A Non-linear Model Coupling the Ultrasound Pulse-Echo Procedure and Contrast Agent Excitation and Backscatter: Validation Studies in Water

摘要

By employing microbubbles to enhance ultrasound backscatter, we have recently developed a technique, termed echo particle image velocimetry (Echo PIV), to perform accurate measurements of velocity profiles, multiple velocity vectors and local shear stress in arteries. Maximizing bubble detectability from the surrounding environment is a key issue for Echo PIV, and significant optimization of all aspects from transducer design to bubble characteristics to backscatter signal processing is required for continued improvement of this technique. We present here a numerical model coupling the time-domain FEA simulation of a 1D ultrasonic transducer array and non-linear ultrasound propagation in water with the solution for non-linear equations describing backscatter from bubble populations with varying size distributions to simulate the ultrasound pulse-echo procedure and contrast agent excitation. Experimental validation for the FEA models of the transducer array and wave propagation in water was performed according to industry standards. The backscatter from micron- and sub-micron bubble populations (size range: 0.5 - 5 microns) was simulated by a previously-validated size-integration (SI) method. The coupled model also showed greater ability of the triangular wave to excite subharmonic and ultraharmonic frequency content in bubbles, while minimizing the possibility of bubble rupture. It should be useful as an efficient tool for array transducer simulations in the context of contrast imaging.