Multi‐system repeatability and reproducibility of apparent diffusion coefficient measurement using an ice‐water phantom

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.