Myocardial Kinetics of Potassium-38 in Humans and Comparison with Copper-62-PTSM

The aim of this study was to define the kinetics of {sup 38}K and its suitability to evaluate myocardial blood flow at rest and during pharmacological vasodilation in normal subjects. Potassium-38`s kinetic characteristics were also compared to those of a {sup 62}Cu-pyruvaldehyde bis(n{sup 4}l-methyl-thio-semicarbazone) copper (II) (PTSM) flow tracer. Potassium-38 and {sup 62}Cu-PTSM were injected at rest and after pharmacological vasodilation in six healthy volunteers. Dynamic PET acquisition was performed over 20 min and myocardial tracer retention calculated. Homogeneity of regional myocardial tracer distribution was also evaluated. High image quality of the heart was observed at rest and after dipyridamole with both tracers. Potassium-38 demonstrated prolonged myocardial retention with minimal lung and liver accumulation. in contrast to {sup 38}K, {sup 62}Cu-PTSM demonstrated high liver uptake which may hinder observation of the inferior wall of the myocardium. Copper-62-PTSM dipyridamole-to-rest retention ratio was 1.49. Potassium-38 and {sup 62}Cu-PTSM display suitable kinetics for the qualitative evaluation of blood flow and flow reserve in the human heart. Compared to {sup 62}Cu-PTSM, potassium-38, which does not show high liver uptake, may more accurately estimate blood flow in the inferior wall of the heart. However, accurate quantification of myocardial blood flow using {sup 38}K or {supmore » 62}Cu-PTSM retention appears to be limited to decreasing retention fraction at hyperhemic states. 29 refs., 5 figs.« less