Sun J, Hynynen K
Division of MRI/Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
J Acoust Soc Am. 1998 Sep;104(3 Pt 1):1705-15. doi: 10.1121/1.424383.
A numerical model was developed which can use digitized layer interfaces to calculate ultrasound wave absorption, diffraction, reflection, and refraction. This model was used to evaluate the feasibility of ultrasound therapy and surgery through a human skull. A digitized human skull profile was obtained from magnetic resonance (MR) images and used to calculate the ultrasound field in the brain of a volunteer from a spherically curved phased array. With no phase correction, the focus of the array was shifted and defocused. The phased array technique was used to correct focal shift, reduce side lobes, and enhance focal amplitude. The optimum source element width was estimated for each frequency to obtain a near optimium focus, and an appropriate frequency range for transskull ultrasound therapy and surgery was determined. Acoustic pressure amplitude on the skull surfaces was examined, and it was shown that the skull heating problem could be overcome. Despite high attenuation, complex interface shape, and nonuniform thickness of a human skull, a sharply focused transskull ultrasound field can be generated for noninvasive ultrasound therapy and surgery in the brain.
开发了一种数值模型，该模型可以使用数字化的层界面来计算超声波的吸收、衍射、反射和折射。该模型用于评估通过人类头骨进行超声治疗和手术的可行性。从磁共振（MR）图像中获取数字化的人类头骨轮廓，并用于计算来自球形弯曲相控阵的志愿者大脑中的超声场。在没有相位校正的情况下，阵列的焦点发生了偏移和散焦。相控阵技术用于校正焦点偏移、减少旁瓣并增强焦点振幅。估计了每个频率的最佳源元件宽度以获得接近最佳的焦点，并确定了用于经颅超声治疗和手术的合适频率范围。检查了头骨表面的声压振幅，结果表明可以克服头骨加热问题。尽管人类头骨具有高衰减、复杂的界面形状和不均匀的厚度，但仍可以产生用于大脑无创超声治疗和手术的尖锐聚焦的经颅超声场。
