title: Clinically applied CT arthrography to measure the sulphated glycosaminoglycan content of cartilage.
abstract: OBJECTIVE
  Similar to delayed gadolinium enhanced MRI of cartilage, it might be possible to image cartilage quality using CT arthrography (CTa). This study assessed the potential of CTa as a clinically applicable tool to evaluate cartilage quality in terms of sulphated glycosaminoglycan content (sGAG) and structural composition of the extra-cellular matrix (ECM).
  
  
  METHODS
  Eleven human cadaveric knee joints were scanned on a clinical CT scanner. Of each knee joint, a regular non-contrast CT (ncCT) and an ioxaglate injected CTa scan were performed. Mean X-ray attenuation of both scans was compared to identify contrast influx in seven anatomical regions of interest (ROIs). All ROIs were rescanned with contrast-enhanced μCT, which served as the reference standard for sGAG content. Mean X-ray attenuation from both ncCT and CTa were correlated with μCT results and analyzed with linear regression. Additionally, residual values from the linear fit between ncCT and μCT were used as a covariate measure to identify the influence of structural composition of cartilage ECM on contrast diffusion into cartilage in CTa scans.
  
  
  RESULTS
  CTa resulted in higher X-ray attenuation in cartilage compared to ncCT scans for all anatomical regions. Furthermore, CTa correlated excellent with reference μCT values (sGAG) (R=0.86; R(2)=0.73; P<0.0001). When corrected for structural composition of cartilage ECM, this correlation improved substantially (R=0.95; R(2)=0.90; P<0.0001).
  
  
  CONCLUSIONS
  Contrast diffusion into articular cartilage detected with CTa correlates with sGAG content and to a lesser extent with structural composition of cartilage ECM. CTa may be clinically applicable to quantitatively measure the quality of articular cartilage.
authors.affiliation: Department of Orthopedic Surgery, Erasmus Medical Center, Rotterdam, The Netherlands. m.siebelt@erasmusmc.nl
authors.forename: M
authors.initials: M
authors.lastname: Siebelt
authors.forename: J
authors.initials: J
authors.lastname: van Tiel
authors.forename: J H
authors.initials: JH
authors.lastname: Waarsing
authors.forename: T M
authors.initials: TM
authors.lastname: Piscaer
authors.forename: M
authors.initials: M
authors.lastname: van Straten
authors.forename: R
authors.initials: R
authors.lastname: Booij
authors.forename: M L
authors.initials: ML
authors.lastname: Dijkshoorn
authors.forename: G J
authors.initials: GJ
authors.lastname: Kleinrensink
authors.forename: J A N
authors.initials: JA
authors.lastname: Verhaar
authors.forename: G P
authors.initials: GP
authors.lastname: Krestin
authors.forename: H
authors.initials: H
authors.lastname: Weinans
authors.forename: E H G
authors.initials: EH
authors.lastname: Oei
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001175:Arthrography; D002102:Cadaver; D002358:Cartilage, Articular / Q000737:chemistry / Q000000981:diagnostic imaging*; D003287:Contrast Media; D005109:Extracellular Matrix / Q000000981:diagnostic imaging; D005260:Female; D006025:Glycosaminoglycans / Q000032:analysis*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007485:Ioxaglic Acid; D007719:Knee Joint / Q000166:cytology / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D006025:Glycosaminoglycans; C013786:A73025; D007485:Ioxaglic Acid