title: Two year longitudinal change and test-retest-precision of knee cartilage morphology in a pilot study for the osteoarthritis initiative.
abstract: OBJECTIVE
  Fast low angle shot (FLASH) and double echo steady state (DESS) magnetic resonance imaging (MRI) acquisitions were recently cross-calibrated for quantification of cartilage morphology at 3T. In this pilot study for the osteoarthritis (OA) initiative we compare their test-retest-precision and sensitivity to longitudinal change.
  
  
  METHODS
  Nine participants with mild to moderate clinical OA were imaged twice each at baseline, year 1 (Y1) and year 2 (Y2). Coronal 1.5mm FLASH and sagittal 0.7mm DESS sequences were acquired; 1.5mm coronal multiplanar reformats (MPR) were obtained from the DESS. Patellar, femoral and tibial cartilage plates were quantified in a paired fashion, with blinding to time point.
  
  
  RESULTS
  In the weight-bearing femorotibial joint, average precision errors across plates were 1.8% for FLASH, 2.6% for DESS, and 3.0% for MPR-DESS. Volume loss at Y1 was not significant; at Y2 the average change across the femorotibial cartilage plates was -1.7% for FLASH, -2.8% for DESS, and -0.3% for MPR-DESS. Volume change in the lateral tibia (-5.5%; P<0.03), and in the medial (-2.9%; P<0.04) and lateral femorotibial compartments (-3.8%; P<0.03) were significant for DESS.
  
  
  CONCLUSIONS
  FLASH, DESS and MPR-DESS all displayed adequate test-retest precision. Although the comparison between protocols is limited by the small number of participants and by the relatively small longitudinal change in cartilage morphology in this pilot study, the data suggest that significant change can be detected with MRI in a small sample of OA subjects over 2 years.
authors.affiliation: Institute of Anatomy and Musculoskeletal Research, Paracelsus Private Medical University (PMU), Salzburg, Austria. felix.eckstein@pmu.ac.at
authors.forename: F
authors.initials: F
authors.lastname: Eckstein
authors.forename: M
authors.initials: M
authors.lastname: Kunz
authors.forename: M
authors.initials: M
authors.lastname: Schutzer
authors.forename: M
authors.initials: M
authors.lastname: Hudelmaier
authors.forename: R D
authors.initials: RD
authors.lastname: Jackson
authors.forename: J
authors.initials: J
authors.lastname: Yu
authors.forename: C B
authors.initials: CB
authors.lastname: Eaton
authors.forename: E
authors.initials: E
authors.lastname: Schneider
mesh_terms: D000328:Adult; D002358:Cartilage, Articular / Q000473:pathology*; D005260:Female; D005269:Femur; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000473:pathology*; D010865:Pilot Projects; D015203:Reproducibility of Results; D013977:Tibia