IEEE Trans Ultrason Ferroelectr Freq Control. 2024 Oct;71(10):1199-1216. doi: 10.1109/TUFFC.2024.3456048. Epub 2024 Oct 10.
Transcranial ultrasound stimulation (TUS) holds promise for noninvasive neural modulation in treating neurological disorders. Most clinically relevant targets are deep within the brain (near or at its geometric center), surrounded by other sensitive regions that need to be spared clinical intervention. However, in TUS, increasing frequency with the goal of improving spatial resolution reduces the effective penetration depth. We show that by using a pair of 1-MHz orthogonally arranged transducers, we improve the spatial resolution afforded by each of the transducers individually, by nearly 40 folds, achieving a subcubic millimeter target volume of [Formula: see text]. We show that orthogonally placed transducers generate highly localized standing waves with acoustic radiation force (ARF) arranged into periodic regions of compression and tension near the target. We further present an extended capability of the orthogonal setup, which is to impart selective pressures-either positive or negative, but not both-on the target. Finally, we share our preliminary findings that strain can arise from both particle motion (PM) and ARF with the former reaching its maximum value at the focus and the latter remaining null at the focus and reaching its maximum around the focus. As the field is investigating the mechanism of interaction in TUS by way of elucidating the mapping between ultrasound parameters and neural response, orthogonal transducers expand our toolbox by making it possible to conduct these investigations at much finer spatial resolutions, with localized and directed (compression versus tension) ARF and the capability of applying selective pressures at the target.
经颅超声刺激（TUS）有望成为治疗神经疾病的非侵入性神经调节方法。大多数临床相关的靶点都位于大脑深部（接近或处于其几何中心），周围是需要避免临床干预的其他敏感区域。然而，在 TUS 中，为了提高空间分辨率而增加频率会降低有效穿透深度。我们表明，通过使用一对 1MHz 的正交排列换能器，我们可以将每个换能器单独提供的空间分辨率提高近 40 倍，达到[公式：见正文]的亚立方毫米目标体积。我们表明，正交放置的换能器在靠近目标的位置产生具有声辐射力（ARF）的高度局域驻波，ARF 排列成压缩和拉伸的周期性区域。我们进一步展示了正交设置的扩展功能，即可以在目标上施加选择性压力——无论是正压还是负压，但不能同时施加两种压力。最后，我们分享了初步发现，应变既可以来自粒子运动（PM），也可以来自 ARF，前者在焦点处达到最大值，后者在焦点处为零，并在焦点周围达到最大值。随着该领域通过阐明超声参数与神经反应之间的映射关系来研究 TUS 的相互作用机制，正交换能器通过使其能够以更高的空间分辨率进行这些研究，以及具有局部和定向（压缩与拉伸）的 ARF 以及在目标上施加选择性压力的能力，扩展了我们的工具包。
