Department of Medical Technology, SINTEF Technology and Society, Trondheim, Norway.
J Acoust Soc Am. 2011 Feb;129(2):1117-27. doi: 10.1121/1.3518753.
A method of acoustic imaging is discussed that potentially can improve the diagnostic capabilities of medical ultrasound. The method, given the name second order ultrasound field imaging, is achieved by the processing of the received signals from transmitted dual frequency band pulse complexes with at least partly overlapping high frequency (HF) and low frequency (LF) pulses. The transmitted HF pulses are used for image reconstruction whereas the transmitted LF pulses are used to manipulate the elastic properties of the medium observed by the HF imaging pulses. In the present paper, nonlinear propagation effects observed by a HF imaging pulse due to the presence of a LF manipulation pulse is discussed. When using dual frequency band transmit pulse complexes with a large separation in center frequency (e.g., 1:10), these nonlinear propagation effects are manifested as a nonlinear HF propagation delay and a HF pulse distortion different from conventional harmonic distortion. In addition, with different transmit foci for the HF and LF pulses, nonlinear aberration will occur.
讨论了一种潜在的可以提高医学超声诊断能力的声学成象方法。该方法名为二次超声场成象，通过对发射的双频带脉冲串的接收信号进行处理来实现，这些脉冲串的高频（HF）和低频（LF）部分至少有部分重叠。发射的 HF 脉冲用于图像重建，而发射的 LF 脉冲用于控制 HF 成象脉冲所观察到的介质的弹性特性。本文讨论了由于 LF 调制脉冲的存在而观察到的 HF 成象脉冲的非线性传播效应。当使用中心频率间隔较大的双频带发射脉冲串（例如 1:10）时，这些非线性传播效应表现为非线性 HF 传播延迟和不同于传统谐波失真的 HF 脉冲失真。此外，对于 HF 和 LF 脉冲的不同发射焦点，将发生非线性像差。
