title: Cartilaginous end plates: Quantitative MR imaging with very short echo times-orientation dependence and correlation with biochemical composition.
abstract: OBJECTIVE
  To measure the T2* of the human cartilaginous end plate by using magnetic resonance (MR) imaging with very short echo times and to determine the effect of the orientation of the end plate on T2* and on relationships between T2* and biochemical composition.
  
  
  METHODS
  This study was exempt from institutional review board approval, and informed consent was not required. Thirty-four samples of three cadaveric lumbar spines (from subjects who died at ages 51, 57, and 66 years) containing cartilaginous end plates and subchondral bone were prepared. Samples were imaged with a 3-T imager for T2* quantification by using a three-dimensional very short echo time sequence (repetition time msec/echo times msec, 30/0.075, 2, 5, 12, 18). Samples were imaged with the end plate at three orientations with respect to the constant magnetic induction field: 0°, 54.7°, and 90°. After imaging, the cartilage was assayed for its water, glycosaminoglycan, and collagen content. Pearson correlations were used to investigate the effect of orientation on the relationships between T2* and biochemical composition.
  
  
  RESULTS
  T2* was significantly longer when measured at an orientation of 54.7° (21.8 msec ± 2.8 [± standard error of the mean]) than at 0° (10.0 msec ± 0.7, P < .001) or 90° (9.9 msec ± 0.4, P < .001). At 54.7°, T2* was highly correlated with glycosaminoglycan content (r = 0.85, P < .001), the collagen-to-glycosaminoglycan ratio (r = -0.79, P < .001), and water content (r = 0.62, P = .02); at 0° and 90°, there were no significant differences in these relationships, with a minimum P value of .19.
  
  
  CONCLUSIONS
  T2* evaluation can allow noninvasive estimation of the degeneration of the cartilaginous end plate; however, the accuracy of T2*-based estimates of biochemical composition depends on the orientation of the end plate.
authors.affiliation: From the Department of Orthopaedic Surgery (A.J.F., R.K., J.C.L.) and Department of Radiology and Biomedical Imaging (M.H., R.K.), University of California-San Francisco, 513 Parnassus Ave, Room S-1161, San Francisco, CA 94143-0514.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Fields
authors.forename: Misung
authors.initials: M
authors.lastname: Han
authors.forename: Roland
authors.initials: R
authors.lastname: Krug
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Lotz
mesh_terms: D000368:Aged; D001834:Body Water; D002102:Cadaver; D002358:Cartilage, Articular / Q000033:anatomy & histology* / Q000737:chemistry; D003094:Collagen / Q000032:analysis; D006025:Glycosaminoglycans / Q000032:analysis; D006801:Humans; D007403:Intervertebral Disc / Q000033:anatomy & histology* / Q000737:chemistry; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged
chemical_list: D006025:Glycosaminoglycans; D003094:Collagen