title: T2 star relaxation times for assessment of articular cartilage at 3 T: a feasibility study.
abstract: OBJECTIVE
  T2 mapping techniques use the relaxation constant as an indirect marker of cartilage structure, and the relaxation constant has also been shown to be a sensitive parameter for cartilage evaluation. As a possible additional robust biomarker, T2* relaxation time is a potential, clinically feasible parameter for the biochemical evaluation of articular cartilage.
  
  
  METHODS
  The knees of 15 healthy volunteers and 15 patients after microfracture therapy (MFX) were evaluated with a multi-echo spin-echo T2 mapping technique and a multi-echo gradient-echo T2* mapping sequence at 3.0 Tesla MRI. Inline maps, using a log-linear least squares fitting method, were assessed with respect to the zonal dependency of T2 and T2* relaxation for the deep and superficial regions of healthy articular cartilage and cartilage repair tissue.
  
  
  RESULTS
  There was a statistically significant correlation between T2 and T2* values. Both parameters demonstrated similar spatial dependency, with longer values measured toward the articular surface for healthy articular cartilage. No spatial variation was observed for cartilage repair tissue after MFX.
  
  
  CONCLUSIONS
  Within this feasibility study, both T2 and T2* relaxation parameters demonstrated a similar response in the assessment of articular cartilage and cartilage repair tissue. The potential advantages of T2*-mapping of cartilage include faster imaging times and the opportunity for 3D acquisitions, thereby providing greater spatial resolution and complete coverage of the articular surface.
authors.affiliation: Department of Orthopedic Surgery, Inselspital, University Bern, Bern, Switzerland. mamisch@bwh.harvard.edu
authors.forename: Tallal Charles
authors.initials: TC
authors.lastname: Mamisch
authors.forename: Timothy
authors.initials: T
authors.lastname: Hughes
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Mosher
authors.forename: Christoph
authors.initials: C
authors.lastname: Mueller
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
authors.forename: Chris
authors.initials: C
authors.lastname: Boesch
authors.forename: Goetz Hannes
authors.initials: GH
authors.lastname: Welsch
mesh_terms: D000328:Adult; D000465:Algorithms; D054544:Arthroplasty, Subchondral; D002358:Cartilage, Articular / Q000293:injuries* / Q000473:pathology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007718:Knee Injuries / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity