Identification of ultrasound-contrast-agent dilution systems for cardiac quantification

This study presents a new minimally-invasive indicator dilution technique for cardiac quantification. An ultrasound contrast agent bolus is injected in a peripheral vein and detected by an ultrasound transducer. Several acoustic-intensity time curves are measured in specific regions of interest. After calibration, the resulting curves are processed by a Wiener deconvolution filter to identify the dilution system between different measurement sites, which is characterized by its impulse response function. This is interpolated and interpreted by specific models for the assessment of ejection fraction (EF) and pulmonary blood volume. The EF assessment is tested on a group of 20 patients with left ventricular EF going from 10% to 70%. The results show a 0.93 correlation coefficient with echographic hi-plane measurements. Blood volume measurements are validated in vitro and show a 0.99 correlation coefficient with the real volumes. The method feasibility is also tested in patients with promising results. In conclusion, the echographic identification of biological dilution systems is feasible. It allows a minimally invasive measurement of pulmonary blood volume and EF. The promising results encourage further validation and investigation for new applications.