title: Contrast-enhanced CT of articular cartilage: experimental study for quantification of glycosaminoglycan content in articular cartilage.
abstract: OBJECTIVE
  To investigate the diagnostic potential of delayed contrast material-enhanced computed tomography (CT) of articular cartilage in quantification of glycosaminoglycan (GAG) concentration in normal and degenerated articular cartilage ex vivo by using a clinical CT scanner.
  
  
  METHODS
  This study was exempted by the institutional and animal review boards, and informed consent was not required. Forty intact porcine patellae were extracted and assigned to either a control (n = 20) or a trypsin-treated group (ie, GAG-depleted group) (n = 20). Ten patellae in each group were immersed in anionic contrast agent (ioxaglate, 40%) and the other ten in neutral contrast agent (iopromide, 35%) for 2 hours. To determine the contrast agent concentration within cartilage, samples were scanned with a clinical CT scanner immediately after the immersion time, and the x-ray attenuation of cartilage was measured. CT images were compared with safranin O-stained histologic sections, and actual GAG contents were determined with a dimethylmethylene blue assay.
  
  
  RESULTS
  Ioxaglate was taken up by GAG-depleted cartilage to a greater extent than by normal cartilage (P = .01). In contrast, the penetration of iopromide was not significantly different between GAG-depleted and normal cartilage (P = .1). The loss of GAGs in trypsin-treated cartilage was confirmed microscopically by using safranin O-stained sections, and a dimethylmethylene blue assay also confirmed that GAG content was markedly decreased in trypsin-treated cartilage (P = .003).
  
  
  CONCLUSIONS
  This study showed that contrast-enhanced CT images of articular cartilage could reflect the GAG content within the cartilage by allowing measurement of the concentration of anionic iodine-based contrast agent accumulated in the cartilage.
authors.affiliation: Department of Radiology and Institute of Radiation Medicine, Seoul National University Hospital, Seoul National University College of Medicine, 101 Daehang-Ro, Jongno-Gu, Seoul 110-744, Korea.
authors.forename: Hye Jin
authors.initials: HJ
authors.lastname: Yoo
authors.forename: Sung Hwan
authors.initials: SH
authors.lastname: Hong
authors.forename: Ja-Young
authors.initials: JY
authors.lastname: Choi
authors.forename: In Joon
authors.initials: IJ
authors.lastname: Lee
authors.forename: Su Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Jung-Ah
authors.initials: JA
authors.lastname: Choi
authors.forename: Heung Sik
authors.initials: HS
authors.lastname: Kang
mesh_terms: D000465:Algorithms; D000818:Animals; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000378:metabolism*; D003287:Contrast Media / Q000493:pharmacokinetics*; D006025:Glycosaminoglycans / Q000378:metabolism*; D066298:In Vitro Techniques; D007472:Iohexol / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D007485:Ioxaglic Acid / Q000493:pharmacokinetics*; D010329:Patella / Q000000981:diagnostic imaging / Q000378:metabolism; D011857:Radiographic Image Interpretation, Computer-Assisted; D013552:Swine; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014357:Trypsin
chemical_list: D003287:Contrast Media; D006025:Glycosaminoglycans; D007472:Iohexol; C038192:iopromide; D014357:Trypsin; D007485:Ioxaglic Acid