title: Characterization of the collagen component of cartilage repair tissue of the talus with quantitative MRI: comparison of T2 relaxation time measurements with a diffusion-weighted double-echo steady-state sequence (dwDESS).
abstract: OBJECTIVE
  The purpose of this study was to characterize the collagen component of repair tissue (RT) of the talus after autologous matrix-induced chondrogenesis (AMIC) using quantitative T2 and diffusion-weighted imaging.
  
  
  METHODS
  Mean T2 values and diffusion coefficients of AMIC-RT and normal cartilage of the talus of 25 patients with posttraumatic osteochondral lesions and AMIC repair were compared in a cross-sectional design using partially spoiled steady-state free precession (pSSFP) for T2 quantification, and diffusion-weighted double-echo steady-state (dwDESS) for diffusion measurement. RT and cartilage were graded with modified Noyes and MOCART scores on morphological sequences. An association between follow-up interval and quantitative MRI measures was assessed using multivariate regression, after stratifying the cohort according to time interval between surgery and MRI.
  
  
  RESULTS
  Mean T2 of the AMIC-RT and cartilage were 43.1 ms and 39.1 ms, respectively (p = 0.26). Mean diffusivity of the RT (1.76 μm(2)/ms) was significantly higher compared to normal cartilage (1.46 μm(2)/ms) (p = 0.0092). No correlation was found between morphological and quantitative parameters. RT diffusivity was lowest in the subgroup with follow-up >28 months (p = 0.027).
  
  
  CONCLUSIONS
  Compared to T2-mapping, dwDESS demonstrated greater sensitivity in detecting differences in the collagen matrix between AMIC-RT and cartilage. Decreased diffusivity in patients with longer follow-up times may indicate an increased matrix organization of RT.
  
  
  CONCLUSIONS
  • MRI is used to assess morphology of the repair tissue during follow-up. • Quantitative MRI allows an estimation of biochemical properties of the repair tissue. • Differences between repair tissue and cartilage were more significant with dwDESS than T2 mapping.
authors.affiliation: Department of Radiology, University Hospital Basel, Petersgraben 4, 4031, Basel, Switzerland, martin.kretzschmar@ucsf.edu.
authors.forename: M
authors.initials: M
authors.lastname: Kretzschmar
authors.forename: O
authors.initials: O
authors.lastname: Bieri
authors.forename: M
authors.initials: M
authors.lastname: Miska
authors.forename: M
authors.initials: M
authors.lastname: Wiewiorski
authors.forename: N
authors.initials: N
authors.lastname: Hainc
authors.forename: V
authors.initials: V
authors.lastname: Valderrabano
authors.forename: U
authors.initials: U
authors.lastname: Studler
mesh_terms: D000293:Adolescent; D000328:Adult; D002357:Cartilage Diseases / Q000601:surgery*; D002358:Cartilage, Articular / Q000601:surgery; D020219:Chondrogenesis / Q000502:physiology*; D003094:Collagen; D003430:Cross-Sectional Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D013628:Talus / Q000601:surgery*; D014182:Transplantation, Autologous; D016896:Treatment Outcome; D014945:Wound Healing / Q000502:physiology*; D055815:Young Adult
chemical_list: D003094:Collagen