Evaluation of sequential subtraction processing for radionuclide angiography

Sequential subtraction processing of successive time frames acquired by conventional radionuclide angiography was evaluated fundamentally and clinically. The processing reduced efficiently blood back-ground, which resulted from mutual superimposition of vascular system, by means of subtracting a posterior component of the intravascular distribution of first-pass radioactivity. Upon phantom experiment, an appropriate method of the processing was established by evaluating signal-to-noise ratio of the image, quantitative accuracy of the time-activity curve and the consequential artifact. Upon clinical application, the processed time frames could demonstrated regional components of vascular system such as the left atrium or abnormal blood flow appearances such as shunt more distinctly than the original frames. And, time-activity curves obtained from the processed time frames revealed narrow dispersion of cardiac output values measured from the right ventricular, pulmonary and left ventricular curve in all cases with congestive heart failure, and described clear shunt curve providing reproducible and reasonable value of pulmonary-to-systemic flow ratio in all cases with left-to-right cardiac shunt