Tellurium-123m-labeled-9-telluraheptadecanoic acid: a possible cardiac imaging agent.

Abstract

To study the value of the fatty acid analog 99mTe-labeled-9-telluraheptadecanoic acid (123mTe-THDA) as a cardiac imaging agent, 5 dogs had partial occlusion of the left anterior descending coronary artery. One hour later, 46Sc microspheres were injected into the left atrium, followed immediately by the i.v. 123mTe-THDA. After injection, regional myocardial 123mTe activity was monitored continuously with implanted miniature cadmium telluride radiation detectors in both ischemic and nonischemic zones. After 4 h, stannum 113 microspheres were injected into the left atrium and the dogs were killed. Ischemic and nonischemic areas of myocardium were section and counted in a well counter. Nonischemic myocardial 123mTe activity reached 88 .+-. 10% (mean .+-. SD) of peak activity within 1 min after injection, peaked in 8 .+-. 9 min, then decreased 2 .+-. 8% over the next 4 h. Ischemic myocardial 123mTe activity reached 97 .+-. 4% of peak activity within 1 min after injection, peaked in 5 .+-. 5 min, then decreased 5 .+-. 7% over the next 4 h. There was a linear correlation between 123mTe activity at 1 h and at 4 h and the initial 46Sc microsphere-determined regional myocardial blood flow (r = 0.93-0.96). Ischemic and nonischemic zone myocardial blood flows did not change significantly during the experiment. Cardiac images of excellent quality were obtained after 123mTe-THDA administration in 3 additional dogs with left anterior descending occlusions and 2 additional dogs with no occlusions using a conventional .gamma.-scintillation camera and a low-energy collimator. The linear relationship with regional myocardial blood flow, the minimal myocardial washout after a rapid peak, and the 159-keV gamma make 123mTe-THDA a promising new cardiac perfusion imaging agent.