Enhanced ultrasound transmission through the human skull using shear mode conversion
Enhanced ultrasound transmission through the human skull using shear mode conversion
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DOI：
10.1121/1.1645610
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发表时间：
2004-03-01
影响因子：
2.4
通讯作者：
Hynynen, K
中科院分区：
文献类型：
--
作者：
Clement, GT;White, PJ;Hynynen, K
研究了一种新的经颅传播技术，该技术有意地在颅骨中诱导剪切模式。超出Snell临界角的入射波经历从入射纵波到骨层中的剪切波的模式转换，然后回到脑中的纵波。头骨的剪切速度提供了更好的阻抗匹配，更少的折射，和更少的相位变化比其纵向对应。因此，我们研究了利用剪切波将超声聚焦到大脑中的想法。演示的现象，和数值预测首先研究与塑料幻影，然后使用离体人类头骨。结果表明，在0.74 MHz的频率transskull剪切方法产生的振幅的顺序，有时高于纵向传播。此外，由于剪切波经历减小的总相移，这表明简化现有的非侵入性经颅聚焦方法[Clement，Phys.Med.Biol.47（8），1219-1236（2002）]并将其扩展到大脑中的更大区域是合理的。(C)2004年，美国声学学会。
A new transskull propagation technique, which deliberately induces a shear mode in the skull bone, is investigated. Incident waves beyond Snell's critical angle experience a mode conversion from an incident longitudinal wave into a shear wave in the bone layers and then back to a longitudinal wave in the brain. The skull's shear speed provides a better impedance match, less refraction, and less phase alteration than its longitudinal counterpart. Therefore, the idea of utilizing a shear wave for focusing ultrasound in the brain is examined. Demonstrations of the phenomena, and numerical predictions are first studied with plastic phantoms and then using an ex vivo human skull. It is shown that at a frequency of 0.74 MHz the transskull shear method produces an amplitude on the order of-and sometimes higher than-longitudinal propagation. Furthermore, since the shear wave experiences a reduced overall phase shift, this indicates that it is plausible for an existing noninvasive transskull focusing method [Clement, Phys. Med. Biol. 47(8), 1219-1236 (2002)] to be simplified and extended to a larger region in the brain. (C) 2004 Acoustical Society of America.