title: Multi-system repeatability and reproducibility of apparent diffusion coefficient measurement using an ice-water phantom.
abstract: OBJECTIVE
  To determine quantitative quality control procedures to evaluate technical variability in multi-center measurements of the diffusion coefficient of water as a prerequisite to use of the biomarker apparent diffusion coefficient (ADC) in multi-center clinical trials.
  
  
  METHODS
  A uniform data acquisition protocol was developed and shared with 18 participating test sites along with a temperature-controlled diffusion phantom delivered to each site. Usable diffusion weighted imaging data of ice water at five b-values were collected on 35 clinical MRI systems from three vendors at two field strengths (1.5 and 3 Tesla [T]) and analyzed at a central processing site.
  
  
  RESULTS
  Standard deviation of bore-center ADCs measured across 35 scanners was <2%; error range: -2% to +5% from literature value. Day-to-day repeatability of the measurements was within 4.5%. Intra-exam repeatability at the phantom center was within 1%. Excluding one outlier, inter-site reproducibility of ADC at magnet isocenter was within 3%, although variability increased for off-center measurements. Significant (>10%) vendor-specific and system-specific spatial nonuniformity ADC bias was detected for the off-center measurement that was consistent with gradient nonlinearity.
  
  
  CONCLUSIONS
  Standardization of DWI protocol has improved reproducibility of ADC measurements and allowed identifying spatial ADC nonuniformity as a source of error in multi-site clinical studies.
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Dariya
authors.initials: D
authors.lastname: Malyarenko
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Galbán
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Londy
authors.forename: Charles R
authors.initials: CR
authors.lastname: Meyer
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Johnson
authors.forename: Alnawaz
authors.initials: A
authors.lastname: Rehemtulla
authors.forename: Brian D
authors.initials: BD
authors.lastname: Ross
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Chenevert
mesh_terms: D038524:Diffusion Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D019544:Equipment Failure Analysis / Q000295:instrumentation / Q000592:standards; D007053:Ice; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000592:standards*; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014481:United States; D014867:Water
chemical_list: D007053:Ice; D014867:Water