Multi‐Center, Multi‐Vendor Validation of Simultaneous MRI‐Based Proton Density Fat Fraction and R2* Mapping Using a Combined Proton Density Fat Fraction‐R2* Phantom

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Background Fat and iron deposition confound measurements of R2* and proton density fat fraction (PDFF), respectively, yet their combined impact on reproducibility is poorly understood. Purpose To evaluate the multi‐center, multi‐vendor reproducibility of PDFF and R2* quantification using a PDFF‐R2* phantom. Study Type Prospective multi‐center, phantom study. Phantom Commercial PDFF‐R2* phantom with simultaneously controlled combination of PDFF (0%–30%) and R2* (50–600 s −1 ) values. Field Strength/Sequence 1.5‐T and 3‐T, three‐dimensional ( 3D ) multi‐echo, spoiled‐gradient‐echo sequences, in four different centers, each with a different vendor. Assessment Two acquisition protocols were used, optimized for moderate R2* (Protocol 1) and high R2 * (Protocol 2), respectively. The phantom was imaged multiple times at one of the centers to assess its stability. Statistical Tests Intraclass correlation coefficient (ICC), linear regression analysis, reproducibility coefficient (RDC) and repeatability coefficient (RC). Results Excellent agreement was observed for PDFF measurements between centers, vendors, field strengths, and protocols (ICC = 0.97). Stratified by protocol, excellent agreement was observed, with ICC = 0.96 (RDC = 6.2%) for Protocol 1 and ICC = 0.99 (RDC = 3.8%) for Protocol 2. Increased variability in PDFF measurements was observed with increasing PDFF and especially with higher R2*. Excellent agreement was observed for R2* between centers, vendors, field strengths, and protocols (ICC = 0.99). Stratified by protocol, strong agreement was observed, with ICC = 0.988 (RDC = 66.7 s −1 ) for Protocol 1 and ICC = 0.99 (RDC = 57.7 s −1 ) for Protocol 2. Higher variability in R2* measurements was observed in vials with higher PDFF or R2*. Stability tests demonstrated an ICC = 1.0 for PDFF and R2*, and RC of 0.4% for PDFF and 12 s −1 for R2*. Data Conclusion Excellent PDFF and R2* reproducibility was observed across centers, vendors, field strengths, and acquisition protocols. Reproducibility decreased slightly with increasing PDFF and R2*, especially for PDFF measurements in vials with high R2*. Evidence Level N/A. Technical Efficacy Stage 1.