RT Journal Article SR Electronic T1 PET measurement of regional rates of cerebral protein synthesis with L-[1-11C]leucine in young adult males JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 60P OP 60P VO 48 IS supplement 2 A1 S. Bishu A1 K. Schmidt A1 T. Burlin A1 M. Channing A1 T. Huang A1 Z. Liu A1 M. Qin A1 B. Vuong A1 Z. Xia A1 A. Zametkin A1 P. Herscovitch A1 C. Smith YR 2007 UL http://jnm.snmjournals.org/content/48/supplement_2/60P.2.abstract AB 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