Serial radionuclide determinations of the electron fraction with 99mTc-labeled red blood cells.

The reproducibility of area/length ejection fraction determinations was evaluated in 21 subjects using 99mTc-labeled red blood cells (99mTc-RBCs). The ejection fraction was determined within 30 minutes and 3-5 hours after a single injection of 99mTc-RBCs. The mean absolute difference between the initial and subsequent ejection fractions was 7% (maximum, 15%) (r = 0.90). 99mTc-RBCs offer a reproducible method of determining the ejection fraction which is suitable for serial noninvasive evaluations of left ventricular function.