Development of 11C-Labeled ω-sulfhydryl fatty acid tracer for myocardial imaging with PET.

[11C]-S-methyl-16-thiopalmitic acid (a) was developed with excellent heart-to-background uptake ratios and higher retention in heart. Myocardial uptake and metabolism of the tracer is markedly higher CPT I dependent. When compared to [11C]-S-methyl-14-thiomyristic acid (b), [11C]-S-methyl-12-thiododecanoic acid (c) and [11C]-palmitate, a showed an early high uptake and a significantly slower late clearance in heart and a prolonged myocardial elimination half-life (30 min). Analysis of heart tissue and urine samples showed that a was metabolized via beta-oxidation in myocardium. Small animal PET images of the accumulation of a in the rat myocardium were clearly superior to [11C]-palmitate. These initial studies suggest that a could be a potentially useful clinical PET tracer to assess myocardial fatty acid metabolism.