Optimization of Second Harmonic Focusing Device and Imaging Using Microbubble Contrast Agents

Abstract We have developed a focused second-harmonic generator using microbubble contrast agents. However, this study does not provide an in-depth discussion on the influence of various device parameters on the focusing effect of the second harmonic acoustic field or the optimal values for each parameter. Therefore, there remains room for optimization in aspects such as the structural configuration and parametric design of this device. This study optimizes a microbubble-based harmonic-focusing device to produce a more stable and better-focused second-harmonic field for imaging. We analyze key structural parameters, including overall thickness, unit radius, and unit spacing on the effects of the emitted harmonic field properties such as peak pressure, main-lobe ratio, and full width at half maximum through numerical simulations. Theoretical results before and after optimization are compared and experimentally validated. The optimized device is then applied to ultrasound harmonic imaging. It produces significantly better image quality compared to the original device. This work offers a useful strategy for generating and focusing second harmonics. It contributes to improving harmonic generation in medical ultrasound through device design.