The use of ultrasound-stimulated acoustic emission in the monitoring of modulus changes with temperature
The use of ultrasound-stimulated acoustic emission in the monitoring of modulus changes with temperature
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DOI：
10.1016/s0041-624x(03)00125-2
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发表时间：
2003-07-01
期刊：
影响因子：
4.2
通讯作者：
Hynynen, K
中科院分区：
文献类型：
--
作者：
Konofagou, E;Thierman, J;Hynynen, K
以前已经表明，超声刺激的声发射(USAE)信号的幅度对组织温度敏感，因此可以帮助检测它。然而，它的幅度对声学和机械参数都很敏感，而在大多数频率上，由于温度的原因，这些参数会产生相反的影响。在本文中，我们探索了利用USAE信号的共振峰的频移来监测组织硬度随温度变化的可行性。在数值模拟中，给出了不同温度下频移的变化情况。然后，在一系列涉及凝胶体模和猪肌肉组织的实验中，频移的变化被证明遵循已知的由于温度引起的刚度变化。这一转变也预示着可逆性变化和热凝固性坏死的开始。坏死的特点是单调递增的正频移。结果表明，当刚度减小时，USAE谱峰发生负移(或下移)，而当刚度增大时，USAE谱峰发生正移(或上移)。在25-70℃和30-70℃的温度下，凝胶和肌肉组织的实验频率分别在-250到80赫兹和-200到250赫兹的范围内在22.1-22.5千赫的峰值附近移动。仿真和体外实验结果表明，USAE频移法可以将机械参数与声学参数的依赖关系解耦，并能检测到热凝固性坏死的发生。(C)2003 Elsevier Science B.V.保留所有权利。
It has been previously shown that the amplitude of the ultrasound-stimulated acoustic emission (USAE) signal is sensitive to tissue temperature and, therefore, can help detect it. Its amplitude, however, is sensitive to both acoustical and mechanical parameters, that at most frequencies have opposite effects due to temperature. In this paper, we explore the feasibility of using a frequency shift of the resonant peaks of the USAE signal for monitoring the tissue stiffness variation with temperature. In a numerical simulation, the variation of the frequency shift at different temperatures is shown. Then, in a series of experiments involving a gel phantom and porcine muscle tissue, the frequency shift variation is shown to follow the known stiffness changes due to temperature. It is also shown that this shift indicates reversible changes as well as the onset of thermal coagulative necrosis. The necrosis is marked by a monotonically increasing positive frequency shift. It was thus shown that the USAE spectrum peaks undergo a negative shift (or, downshift) when the stiffness decreases and a positive shift (or, upshift) when the stiffness increases. The experimental frequency shifted around a peak at 22.1-22.5 kHz within a range of -250 to 80 Hz and -200 to 250 Hz for the gel and muscle tissue for the temperatures of 25-70 and 30-70 degreesC, respectively. Simulation and ex vivo experimental results indicate that the USAE frequency shift method can help decouple the mechanical from the acoustical parameter dependence as well as detect the onset of thermal coagulative necrosis. (C) 2003 Elsevier Science B.V. All rights reserved.