Three-Dimensional Vector MR Elastography for Evaluating Tissue Mechanical Heterogeneity to Assess Liver Disease Progression

Background Metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing global health challenge, with evidence indicating that hepatic inflammation and fibrosis are heterogeneous processes. Purpose To measure liver mechanical property heterogeneity using MR elastography (MRE) and evaluate its potential as a biomarker for tissue inflammation and fibrosis in patients with MASLD. Materials and Methods Mechanical tissue heterogeneity in MASLD was assessed at three-dimensional vector MRE pixel-wise histogram analysis of shear stiffness and loss modulus in preclinical and clinical studies. The preclinical study involved 25 rats that were examined monthly, whereas the clinical study analyzed data from 179 participants across two prospective studies (September 2015 to November 2022), including some who underwent bariatric surgery at pretreatment and posttreatment MRE examinations. Mean and coefficient of variation (CV) of shear stiffness and loss modulus were calculated for each examination. Nonparametric tests and Spearman correlation coefficient were used to compare MRE-derived tissue mechanics with biopsy-confirmed fibrosis and inflammation and assess correlations with portal pressure and histopathologic hepatic fibrosis. Results The preclinical study showed that, in cirrhotic livers, CV of loss modulus positively correlated with portal pressure and fibrosis area ratio variation (ρ = 0.52 [<i>P</i> = .008] and 0.55 [<i>P</i> = .005], respectively). The clinical study showed that, in 10 healthy volunteers (median age, 36.5 years; IQR, 34.0-38.8 years; five females) and 169 participants with MASLD (median age, 50.1 years; IQR, 41.0-58.2 years; 118 females), CV of sheer stiffness (from 0.12 to 0.30 in healthy participants to participants with stage 4 fibrosis) and loss modulus (from 0.31 to 0.51 in healthy participants to participants with grade 3 inflammation) increased with increasing severity of fibrosis and inflammation, respectively. In 36 participants who underwent bariatric surgery, the CV of sheer stiffness decreased at the 1-year follow-up, from 0.16 (IQR, 0.14-0.18) to 0.14 (IQR, 0.12-0.16) (<i>P</i> = .009). Conclusion Tissue mechanical heterogeneity assessed at MRE positively correlated with progression of MASLD, demonstrating potential as a biomarker for liver disease severity and therapeutic intervention. ClinicalTrials.gov Identifier: NCT02565446 Published under a CC BY 4.0 license. <i>Supplemental material is available for this article.</i> See also the editorial by Moura Cunha in this issue.