Multisite MRI Intravoxel Incoherent Motion Repeatability and Reproducibility across 3 T Scanners in a Breast Diffusion Phantom: A BReast Intravoxel Incoherent Motion Multisite (BRIMM) Study

Background Monoexponential apparent diffusion coefficient (ADC) and biexponential intravoxel incoherent motion (IVIM) analysis of diffusion‐weighted imaging is helpful in the characterization of breast tumors. However, repeatability/reproducibility studies across scanners and across sites are scarce. Purpose To evaluate the repeatability and reproducibility of ADC and IVIM parameters (tissue diffusivity ( D t ), perfusion fraction ( F p ) and pseudo‐diffusion ( D p )) within and across sites employing MRI scanners from different vendors utilizing 16‐channel breast array coils in a breast diffusion phantom. Study Type Phantom repeatability. Phantom A breast phantom containing tubes of different polyvinylpyrrolidone (PVP) concentrations, water, fat, and sponge flow chambers, together with an MR‐compatible liquid crystal (LC) thermometer. Field Strength/Sequence Bipolar gradient twice‐refocused spin echo sequence and monopolar gradient single spin echo sequence at 3 T. Assessment Studies were performed twice in each of two scanners, located at different sites, on each of 2 days, resulting in four studies per scanner. ADCs of the PVP and water were normalized to the vendor‐provided calibrated values at the temperature indicated by the LC thermometer for repeatability/reproducibility comparisons. Statistical Tests ADC and IVIM repeatability and reproducibility within and across sites were estimated via the within‐system coefficient of variation (wCV). Pearson correlation coefficient ( r ) was also computed between IVIM metrics and flow speed. A P value <0.05 was considered statistically significant. Results ADC and D t demonstrated excellent repeatability (<2%; <3%, respectively) and reproducibility (both <5%) at the two sites. F p and D p exhibited good repeatability (mean of two sites 3.67% and 5.59%, respectively) and moderate reproducibility (mean of two sites 15.96% and 13.3%, respectively). The mean intersite reproducibility (%) of F p /D p /D t was 50.96/13.68/5.59, respectively. F p and D t demonstrated high correlations with flow speed while D p showed lower correlations. F p correlations with flow speed were significant at both sites. Data Conclusion IVIM reproducibility results were promising and similar to ADC, particularly for D t . The results were reproducible within both sites, and a progressive trend toward reproducibility across sites except for F p . Level of Evidence 2 Technical Efficacy Stage 1