Department of Radiology, Stanford University, Palo Alto, CA 94304, United States of America.
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America.
Phys Med Biol. 2024 Nov 11;69(22):225006. doi: 10.1088/1361-6560/ad8d9f.
A 750 kHz, 360-element ultrasound array has been built for transcranial histotripsy applications. This study aims to evaluate its performance to determine whether this array is adequate for treating a wide range of brain locations through a human skull. Treatment location profiles in 2 excised human skulls were experimentally characterized based on passive cavitation mapping. Full-wave acoustic simulations were performed in 8 human skulls to analyze the ultrasound propagation at shallow targets in skulls with different properties. Results showed that histotripsy successfully generated cavitation from deep to shallow targets within 5 mm from the skull surface in the skull with high SDR and small thickness, whereas in the skull with low SDR and large thickness, the treatment envelope was limited up to 16 mm from the skull surface. Simulation results demonstrated that the treatment envelope was highly dependent on the skull acoustic properties. Pre-focal pressure hotspots were observed in both simulation and experiments when targeting near the skull. For each skull, the acoustic pressure loss increases significantly for shallow targets compared to central targets due to high attenuation, large incident angles, and pre-focal pressure hotspots. Strategies including array design optimization, pose optimization, and amplitude correction, are proposed to broaden the treatment envelope. This study identifies the capabilities and limitations of the 360-element transcranial histotripsy array and suggests strategies for designing the next-generation transcranial histotripsy array to expand the treatment location profile for a future clinical trial.
已构建了一个 750 kHz、360 个阵元的超声换能器阵列，用于经颅组织破碎治疗。本研究旨在评估其性能，以确定该阵列是否足以通过人类颅骨治疗广泛的脑区。基于被动空化测绘，在 2 个人头骨中对处理位置分布进行了实验特征描述。在 8 个人头骨中进行了全波声学模拟，以分析不同特性头骨中浅层目标的超声传播。结果表明，在高 SDR 和小厚度头骨中，从深层到浅层目标的组织破碎可在颅骨表面下 5mm 范围内成功产生空化，而在低 SDR 和大厚度头骨中，处理范围仅限于颅骨表面下 16mm。模拟结果表明，处理范围高度依赖于颅骨的声学特性。当接近颅骨时，在模拟和实验中都观察到了焦前压力热点。对于每个头骨，由于高衰减、大入射角和焦前压力热点，与中央靶点相比，浅层靶点的声压损失显著增加。提出了包括阵列设计优化、位姿优化和幅度校正在内的策略，以扩大处理范围。本研究确定了 360 个阵元经颅组织破碎换能器阵列的能力和局限性，并提出了设计下一代经颅组织破碎换能器阵列的策略，以扩大未来临床试验的治疗位置分布。
