title: Variability of CubeQuant T1ρ, quantitative DESS T2, and cones sodium MRI in knee cartilage.
abstract: OBJECTIVE
  To measure the variability of T1ρ relaxation times using CubeQuant, T2 relaxation times using quantitative double echo in steady state (DESS), and normalized sodium signals using 3D cones sodium magnetic resonance imaging (MRI) of knee cartilage in vivo at 3 T.
  
  
  METHODS
  Eight healthy subjects were scanned at 3 T at baseline, 1 day, 5 months, and 1 year. Ten regions of interest (ROIs) of knee cartilage were segmented in the medial and lateral compartments of each subject's knee. T1ρ and T2 relaxation times and normalized sodium signals were measured and the root-mean-square coefficient of variation (CVRMS) was calculated. Intra-subject variability was measured over short, moderate and long-term, as well as intra-observer and inter-observer variability.
  
  
  RESULTS
  The average intra-subject CVRMS measurements over short, moderate, and long-term time periods were 4.6%, 6.1%, and 6.0% for the T1ρ measurements, 6.4%, 9.3%, and 10.7% for the T2 measurements and 11.3%, 11.6%, and 12.9% for the sodium measurements, respectively. The average CVRMS measurements for intra-observer and inter-observer segmentation were 3.8% and 5.7% for the T1ρ measurements, 4.7% and 6.7% for the T2 measurements, and 8.1% and 11.4% for the sodium measurements, respectively.
  
  
  CONCLUSIONS
  These CVRMS measurements are substantially lower than previously measured changes expected in patients with advanced osteoarthritis compared to healthy volunteers, suggesting that CubeQuant T1ρ, quantitative DESS T2 and 3D cones sodium measurements are sufficiently sensitive for in vivo cartilage studies.
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA, United States; Department of Bioengineering, Stanford University, Stanford, CA, United States. Electronic address: cjordan@alumni.stanford.edu.
authors.forename: C D
authors.initials: CD
authors.lastname: Jordan
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA, United States. Electronic address: mcwalter@stanford.edu.
authors.forename: E J
authors.initials: EJ
authors.lastname: McWalter
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA, United States; Department of Electrical Engineering, Stanford University, Stanford, CA, United States. Electronic address: udmonu@stanford.edu.
authors.forename: U D
authors.initials: UD
authors.lastname: Monu
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA, United States. Electronic address: watkinsr@stanford.edu.
authors.forename: R D
authors.initials: RD
authors.lastname: Watkins
authors.affiliation: GE Applied Science Laboratory, Menlo Park, CA, United States. Electronic address: weitian.chen@ge.com.
authors.forename: W
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Electrical and Computer Engineering, Brigham Young University, Provo, UT, United States. Electronic address: nealb@ee.byu.edu.
authors.forename: N K
authors.initials: NK
authors.lastname: Bangerter
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA, United States; Department of Bioengineering, Stanford University, Stanford, CA, United States; Department of Electrical Engineering, Stanford University, Stanford, CA, United States. Electronic address: bah@stanford.edu.
authors.forename: B A
authors.initials: BA
authors.lastname: Hargreaves
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA, United States; Department of Bioengineering, Stanford University, Stanford, CA, United States; Department of Orthopaedic Surgery, Stanford University, Stanford, CA, United States. Electronic address: gold@stanford.edu.
authors.forename: G E
authors.initials: GE
authors.lastname: Gold
mesh_terms: D000328:Adult; D002358:Cartilage, Articular / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007719:Knee Joint / Q000033:anatomy & histology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012964:Sodium; D055815:Young Adult
chemical_list: D012964:Sodium
keywords: Cartilage; Knee; MRI; Quantitative; Repeatability; Variability