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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
Basukala et al. (Wed,) studied this question.