title: Quantitative T2 mapping to characterize the process of intervertebral disc degeneration in a rabbit model.
abstract: BACKGROUND
  To investigate the potential of T2 mapping for characterizing the process of intervertebral disc degeneration (IDD) in a rabbit model.
  
  
  METHODS
  Thirty-five rabbits underwent an annular stab to the L4/5 discs (L5/6 discs served as internal normal controls). Degenerative changes were graded according to the modified Thompson classification and quantified in T2 respectively at pre-operation, 1, 3, 6, 12 and 24 weeks postoperatively. After MRI analysis, expression analysis of aggrecan and type II collagen gene in nucleus pulposus (NP) was performed using real time polymerase chain reaction (real-time PCR). The longitudinal changes in NP T2 and gene expressions were studied by repeated measures and ANOVA, linear regression was performed for their correlations through the process of IDD. The reliability analysis of method of measurement of NP T2 was also performed.
  
  
  RESULTS
  There was a strong inverse correlation between NP T2 and Thompson grades (r = -0.85). The decline of L4/5 NP T2 through 24 weeks was nonlinear, the most significant decrease was observed in 3 weeks postoperatively (P<0.05). The tendency was confirmed at gene expression levels. NP T2 correlated strongly with aggrecan (R² = 0.85, P<0.01) and type II collagen (R² = 0.78, P<0.01) gene expressions. The intraclass correlation coefficients for interobserver and intraobserver reliability were 0.963 and 0.977 respectively.
  
  
  CONCLUSIONS
  NP T2 correlates well with aggrecan and type II collagen gene expressions. T2 mapping could act as a sensitive, noninvasive tool for quantitatively characterizing the process of IDD in longitudinal study, help better understanding of the pathophysiology of IDD, assist us to detect the degenerative cascade, and develop a T2-based quantification scale for evaluation of IDD and efficacy of therapeutic interventions.
authors.forename: Wei
authors.initials: W
authors.lastname: Sun
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Chang-qing
authors.initials: CQ
authors.lastname: Zhao
authors.forename: Wei
authors.initials: W
authors.lastname: Ding
authors.forename: Jun-jie
authors.initials: JJ
authors.lastname: Yuan
authors.forename: Qi
authors.initials: Q
authors.lastname: Sun
authors.forename: Xiao-jiang
authors.initials: XJ
authors.lastname: Sun
authors.forename: You-zhuan
authors.initials: YZ
authors.lastname: Xie
authors.forename: Hua
authors.initials: H
authors.lastname: Li
authors.affiliation: Shanghai Key Laboratory of Orthopaedic Implant, Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, PR China. swyx718323@163.com.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D055959:Intervertebral Disc Degeneration / Q000209:etiology* / Q000378:metabolism; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011817:Rabbits