Accurate liver stiffness measurement is important for adults with metabolic dysfunction-associated steatotic liver disease, particularly when fibrosis assessment may influence clinical categorisation. Severe obesity can make imaging more difficult by reducing signal quality, increasing artefacts and adding measurement variability. A prospective dual-centre analysis published in Radiology compared two-dimensional and three-dimensional MR elastography in adults with severe obesity who were scheduled for standard-of-care bariatric surgery. The comparison focused on how consistently each method measured liver stiffness when scans were repeated, performed on different days or conducted at different magnetic field strengths. Three-dimensional MR elastography provided more precise liver stiffness measurements than the two-dimensional approach in several comparisons, although it also failed more often.
Comparing 2D and 3D MR Elastography
MR elastography is a non-invasive imaging method used to quantify liver stiffness as a marker of liver fibrosis. Two-dimensional MR elastography captures wave motion in individual sections by using motion encoding in one direction. Three-dimensional MR elastography captures a wider wavefield by applying motion encoding in three directions across a volume. This difference allows the three-dimensional method to generate additional viscoelastic measures, although liver stiffness remained the main comparison.
The protocol included adults with severe obesity and planned bariatric surgery. Participants underwent imaging at a visit before surgery and two visits after surgery. Some also had an additional previsit examination shortly before the first visit. At each relevant visit, imaging was repeated either after repositioning on the same scanner or across different field strengths. These repeated acquisitions allowed comparison of short-term repeatability, between-day reproducibility and reproducibility between 1.5 T and 3 T systems.
Both two-dimensional and three-dimensional examinations used a passive driver placed over the right liver lobe. The two-dimensional method acquired data from four liver section locations. The three-dimensional method acquired more section locations, although analysis was restricted to four central sections to support a direct comparison.
Precision Advantages for 3D MRE
The final cohort included 103 adults with severe obesity, with a mean age of 44 years and most participants being women. Liver stiffness values were generally low in the cohort, with average values of about 2 kPa across both approaches. This narrow range is relevant because small measurement differences can matter when liver stiffness values are close to fibrosis thresholds.
At 3 T, three-dimensional MR elastography produced more consistent liver stiffness values when scans were repeated after repositioning. Its repeatability coefficient was lower than that of two-dimensional MR elastography, indicating less variation between repeated measurements. The three-dimensional method also produced a higher intraclass correlation coefficient, supporting stronger agreement between repeated measurements.
Reproducibility across scanner field strengths also favoured the three-dimensional approach. When measurements at 1.5 T and 3 T were compared, three-dimensional MR elastography showed a lower reproducibility coefficient than the two-dimensional method. Between-day reproducibility at 3 T also favoured three-dimensional imaging. At 1.5 T, however, the two methods did not differ clearly across precision measures.
The two approaches did not produce identical liver stiffness values. Two-dimensional MR elastography measured liver stiffness slightly higher than three-dimensional MR elastography at both field strengths. This systematic difference means the two methods should not be treated as interchangeable for longitudinal follow-up.
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Technical Failures and Practical Limits
The precision advantage of three-dimensional MR elastography came with a practical trade-off. Across all attempted examinations, the three-dimensional method failed more often than the two-dimensional method. The overall failure rate was 4.9% for three-dimensional MR elastography and 2.9% for two-dimensional MR elastography. The difference was most apparent at 3 T.
Several technical factors may contribute to the higher failure rate of the three-dimensional method. The technique requires multiple breath-holds, thinner sections and greater sensitivity to motion. Reconstruction challenges may also play a role. Severe obesity can add further imaging difficulties through reduced signal-to-noise ratio and reduced wave transmission through the abdominal wall.
Three-dimensional MR elastography also requires more and longer breath-holds than the two-dimensional method. This may limit routine use in patients who cannot tolerate repeated breath-holding. Free-breathing three-dimensional sequences are under development and could reduce this barrier, but the current comparison reflects the methods used during the study period.
The three-dimensional method generated additional measures beyond liver stiffness. Storage modulus showed precision similar to liver stiffness, while loss modulus and damping ratio showed more variation and weaker robustness. These additional measures may need further technical development and standardisation before being used as reliable endpoints.
Three-dimensional MR elastography measured liver stiffness with higher precision than two-dimensional MR elastography in adults with severe obesity, including stronger repeatability at 3 T and better reproducibility across field strengths. The method also performed better for between-day reproducibility at 3 T, but not at 1.5 T. Its higher failure rate and greater breath-hold burden remain important limitations. Two-dimensional MR elastography therefore remains a practical option when three-dimensional imaging is unavailable, unsuitable or difficult to complete.
Source: Radiology
Image Credit: iStock
References:
Müller L, Ceriani L, Harris DT et al. (2026) Comparative Precision of 3D MRE and 2D MRE for Measurement of Liver Stiffness in Adults with Severe Obesity. Radiology; 319(2):e253243.
