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), perfusion fraction (F) and pseudo-diffusion (D)) 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 demonstrated excellent repeatability (<2%; <3%, respectively) and reproducibility (both <5%) at the two sites. F and D 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/D/D was 50.96/13.68/5.59, respectively. F and D demonstrated high correlations with flow speed while D showed lower correlations. F correlations with flow speed were significant at both sites.

Data Conclusion: IVIM reproducibility results were promising and similar to ADC, particularly for D. The results were reproducible within both sites, and a progressive trend toward reproducibility across sites except for F.

Level Of Evidence: 2 TECHNICAL EFFICACY: Stage 1.