title: Articular cartilage: in vivo diffusion-tensor imaging.
abstract: OBJECTIVE
  To investigate technical feasibility, test-retest reproducibility, and the ability to differentiate healthy subjects from subjects with osteoarthritis (OA) with diffusion-tensor (DT) imaging parameters and T2 relaxation time.
  
  
  METHODS
  This study was approved by the institutional review board and was HIPAA compliant. All subjects provided written informed consent. DT imaging parameters and T2 (resolution=0.6×0.6×2 mm) of patellar cartilage were measured at 7.0 T in 16 healthy volunteers and 10 patients with OA with subtle inhomogeneous signal intensity but no signs of cartilage erosion at clinical magnetic resonance (MR) imaging. Ten volunteers were imaged twice to determine test-retest reproducibility. After cartilage segmentation, maps of mean apparent diffusion coefficient (ADC), fractional anisotropy (FA), and T2 relaxation time were calculated. Differences for ADC, FA, and T2 between the healthy and OA populations were assessed with nonparametric tests. The ability of each MR imaging parameter to help discriminate healthy subjects from subjects with OA was assessed by using receiver operating characteristic curve analysis.
  
  
  RESULTS
  Test-retest reproducibility was better than 10% for mean ADC (8.1%), FA (9.7%), and T2 (5.9%). Mean ADC and FA differed significantly (P<.01) between the OA and healthy populations, but T2 did not. For ADC, the optimal threshold to differentiate both populations was 1.2×10(-3) mm2/sec, achieving specificity of 1.0 (16 of 16) and sensitivity of 0.80 (eight of 10). For FA, the optimal threshold was 0.25, yielding specificity of 0.88 (14 of 16) and sensitivity of 0.80 (eight of 10). T2 showed poor differentiation between groups (optimal threshold=22.9 msec, specificity=0.69 [11 of 16], sensitivity=0.60 [six of 10]).
  
  
  CONCLUSIONS
  In vivo DT imaging of patellar cartilage is feasible, has good test-retest reproducibility, and may be accurate in discriminating healthy subjects from subjects with OA. ADC and FA are two promising biomarkers for early OA.
authors: Department of Radiology, New York University Langone Medical Center, 660 First Ave, 4th Floor, New York, NY 10016, USA. jose.raya@nyumc.org
authors: José G
authors: JG
authors: Raya
authors: Annie
authors: A
authors: Horng
authors: Olaf
authors: O
authors: Dietrich
authors: Svetlana
authors: S
authors: Krasnokutsky
authors: Luis S
authors: LS
authors: Beltran
authors: Pippa
authors: P
authors: Storey
authors: Maximilian F
authors: MF
authors: Reiser
authors: Michael P
authors: MP
authors: Recht
authors: Daniel K
authors: DK
authors: Sodickson
authors: Christian
authors: C
authors: Glaser
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002358:Cartilage, Articular / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity