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Keywords:

  • diffusion;
  • MRI;
  • phantom;
  • ice-water;
  • quality control;
  • gradient nonlinearity

Abstract

Purpose:

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.

Materials and 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.

Conclusion:

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. J. Magn. Reson. Imaging 2013;37:1238–1246. © 2012 Wiley Periodicals, Inc.