. Channing and T. Huang and Z. Liu and M. Qin and B. Vuong and Z. Xia and A. Zametkin and P. Herscovitch and C. Smith}, title = {PET measurement of regional rates of cerebral protein synthesis with L-[1-11C]leucine in young adult males}, volume = {48}, number = {supplement 2}, pages = {60P--60P}, year = {2007}, publisher = {Society of Nuclear Medicine}, abstract = {200 Objectives: We studied conscious, young adult men with the L-[1-11C]leucine PET method (Schmidt et al., 2005, JCBF\&M 25:617-628; Smith et al., 2005, JCBF\&M 25:629-640) to determine normal rates of cerebral protein synthesis (rCPS). Methods: Subjects (21-23y) were dynamically scanned with the HRRT scanner for 75 min following injection of L-[1-11C]leucine (19-26 mCi). ROI-based analyses were used to estimate kinetic model rate constants. rCPS was computed as [(K1k4)/(k2+k3+k4)]x(Cp/λ) where Cp is the arterial plasma leucine concentration. K1-k4 are rate constants for transport of leucine from plasma to brain, from brain to plasma, for catabolism of leucine, and for leucine incorporation into protein, respectively. Lambda equals (k2+k3)/(k2+k3+k4), the fraction of the precursor pool for protein synthesis derived from arterial plasma. Results: Our results (Table) show that in human brain 68\% of the precursor pool for protein synthesis comes from arterial plasma and 32\% from endogenous protein degradation. rCPS showed an expected regional pattern, while λ was relatively uniform throughout brain. Coefficients of variation (COV) for λ were 8\% in whole brain and 4-10\% in the five brain regions studied. For rCPS, COV were 9\% in whole brain and 8-18\% regionally.[table] Conclusions: Knowledge of the variance in rCPS measurements will be critical to design future clinical studies where group differences may be \<20\%. Computed sample size requirements to detect a 10\% change (P\<0.05) in whole brain rCPS with 75\% probability are 15 per group. Our results demonstrate the anticipated utility of the L-[1-11C]leucine PET method to measure changes in rCPS and λ in different interventions and clinical conditions. Research Support (if any): Supported by the Fragile X Research Foundation; Intramural Research Program, NIMH; CC, NIH}, issn = {0161-5505}, URL = {https://jnm.snmjournals.org/content/48/supplement_2/60P.2}, eprint = {https://jnm.snmjournals.org/content}, journal = {Journal of Nuclear Medicine} }