Fatty Acid Imaging from Basic to Clinical
- Pp. 104-146 (43)Iichiro Osawa, Takashi Ushimi, Nanami Okano, Eito Kozawa and Ichiro Matsunari
A number of radiolabeled fatty acids have been developed to assess myocardial fatty acid metabolism. Radioactive fatty acid analogues are classified into PET and SPECT tracers; carbon-11 is the most common isotope for PET, while iodine- 123 is typically used in SPECT. The main approaches for the development in fatty acid tracers include shift from PET tracers to SPECT tracers, iodine stabilization, and prolonged retention of tracers in the myocardium. 15-(p-iodophenyl)-3-(R, S)-methyl pentadecanoic acid (BMIPP), an iodine-123 labeled branched-chain fatty acid analogue, has been widely available for routine clinical SPECT in Japan, and provides useful information on abnormal fatty acid metabolism in ischemic heart disease as well as nonischemic cardiomyopathy. This agent plays a crucial role in the diagnosis of these diseases, and the prediction of therapeutic effect and prognosis. Reduced BMIPP uptake than perfusion is often observed in ischemic heart disease such as myocardial infarction and angina pectoris. This mismatched uptake may reflect ischemic but viable myocardium, and is associated with stunned or hibernating myocardium. In addition, BMIPP can serve as a memory marker of transient myocardial ischemia because BMIPP abnormality may persist even after perfusion recovery following ischemia. On the other hand, heart-to-mediastinum (H/M) ratio is commonly used as an index of BMIPP uptake in nonischemic cardiomyopathy. This topic will overview basic principles and clinical applications of fatty acid metabolic imaging.