Assessment of myocardial perfusion using cardiac positron emission tomography

Positron emission tomography (PET) of the heart has gained widespread scien tific and clinical acceptance with regard to two indications: 1) The detect ion of perfusion abnormalities by qualitative and semiquantitative analyses of perfusion images at rest and during physical or pharmacological stress using well-validated perfusion tracers, such as N-13 ammonia, Rb-82 rubidiu m. chloride, or O-15 labeled water. 2) Viability imaging of myocardial regi ons with reduced contractility by combining perfusion measurements with sub strate metabolism as assessed from F-18 deoxyglucose utilization. This overview summarizes the use of PET as a perfusion imaging method. With a sensitivity > 90% in combination with high specificity, PET is today the best-validated available nuclear imaging technique for the diagnosis of co ronary artery disease (CAD). The short half-life of the perfusion tracers i n combination with highly sophisticated hard- and software enables rapid PE T studies with high patient throughput. The high diagnostic accuracy and th e methological advantages as compared to conventional scintigraphy allows o ne to use PET perfusion imaging to detect subtle changes in the perfusion r eserve for the detection of CAD in high risk but asymptomatic patients as w ell as in patients with proven CAD undergoing various treatment forms such as risk factor reduction or coronary revascularization. In patients followi ng orthotopic heart transplantation, evolving transplant vasculopathy can b e detected at an early stage. Quantitative PET imaging at rest allows for d etection of myocardial viability since cellular survival is based on mainte nance of a minimal perfusion and structural changes correlate to the degree of perfusion reduction. Furthermore, quantitative assessment of the myocar dial perfusion reserve detects the magnitude and competence of collaterals in regions with occluded epicardial collaterals and, thus, imaging of sever al coronary distribution territories in one noninvasive study. The cost of PET in combination with the cost of a cyclotron facility togeth er with the demanding methological problems have limited the availability o f perfusion PET to a few sophisticated centers. Therefore, quantitative PET investigations of myocardial perfusion have been performed predominantly f or scientific purposes, and the cost-effectiveness of PET in the everyday c linical setting is not yet finally proven. However, the unique possibilitie s of PET to study non-invasively and quantitatively myocardial perfusion an d metabolism as well as cardiac innervation and pharmacokinetics of cardiac drugs have established cardiac PET as a scientific tool of the highest qua lity for the future.