title: Quantitative T2 mapping of knee cartilage: differentiation of healthy control cartilage and cartilage repair tissue in the knee with unloading--initial results.
abstract: OBJECTIVE
  To prospectively determine on T2 cartilage maps the effect of unloading during a clinical magnetic resonance (MR) examination in the postoperative follow-up of patients after matrix-associated autologous chondrocyte transplantation (MACT) of the knee joint.
  
  
  METHODS
  Ethical approval for this study was provided by the local ethics commission, and written informed consent was obtained. Thirty patients (mean age, 35.4 years +/- 10.5) with a mean postoperative follow-up period of 29.1 months +/- 24.4 were enrolled. A multiecho spin-echo T2-weighted sequence was performed at the beginning (early unloading) and end (late unloading) of the MR examination, with an interval of 45 minutes. Mean and zonal region of interest T2 measurements were obtained in control cartilage and cartilage repair tissue. Statistical analysis of variance was performed.
  
  
  RESULTS
  The change in T2 values of control cartilage (early unloading, 50.2 msec +/- 8.4; late unloading, 51.3 msec +/- 8.5) was less pronounced than the change in T2 values of cartilage repair tissue (early unloading, 51.8 msec +/- 11.7; late unloading, 56.1 msec +/- 14.4) (P = .024). The difference between control cartilage and cartilage repair tissue was not significant for early unloading (P = .314) but was significant for late unloading (P = .036). Zonal T2 measurements revealed a higher dependency on unloading for the superficial cartilage layer.
  
  
  CONCLUSIONS
  Our results suggest that T2 relaxation can be used to assess early and late unloading values of articular cartilage in a clinical setting and that the time point of the quantitative T2 measurement affects the differentiation between native and abnormal articular cartilage. (c) RSNA, 2010.
authors.affiliation: Department of Orthopedic Surgery, University of Berne, Berne, Switzerland.
authors.forename: Tallal C
authors.initials: TC
authors.lastname: Mamisch
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
authors.forename: Sebastian
authors.initials: S
authors.lastname: Quirbach
authors.forename: Stefan
authors.initials: S
authors.lastname: Marlovits
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: White
authors.forename: Goetz H
authors.initials: GH
authors.lastname: Welsch
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001182:Arthroscopy; D002358:Cartilage, Articular / Q000473:pathology / Q000601:surgery*; D019902:Chondrocytes / Q000637:transplantation; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006820:Hyaluronic Acid / Q000494:pharmacology; D007091:Image Processing, Computer-Assisted; D007719:Knee Joint / Q000473:pathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D023822:Tissue Engineering; D016896:Treatment Outcome; D014945:Wound Healing
chemical_list: D006820:Hyaluronic Acid