title: 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.
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands.|Orthopedic Research Laboratory, Radboud UMC, Nijmegen, the Netherlands.|Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands.
authors.forename: Valentina
authors.identifier: 0000-0002-6700-8424
authors.initials: V
authors.lastname: Mazzoli
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Oudeman
authors.affiliation: Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands.
authors.forename: Klaas
authors.initials: K
authors.lastname: Nicolay
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Mario
authors.initials: M
authors.lastname: Maas
authors.affiliation: Orthopedic Research Laboratory, Radboud UMC, Nijmegen, the Netherlands.
authors.forename: Nico
authors.initials: N
authors.lastname: Verdonschot
authors.affiliation: Orthopedic Research Laboratory, Radboud UMC, Nijmegen, the Netherlands.
authors.forename: Andre M
authors.initials: AM
authors.lastname: Sprengers
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Aart J
authors.initials: AJ
authors.lastname: Nederveen
authors.affiliation: Department of Radiology, University Medical Center, Utrecht, the Netherlands.
authors.forename: Martijn
authors.identifier: 0000-0003-3841-0497
authors.initials: M
authors.lastname: Froeling
authors.affiliation: Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Gustav J
authors.initials: GJ
authors.lastname: Strijkers
mesh_terms: D000328:Adult; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000166:cytology* / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000000981:diagnostic imaging* / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D013718:Tensile Strength / Q000502:physiology
keywords: diffusion tensor imaging; fiber length; passive contraction; radial diffusivity; skeletal muscles