title: Cartilage T1ρ and T2 relaxation times: longitudinal reproducibility and variations using different coils, MR systems and sites.
abstract: OBJECTIVE
  To evaluate the longitudinal reproducibility and variations of cartilage T1ρ and T2 measurements using different coils, MR systems and sites.
  
  
  METHODS
  Single-Site study: Phantom data were collected monthly for up to 29 months on four GE 3T MR systems. Data from phantoms and human subjects were collected on two MR systems using the same model of coil; and were collected on one MR system using two models of coils. Multi-site study: Three participating sites used the same model of MR systems and coils, and identical imaging protocols. Phantom data were collected monthly. Human subjects were scanned and rescanned on the same day at each site. Two traveling human subjects were scanned at all three sites.
  
  
  RESULTS
  Single-Site Study: The phantom longitudinal RMS-CVs ranged from 1.8% to 2.7% for T1ρ and 1.8-2.8% for T2. Significant differences were found in T1ρ and T2 values using different MR systems and coils. Multi-Site Study: The phantom longitudinal RMS-CVs ranged from 1.3% to 2.6% for T1ρ and 1.2-2.7% for T2. Across three sites (n = 16), the in vivo scan-rescan RMS-CV was 3.1% and 4.0% for T1ρ and T2, respectively. Phantom T1ρ and T2 values were significantly different between three sites but highly correlated (R > 0.99). No significant difference was found in T1ρ and T2 values of traveling controls, with cross-site RMS-CV as 4.9% and 4.4% for T1ρ and T2, respectively.
  
  
  CONCLUSIONS
  With careful quality control and cross-calibration, quantitative MRI can be readily applied in multi-site studies and clinical trials for evaluating cartilage degeneration.
authors.affiliation: University of California, San Francisco, CA, USA. Electronic address: xiaojuan.li@ucsf.edu.
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.affiliation: University of California, San Francisco, CA, USA.
authors.forename: V
authors.initials: V
authors.lastname: Pedoia
authors.affiliation: University of California, San Francisco, CA, USA; Division of Physical Therapy, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: D
authors.initials: D
authors.lastname: Kumar
authors.affiliation: University of California, San Francisco, CA, USA.
authors.forename: J
authors.initials: J
authors.lastname: Rivoire
authors.affiliation: University of California, San Francisco, CA, USA.
authors.forename: C
authors.initials: C
authors.lastname: Wyatt
authors.affiliation: University of California, San Francisco, CA, USA.
authors.forename: D
authors.initials: D
authors.lastname: Lansdown
authors.affiliation: University of California, San Francisco, CA, USA.
authors.forename: K
authors.initials: K
authors.lastname: Amano
authors.affiliation: University of California, San Francisco, CA, USA.
authors.forename: N
authors.initials: N
authors.lastname: Okazaki
authors.affiliation: University of California, San Francisco, CA, USA.
authors.forename: D
authors.initials: D
authors.lastname: Savic
authors.affiliation: Hospital for Special Surgery, New York, NY, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Koff
authors.affiliation: Mayo Clinic, Rochester, MN, USA.
authors.forename: J
authors.initials: J
authors.lastname: Felmlee
authors.affiliation: Mayo Clinic, Rochester, MN, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Williams
authors.affiliation: University of California, San Francisco, CA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Majumdar
mesh_terms: D002358:Cartilage, Articular / Q000473:pathology*; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007719:Knee Joint / Q000473:pathology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D020370:Osteoarthritis, Knee / Q000175:diagnosis*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results
keywords: Cartilage; Multi-site study; Quantitative MRI; Reproducibility; T(1ρ); T(2)