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

To study the value of the fatty acid analog tellurium-123m-labeled-9-telluraheptadecanoic acid (^123mTe-THDA) as a cardiac imaging agent, five dogs had partial occlusion of the left anterior descending coronary artery. One hour later, scandium-46 (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 hours, stannum-113 microspheres were injected into the left atrium and the dogs were killed. Ischemic and nonischemic areas of myocardium were sectioned and counted in a well counter. Nonischemic myocardial ^123mTe activity reached 88 ± 10% (mean ± SD) of peak activity within 1 minute after injection, peaked in 8 ± 9 minutes, then decreased 2 ± 8% over the next 4 hours. Ischemic myocardial ^123mTe activity reached 97 ± 4% of peak activity within 1 minute after injection, peaked in 5 ± 5 minutes, then decreased 5 ± 7% over the next 4 hours. There was a linear correlation between ^123mTe activity at 1 hour and at 4 hours 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 three additional dogs with left anterior descending occlusions and two 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.