title: Correlations between X-ray attenuation and GAG content of different cartilage layers based on contrast agent enhanced Micro-CT.
abstract: OBJECTIVE
  To build the quantitative relationships between X-ray attenuation and glycosaminoglycan (GAG) content of different layers of progressive trypsin digested articular cartilage (AC) models based on the contrast agent enhanced Micro-CT.
  
  
  METHODS
  Bovine AC samples were treated with 0.5% concentration of trypsin for different degeneration time, immersed in contrast agent and then scanned by Micro-CT to obtain the X-ray attenuation. Combining with histological analysis, the relationships between the X-ray attenuation and GAG optical density of the superficial and middle layer were analyzed.
  
  
  RESULTS
  The X-ray mean attenuation increased about 16.48% (p<;0.01) in the superficial layer within the first 10-minute degeneration, 26.99% (p<;0.05) in the middle layer within the first 40-minute degeneration, but merely changed in the deep layer in the entire experiment. Contrary to the change of X-ray mean attenuation, the GAG optical density decreased from 31.98±13.00 to 11.69±4.23 (p<;0.01) in the superficial layer within the first 10-minute degeneration, from 82.94±7.35 to 3.85±3.31 (p<;0.01) in the middle layer within the entire degeneration and didn't slightly decrease from 96.10±2.50 to 91.45±1.90 (p<;0.05) until the last 10-minute degeneration in deep layer. In addition, the changes of the X-ray mean attenuation showed negative linear correlations with the GAG content in the superficial (r = -0.984, p<;0.01) and the middle layer (r = -0.960, p<;0.01), respectively.
  
  
  CONCLUSIONS
  The contrast agent enhanced Micro-CT can elucidate the variation of GAG content in trypsin-induced progressive AC models by X-ray mean attenuation of different cartilage layers.
authors.forename: Fan
authors.initials: F
authors.lastname: Fan
authors.forename: Li
authors.initials: L
authors.lastname: Xiaofei
authors.forename: Ren
authors.initials: R
authors.lastname: Pengling
authors.forename: Cai
authors.initials: C
authors.lastname: Xiran
authors.forename: Yan
authors.initials: Y
authors.lastname: Yan
authors.forename: Fan
authors.initials: F
authors.lastname: Yubo
authors.forename: Niu
authors.initials: N
authors.lastname: Haijun
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000737:chemistry / Q000000981:diagnostic imaging; D002417:Cattle; D003287:Contrast Media / Q000737:chemistry*; D006025:Glycosaminoglycans / Q000032:analysis / Q000737:chemistry / Q000528:radiation effects; D055114:X-Ray Microtomography / Q000379:methods*
chemical_list: D003287:Contrast Media; D006025:Glycosaminoglycans