Department of Electrical Engineering, Center for Fast Ultrasound Imaging, Technical University of Denmark, Building 348, 2800 Kgs. Lyngby, Denmark.
J Acoust Soc Am. 2009 Dec;126(6):3350-8. doi: 10.1121/1.3242359.
Measurements on microbubbles clearly indicate a relation between the ambient pressure and the acoustic behavior of the bubble. The purpose of this study was to optimize the sensitivity of ambient pressure measurements, using the subharmonic component, through microbubble response simulations. The behavior of two microbubbles corresponding to two different contrast agents was investigated as a function of driving pulse and ambient overpressure p(ov). Simulations of Levovist using a rectangular driving pulse show an almost linear reduction in the subharmonic component as p(ov) is increased. For a 20 cycle driving pulse, a reduction of 4.6 dB is observed when changing p(ov) from 0 to 25 kPa. Increasing the pulse duration makes the reduction even clearer. For a pulse with 64 cycles, the reduction is 9.9 dB. This simulation is in good correspondence with measurement results presented in the literature. Further simulations of Levovist show that also the shape and the acoustic pressure of the driving pulse are very important factors. The best pressure sensitivity of Levovist was found to be 0.88 dB/kPa. For Sonazoid, a sensitivity of 1.14 dB/kPa has been found, although the reduction is not completely linear as a function of the ambient pressure.
对微泡的测量结果清楚地表明了环境压力与泡内声学行为之间存在一定的关系。本研究的目的是通过微泡响应模拟，利用次谐波分量优化环境压力测量的灵敏度。本文研究了两种不同对比剂的微泡的行为，考察了它们随驱动脉冲和环境过压 p(ov)的变化规律。采用矩形驱动脉冲对声诺维（Levovist）进行的模拟显示，随着 p(ov)的增加，次谐波分量几乎呈线性下降。对于 20 个周期的驱动脉冲，当 p(ov)从 0 增加到 25 kPa 时，次谐波分量会降低 4.6 dB。增加脉冲持续时间会使降低幅度更加明显。对于 64 个周期的脉冲，降低幅度为 9.9 dB。该模拟结果与文献中呈现的测量结果具有良好的一致性。进一步对声诺维（Levovist）的模拟显示，驱动脉冲的形状和声压也是非常重要的因素。发现声诺维（Levovist）的最佳压力灵敏度为 0.88 dB/kPa。对于声诺维（Sonazoid），则发现了 1.14 dB/kPa 的灵敏度，尽管其降低幅度并不完全呈线性关系。
