A New Tc-99m-labeled Myocardial Imaging Agent, Hexakis(t-butylisonitrile)-technetium(I) [Tc-99m TBI]: Initial Experience in the Human

The cationic complex Tc-99m hexakis(t-butylisonitrile)technetium(I) (TBI) has been shown to concentrate in the myocardial tissue of several animal species. In the present preliminary study, the biodistribution of this material was examined in four normal subjects and in two patients with coronary artery disease. In three normal humans injected at rest, planar, tomographic, and gated myocardial images of high technical quality were obtained between 1 and 4 hr after injection. In one subject studied both at rest and during maximal exercise, the lung and heart activities were similar, whereas the liver-to-heart activity ratio was 3:1 at 60 min at rest compared with 1.8:1 with maximal exercise. In two patients with coronary artery disease, transient ischemia appeared as a perfusion defect up to 4 hr after injection at maximal exercise, and the image appeared normal when Tc-99m TBI was administered at rest. The images of areas of infarction appeared abnormal after injection at rest and after injection during exercise. Technetium-99m TBI is a promising myocardial imaging agent that may permit high-quality planar, gated, and tomographic imaging of myocardial ischemia and infarction.