title: Magnetic resonance imaging of graded skeletal muscle injury in live rats.
abstract: BACKGROUND
  Increasing number of stretch-shortening contractions (SSCs) results in increased muscle injury.
  
  
  METHODS
  Fischer Hybrid rats were acutely exposed to an increasing number of SSCs in vivo using a custom-designed dynamometer. Magnetic resonance imaging (MRI) imaging was conducted 72 hours after exposure when rats were infused with Prohance and imaged using a 7T rodent MRI system (GE Epic 12.0). Images were acquired in the transverse plane with typically 60 total slices acquired covering the entire length of the hind legs. Rats were euthanized after MRI, the lower limbs removed, and tibialis anterior muscles were prepared for histology and quantified stereology.
  
  
  RESULTS
  Stereological analyses showed myofiber degeneration, and cellular infiltrates significantly increased following 70 and 150 SSC exposure compared to controls. MRI images revealed that the percent affected area significantly increased with exposure in all SSC groups in a graded fashion. Signal intensity also significantly increased with increasing SSC repetitions.
  
  
  CONCLUSIONS
  These results suggest that contrast-enhanced MRI has the sensitivity to differentiate specific degrees of skeletal muscle strain injury, and imaging data are specifically representative of cellular histopathology quantified via stereological analyses.
authors.affiliation: West Virginia University, School of Medicine, Morgantown, WV, USA.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Cutlip
authors.affiliation: West Virginia University, Office of Research Integrity and Compliance Morgantown, WV, USA.
authors.forename: Melinda S
authors.initials: MS
authors.lastname: Hollander
authors.affiliation: Duke University Medical Center, Durham, NC, USA.
authors.forename: G Allan
authors.initials: GA
authors.lastname: Johnson
authors.affiliation: MRPath Inc., Durham, NC, USA.
authors.forename: Brice W
authors.initials: BW
authors.lastname: Johnson
authors.affiliation: Centers for Disease Control, National Institute for Occupational Safety and Health (NIOSH/CDC), Morgantown, WV, USA.
authors.forename: Sherri A
authors.initials: SA
authors.lastname: Friend
authors.affiliation: Centers for Disease Control, National Institute for Occupational Safety and Health (NIOSH/CDC), Morgantown, WV, USA.
authors.forename: Brent A
authors.initials: BA
authors.lastname: Baker
keywords: MRI; inflammation; myofiber degeneration; skeletal muscle injury; stretch–shortening contraction