Department of Biomedical Engineering, Columbia University, New York, NY, United States of America.
Phys Med Biol. 2018 Mar 15;63(6):065009. doi: 10.1088/1361-6560/aab05c.
Image-guided monitoring of microbubble-based focused ultrasound (FUS) therapies relies on the accurate localization of FUS-stimulated microbubble activity (i.e. acoustic cavitation). Passive cavitation imaging with ultrasound arrays can achieve this, but with insufficient spatial resolution. In this study, we address this limitation and perform high-resolution monitoring of acoustic cavitation-mediated blood-brain barrier (BBB) opening with a new technique called power cavitation imaging. By synchronizing the FUS transmit and passive receive acquisition, high-resolution passive cavitation imaging was achieved by using delay and sum beamforming with absolute time delays. Since the axial image resolution is now dependent on the duration of the received acoustic cavitation emission, short pulses of FUS were used to limit its duration. Image sets were acquired at high-frame rates for calculation of power cavitation images analogous to power Doppler imaging. Power cavitation imaging displays the mean intensity of acoustic cavitation over time and was correlated with areas of acoustic cavitation-induced BBB opening. Power cavitation-guided BBB opening with FUS could constitute a standalone system that may not require MRI guidance during the procedure. The same technique can be used for other acoustic cavitation-based FUS therapies, for both safety and guidance.
基于微泡的聚焦超声（FUS）治疗的图像引导监测依赖于 FUS 刺激微泡活动（即声空化）的准确定位。超声阵列的被动式空化成像是可以实现这一目标的，但空间分辨率不足。在这项研究中，我们解决了这一限制，采用一种称为功率空化成像的新技术，对声空化介导的血脑屏障（BBB）开放进行高分辨率监测。通过同步 FUS 发射和被动接收采集，使用具有绝对时间延迟的延迟求和波束形成实现了高分辨率的被动式空化成像。由于轴向图像分辨率现在取决于接收声空化发射的持续时间，因此使用短的 FUS 脉冲来限制其持续时间。以高帧率采集图像集，以类似于功率多普勒成像的方式计算功率空化图像。功率空化成像显示了随时间的平均声空化强度，并与声空化诱导的 BBB 开放区域相关联。FUS 引导的功率空化 BBB 开放可以构成一个独立的系统，在该过程中可能不需要 MRI 引导。该技术还可用于其他基于声空化的 FUS 治疗，以实现安全性和引导性。
