Alternative method for calculating right ventricular ejection fraction from first-pass time-activity curves.

Single-beat right ventricular ejection fraction (RVEF) determined using the first-pass method changes with rapid variations in the concentration of radionuclide tracer in the ventricle. Underestimation of single-beat RVEF occurs when radionuclide tracer rapidly enters the ventricle, and overestimation results when the tracer quickly flows out of the ventricle. In order to attenuate this effect, a data processing technique employing the relative "time-volume" curve was proposed. In the present paper, it was assumed that this time-volume curve could be approximated by dividing the original time-activity curve by a gamma variate function representing the time-concentration curve. Each single-beat ejection fraction calculated from the time-volume curve agreed well with the known phantom ejection fraction although the concentration of tracer varied rapidly. This new method was applied to several clinical cases.