Assessment of passive muscle elongation using Diffusion Tensor MRI: Correlation between fiber length and diffusion coefficients

Abstract

In this study we investigated the changes in fiber length and diffusion parameters as a consequence of passive lengthening and stretching of the calf muscles. We hypothesized that changes in radial diffusivity (RD) are caused by changes in the muscle fiber cross sectional area (CSA) as a consequence of lengthening and shortening of the muscle. Diffusion Tensor MRI (DT-MRI) measurements were made twice in five healthy volunteers, with the foot in three different positions (30° plantarflexion, neutral position and 15° dorsiflexion). The muscles of the calf were manually segmented on co-registered high resolution anatomical scans, and maps of RD and axial diffusivity (AD) were reconstructed from the DT-MRI data. Fiber tractography was performed and mean fiber length was calculated for each muscle group. Significant negative correlations were found between the changes in RD and changes in fiber length in the dorsiflexed and plantarflexed positions, compared with the neutral foot position. Changes in AD did not correlate with changes in fiber length. Assuming a simple cylindrical model with constant volume for the muscle fiber, the changes in the muscle fiber CSA were calculated from the changes in fiber length. In line with our hypothesis, we observed a significant positive correlation of the CSA with the measured changes in RD. In conclusion, we showed that changes in diffusion coefficients induced by passive muscle stretching and lengthening can be explained by changes in muscle CSA, advancing the physiological interpretation of parameters derived from skeletal muscle DT-MRI.

Anatomically accurate model of EMG during index finger flexion and abduction derived from diffusion tensor imaging

“…A close agreement in terms of muscle fiber architecture was observed between the estimated fiber tracks and the cadaveric reference in both superficial and deep heads of the muscle, Fig 1c. Tissue diffusivity measurements also agreed well with values verified previously for other muscles [23,24,28], Table 4.…”

Paraspinal Muscle DTI Metrics Predict Muscle Strength

“…34 The study of the differences between λ2 and λ3 was outside the scope of the present work. 35 Mazzoli et al 36 investigated associations between diffusion parameters and changes in muscle fiber CSA of the calf muscles caused by passive lengthening and shortening and observed significant positive correlations between CSA and changes in RD in the dorsiflexed and plantarflexed positions. We did not observe significant correlations between diffusion parameters and CSA of the lumbar erector spinae muscle.…”

Cardiac magnetic resonance assessment of central and peripheral vascular function in patients undergoing renal sympathetic denervation as predictor for blood pressure response

“…Retrospective gating can be applied using additional sensors (164) or self-gating approaches (165), assuming that the timing variations have a negligible impact on kinematic estimates.…”