中国物理B ›› 2018, Vol. 27 ›› Issue (2): 24302-024302.doi: 10.1088/1674-1056/27/2/024302

• ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS • 上一篇    下一篇

Influence of mode conversions in the skull on transcranial focused ultrasound and temperature fields utilizing the wave field separation method: A numerical study

Xiang-Da Wang(王祥达), Wei-Jun Lin(林伟军), Chang Su(苏畅), Xiu-Ming Wang(王秀明)   

  1. 1. State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China;
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • 收稿日期:2017-09-29 修回日期:2017-11-13 出版日期:2018-02-05 发布日期:2018-02-05
  • 通讯作者: Wei-Jun Lin E-mail:linwj@mail.ioa.ac.cn
  • 基金资助:

    Project supported by the National Natural Science Foundation of China (Grant Nos. 81527901, 11604361, and 91630309).

Influence of mode conversions in the skull on transcranial focused ultrasound and temperature fields utilizing the wave field separation method: A numerical study

Xiang-Da Wang(王祥达)1,2, Wei-Jun Lin(林伟军)1, Chang Su(苏畅)1, Xiu-Ming Wang(王秀明)1   

  1. 1. State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China;
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2017-09-29 Revised:2017-11-13 Online:2018-02-05 Published:2018-02-05
  • Contact: Wei-Jun Lin E-mail:linwj@mail.ioa.ac.cn
  • About author:43.35.+d; 43.80.+p; 87.50.Y-; 43.35.Cg
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Grant Nos. 81527901, 11604361, and 91630309).

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摘要：

Transcranial focused ultrasound is a booming noninvasive therapy for brain stimuli. The Kelvin-Voigt equations are employed to calculate the sound field created by focusing a 256-element planar phased array through a monkey skull with the time-reversal method. Mode conversions between compressional and shear waves exist in the skull. Therefore, the wave field separation method is introduced to calculate the contributions of the two waves to the acoustic intensity and the heat source, respectively. The Pennes equation is used to depict the temperature field induced by ultrasound. Five computational models with the same incident angle of 0° and different distances from the focus for the skull and three computational models at different incident angles and the same distance from the focus for the skull are studied. Numerical results indicate that for all computational models, the acoustic intensity at the focus with mode conversions is 12.05% less than that without mode conversions on average. For the temperature rise, this percentage is 12.02%. Besides, an underestimation of both the acoustic intensity and the temperature rise in the skull tends to occur if mode conversions are ignored. However, if the incident angle exceeds 30°, the rules of the over-and under-estimation may be reversed. Moreover, shear waves contribute 20.54% of the acoustic intensity and 20.74% of the temperature rise in the skull on average for all computational models. The percentage of the temperature rise in the skull from shear waves declines with the increase of the duration of the ultrasound.

关键词: transcranial focused ultrasound, temperature rise, mode conversion, wave field separation

Abstract:

Transcranial focused ultrasound is a booming noninvasive therapy for brain stimuli. The Kelvin-Voigt equations are employed to calculate the sound field created by focusing a 256-element planar phased array through a monkey skull with the time-reversal method. Mode conversions between compressional and shear waves exist in the skull. Therefore, the wave field separation method is introduced to calculate the contributions of the two waves to the acoustic intensity and the heat source, respectively. The Pennes equation is used to depict the temperature field induced by ultrasound. Five computational models with the same incident angle of 0° and different distances from the focus for the skull and three computational models at different incident angles and the same distance from the focus for the skull are studied. Numerical results indicate that for all computational models, the acoustic intensity at the focus with mode conversions is 12.05% less than that without mode conversions on average. For the temperature rise, this percentage is 12.02%. Besides, an underestimation of both the acoustic intensity and the temperature rise in the skull tends to occur if mode conversions are ignored. However, if the incident angle exceeds 30°, the rules of the over-and under-estimation may be reversed. Moreover, shear waves contribute 20.54% of the acoustic intensity and 20.74% of the temperature rise in the skull on average for all computational models. The percentage of the temperature rise in the skull from shear waves declines with the increase of the duration of the ultrasound.

Key words: transcranial focused ultrasound, temperature rise, mode conversion, wave field separation

中图分类号:  (Ultrasonics, quantum acoustics, and physical effects of sound)

  • 43.35.+d
43.80.+p (Bioacoustics) 87.50.Y- (Biological effects of acoustic and ultrasonic energy) 43.35.Cg (Ultrasonic velocity, dispersion, scattering, diffraction, and Attenuation in solids; elastic constants)