A Frequency-Shift Method to Measure Shear-Wave Attenuation in Soft Tissues
A Frequency-Shift Method to Measure Shear-Wave Attenuation in Soft Tissues
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DOI：
10.1109/tuffc.2016.2634329
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发表时间：
2017-03-01
影响因子：
3.6
通讯作者：
Cloutier, Guy
中科院分区：
文献类型：
--
作者：
Bernard, Simon;Kazemirad, Siavash;Cloutier, Guy
在体内量化软组织中的剪切波衰减可能有助于更好地了解人体组织流变学，并导致新的诊断策略。在声辐射力弹性成像中，衰减是难以测量的，因为剪切波振幅由于衍射和粘性衰减的组合而减小。衍射校正需要假设圆柱形波前和各向同性传播介质，这在某些应用中可能不是这种情况。本文将超声成像和地震学中常用的频移法用于弹性成像中剪切波衰减的测量。这种方法对衍射效应不敏感。对于衰减的线性频率依赖性，得到了伽马分布波振幅谱的峰值频率的降低与传播介质的衰减系数之间的闭合形式的关系。所提出的方法进行了测试，对平面波参考方法在均匀的琼脂-明胶phanteles与0%，10%，和20%的油浓度，因此不同的衰减0.117，0.202，和0.292 Np。m（-1）/Hz。用两个离体猪肝样品（0.79和1.35 Np . m（-1）/Hz）和体内人体肌肉，沿沿着测量（0.43 Np . m（-1）/Hz）和跨（1.77 Np . m（-1）/Hz）。在所有情况下，数据支持源的伽马分布频谱和组织的线性频率衰减的假设。除了用于评估弹性的剪切波速度之外，该方法还提供组织衰减，这是与粘性模型相关的诊断信息。数据处理简单，可以在真实的时间内自动执行，以供临床应用。
In vivo quantification of shear-wave attenuation in soft tissues may help to better understand human tissue rheology and lead to new diagnostic strategies. Attenuation is difficult to measure in acoustic radiation force elastography because the shear-wave amplitude decreases due to a combination of diffraction and viscous attenuation. Diffraction correction requires assuming a cylindrical wavefront and an isotropic propagation medium, which may not be the case in some applications. In this paper, the frequency-shift method, used in ultrasound imaging and seismology, was adapted for shear-wave attenuation measurement in elastography. This method is not sensitive to diffraction effects. For a linear frequency dependence of the attenuation, a closed-form relation was obtained between the decrease in the peak frequency of the gamma-distributed wave amplitude spectrum and the attenuation coefficient of the propagation medium. The proposed method was tested against a plane-wave reference method in homogeneous agar-gelatin phantoms with 0%, 10%, and 20% oil concentrations, and hence different attenuations of 0.117, 0.202, and 0.292 Np . m(-1)/Hz, respectively. Applicability to biological tissues was demonstrated with two ex vivo porcine liver samples (0.79 and 1.35 Np . m(-1)/Hz) and an in vivo human muscle, measured along (0.43 Np . m(-1)/Hz) and across (1.77 Np . m(-1)/Hz) the tissue fibers. In all cases, the data supported the assumptions of a gamma-distributed spectrum for the source and linear frequency attenuation for the tissue. This method provides tissue attenuation, which is relevant diagnostic information to model viscosity, in addition to shear-wave velocity used to assess elasticity. Data processing is simple and could be performed automatically in real time for clinical applications.