IEEE Trans Ultrason Ferroelectr Freq Control. 2021 Jul;68(7):2361-2369. doi: 10.1109/TUFFC.2021.3062357. Epub 2021 Jun 29.
Passive cavitation mapping (PCM), which generates images using bubble acoustic emission signals, has been increasingly used for monitoring and guiding focused ultrasound surgery (FUS). PCM can be used as an adjunct to magnetic resonance imaging to provide crucial information on the safety and efficacy of FUS. The most widely used algorithm for PCM is delay-and-sum (DAS). One of the major limitations of DAS is its suboptimal computational efficiency. Although frequency-domain DAS can partially resolve this issue, such an algorithm is not suitable for imaging the evolution of bubble activity in real time and for cases in which cavitation events occur asynchronously. This study investigates a transient angular spectrum (AS) approach for PCM. The working principle of this approach is to backpropagate the received signal to the domain of interest and reconstruct the spatial-temporal wavefield encoded with the bubble location and collapse time. The transient AS approach is validated using an in silico model and water bath experiments. It is found that the transient AS approach yields similar results to DAS, but it is one order of magnitude faster. The results obtained by this study suggest that the transient AS approach is promising for fast and accurate PCM.
被动空化映射（PCM）使用气泡声发射信号生成图像，已越来越多地用于监测和引导聚焦超声手术（FUS）。PCM 可以作为磁共振成像的辅助手段，提供有关 FUS 安全性和有效性的关键信息。最广泛使用的 PCM 算法是延迟求和（DAS）。DAS 的主要限制之一是其计算效率不理想。虽然频域 DAS 可以部分解决此问题，但此类算法不适用于实时成像气泡活动的演变，也不适用于异步发生空化事件的情况。本研究探讨了用于 PCM 的瞬态角谱（AS）方法。该方法的工作原理是将接收到的信号反向传播到感兴趣的域，并重建带有气泡位置和坍塌时间的时空波场。使用数值模型和水浴实验验证了瞬态 AS 方法。结果表明，瞬态 AS 方法的结果与 DAS 相似，但速度快一个数量级。本研究的结果表明，瞬态 AS 方法有望实现快速准确的 PCM。
