Equivalence of arterial and venous blood for [11C]CO2-metabolite analysis following intravenous administration of 1-[11C]acetate and 1-[11C]palmitate

PurposeSampling of arterial blood for metabolite correction is often required to define a true radiotracer input function in quantitative modeling of PET data. However, arterial puncture for blood sampling is often undesirable. To establish whether venous blood could substitute for arterial blood in metabolite analysis for quantitative PET studies with 1-[11C]acetate and 1-[11C]palmitate, we compared the results of [11C]CO2-metabolite analyses performed on simultaneously collected arterial and venous blood samples.MethodsPaired arterial and venous blood samples were drawn from anesthetized pigs at 1, 3, 6, 8, 10, 15, 20, 25 and 30 min after i.v. administration of 1-[11C]acetate and 1-[11C]palmitate. Blood radioactivity present as [11C]CO2 was determined employing a validated 10-min gas-purge method. Briefly, total blood 11C radioactivity was counted in base-treated [11C]-blood samples, and non-[11C]CO2 radioactivity was counted after the [11C]-blood was acidified using 6 N HCl and bubbled with air for 10 min to quantitatively remove [11C]CO2.ResultsAn excellent correlation was found between concurrent arterial and venous [11C]CO2 levels. For the [11C]acetate study, the regression equation derived to estimate the venous [11C]CO2 from the arterial values was: y = 0.994x + 0.004 (r2 = 0.97), and for the [11C]palmitate: y = 0.964x − 0.001 (r2 = 0.9). Over the 1–30 min period, the fraction of total blood 11C present as [11C]CO2 rose from 4% to 64% for acetate, and 0% to 24% for palmitate. The rate of [11C]CO2 appearance in venous blood appears similar for the pig model and humans following i.v. [11C]-acetate administration.ConclusionVenous blood [11C]CO2 values appear suitable as substitutes for arterial blood samples in [11C]CO2 metabolite analysis after administration of [11C]acetate or [11C]palmitateAdvances in Knowledge and Implications for Patient CareQuantitative PET studies employing 1-[11C]acetate and 1-[11C]palmitate can employ venous blood samples for metabolite correction of an image-derived tracer arterial input function, thereby avoiding the risks of direct arterial blood sampling.