Gijsbertse K, Sprengers A M J, Nillesen M M, Hansen H H G, Lopata R G P, Verdonschot N, de Korte C L
Department of Orthopedics, Orthopaedic Research Laboratory, Radboud university medical center, Nijmegen, The Netherlands.
Phys Med Biol. 2017 Jan 21;62(2):596-611. doi: 10.1088/1361-6560/aa5077. Epub 2016 Dec 29.
In this study, a multi-dimensional strain estimation method is presented to assess local relative deformation in three orthogonal directions in 3D space of skeletal muscles during voluntary contractions. A rigid translation and compressive deformation of a block phantom, that mimics muscle contraction, is used as experimental validation of the 3D technique and to compare its performance with respect to a 2D based technique. Axial, lateral and (in case of 3D) elevational displacements are estimated using a cross-correlation based displacement estimation algorithm. After transformation of the displacements to a Cartesian coordinate system, strain is derived using a least-squares strain estimator. The performance of both methods is compared by calculating the root-mean-squared error of the estimated displacements with the calculated theoretical displacements of the phantom experiments. We observe that the 3D technique delivers more accurate displacement estimations compared to the 2D technique, especially in the translation experiment where out-of-plane motion hampers the 2D technique. In vivo application of the 3D technique in the musculus vastus intermedius shows good resemblance between measured strain and the force pattern. Similarity of the strain curves of repetitive measurements indicates the reproducibility of voluntary contractions. These results indicate that 3D ultrasound is a valuable imaging tool to quantify complex tissue motion, especially when there is motion in three directions, which results in out-of-plane errors for 2D techniques.
在本研究中，提出了一种多维应变估计方法，以评估骨骼肌在三维空间中三个正交方向上的局部相对变形，该变形发生在自主收缩过程中。模拟肌肉收缩的块状体模的刚性平移和压缩变形，被用作三维技术的实验验证，并用于将其性能与基于二维的技术进行比较。使用基于互相关的位移估计算法估计轴向、横向和（三维情况下的）高程位移。在将位移转换到笛卡尔坐标系后，使用最小二乘应变估计器得出应变。通过计算估计位移的均方根误差与体模实验计算出的理论位移，比较了两种方法的性能。我们观察到，与二维技术相比，三维技术能提供更准确的位移估计，特别是在平移实验中，平面外运动会妨碍二维技术。三维技术在股中间肌的体内应用显示，测量应变与力模式之间具有良好的相似性。重复测量的应变曲线的相似性表明了自主收缩的可重复性。这些结果表明，三维超声是一种用于量化复杂组织运动的有价值的成像工具，特别是当存在三个方向的运动时，这会导致二维技术出现平面外误差。
