[Clearance of 99mTc-Tetrofosmin from the myocardium and the adjacent organs]

We studied clearance of a new myocardial perfusion imaging agent, 99mTc-Tetrofosmin, from the myocardium and the adjacent organs in nine patients. 99mTc-Tetrofosmin was injected intravenously at stress and at rest, and SPECT images were obtained 25 min and 120 min later. Anterior view images were also obtained 10 min and 150 min after the injection to compare the myocardial clearance with those from the liver and lung. Clearance from the liver was faster than those from the myocardium and lung. Washout rate calculated with SPECT was higher for the inferior wall than for the anterior wall and lateral wall (p < 0.05 at rest, N.S. at stress). The value was higher at stress in any region than at rest (the anterior wall and lateral wall, p < 0.01; the septum, p < 0.05; the inferior wall, N.S.). Washout rate for the anterior wall was 3.4 +/- 14.0% at rest and 18.0 +/- 10.6% at stress. The rate for the lateral wall was 2.7 +/- 22.5% at rest and 15.8 +/- 7.9% at stress. It was suggested that rapid hepatic clearance and high myocardial washout at stress may be important in determining the period between the injection of 99mTc-Tetrofosmin and the data acquisition for SPECT imaging.