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December 2022 (1)

Liver stiffness measurement by magnetic resonance elastography is not affected by hepatic steatosis

Journal Watch by Michaela Plaikner

Liver stiffness measurement by magnetic resonance elastography is not affected by hepatic steatosis.

Jie Chen, Alina M. Allen, Terry M. Therneau, Jun Chen, Jiahui Li, Safa Hoodeshenas, Jingbiao Chen, Xin Lu, Zheng Zhu, Sudhakar K. Venkatesh, Bin Song, Richard L. Ehman, Meng Yin

European Radiology (2022) 32:950–958

Magnetic resonance elastography (MRE) is an excellent tool for the non-invasive detection of liver fibrosis. [1] It quantitatively evaluates liver stiffness (LS) and is increasingly demanded in clinical routine. This diagnostic technique can be performed using additionally hard- and software representing an objective, reliable and reproducible method without significant variability across vendors and magnetic field strengths. [2]

Continuous acoustic waves generated by an active driver induce a tissue stimulation; with a phase contrast sequence the propagating waves are visualized and then automatically converted into quantitative sectional images so-called elastograms. [3] Typical and recommended parameters of either GRE or SE-EPI MRE performed sequences are listed in the regularly updated QIBA profile. [4] Usually four axial slices are taken through the liver in different positions. The image evaluation takes place on the 95% confidence maps, considering the wave and magnitude images. In the liver, partially automatically, an as large as possible or several subcapsular regions of interest (ROIs) are drawn. [5] Finally, the MRE result (specification in kPa, SI unit for pressure/mechanical stress) is an indication of the fibrosis score, from F0 (no fibrosis) to F4 (cirrhosis). [6] The interpretation of MRE results should always consider the clinical context, as MRE assessment of liver fibrosis may be affected by other pathologic changes as inflammation, passive congestion, biliary obstruction, or diffuse infiltrative disorders which may also increase liver stiffness values. [1; 7]

In diffuse liver disease, steatosis is an important entity, representing the most common form of diffuse liver disease. With a worldwide prevalence of 25-45% nonalcoholic fatty liver disease (NAFLD) has become a medical burden. [8] Patients with NAFLD can progress to liver fibrosis or even cirrhosis. It is of great clinical relevance among all NAFLD patients, to non-invasively differentiate those with non-alcoholic steatohepatitis (NASH) and advanced fibrosis, as these have the greatest risk of developing liver-related increased morbidity and mortality.

The authors of the present retrospective study aimed to evaluate the relationship between pathology-assessed hepatic steatosis, MR-measured proton density fat-fraction (PDFF), and MRE-gaged liver stiffness in a large patient cohort with biopsy-proven or high risk of NAFLD.  The study focuses on the impact of hepatic steatosis/liver fat on liver stiffness measurement (LSM).

256 patients with liver biopsy and MRI/MRE examination carried out within one year were included. The MRI protocol was performed on a 1.5T device and consisted of a 2-point or 6-point Dixon to estimate the PDFF and of a 2D MRE to measure the LS. NAFLD was defined by imaging or histology.

The PDFF correlated significantly with steatosis grades. An excellent correlation (r = 0.97, p < 0.001) was found in 87 patients. Age, fibrosis stage and biopsy-based steatosis were significant covariates influencing the LS. Patients without histopathologic steatosis showed significant lower LS as patients with steatosis but no significant difference of LS was found between the different degrees of steatosis severity. Finally, no statistically significant relationship between LS and PDFF could be confirmed.

The results indicate that the severity of hepatic steatosis in patients with NAFLD, as assessed quantitatively with MRI-PDFF methods, does not have a significant effect on MRE-assessed LS. Steatosis is therefore not a relevant variable in the setting of MRE measurements. This observation is consistent with other publications in which no or only little effect of the severity of hepatic steatosis on MRE was found. [9]

The authors further hypothesize that the apparent correlation between LS and hepatic steatosis, that is reported in literature [10], could be linked to other histopathologic processes as inflammation.

This study shows that the severity of hepatic steatosis has no significant effect on MRE-based LSM. It should be considered that adjustment for fibrosis stage and other independent factors is important. The conclusion has an impact to our daily clinical routine. MRE is a valuable tool, but possible confounders, e.g. iron, must be addressed. This problem exists in many quantitative investigations regarding diffuse liver diseases and shows that a multi-parametric access should be chosen. Nevertheless, steatosis in MRE does not appear to have a significant impact on the results, which in turn facilitates clinical application.

1. Venkatesh SK, Wells ML, Miller FH et al (2018) Magnetic resonance elastography: beyond liver fibrosis-a case-based pictorial review. Abdom Radiol (NY) 43:1590-1611
2. Ozturk A, Olson MC, Samir AE, Venkatesh SK (2022) Liver fibrosis assessment: MR and US elastography. Abdom Radiol (NY) 47:3037-3050
3. Pepin KM, Welle CL, Guglielmo FF, Dillman JR, Venkatesh SK (2022) Magnetic resonance elastography of the liver: everything you need to know to get started. Abdom Radiol (NY) 47:94-114
4. QIBA, MR, Biomarker, Committee. MR Elastography of the Liver, Quantitative Imaging Biomarkers Alliance. Profile Stage: Technically Confirmed. February 14, 2022. Available via
5. Tang A, Cloutier G, Szeverenyi NM, Sirlin CB (2015) Ultrasound Elastography and MR Elastography for Assessing Liver Fibrosis: Part 1, Principles and Techniques. AJR Am J Roentgenol 205:22-32
6. Brunt EM (2016) Nonalcoholic Fatty Liver Disease: Pros and Cons of Histologic Systems of Evaluation. Int J Mol Sci 17
7. Tang A, Cloutier G, Szeverenyi NM, Sirlin CB (2015) Ultrasound Elastography and MR Elastography for Assessing Liver Fibrosis: Part 2, Diagnostic Performance, Confounders, and Future Directions. AJR Am J Roentgenol 205:33-40
8. Younossi ZM, Koenig AB, Abdelatif D, Fazel Y, Henry L, Wymer M (2016) Global epidemiology of nonalcoholic fatty liver disease-Meta-analytic assessment of prevalence, incidence, and outcomes. Hepatology 64:73-84
9. Leitao HS, Doblas S, Garteiser P et al (2017) Hepatic Fibrosis, Inflammation, and Steatosis: Influence on the MR Viscoelastic and Diffusion Parameters in Patients with Chronic Liver Disease. Radiology 283:98-107
10. Joshi M, Dillman JR, Singh K et al (2018) Quantitative MRI of fatty liver disease in a large pediatric cohort: correlation between liver fat fraction, stiffness, volume, and patient-specific factors. Abdom Radiol (NY) 43:1168-1179

Dr. Michaela Plaikner is radiologist at the Medical University of Innsbruck. She has a wide range of interests in diagnostic and interventional imaging with focus of the abdomen and the musculoskeletal system. She is actively involved in different areas of clinical research, mainly in the field of MR based diagnosis of diffuse liver disease and is first and co-author in several publications. She also completed her PhD thesis with research focused on the evaluation of different MRI sequences analyzing diffuse liver disease.

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