Research Progress on Application of Nonlinear Acoustics in Medical Imaging

نویسندگان

  • Xiufen Gong
  • Dong Zhang
  • Jiehui Liu
چکیده

In recent years many works have indicated that a series of interesting nonlinear acoustical effects have been observed in the range of biomedical intensities and frequencies. This new phenomenon in medical ultrasound has attracted immediate interest of many researchers. Two topics on this aspect will be presented in this paper. (1) The acoustical nonlinearity parameter imaging in reflection mode. Three novel methods for this kind of imaging have been developed. Theoretical Principles and experimental measurements are presented. The results show that using nonlinearity parameter imaging we can more easily distinguish the diseased tissue from the normal tissue than using the linear acoustic parameters. (2) Nonlinear behavior of ultrasound contrast agent (UCA). The existence of micro-bubbles in UCA will cause the excitation of not only the high harmonics but also the subharmonics. The extremely large values of acoustic nonlinearity parameter for UCA and its dependence on the bubble concentrations and on the frequencies are studied. Concerning the subharmonics, it has a special amplitude dependency on the exciting sound pressure, which is different from that of the second harmonic and the fundamental frequency wave. Besides, recent new development of higher order nonlinear ultrasonic imaging and third order nonlinearity parameter with perspective application will be discussed.

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تاریخ انتشار 2004