Thallium-201 kinetics in nonischemic canine myocardium.

Myocardial thallium-201 (20TI) kinetics have not been precisely defined because reliable techniques to determine continuous activity in vivo have not been available. In this study, an implantable miniature cadmium telluride radiation detection device was inserted through the left ventricular apex, positioned against the endocardium, and used for continuous on-line monitoring of myocardial 201TI activity for 260-810 minutes in 18 dogs. Blood was serially sampled and counted. Microsphere-determined myocardial blood flow was measured before administration of 201TI and was not significantly different from that measured at the end of the experiment in 11 of 18 dogs. Thallium was administered intravenously. Myocardial and blood activity curves