DECONVOLVING OUT INDICATOR SMEARING IN THE RIGHT VENTRICLE FACILITATES LEFT-TO-RIGHT SHUNT QUANTITATION

A simple algorithm is developed to enhance the resolution of components of multimodal pulmonary radiohistograms. Based on the assessed right ventricular ejection fraction (RVEF), it deconvolves out the effect of indicator smearing in the right ventricle on the heart rate samples of the pulmonary radiohistogram, c(k). The output is the ideal curve, c(k)'=c(k)/RVEF - (1-RVEF).c(k-1)/RVEF, that would be obtained if RVEF equalled unity. Since the formula is not a recursive one, it does not suffer from error propagation pertinent to numerical deconvolution. Once RVEF is known, implementation of the algorithm is simple. If RVEF is not known accurately it may be replaced with its upper estimate, RVEF(up)>RVEF, yielding a partial deconvolution of the curve. When applied to studies of patients with left-to-right shunt the method improves the accuracy and lessens the interobserver variation of the Maltz-Treves method.