Age-related differences in strain rate tensor of the medial gastrocnemius muscle during passive plantarflexion and active isometric contraction using velocity encoded MR imaging: Potential index of lateral force transmission

Abstract

Purpose The strain rate (SR) tensor measures the principal directions and magnitude of the instantaneous deformation; this study aims to track age related changes in the 2D SR tensor in the medial gastrocnemius during passive joint rotation and active isometric contraction. Methods SR tensors were derived from velocity encoded magnetic resonance phase-contrast images in nine young (28 yrs) and eight senior (78 yrs) women. Strain rates along and in the cross-section of the fiber were calculated from the SR tensor and used to derive the out-plane SR. Age related and regional differences in the SR eigenvalues, orientation, and the angle between the SR and muscle fiber (SR-fiber angle) were statistically analyzed. Results SR along the fiber was significantly different between the cohorts during isometric contraction with higher values in the young (P<0.05). The SR-fiber angle was larger in the young for both motion types but this difference was not statistically significant. Significant regional differences in the SR indices was seen in passive joint rotation (P<0.05) for both cohorts. Conclusion SR mapping reflects age related and regional differences during active and passive motion respectively; this may arise from differences in contractility (active motion) and elastic properties (active and passive motion).

Shear strain rate from phase contrast velocity encoded MRI: Application to study effects of aging in the medial gastrocnemius muscle

“…All subjects were included in this study after obtaining informed consent. Six young (26.1 ± 2.3 years, height: 158.6 ± 5.6 cm, mass: 50.8 ± 3.7 kg) and six senior (76.7 ± 8.3 years, height: 153.0 ± 2.0 cm, mass: 57.4 ± 4.3 kg) healthy, moderately active, female subjects were included in this study after informed consent . Two subjects (one young: 25 years, one old: 65 years) were scanned on three separate days to determine the coefficient of variation (CV) and the repeatability coefficients (RC) of the SR components.…”

“…This provides a number of parameters including SR tensor components in the principal basis, in the muscle fiber basis, and the maximum shear strain. Specifically, the SR tensor provides information on tissue deformation along two orthogonal axes as well as on tissue shear through the off‐diagonal terms of the tensor . These SR components reflect underlying muscle fiber properties like contractility and extracellular matrix material properties like stiffness.…”

“…This article extends an earlier study that explored the changes in muscle SR with age where the analysis was limited to normal SRs in the principal basis . The earlier study identified the SR components in the principal basis that significantly differed between young and old subjects.…”

Accelerated 4D phase contrast MRI in skeletal muscle contraction

“…For instance, it is often assumed that muscles shorten uniformly along their longitudinal axis, whereas evidence has been provided for more complex contraction patterns and it was shown that the direction of shortening is not aligned with the muscle fiber direction . Furthermore, differences in deformation patterns were observed between deep and superficial muscles and between proximal and distal locations . Due to the highly complex pattern in muscle contraction and deformation, 3D visualization of subject‐specific contracting muscles would be extremely valuable.…”

MRI‐Derived Biomarkers Related to Sarcopenia: A Systematic Review

“…In these studies, diffusion tensor imaging, fractional anisotropy, and T 2 ‐maps were used to investigate muscle quality. On the one hand, diffusion‐weighted imaging and diffusion tensor imaging provide quantitative markers of muscle microstructure, with an increased value of fractional anisotropy as a result asymmetric diffusion in atrophic skeletal muscles . On the other hand, increased T 2 values may suggest significant changes in fiber architecture …”