Department of Diagnostic and Interventional Imaging, Ultrasonics and Elastographics Laboratory, The University of Texas Medical School, Houston, TX, USA.
Ultrasound Med Biol. 2012 Nov;38(11):2031-7. doi: 10.1016/j.ultrasmedbio.2012.06.011. Epub 2012 Sep 10.
Axial-shear strain elastography was described recently as a method to visualize the state of bonding at an inclusion boundary. Although total shear strain elastography was initially proposed for this purpose, it did not evolve beyond the initial reported finite element model (FEM) and simulation studies. One of the major reasons for this was the practical limitation in estimating the tissue motion perpendicular (lateral) to the ultrasound (US) beam as accurately as the motion along the US beam (axial). Nevertheless, there has been a sustained effort in developing methods to improve the lateral motion tracking accuracy and thereby obtain better quality total shear strain elastogram (TSSE). We hypothesize that in some cases, even if good quality TSSE becomes possible, it may still be advantageous to utilize only the axial-shear strain (one of the components of the total shear strain) elastogram (ASSE). Specifically, we show through FEM and corroborating tissue-mimicking gelatin phantom experiments that the unique "fill-in" discriminant feature that was introduced recently for asymmetric breast lesion classification is depicted only in the ASSE and not in the TSSE. Note that the presence or conspicuous absence of this feature in ASSE was shown to characterize asymmetric inclusions' boundaries as either loosely-bonded or firmly-bonded to the surrounding, respectively. This might be an important observation because the literature suggests that benign breast lesions tend to be loosely-bonded, while malignant tumors are usually firmly-bonded. The results from the current study demonstrate that the use of shear strain lesion "fill-in" as a discriminant feature in the differentiation between asymmetric malignant and benign breast lesions is only possible when using the ASSEs and not the TSSEs.
轴剪应变弹性成像是最近描述的一种可视化夹杂物边界结合状态的方法。尽管最初提出总剪切应变弹性成像就是为此目的，但它并没有超越最初报道的有限元模型（FEM）和模拟研究。造成这种情况的一个主要原因是，在准确估计与超声（US）束垂直（侧向）的组织运动方面存在实际限制，而沿 US 束（轴向）的运动则不然。尽管如此，人们一直在努力开发改进侧向运动跟踪精度的方法，从而获得更好质量的总剪切应变弹性图（TSSE）。我们假设，在某些情况下，即使可以获得高质量的 TSSE，利用仅轴剪切应变（总剪切应变的一个分量）弹性图（ASSE）可能仍然是有利的。具体来说，我们通过 FEM 和组织模拟明胶体模实验证明，最近引入的用于不对称性乳房病变分类的独特“填充”判别特征仅在 ASSE 中而不在 TSSE 中描绘。请注意，ASSE 中存在或明显不存在此特征被证明可以将不对称性夹杂物的边界分别表征为与周围组织松散结合或牢固结合。这可能是一个重要的观察结果，因为文献表明良性乳房病变倾向于松散结合，而恶性肿瘤通常牢固结合。当前研究的结果表明，仅当使用 ASSE 而不是 TSSE 时，使用剪切应变病变“填充”作为区分不对称性良性和恶性乳房病变的判别特征才是可能的。
