Nonlinear propagation acoustics of dual-frequency wide-band excitation pulses in a focused ultrasound system

作者：Masoy Svein Erik^*; Standal Oyvind; Deibele Jochen M; Nasholm Sven Peter; Angelsen Bjorn; Johansen Tonni F; Tangen Thor Andreas; Hansen Rune

来源：Journal of the Acoustical Society of America, 2010, 128(5): 2695-2703.

DOI：10.1121/1.3488308

In this article, acoustic propagation effects of dual-frequency wide-band excitation pulses in a focused ultrasound system are demonstrated in vitro. A designed and manufactured dual-frequency band annular array capable of transmitting 0.9/7.5 MHz center frequency wide-band pulses was used for this purpose. The dual-frequency band annular array, has been designed using a bi-layer piezo-electric stack. Water tank measurements demonstrate the function of the array by activating the low-and high-frequency layers individually and simultaneously. The results show that the array works as intended. Activating the low-and high-frequency layers individually, results in less than 50 dB signal level from the high-and low-frequency layers respectively. Activating both layers simultaneously, produce a well defined dual-frequency pulse. The presence of the low-frequency pulse leads to compression, expansion, and a time delay of the high-frequency pulse. There is a phase shift between the low-and high-frequency pulse as it propagates from the array to the focus. This makes the latter described effects also dependent on the array configuration. By varying the low-frequency pressure, a shift of up to 0.5 MHz in center frequency of a 8.0 MHz transmitted high-frequency pulse is observed at the array focus. The results demonstrate the high propagation complexity of dual-frequency pulses.

• 出版日期2010-11