title: Repeatability of T1-quantification in dGEMRIC for three different acquisition techniques: two-dimensional inversion recovery, three-dimensional look locker, and three-dimensional variable flip angle.
abstract: OBJECTIVE
  To evaluate the repeatability of the dGEMRIC (delayed gadolinium enhanced MRI of cartilage) method in osteoarthritis-prone knee joints for three different T1 quantification techniques: two-dimensional inversion recovery (2D-IR), three-dimensional Look-Locker (3D-LL), and three-dimensional variable flip angle (3D-VFA).
  
  
  METHODS
  Nine subjects were examined twice, with a 2-week interval, using all three measurement techniques. Four regions of interest were defined in the central medial and lateral femoral cartilage. The repeatability was evaluated for each measurement technique. For the 3D techniques, the variation between different slices was also evaluated.
  
  
  RESULTS
  Repeatability expressed by root-mean-square coefficient of variation (CV(RMS)) showed similar results for 2D-IR and 3D-LL (5.4-8.4%). For 3D-VFA CV(RMS) was higher (9.3-15.2%). Intraclass correlation coefficient showed both 2D-IR and 3D-LL reliability to be moderate, while 3D-VFA reliability was low. Inter-slice CV(RMS) and ICC was of the same magnitude as the repeatability. No clear differences could be interpreted between the condyles.
  
  
  CONCLUSIONS
  Both 2D-IR and 3D-LL perform well in generating repeatable dGEMRIC results, while 3D-VFA results are somewhat inferior. Furthermore, repeatability results in this study are similar to previously published results for healthy subjects. Finally, the positioning of the analyzed images is crucial to generate reliable repeatability results.
authors.affiliation: Department of Radiation Physics, Lund University, Malmö, Sweden. carl.siversson@med.lu.se
authors.forename: Carl
authors.initials: C
authors.lastname: Siversson
authors.forename: Carl-Johan
authors.initials: CJ
authors.lastname: Tiderius
authors.forename: Paul
authors.initials: P
authors.lastname: Neuman
authors.forename: Leif
authors.initials: L
authors.lastname: Dahlberg
authors.forename: Jonas
authors.initials: J
authors.lastname: Svensson
mesh_terms: D000465:Algorithms; D016118:Anterior Cruciate Ligament / Q000473:pathology*; D000070598:Anterior Cruciate Ligament Injuries; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity