Metabolic dysfunction–associated steatotic liver disease (MASLD) is a global health concern due to its rising prevalence and potential to progress into severe liver conditions such as fibrosis, cirrhosis and hepatocellular carcinoma. Traditional methods like liver biopsy can overlook regional differences in disease manifestation, making the need for noninvasive, organ-wide assessment tools more urgent. Magnetic resonance elastography (MRE) has emerged as a powerful diagnostic technique, particularly in evaluating liver stiffness and other viscoelastic properties. A recent study published in Radiology explored the role of three-dimensional (3D) vector MRE in measuring liver tissue mechanical heterogeneity, highlighting its potential as a biomarker for disease progression and therapeutic response in MASLD.
Mechanical Heterogeneity and Disease Progression
The study demonstrated that liver tissue affected by MASLD exhibits increasing mechanical heterogeneity as the disease advances. In a preclinical model using rats, animals subjected to a choline-deficient high-fat diet developed progressive stages of liver disease, from steatosis to cirrhosis. MRE-derived measurements showed that both the mean and coefficient of variation (CV) of shear stiffness and loss modulus increased significantly throughout this progression. Importantly, CV remained stable in control animals but escalated in diseased rats, reinforcing the notion that tissue mechanical heterogeneity correlates with pathologic severity.
Pixel-wise histogram analysis revealed that spatial variations in liver stiffness and viscosity closely followed changes in portal pressure and histologically measured fibrosis. In particular, CV values for loss modulus had stronger correlations with fibrosis area variation and portal pressure than mean values alone. This finding supports the use of heterogeneity metrics for assessing the complex, regionally variable nature of fibrotic tissue and inflammatory processes, providing insight that single-point measures may miss.
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Clinical Validation and Repeatability
Extending these findings to human subjects, the clinical component of the study evaluated 179 participants using 3D vector MRE. Among them were 10 healthy volunteers and 169 individuals diagnosed with MASLD who underwent paired MRE and liver biopsy examinations. The results confirmed the preclinical observations: both mean shear stiffness and CV of stiffness increased with advancing fibrosis stage. Similarly, the CV of loss modulus rose alongside histologic grades of liver inflammation.
Importantly, the study established the technical repeatability of CV measurements in healthy participants. Although variability was somewhat higher for CV than for mean values, intraclass correlation coefficients showed moderate agreement for repeated measures of tissue heterogeneity. This indicates that MRE-derived heterogeneity metrics are reliable for clinical use, offering consistent insights into tissue mechanics when applied with standardised imaging protocols.
Furthermore, the ROI volumes assessed using 3D MRE in patients were significantly larger than those covered by alternative methods such as shear-wave elastography and liver biopsy. This allowed for a more comprehensive evaluation of the liver and enabled detection of spatial variation across different regions. These larger volumetric assessments are crucial for capturing heterogeneous disease patterns that may be missed by techniques limited to small sampling areas.
Therapeutic Response Assessment
The utility of MRE-derived heterogeneity metrics was further validated in a subgroup of 36 patients who underwent bariatric surgery and completed one-year follow-up evaluations. While there were no significant changes in mean liver stiffness and loss modulus at follow-up, the CV of shear stiffness showed a notable decrease. This suggests that heterogeneity metrics may be more sensitive indicators of tissue-level therapeutic response than mean measurements alone.
These findings are particularly relevant given that MASLD is often a heterogeneous disease, with fibrotic and inflammatory changes distributed unevenly across the liver. The ability of CV to capture improvements in mechanical uniformity following treatment indicates its value in monitoring therapeutic effects, even in cases where average stiffness values remain largely unchanged.
Moreover, the observation that loss modulus and its spatial variation may reflect interstitial fluid volume and microvascular changes associated with portal hypertension provides a potential link between mechanical imaging markers and the pathophysiological mechanisms driving disease progression. This insight opens avenues for using tissue heterogeneity not only as a diagnostic tool but also for risk stratification and long-term outcome prediction in MASLD.
The assessment of liver tissue mechanical heterogeneity using 3D vector MRE offers a valuable addition to the current repertoire of diagnostic tools for MASLD. By capturing spatial variations in shear stiffness and loss modulus, this technique provides a more nuanced understanding of disease progression and treatment response. The findings from both preclinical and clinical settings support the use of heterogeneity metrics as complementary biomarkers to traditional mean values. As imaging protocols and analysis tools continue to evolve, MRE has the potential to play a pivotal role in personalised liver disease management, offering clinicians a more complete picture of tissue dynamics across the entire organ.
Source: Radiology
Image Credit: iStock
