[Clinical usefulness of exercise/rest 99mTc-teboroxime SPECT imaging: results of a Japanese multi-center phase II study].

99mTc-Teboroxime [Chloro[tris(cyclohexyldioxime)methaneboronic acid] (99mTc)technetium], a perfusion agent for myocardial imaging, has a distinct advantage over 201Tl because of its very high myocardial extraction and is a 99mTc compound ideal for gamma camera imaging. This agent also demonstrates rapid myocardial washout, which allows completion of exercise and rest imaging studies in a short interval (to 1 hour). However, the rapid washout necessitates the completion of image acquisition very quickly after injection and therefore may require nonconventional SPECT imaging. In this Phase II study we evaluate the safety and efficacy of 99mTc-Teboroxime to detect coronary artery disease by exercise and rest SPECT imaging in 38 patients with prior myocardial infarction, 31 patients with angina pectoris, and 4 patients with non-coronary cardiac diseases. The 99mTc-Teboroxime dose used was 370-740 MBq in each study. The findings were compared with coronary angiography or 201Tl exercise and redistribution SPECT. No significant adverse reactions or laboratory abnormalities attributable to 99mTc-Teboroxime were observed. The quality of SPECT images was optimal in 62.5% of all patients. The relatively large population of suboptimal cases (37.5%) was attributed to the delay of the start and prolongation of the image acquisition time. In 85.7% of patients whose imaging was started within 5 minutes and completed within 11 minutes after injection, optimal quality was observed. Thus, 99mTc-Teboroxime SPECT requires the rapid completion of image acquisition after injection to achieve optimal image quality. Abnormalities of 99mTc-Teboroxime distribution were detected in 97.1% and 62.1% of patients with prior myocardial infarction or angina pectoris, respectively. The concordance with coronary angiography was 84.4% and 68.0%, and with 201Tl was 78.1% and 74.1%, respectively. Although standardization of the image protocol suitable for this agent is needed for the next study, these high correlations suggest the potential usefulness of 99mTc-Teboroxime SPECT imaging.