Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada.
Phys Med Biol. 2013 Jul 21;58(14):4981-5005. doi: 10.1088/0031-9155/58/14/4981. Epub 2013 Jun 27.
The feasibility of transcranial passive acoustic mapping with hemispherical sparse arrays (30 cm diameter, 16 to 1372 elements, 2.48 mm receiver diameter) using CT-based aberration corrections was investigated via numerical simulations. A multi-layered ray acoustic transcranial ultrasound propagation model based on CT-derived skull morphology was developed. By incorporating skull-specific aberration corrections into a conventional passive beamforming algorithm (Norton and Won 2000 IEEE Trans. Geosci. Remote Sens. 38 1337-43), simulated acoustic source fields representing the emissions from acoustically-stimulated microbubbles were spatially mapped through three digitized human skulls, with the transskull reconstructions closely matching the water-path control images. Image quality was quantified based on main lobe beamwidths, peak sidelobe ratio, and image signal-to-noise ratio. The effects on the resulting image quality of the source's emission frequency and location within the skull cavity, the array sparsity and element configuration, the receiver element sensitivity, and the specific skull morphology were all investigated. The system's resolution capabilities were also estimated for various degrees of array sparsity. Passive imaging of acoustic sources through an intact skull was shown possible with sparse hemispherical imaging arrays. This technique may be useful for the monitoring and control of transcranial focused ultrasound (FUS) treatments, particularly non-thermal, cavitation-mediated applications such as FUS-induced blood-brain barrier disruption or sonothrombolysis, for which no real-time monitoring techniques currently exist.
使用基于 CT 的像差校正的半球形稀疏阵列（直径 30cm，16 到 1372 个单元，2.48mm 接收器直径）进行经颅被动声映射的可行性通过数值模拟进行了研究。开发了一种基于多层射线声经颅超声传播模型，该模型基于 CT 得出的颅骨形态。通过将颅骨特定的像差校正纳入传统的被动波束形成算法（Norton 和 Won 2000 IEEE Trans. Geosci. Remote Sens. 38 1337-43），模拟的声源场代表了受声刺激的微泡的发射，通过三个数字化的人类颅骨进行了空间映射，经颅重建与水路径控制图像非常匹配。基于主瓣波束宽度、峰值旁瓣比和图像信噪比来量化图像质量。还研究了声源的发射频率和位置、阵列稀疏度和单元配置、接收器元件灵敏度以及特定颅骨形态对图像质量的影响。还估计了该系统在各种程度的阵列稀疏度下的分辨率能力。通过完整的颅骨对声源进行被动成像成为可能，这可能对经颅聚焦超声（FUS）治疗的监测和控制有用，特别是对于没有实时监测技术的非热、空化介导的应用，例如 FUS 诱导的血脑屏障破坏或声溶栓。
