title: Quantitative MRI analysis of menisci using biexponential T2* fitting with a variable echo time sequence.
abstract: OBJECTIVE
  The goal of this study was to differentiate between normal, degenerative meniscus, and meniscal tears using monoexponentially and biexponentially calculated T2*. Meniscal disease, characterized by an altered collagen fiber matrix, might be detectable in vivo using quantitative T2* mapping.
  
  
  METHODS
  A 3D Cartesian spoiled gradient echo technique was adapted to enable the use of a variable echo time approach in combination with a highly asymmetric readout. T2* was calculated monoexponentially and biexponentially using three- and five-parametric non-linear fits, respectively.
  
  
  RESULTS
  From a total of 68 evaluated menisci, 48 were normal, 12 were degenerated, and eight had tears. Mean values for the short (T2*s) and long (T2*l) T2* components were as follows: in normal menisci, 0.82 ± 0.38/15.0 ± 5.4 ms, respectively; in degenerated menisci, 1.29 ± 0.53/19.97 ± 5.59 ms, respectively; and, in meniscal tears, 2.05 ± 0.73 and 26.83 ± 7.72 ms, respectively. Biexponentially fitted T2* demonstrated a greater ability to distinguish normal and degenerated menisci using receiver operating characteristic (ROC) analysis (higher area under curve as well as higher specificity and sensitivity).
  
  
  CONCLUSIONS
  This study suggests that biexponential fitting, used for T2* calculation in the menisci, provides better results compared to monoexponential fitting. Observed changes in T2* result from the matrix reorganization in degenerative processes in the menisci, which affects the collagen fiber orientation, as well as content.
authors.affiliation: Center of Excellence for High field MR, Department of Radiology, Medical University of Vienna Waehringer Guertel 18-20, Vienna, Austria; Institute of Measurement Science, Department of Imaging Methods, Dubravska cesta 9, Bratislava, Slovakia.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Juras
authors.forename: Sebastian
authors.initials: S
authors.lastname: Apprich
authors.forename: Štefan
authors.initials: Š
authors.lastname: Zbýň
authors.forename: Lukas
authors.initials: L
authors.lastname: Zak
authors.forename: Xeni
authors.initials: X
authors.lastname: Deligianni
authors.forename: Pavol
authors.initials: P
authors.lastname: Szomolanyi
authors.forename: Oliver
authors.initials: O
authors.lastname: Bieri
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007718:Knee Injuries / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008592:Menisci, Tibial / Q000473:pathology*; D020370:Osteoarthritis, Knee / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000070600:Tibial Meniscus Injuries