RESUMO
The left-ventricle ejection fraction is an important cardiac-efficiency measure that is regularly used in cardiology. Standard estimations are based on time-consuming geometrical analysis and modelling, which requires experienced cardiologists. Alternative methods are very invasive due to the need for cardiac catheterization. In this paper we present and study a minimally-invasive indicator dilution technique for ejection fraction quantification that has recently been developed. It is based on a peripheral injection of an ultrasound contrast agent bolus. Left-atrium and left-ventricle acoustic intensities are recorded versus time by transthoracic echocardiography during contrast bolus passage. The measured curves are corrected for attenuation distortion, filtered to suppress the measurement noise, and processed by an adaptive Wiener deconvolution algorithm for the estimation of the left-ventricle impulse response. The estimated impulse response is interpolated by a mono-compartment exponential model for the ejection fraction assessment. An adaptive search of the interval for the model fitting is also included. The feasibility of the method is tested on 52 measurements in patients with left-ventricle ejection fractions between 10% and 80%. The results are promising and show a 0.83 correlation coefficient with echographic biplane ejection fraction measurements.