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首页> 外文期刊>IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control >The effects of frequency-dependent attenuation and dispersion on sound speed measurements: applications in human trabecular bone
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The effects of frequency-dependent attenuation and dispersion on sound speed measurements: applications in human trabecular bone

机译：频率相关衰减和色散对声速测量的影响：在人小梁骨中的应用

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摘要

Sound speed may be measured by comparing the transit time of a broadband ultrasonic pulse transmitted through an object with that transmitted through a reference water path. If the speed of sound in water and the thickness of the sample are known, the speed of sound in the object may be computed. To measure the transit time differential, a marker such as a zero-crossing, may be used. A sound speed difference between the object and water shifts all markers backward or forward. Frequency-dependent attenuation and dispersion may alter the spectral characteristics of the waveform, thereby distorting the locations of markers and introducing variations in sound-speed estimates. Theory is derived to correct for this distortion for Gaussian pulses propagating through linearly attenuating, weakly dispersive media. The theory is validated using numerical analysis, measurements on a tissue mimicking phantom, and on 24 human calcaneus samples in vitro. Variations in soft tissue-like media are generally not exceptionally large for most applications but can be substantial, particularly for high bandwidth pulses propagating through media with high attenuation coefficients. At 500 kHz, variations in velocity estimates in bone can be very substantial, on the order of 40 to 50 m/s because of the high attenuation coefficient of bone. In trabecular bone, the effects of frequency-dependent attenuation are considerable, and the effects of dispersion are negligible.
机译：可以通过将通过物体传输的宽带超声波脉冲与通过参考水路传输的宽带超声波脉冲的传输时间进行比较来测量声速。如果已知水中的声速和样品的厚度，则可以计算物体中的声速。为了测量渡越时间差，可以使用诸如零交叉的标记。物体和水之间的声速差会使所有标记向后或向前移动。频率相关的衰减和色散可能会改变波形的频谱特性，从而使标记的位置失真并在声速估计中引入变化。推导理论来校正通过线性衰减，弱色散介质传播的高斯脉冲的这种失真。该理论通过数值分析，对模拟人体模型的组织以及体外24个人类跟骨样本的测量得到了验证。对于大多数应用，软组织样介质的变化通常不会特别大，但变化可能很大，尤其是对于传播通过具有高衰减系数的介质的高带宽脉冲而言。在500 kHz时，由于骨骼的高衰减系数，骨骼中速度估算的变化可能非常大，约为40至50 m / s。在小梁骨中，频率相关衰减的影响很大，而色散的影响可以忽略不计。

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