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

Abstract

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1351-1357.

Role of the Extracellular Matrix in Loss of Muscle Force With Age and Unloading Using Magnetic Resonance Imaging, Biochemical Analysis, and Computational Models

“…Frontiers in Physiology | www.frontiersin.org shear in the ECM and this is confirmed in the experimental studies (Sinha et al, 2018). Recent advances in fast sequences integrating compressed sensing with VE-PC acquisitions have enabled the study of the full 3D strain tensor at different %MVC at significantly lesser number of contraction cycles (Malis et al, 2019b(Malis et al, , 2020.…”

“…The experimentally measured MR shear strain was potentially attributed to the shear in the endomysium (Sinha et al, 2015a;Malis et al, 2018a). Further, shear SR was a significant predictor of force in the age and disuse studies highlighting that if shear strain is a measure of LTF, these results indicate the decreasing magnitude of LTF with age and with disuse (Sinha et al, 2015a(Sinha et al, , 2018Malis et al, 2018a). The studies highlight that, while a direct noninvasive measurement of LTF is not possible, shear strain rate may potentially serve as a surrogate measure of LTF (Sinha et al, 2015a;Malis et al, 2018a).…”

“…Recent studies focus on the extraction of strain rate (SR) indices from VE-PC images and the changes of these indices with age and with disuse (Sinha et al, 2015a(Sinha et al, , 2018Malis et al, 2018a). The SR tensor was calculated from the spatial gradient of the velocity images (acquired during isometric contraction) and diagonalized to obtain the eigenvalues (SR fiber and SR in-plane ) and eigenvectors.…”

“…The thick (unfilled) arrows show the lateral transmission of force pathways: from the cross-bridges of the myofilaments through the protein network on the sarcolemma to the extracellular matrix. Arrows indicate normal and shear strains (A) reproduced with permission from Wiley publisher of Sinha et al (2018). Strain rate maps of the normal strain rates (SR fiber and SR in-plane ) and shear strain rates (SR max ) in a young and aging subject at the same force level.…”

“…The color maps are color-coded according to the legend provided with the figure. Color maps are overlaid on the magnitude image at the corresponding frame; maps show lower values in both the normal strain rates in the aging cohort (B) reproduced with permission from Wiley publisher of Sinha et al (2018). Streamlines of eigenvectors corresponding to SR fiber overlaid on fiber directions (in black, tracked from fascicle orientations) for one slice of the same subject preand post-suspension at the peak of the contraction phase.…”