Abstract The current diagnostic gold standard for metabolic dysfunction-associated steatohepatitis (MASH) requires invasive biopsy to assess steatosis, inflammation, and ballooning. While MRI-based proton density fat fraction (PDFF) and MR elastography address steatosis and fibrosis, non-invasive methods for evaluating hepatic inflammation remain lacking. This study developed a diffusion MRI (dMRI)-based MR cytometry technique to map liver cellular properties, including MRI-derived cell size (excluding fat content) and cell density. Validation through histology-driven simulations and ex vivo MRI of fixed human liver specimens demonstrated that stromal regions exhibit smaller MRI-derived cell sizes and higher cell densities than both normal and fatty tissues. An in vivo feasibility study, conducted on healthy subjects (n = 5) and MASH patients (n = 5) using a clinical 3 T MRI system, further showcased the potential of MR cytometry to characterize pathological changes in liver microstructure.
