Myocardial imaging with extractable cations and inert tracers: the effects of flow and metabolism

The physical and biological properties of 201thallium (Tl) have been investigated and are discussed in this review. A new technique using the ultra-short lived 81mkrypton (81mKr) as a continuous infusion into the aortic root in dogs and man is described. This provides a dynamic assessment of changes in regional myocardial perfusion. Experiments using 201Tl and 81mKr in dogs have shown that regional decreases in myocardial perfusion alone cannot be detected in images of the heart using 201Tl. The effects of perfusion and a variety of factors on the energy dependent cellular uptake of 201Tl are discussed as being of primary importance in changing the regional myocardial distribution of this tracer. The constant infusion of 81mKr in patients with anginal chest pain provides continuous measurement of regional myocardial perfusion in high spatial resolution images. This dynamic method provides a physiological assessment of stenosed coronary arteries at rest and during stress.