ECG-gated scintillation probe measurement of left ventricular function.

A nonimaging, ECG-gated scintillation-probe system is described that permits real-time quantification, at high temporal resolution, of the time variation of left ventricular (LV) volume over a complete, average cardiac cycle. Linearity between counting rate and volume, probe positioning, and background correction were investigated for both cylindrically collimated (CC) and parallel-hole-collimated (PC) detectors. In 53 patient studies, results obtained with these probes were compared with results obtained from an ECG-gated gamma camera system (CS) with high temporal resolution. Time-activity curves obtained by all three devices were essentially identical in shape (for CC against CS, r=0.93; for PC against CS, r=0.98) and in intracycle timing. Left-ventricular ejection fractions obtained with the probes showed workable agreement with the camera; for CC against CS, r=0.85 (N=31; for PC against CS, r=0.90 (N=21). When LV background is removed as a source of error, the correlation between (PC) probe and camera is improved (r=0.95, N=21). This suggests that the portable probe system be used in circumstances where exact knowledge of LV background is minimally important--e.g., continuous bedside monitoring of changes in LV function.