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首页> 外文期刊>IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control >Tissue Attenuation Estimation by Mean Frequency Downshift and Bandwidth Limitation
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Tissue Attenuation Estimation by Mean Frequency Downshift and Bandwidth Limitation

机译：平均频率下移和带宽限制的组织衰减估计

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摘要

Attenuation of ultrasound in tissue can be estimated from the propagating pulse center frequency downshift. This method assumes that the envelope of the emitted pulse can be approximated by a Gaussian function and that the attenuation linearly depends on frequency. The resulting downshift of the mean frequency depends not only on attenuation but also on pulse bandwidth and propagation distance. This kind of approach is valid for narrowband pulses and shallow penetration depth. However, for short pulses and deep penetration, the frequency downshift is rather large and the received spectra are modified by the limited bandwidth of the receiving system. In this paper, the modified formula modeling the mean frequency of backscattered echoes is presented. The equation takes into account the limitation of the bandwidth due to bandpass filtration of the received echoes. This approach was applied to simulate the variation of the mean frequency of the pulse propagating for both weakly and strongly attenuating media and for narrowband and wideband pulses. The behavior of both the standard and modified estimates of attenuation has been validated using RF data from a tissue-mimicking phantom. The ultrasound attenuation of the phantom, determined with a corrected equation, was close to its true value, while the result obtained using the original formula was lower by as much as 50% at a depth of 8 cm.
机译：可以从传播的脉冲中心频率降档估计组织中超声的衰减。该方法假定发射脉冲的包络可以通过高斯函数近似，并且衰减线性地取决于频率。平均频率的下降不仅取决于衰减，还取决于脉冲带宽和传播距离。这种方法适用于窄带脉冲和浅穿透深度。但是，对于短脉冲和深穿透，频率降频相当大，并且接收频谱受到接收系统有限带宽的影响。在本文中，提出了对反向散射回波的平均频率进行建模的改进公式。该公式考虑了由于接收回波的带通滤波而导致的带宽限制。该方法用于模拟弱衰减介质和强衰减介质以及窄带和宽带脉冲的脉冲传播平均频率的变化。使用来自组织模拟体模的RF数据已经验证了衰减的标准估计值和修改后估计值的行为。通过校正方程确定的体模的超声衰减接近其真实值，而使用原始公式获得的结果在8 cm的深度处降低了多达50％。

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