Ouared Abderrahmane, Montagnon Emmanuel, Cloutier Guy
Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, QC, Canada. Institute of Biomedical Engineering, University of Montréal, Montréal, QC, Canada.
Phys Med Biol. 2015 Oct 21;60(20):8161-85. doi: 10.1088/0031-9155/60/20/8161. Epub 2015 Oct 6.
A method based on adaptive torsional shear waves (ATSW) is proposed to overcome the strong attenuation of shear waves generated by a radiation force in dynamic elastography. During the inward propagation of ATSW, the magnitude of displacements is enhanced due to the convergence of shear waves and constructive interferences. The proposed method consists in generating ATSW fields from the combination of quasi-plane shear wavefronts by considering a linear superposition of displacement maps. Adaptive torsional shear waves were experimentally generated in homogeneous and heterogeneous tissue mimicking phantoms, and compared to quasi-plane shear wave propagations. Results demonstrated that displacement magnitudes by ATSW could be up to 3 times higher than those obtained with quasi-plane shear waves, that the variability of shear wave speeds was reduced, and that the signal-to-noise ratio of displacements was improved. It was also observed that ATSW could cause mechanical inclusions to resonate in heterogeneous phantoms, which further increased the displacement contrast between the inclusion and the surrounding medium. This method opens a way for the development of new noninvasive tissue characterization strategies based on ATSW in the framework of our previously reported shear wave induced resonance elastography (SWIRE) method proposed for breast cancer diagnosis.
提出了一种基于自适应扭转剪切波（ATSW）的方法，以克服动态弹性成像中辐射力产生的剪切波的强衰减。在ATSW向内传播过程中，由于剪切波的汇聚和相长干涉，位移大小会增强。该方法包括通过考虑位移图的线性叠加，从准平面剪切波前的组合生成ATSW场。在均匀和非均匀组织模拟体模中实验生成了自适应扭转剪切波，并与准平面剪切波传播进行了比较。结果表明，ATSW产生的位移大小可比准平面剪切波获得的位移大小高3倍，剪切波速度的变异性降低，位移的信噪比提高。还观察到，ATSW可使非均匀体模中的机械内含物发生共振，这进一步增加了内含物与周围介质之间的位移对比度。在我们先前报道的用于乳腺癌诊断的剪切波诱导共振弹性成像（SWIRE）方法框架内，该方法为基于ATSW的新的非侵入性组织表征策略的开发开辟了一条道路。
