Placed Beacons for Time Reversal Aberration Correction

描述（由申请人提供）：我们建议通过结合时间反转（TR）声学和声学液滴汽化（ADV）技术创建一种用于高选择性经颅组织消融和凝固的系统。该项目分为R21阶段，我们创建必要的基本设备和技术，以及R33阶段，我们应用设备和技术，最终使用尖锐聚焦的超声波束进行体内经颅组织消融。R21阶段的关键硬件组件是一个高效的混沌混响腔（CRC），它接近完整的2D阵列的能力，成本大大降低，复杂性和脆弱性降低。它将由TR系统驱动，该TR系统与点信标一起操作以克服CRC和信标之间的任何畸变。声学蒸发的液滴将产生大约30-60微米直径的气泡，这些气泡将用作重新聚焦的点信标。为CRC开发聚焦光束库将使我们能够在未知/无像差的3D空间中扫描和成像。在该项目的R33阶段，我们将扩展CRC的频率范围，包括100 kHz至5 MHz。这将使我们能够以非线性方式驱动气泡，并增强气泡检测和散射。此外，更高的频率将允许更容易的蒸发，但是更容易受到更高的插入损耗和入射波的衰减的影响。可能地，更高的频率也将在像差校正之后导致更好的空间分辨率。将使用具有空间分布的液滴/气泡的激光束来演示迭代聚焦技术，以单独识别和利用多个信标。从这个能力中，我们将分析系统执行动态聚焦的能力（关于位置和聚焦区形状）。最后，将通过离体人类颅骨帽结合1）组织模拟US体模、2）离体兔脑和3）去除兔颅骨帽的体内兔脑，分析系统的（畸变校正）性能。将在畸变校正后确定损伤发生的压力阈值。在体内部分的阳性结果后，我们将设计该方法在人体中应用的临床研究。

DESCRIPTION (provided by applicant): We propose to create a system for highly selective transcranial tissue ablation and coagulation by combining the techniques of time reversal (TR) acoustics and acoustic droplet vaporization (ADV). The project is subdivided into an R21 phase, where we create the necessary fundamental apparatus and techniques and an R33 phase where we apply the apparatus and techniques to eventually perform in vivo, transcranial tissue ablation with a sharply focused ultrasound beam. The crucial hardware component in the R21 phase is an efficient chaotic reverberant cavity (CRC) that approaches the capabilities of a full, 2D array, at a much reduced cost and with less complexity and fragility. It will be driven by a TR-system operating with point beacons to overcome any aberrators between the CRC and the beacon. Acoustically vaporized droplets will yield approximately 30-60 micron diameter gas bubbles that will be used as point beacons for refocusing. Development of a library of focused beams for the CRC will allow us to scan and image in an unknown/unaberrated 3D space. In the R33 phase of this project, we will extend the CRC's frequency range to include 100 kHz to 5 MHz. This will allow us to drive bubbles in a nonlinear manner and enhance bubble detection and scattering. Moreover, higher frequencies will allow for easier vaporization but are more subject for higher insertion loss and attenuation of incident waves. Possibly, higher frequencies will also result in better spatial resolution after aberration correction. Phantoms with spatially distributed droplets/gas bubbles will be used to demonstrate an iterative focusing technique to identify and utilize multiple beacons individually. From this ability we will then analyze the system's capability to perform dynamic focusing (both with regard to location and focal zone shape). Finally, the system will be analyzed for its (aberration correction) performance through an ex vivo human skull cap in conjunction with 1) a tissue mimicking US phantom, 2) ex vivo rabbit brain, and 3) in vivo rabbit brain with the rabbit's skull cap removed. The pressure threshold for the onset of lesions will be determined after aberration correction. Upon positive outcome of the in vivo section we will design a clinical study for in human application of this methodology.