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We propose a novel technique for measuring directly in real time, locally and non-invasively the pulse wave velocity (PWV) on peripheral arteries. Very high frame rate ultrasonic imaging (> 1000 frames/s) was achieved for tracking in 2D the propagation of transient vibrations along arterial wall. The arterial pulse waves are observed within a single cardiac cycle allowing the estimation of the pulse wave velocity with a good accuracy. In this study, this technique was validated for PWV evaluation on 25 healthy patients using conventional sonographic probes. The mean carotid PWV was found to be 5.5 ± 1.2 m/s (from 4.5 m/s to 7 m/s) with good intra and interobserver variability (inferior of 10% of the mean). These data suggest a good accuracy and reproducibility of the technique for real time PWV evaluation in vitro and on healthy volunteers.

The concept of shear wave elastography is applied to the heart. The goal of this study is to demonstrate the potential of this technique for quantifying the elasticity time variation of the myocardium. Experiments are performed in vivo on N=10 sheep with a linear high frequency probe placed directly on the myocardium. The feasibility of generating and imaging the propagation of shear wave in the beating heart and estimating locally the myocardium elasticity at each stage of a single heart cycle is investigated by repeating acquisition of shear wave propagation between 10 and 20 times per second. The dependence of estimated shear modulus with probe angle (short axis to long axis), depth and left ventricle pressure is studied in vivo and ex vivo. The short term effect of a local ischemia is also studied by coronary arteries ligature, showing the sensitivity of the technique to a local loss of contractility in the myocardium. Finally, this study shows the potential of shear wave elastography as a quantification tool of myocardium mechanical properties.

The concept of synthetic imaging using circular wave is proposed to image with a very large field of view and at a very high frame rate (≫1000 images/sec) heart motions with a conventional cardiac phased array probe. The goal of this study is to demonstrate in vivo the feasibility of this technique. Experiments are first performed in-vitro on ultrasound phantoms to optimize the trade-off between image quality and frame rate. An in vivo study is then performed on 10 sheep with a conventional phased array probe placed directly on the epicardium at different locations to obtain cine-loop of a complete heart cycle in the conventional imaging planes (long and short axis). After classical post processing of acquired cine-loop (wall tracking and tissue Doppler velocity estimation), the propagation of mechanical waves induced naturally during the heart cycle such as aortic and mitral valves closure can be observed.