Résumé: © 1986-2012 IEEE. In this paper, defects in a high density polyethylene pipe are imaged with the total focusing method. The viscoelastic attenuation of this material greatly reduces the signal level and leads to a poor signal-to-noise ratio (SNR) due to electronic noise. To improve the image quality, the decomposition of the time reversal operator method is combined with the spatial Hadamard coded transmissions before calculating images in the time domain. Because the Hadamard coding is not compatible with conventional imaging systems, this paper proposes two modified coding methods based on sparse Hadamard matrices with +1/0 coefficients. The SNRs expected with the different spatial codes are demonstrated, and then validated on both simulated and experimental data. Experiments are performed with a transducer array in contact with the base material of a polyethylene pipe. In order to improve the noise filtering procedure, the singular values associated with electronic noise are expressed on the basis of the random matrix theory. This model of noise singular values allows a better identification of the defect response in noisy experimental data. Finally, the imaging method is evaluated in a more industrial inspection configuration, where an immersion array probe is used to image defects in a butt fusion weld with a complex geometry.

Résumé: © 2017 The Authors The authors propose a novel noninvasive therapeutic approach for degenerative calcified bioprosthetic heart valves based on pulsed cavitational ultrasound (PCU) to improve the valvular function by remotely softening calcified stiff cusps. This study aims to demonstrate both in vivo, using an ovine model with implanted human calcified bioprosthesis, and in vitro that PCU can significantly improve the bioprosthesis function. A 50% decrease of the transvalvular gradient was found, demonstrating a strong improvement of the valve opening function. This new noninvasive approach has the potential to improve the outcomes of patients with severe bioprosthesis stenosis.