title: MRI T2* mapping correlates with biochemistry and histology in intervertebral disc degeneration in a large animal model.
abstract: OBJECTIVE
  To evaluate intervertebral disc (IVD) degeneration and treatments, an objective diagnostic tool is needed. Recently, T2* relaxation time mapping was proposed as a technique to assess early IVD degeneration, yet the correlation with biochemical content and histological features has not been investigated previously. Our objective was to validate T2* mapping for disc degeneration by correlating this technique with accepted parameters of IVD degeneration.
  
  
  METHODS
  Mildly and severely degenerated lumbar discs were obtained from an in vivo large animal study; two healthy goat spines were acquired as control. In total, 48 IVDs were analysed using T2-weighted MRI, T2* relaxation time mapping, biochemical assays, macroscopic and histological scoring. Correlations between variables were expressed with Spearman's rho (ρ) coefficients.
  
  
  RESULTS
  A complete range of degenerative grades were obtained (mean histological grade 2.2, range 0-6). A linear positive correlation was observed between T2* relaxation time and glycosaminoglycan content (ρ = 0.64, p < 0.001). T2* relaxation time decreased linearly with increasing degeneration as assessed with Pfirrmann scoring system (ρ = -0.67, p < 0.001), macroscopic (ρ = -0.33, p < 0.05) and histological (ρ = -0.45, p < 0.05) grading.
  
  
  CONCLUSIONS
  T2* mapping is an MRI technique for IVD evaluation which allows for measurements on a continuous scale thus minimising observer bias compared to grading systems. Although limited by a small sample size, this study showed a relatively good and linear correlation between T2* relaxation time and accepted parameters of disc degeneration. This suggests that T2* mapping is a promising tool to assess disc degeneration in clinical practice.
authors.affiliation: Department of Orthopaedic Surgery, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands, s.detiger@vumc.nl.
authors.forename: Suzanne E L
authors.initials: SE
authors.lastname: Detiger
authors.forename: Roderick M
authors.initials: RM
authors.lastname: Holewijn
authors.forename: Roel J W
authors.initials: RJ
authors.lastname: Hoogendoorn
authors.forename: Barend J
authors.initials: BJ
authors.lastname: van Royen
authors.forename: Marco N
authors.initials: MN
authors.lastname: Helder
authors.forename: Ferco H
authors.initials: FH
authors.lastname: Berger
authors.forename: Joost P A
authors.initials: JP
authors.lastname: Kuijer
authors.forename: Theo H
authors.initials: TH
authors.lastname: Smit
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D006025:Glycosaminoglycans / Q000032:analysis; D006041:Goats; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000175:diagnosis* / Q000473:pathology; D016014:Linear Models; D008159:Lumbar Vertebrae / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015588:Observer Variation
chemical_list: D006025:Glycosaminoglycans
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