title: Quantitative MRI in a non-surgical model of cervical spinal cord injury.
abstract: Quantitative T2 (qT2), diffusion tensor imaging (DTI), and histology were used to investigate a cervical model of spinal cord injury (SCI) in the rat. While quantitative MRI can significantly increase the specificity in the presence of pathology, it must be validated for each type of injury or disease. In the case of traumatic SCI most models are difficult to image, either due to the location of the injury, or as a result of damage to surrounding tissues resulting from invasive surgical procedures. In this study a non-surgical cervical model of SCI, produced using a combination of focused ultrasound and microbubbles, was used to produce pathology similar to that seen in models of contusive and compressive injuries. qT2 and DTI were performed at 24 h and 1 and 2 weeks following injury, and compared with H&E and luxol fast blue histology. In the injured spinal cord, in addition to intra/extracellular (I/E) water and myelin water in white matter, qT2 revealed a large component with very short T2 of about 3 ms, which was highly correlated with the presence of hemorrhage in both gray and white matter at 24 h, and with the presence of hemosiderin in gray matter at 2 weeks following injury. The T2 of the I/E water peak was also elevated at 24 h in both gray and white matter, which was correlated with the presence of vacuolation/edema on histology. Cystic cavities were only seen at the 1 or 2 week timepoints, and were correlated with the presence of a water peak with T2  > 250 ms. No significant changes in diffusivity parameters were observed. Pathologies were often co-occurring, with opposite effects on the average T2 in a given voxel, reducing the visibility of injured tissue on standard T2 -weighted MR images.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Wendy
authors.initials: W
authors.lastname: Oakden
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Jacek M
authors.initials: JM
authors.lastname: Kwiecien
authors.affiliation: Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada.
authors.forename: Meaghan A
authors.initials: MA
authors.lastname: O'Reilly
authors.affiliation: Department of Anaesthesiology and Intensive Therapy, Medical University of Lublin, Lublin, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Dabrowski
authors.affiliation: Orthopaedic Biomechanics Laboratory, Sunnybrook Research Institute, Toronto, Ontario, Canada.|Division of Orthopaedics, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Cari
authors.initials: C
authors.lastname: Whyne
authors.affiliation: Division of Orthopaedics, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.|Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Joel
authors.initials: J
authors.lastname: Finkelstein
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.|Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada.
authors.forename: Kullervo
authors.initials: K
authors.lastname: Hynynen
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.|Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada.
authors.forename: Greg J
authors.initials: GJ
authors.lastname: Stanisz
mesh_terms: D000818:Animals; D002574:Cervical Vertebrae / Q000473:pathology / Q000601:surgery; D056324:Diffusion Tensor Imaging / Q000379:methods*; D004195:Disease Models, Animal; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013010:Sonication / Q000379:methods*; D013119:Spinal Cord Injuries / Q000473:pathology* / Q000601:surgery
keywords: animal model study; myelin; qT2; quantitation; relaxometry; spinal cord injury