[Atraumatic approach in myocardial perfusion, metabolism and receptors by positron emission tomography]

Positron emission tomography (PET) is a noninvasive visualization method that provides a quantitative representation of radioactive molecule distribution on a tissue section within an organ. PET may be compared to the quantitative autoradiography performed in animals on heart sections with carbon 14- or tritium-labelled molecules, but it has the advantages of being applicable to human beings and enabling time-related concentration studies to be carried out on various substances. By using mathematical models fatty acid consumption or cholinergic receptor density can then be measured in e.g. the interventricular septum. Myocardial perfusion is routinely measured using such tracers as rubidium 82, nitrogen 13-labelled ammonia or even oxygen 15 water or gallium 68-labelled albumin microspheres. 82 Rb and 13NH3 ammonia are strongly taken up by the myocardium. 82 Rb has properties that are similar to those of 201Tl used in nuclear medicine, and the kinetics of 13NH3 depend on both myocardial perfusion and myocardial metabolism. The myocardium can metabolize fatty acids, glucose, ketone-bodies and lactic acid. 11C-palmitate is ideal to evaluate the regional utilization of fatty acids. It has been extensively studied in dogs, where a good correlation was found between the size of experimental infarcts and that of the region where a reduction in palmitate concentration was observed. Glucose metabolism is studied by means of an 18F-labelled analogue: fluoro-deoxyglucose. Using this analogue and 11C-palmitate jointly in animals or patients with myocardial ischaemia showed an increase of glucose myocardial extraction and a decrease of palmitate uptake in the ischaemic areas. In necrotic areas, both fluoro-deoxyglucose and palmitate uptakes were extremely low.(ABSTRACT TRUNCATED AT 250 WORDS)