Diffusion-Weighted Imaging-Based Virtual MR Elastography of the Liver: Beyond Mechanical Waves.

Magnetic resonance elastography (MRE) is widely recognized as the most accurate, non-invasive imaging technique for evaluating liver fibrosis. However, MRE requires dedicated hardware, including an external vibration device, which limits its availability. Virtual MRE (VMRE) has recently emerged as a promising alternative technique in which tissue stiffness is estimated using diffusion-weighted imaging data without the need for external mechanical vibrations. VMRE is based on the hypothesis that tissue elasticity and water diffusivity share common mechanical features at the microstructural level. By calculating the shift in the apparent diffusion coefficient from the optimized b-values (200 and 1,500 s/mm²), the virtual stiffness can be derived and calibrated against the MRE-derived stiffness. Studies in cohorts with chronic viral hepatitis have demonstrated strong correlations between VMRE and MRE findings, with both techniques showing good agreement in liver fibrosis staging. Although the utility of VMRE in patients with metabolic dysfunction-associated steatotic liver disease (MASLD) was previously considered debatable because of the confounding effects of steatosis, recent evidence suggests that VMRE performed using an optimized fat-correction method combined with MASLD-specific b-values (200 and 1,200 s/mm²) can achieve diagnostic performance comparable to that of MRE. Beyond liver fibrosis assessment, the combination of VMRE and MRE has shown potential for distinguishing hepatocellular carcinoma from metastatic liver cancers. This article provides a comprehensive overview of VMRE, including its technical basis and current clinical applications in chronic liver diseases and focal liver lesions.