BIOLOGICAL EVALUATION OF 5-METHYL-BRANCHED-CHAIN OMEGA-[F-18]FLUOROFATTY ACID - A POTENTIAL MYOCARDIAL IMAGING TRACER FOR POSITRON EMISSIONTOMOGRAPHY

5-Methyl-17-[F-18]fluoroheptadecanoic acid (5-MFHA) has been proposed as a new myocardial imaging tracer for positron emission tomography (P ET), containing methyl-branching at the odd-numbered position, except the 3-position. To compare the site of methyl-branching of fatty acids on the contribution to myocardial imaging, the biological evaluation of 5 MFHA-using accumulation studies, metabolic studies, and PET studi es of the heart muscle-was investigated. In the comparative biodistrib ution studies for 16-[F-18]fluoropalmitic acid (FPA), 3-methyl-17-[F-1 8]fluoroheptadecanoic acid (3-MFHA) and 5-MFHA, the initial myocardial uptake of 5-MFHA (2.64 [% dose/g tissue]) was relatively high between those of FPA and 3-MFHA (3.45 and 1.58, respectively), and the washou t from myocardium of 5-MFHA was midway between those of FPA and 3-MFHA . In the lipid analysis studies, 5-MFHA was mainly metabolized to trig lycerides in the myocardium, and its metabolic pattern was similar to that of straight chain fatty acids (FPA). In the PET studies using 5-M FHA in canines, good myocardial images were obtained for up to 30 min after injection.