Free Fatty Acid Flux Measured Using [1-C-11]Palmitate Positron Emission Tomography And [U-C-13]Palmitate In Humans

PET radiopharmaceuticals can noninvasiveiy measure tree ratty acid (FFA) tissue uptake. Investigators often use PET scan-derived data to calculate FFA flux. We tested whether the [1-C-11]palmitate PET measures of palmitate flux provide results equivalent to a continuous infusion of [U-C-13]palmitate. Nine volunteers participated in study I to evaluate whether a rapidly (10-20 s) given bolus of [1-C-11]paimitate affects calculated flux results. Thirty volunteers participated in study 2, which was identical to study 1 except that the [1-C-11]palmitate bolus was given over 1 mill. Volunteers in both studies also received a continuous intravenous infusion of [U-C-13] jpalmitate. Plasma palmitale concentrations and cnrichmenl were measured by liquid chromalographymass spectrometry. The PET/CT images were analyzed on a workstation running PMOD. Palmitate flux was estimated using PKT time-activity curve (TAG) data from regions of interest in the left ventricle (LV) and aorta both with and without hybrid TACs that employed the (CO2)-C-11-corrected data for the first 5 min and the (CO2)-C-11-corrected blood radioactivity for the remainder of the PET scan. Palmitate flux in study 1 measured with PKT [1-C-11]palmitate and [U-C-13]palmitate were not correlated, and the PKT [1-C-11]palmitate flux was significantly less than the [U-C-13] palmitate measured flux. In study 2, the palmitate flux using PET [1-C-11]palmitate hybrid LV models provided closer mean estimates of [1-C-13]palmitate measured flux. The best PET calculation approaches predicted 64% of the interindividuai variance in [U-C-13] palmitate measured flux. Palmitate kinetics measured using [1-C-11] palmitate/PET do not provide the same palmitate kinetic results as the continuous infusion [U-C-13]palmitate approach.