Metabolic tracers for PET scan

Metabolic tracers for PET (positron emission tomography) scan include C-11 palmitate, I-123 Beta-methyl-p-[123I]-iodophenyl-pentadecanoic acid (BMIPP) and F18 fluro-deoxy glucose (FDG). BMIPP is useful in assessing the fatty acid metabolism of the myocardium. Fatty acid metabolism may be suppressed for a longer period after an ischemic event because of ischemic memory of the myocardium. F18 FDG evaluates myocardial glucose utilisation. It is phosphorylated and trapped in the myocardium. F18 FDG uptake may be increased in viable myocardium which is hibernating due to chronic ischemia. Hibernation is suggested by FDG uptake in regions of myocardium with reduced blood flow. Fifty to seventy five gram glucose loading is done one to two hours prior to injection of F18 FDG. This is to enhance glucose metabolism and increase FDG uptake by the myocardium to improve the image quality. PET mismatch (termed perfusion–metabolism mismatch) pattern is enhanced uptake of FDG relative to the regional blood flow and is indicative of viable myocardium.

PET viability study is the traditional gold standard. Perfusion imaging is done with N13 ammonia or Rb82, while glucose metabolism is imaged by F18 fluro-deoxy glucose.