Elastografia Supersonic Shear Imaging em músculo esquelético: análise da anisotropia do músculo gastrocnêmio lateral e relação entre a angulação de fibras musculares e sintéticas e o módulo de cisalhamento

Abstract

Shear wave propagation does not occur completely in the fibers direction in pennate muscles, therefore, anisotropy must be considered when obtained shear modulus (μ) by Supersonic Shear Imaging (SSI) elastography. As the pennation angle (PA) varies between muscles, individuals and dynamic conditions, its relation with the μ is not defined. The aim of this study is to explore the relation between synthetic and muscles fibers, i.e., PA with μ. Additionally, evaluate the lateral gastrocnemius (LG) muscle anisotropy in the x2-x3 plane (parallel to surface). In synthetic and vastus lateralis (VL) muscle fibers, μ values with probe across the fibers were significantly lower than for the parallel (x2-x3 plane). In the oblique plane (x1-x3), the μ values were significantly reduced with the probe angle increase only in the polymer fibers. Considering ten distinct angulations in the x2-x3 plane in LG, there were no significant μ changes. As conclusion, it was confirmed an anisotropic behavior in the synthetic and VL muscle fibers (x2-x3 plane) and a μ reduction with angle increase in the synthetic fibers in x1-x3 plane (approximately 0.90 kPa for each degree of PA).