title: In vivo diffusion tensor imaging of the human calf muscle.
abstract: OBJECTIVE
  To demonstrate the feasibility of in vivo calf muscle fiber tracking in human subjects.
  
  
  METHODS
  An EPI-based diffusion tensor imaging (DTI) sequence with six-direction diffusion gradient sensitization was implemented, and DT images were acquired at 3 Tesla on five subjects using an extremity coil. The mean diffusivity, fractional anisotropy (FA), and fiber angle (with respect to the magnet z-axis) were measured in different muscles, and fibers were tracked from several regions of interest (ROIs).
  
  
  RESULTS
  The fiber orientations in the current DTI studies agree well with those determined in previous spectroscopic studies. The orientation angles ranged from 13.4 degrees in the lateral gastrocnemius to 48.5 degrees in the medial soleus. The diffusion ellipsoid in muscle tissue is anisotropic and approximates a prolate model, as shown by color maps of the anisotropy. Fibers were tracked from the different muscle regions, and the unipennate and bipennate structure of muscle fibers was visualized.
  
  
  CONCLUSIONS
  The study clearly shows that in vivo fiber tracking of muscle fibers is feasible and could potentially be applied to study muscle structure function relationships.
authors.affiliation: Department of Radiology, UCSD School of Medicine, University of California-San Diego, San Diego, California, USA. shsinha@ucsd.edu
authors.forename: Shantanu
authors.initials: S
authors.lastname: Sinha
authors.forename: Usha
authors.initials: U
authors.lastname: Sinha
authors.forename: V Reggie
authors.initials: VR
authors.lastname: Edgerton
mesh_terms: D000328:Adult; D016880:Anisotropy; D004058:Diffusion; D015444:Exercise; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D015233:Models, Statistical; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D018482:Muscle, Skeletal / Q000473:pathology*; D009132:Muscles / Q000473:pathology*