Myofiber ellipticity as an explanation for transverse asymmetry of skeletal muscle diffusion MRI in vivo signal

Dimitrios C. Karampinos, Kevin F. King, Bradley P. Sutton, John G. Georgiadis

Research output: Contribution to journalArticle

Abstract

Due to its unique non-invasive microstructure probing capabilities, diffusion tensor imaging (DTI) constitutes a valuable tool in the study of fiber orientation in skeletal muscles. By implementing a DTI sequence with judiciously chosen directional encoding to quantify in vivo the microarchitectural properties in the calf muscles of three healthy volunteers at rest, we report that the secondary eigenvalue is significantly higher than the tertiary eigenvalue, a phenomenon corroborated by prior DTI findings. Toward a physics-based explanation of this phenomenon, we propose a composite medium model that accounts for water diffusion in the space within the muscle fiber and the extracellular space. The muscle fibers are abstracted as cylinders of infinite length with an elliptical cross section, the latter closely approximating microstructural features well documented in prior histological studies of excised muscle. The range of values of fiber ellipticity predicted by our model agrees with these studies, and the spatial orientation of the cross-sectional ellipses is consistent with local muscle strain fields and the putative direction of lateral transmission of stress between fibers in certain regions in three antigravity muscles (Tibialis Anterior, Soleus, and Gastrocnemius), as well as independent measurements of deformation in active calf muscles. As a metric, fiber cross-sectional ellipticity may be useful for quantifying morphological changes in skeletal muscle fibers with aging, hypertrophy, or sarcopenia.

Original languageEnglish (US)
Pages (from-to)2532-2546
Number of pages15
JournalAnnals of Biomedical Engineering
Volume37
Issue number12
DOIs
StatePublished - Dec 2009

Keywords

  • Diffusion tensor imaging
  • Gastrocnemius
  • Myocytes
  • Myofiber ellipticity
  • Skeletal muscle
  • Soleus

ASJC Scopus subject areas

  • Biomedical Engineering

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