Numerical analysis of ultrasonic transmission and absorption of oblique plane waves through the human skull
Numerical analysis of ultrasonic transmission and absorption of oblique plane waves through the human skull
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DOI：
10.1121/1.1410964
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发表时间：
2001-12-01
影响因子：
2.4
通讯作者：
Hynynen, K
中科院分区：
文献类型：
--
作者：
Hayner, M;Hynynen, K
数值分析了1/2~1 MHz频率范围内斜平面波在人体颅骨中的传播和吸收。这些频率对于脑部疾病的非侵入性超声治疗是最佳的，在这种情况下，颅骨传输的数值预测被用来设置相控阵聚焦系统中的源元素的相位和幅度。理想的头骨模型是一个三层固体，外层和内层是象牙色的，中间是骨髓层。每一层都被模拟为具有有效复数波速的平坦、均匀、各向同性的线性固体，以考虑由于材料阻尼和散射而引起的聚焦能量损失。该模型被用来预测透射波的幅度和相位以及体积吸收。结果报告了三种不同的头骨厚度：3毫米，6毫米和9毫米。在所有频率的3毫米头骨和低于0.75 MHz的6毫米头骨的透射波中观察到厚度共振。否则，传输以直达波为主。由于横波引起的颅骨相位误差显示，即使在材料阻尼较低的情况下，入射角度从正常到20度时，焦点处的功率也会降低到最低程度。峰值体积吸收的位置发生在外部象牙层或中间骨髓层，并显示由于波的干扰而不同。(C)2001年，美国声学学会。
Ultrasonic transmission and absorption of oblique plane waves through the human skull are analyzed numerically for frequencies ranging from 1/2 to 1 MHz. These frequencies are optimum for noninvasive ultrasound therapy of brain disorders where numerical predictions of skull transmission are used to set the phase and amplitude of source elements in the phased array focusing system. The idealized model of the skull is a three-layer solid with ivory outer and inner layers and a middle marrow layer. Each layer is modeled as a flat, homogeneous, isotropic, linear solid with effective complex wave speeds to account for focused energy losses due to material damping and scattering. The model is used to predict the amplitude and phase of the transmitted wave and volumetric absorption. Results are reported for three different skull thicknesses: 3 mm, 6 mm, and 9 mm. Thickness resonances are observed in the transmitted wave for 3 mm skulls at all frequencies and for the 6 mm skulls below 0.75 MHz. Otherwise, the transmission is dominated by the direct wave. Skull phase errors due to shear waves are shown to minimally degrade the power at the focus for angles of incidence up to 20 degrees from normal even for low material damping. The location of the peak volumetric absorption occurs either in the outer ivory or middle marrow layer and shown to vary due to wave interference. (C) 2001 Acoustical Society, of America.