First-pass radionuclide cardiographic determination of right ventricular ejection fraction and pulmonary transit time: Reliability with and without background subtraction

Abstract

Interrecording, interobserver, and intraobserver variability of three gamma camera methods (I, II, and III) in calculating right ventricular ejection fraction (RVEF) and a method for determination of mean pulmonary transit time (mPTT) were examined. The RVEF methods all employed ECG-gated recording of a99mtechnetium bolus in the 30° right anterior oblique position with separate end-diastolic and end-systolic right ventricular regions of interest (ROI); in method I, no background subtraction was performed; in method II, background subtraction was done by use of listmode recorded count rates in the right ventricular ROIs just prior to bolus arrival, and in method III a separate “background” ROI just below the right ventricle was used. In a tailored multiway analysis of variance, all three methods behaved statistically equally well with high reproducibility and no significant random or systematic variation. Interindividual range of RVEF values tended to be slightly higher, and systematic variation tended to be slightly lower for method III compared with methods I and II. In the inter- and intraobserver analyses, the mPTT method showed a high reproducibility, but there was a slight systematic increase from first to second recording. A plausible explanation and way of avoiding this phenomenon were identified. The gated first-pass technique with background subtraction allows reproducible repeated measurements of RVEF and mPTT.