Stability of ADC measurements in diffusion MRI: A multicenter phantom study using multi-point b-values

The apparent diffusion coefficient (ADC) from diffusion MRI provides critical insights into tissue microstructure and is influenced by various b-values. This study aimed to evaluate the impact of multiple b-values on ADC measurements using a multicenter observational approach with different MRI scanners and phantoms.

The study utilized a liquid isotropic phantom across eight different 1.5 T MRI scanners from five centers. The phantom contained four fluids with different viscosity and relaxation properties. ADC measurements were obtained at b-values of 0, 50, 500, 1000, and 1500 s/mm² using standardized protocols, which involved applying consistent imaging parameters across all MRI scanners. Each scan was repeated three times, and statistical analyses, including Kruskal-Wallis and Bonferroni-corrected Mann-Whitney U tests, were performed to evaluate variability.

Significant variations in ADC values were observed among different MRI scanners. Higher b-values generally resulted in lower ADC readings, reflecting restricted diffusion. The comparison between 2-point and multiple-point b-value techniques revealed that the latter provides more consistent ADC measurements. Bland-Altman analysis indicated a systematic difference between single-shot echo-planar imaging (ssEPI) and turbo spin echo (TSE) sequences, with TSE showing more homogeneous ADC values.

This study highlights the significant variability in ADC measurements across different MRI scanners and sequences, emphasizing the critical role of standardization in diffusion MRI protocols. The findings demonstrate that multiple-point b-value techniques offer greater consistency compared to 2-point methods, and TSE sequences yield more homogeneous ADC values than ssEPI.

These findings underscore the need for standardized protocols and multicenter guidelines to enhance the reliability of ADC as a diagnostic biomarker in clinical and research settings.