Robin J, Tanter M, Pernot M
Institut Langevin, ESPCI Paris, CNRS UMR 7587, INSERM U979, Université Paris Diderot, PSL Research University, Paris, France.
Phys Med Biol. 2017 Sep 5;62(18):7471-7481. doi: 10.1088/1361-6560/aa8211.
Time reversal cavities (TRC) have been proposed as an efficient approach for 3D ultrasound therapy. They allow the precise spatio-temporal focusing of high-power ultrasound pulses within a large region of interest with a low number of transducers. Leaky TRCs are usually built by placing a multiple scattering medium, such as a random rod forest, in a reverberating cavity, and the final peak pressure gain of the device only depends on the temporal length of its impulse response. Such multiple scattering in a reverberating cavity is a complex phenomenon, and optimisation of the device's gain is usually a cumbersome process, mostly empirical, and requiring numerical simulations with extremely long computation times. In this paper, we present a semi-analytical model for the fast optimisation of a TRC. This model decouples ultrasound propagation in an empty cavity and multiple scattering in a multiple scattering medium. It was validated numerically and experimentally using a 2D-TRC and numerically using a 3D-TRC. Finally, the model was used to determine rapidly the optimal parameters of the 3D-TRC which had been confirmed by numerical simulations.
时间反转腔（TRC）已被提出作为一种用于三维超声治疗的有效方法。它们能够使用较少数量的换能器在大感兴趣区域内对高功率超声脉冲进行精确的时空聚焦。泄漏型TRC通常是通过在一个混响腔内放置一种多重散射介质（如随机棒阵）构建而成，并且该装置的最终峰值压力增益仅取决于其脉冲响应的时间长度。在混响腔内的这种多重散射是一种复杂现象，装置增益的优化通常是一个繁琐的过程，大多基于经验，并且需要计算时间极长的数值模拟。在本文中，我们提出了一种用于TRC快速优化的半解析模型。该模型将超声在空腔内的传播与在多重散射介质中的多重散射解耦。使用二维TRC进行了数值和实验验证，并使用三维TRC进行了数值验证。最后，该模型被用于快速确定三维TRC的最优参数，这些参数已通过数值模拟得到证实。
