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

A simple algorithm is developed to enhance the resolution of component s of multimodal pulmonary radiohistograms. Based on the assessed right ventricular ejection fraction (RVEF), it deconvolves out the effect o f 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. O nce RVEF is known, implementation of the algorithm is simple. If RVEF is not known accurately it may be replaced with its upper estimate, RV EF(up)>RVEF, yielding a partial deconvolution of the curve. When appli ed to studies of patients with left-to-right shunt the method improves the accuracy and lessens the interobserver variation of the Maltz-Tre ves method.