Quantitative evaluation of shear stiffness and the apparent diffusion coefficient using anthropomorphic multi-stiffness liver phantoms under static and motion conditions.

PURPOSE: To evaluate diffusion-weighted imaging (DWI) and MR Elastography (MRE) performance over a clinically relevant stiffness range for liver fibrosis with and without the presence of compressive motion using an in vitro phantom pipeline. METHODS: Five anthropomorphic liver phantoms were created using polyacrylamide (PAA) hydrogels. Phantom stiffness ranged from approximately 1.5-11 kPa. Phantoms were connected to a pulsatile flow circuit to induce compressive motion. Imaging was performed on a 3T MRI system. MRE, conventional DWI, and M1-motion optimized DWI (MODI) were assessed at varying pulsatile flow states (mean flow = 0, 0.5, 1, 1.5 L/min). Conventional and MODI DWI apparent diffusion coefficients (ADC) were correlated to MRE stiffness. RESULTS: Stiffness and ADC maps were obtained for all phantoms and flow states. Conventional and MODI DWI under static conditions exhibited an inverse relationship with MRE stiffness (R2 = 0.94 and R2 = 0.95, respectively). MODI-DWI exhibited reduced motion-induced signal dropout, minimizing ADC bias under motion conditions compared to conventional DWI. Mean MRE stiffness was largely unaffected by motion, except for the lowest and highest stiffness phantoms at the highest flow rate. CONCLUSION: Anthropomorphic liver phantoms were used to systemically investigate the effects of stiffness and motion on the performance of MRE and DWI. MRE and MODI-DWI demonstrated strong insensitivity to motion across stiffness and motion level.