This study evaluated the repeatability, reproducibility, and robustness of Magnetic Resonance Elastography (MRE) in the context of algebraic inversion. The researchers implemented the same excitation system at two different sites equipped with clinical MR scanners of 1.5 T and 3 T. They used a set of four elastic, isotropic, homogeneous calibrated phantoms to represent different levels of liver fibrosis severity. The results showed excellent repeatability and reproducibility between the two platforms, with mean coefficients of variations of 1.62% for shear velocity mean values and 1.95% for associated standard deviations. The MRE velocities were found to be robust against amplitude and pattern variations in the displacement field, with no significant differences observed between outcomes from both magnets at identical excitation frequencies, even when the displacement field amplitude was six times smaller. However, the study also revealed that MRE outcomes were highly sensitive to the number of voxels per wavelength (s) in the recorded displacement field. Relative biases reached up to 62%, and precision decreased by a factor of up to 23.5 when s deviated from established conditions of validity (6 ≤ s ≤ 9). This resulted in estimated shear velocity values that were not significantly different between phantoms representing increasing levels of liver fibrosis severity. Nevertheless, when spatial sampling conditions were fulfilled either prospectively during acquisition or retrospectively before reconstruction, MRE produced quantitative measurements that allowed for unambiguous discrimination between phantoms mimicking different levels of liver fibrosis severity. These measurements had infinitesimal p-values, indicating their high statistical significance. In summary, this study demonstrated that MRE is repeatable, reproducible, and robust when using the same excitation system on clinical MR scanners at different magnetic field strengths. However, it highlighted the importance of adhering to specific spatial sampling conditions to ensure accurate and precise MRE measurements for liver fibrosis assessment.
A study was done to see how well Magnetic Resonance Elastography (MRE) works in measuring liver fibrosis. MRE was tested at two different places using special machines. They used fake livers with different levels of fibrosis to do the tests. The results were very similar between the two places. MRE measurements are not affected by changes in the movement patterns. However, it is important to have a certain number of small parts called voxels for accurate results. If there are too few or too many voxels, the measurements can be wrong."
Definitions
- Magnetic Resonance Elastography (MRE): A method that uses special machines to measure how stiff or soft something is.
- Repeatability: How consistent and similar the results are when doing something multiple times.
- Reproducibility: How well something can be done again by someone else and get similar results.
- Robustness: How well something can work even if there are changes or variations.
- Fibrosis: When an organ has scar tissue that makes it less healthy and function properly.
Understanding the Repeatability, Reproducibility, and Robustness of Magnetic Resonance Elastography (MRE)
Magnetic Resonance Elastography (MRE) is a medical imaging technique used to assess the stiffness of tissue in order to diagnose various diseases. It has been increasingly used for liver fibrosis assessment due to its non-invasive nature and ability to provide quantitative measurements. However, there are still questions about its repeatability, reproducibility, and robustness when using different clinical MR scanners with varying magnetic field strengths.
Study Overview
To address these issues, researchers conducted a study evaluating the repeatability, reproducibility, and robustness of MRE in the context of algebraic inversion. The same excitation system was implemented at two sites equipped with clinical MR scanners of 1.5 T and 3 T respectively. A set of four elastic isotropic homogeneous calibrated phantoms were used to represent different levels of liver fibrosis severity.
Results
The results showed excellent repeatability and reproducibility between the two platforms with mean coefficients of variations being 1.62% for shear velocity mean values and 1.95% for associated standard deviations respectively. The MRE velocities were found to be robust against amplitude and pattern variations in the displacement field as no significant differences were observed between outcomes from both magnets at identical excitation frequencies even when displacement field amplitude was six times smaller than usual conditions.
However, it was also revealed that MRE outcomes were highly sensitive to number of voxels per wavelength (s) in recorded displacement field as relative biases reached up to 62%, precision decreased by factor up 23.5 when s deviated from established conditions (6 ≤ s ≤ 9). This resulted in estimated shear velocity values which were not significantly different between phantoms representing increasing levels of liver fibrosis severity but when spatial sampling conditions were fulfilled either prospectively during acquisition or retrospectively before reconstruction then MRE produced quantitative measurements that allowed unambiguous discrimination between phantoms mimicking different levels liver fibrosis severity having infinitesimal p-values indicating their high statistical significance .
Conclusion
In conclusion this study demonstrated that MRE is repeatable , reproducible ,and robust when using same excitation system on clinical MR scanners at different magnetic field strengths but highlighted importance adhering specific spatial sampling conditions ensure accurate & precise MRE measurements for liver fibrosis assessment .
In the framework of algebraic inversion, Magnetic Resonance Elastography (MRE) repeatability, reproducibility and robustness were evaluated on extracted shear velocities (or elastic moduli). The same excitation system was implemented at two sites equipped with clinical MR scanners of 1.5 T and 3 T. A set of four elastic, isotropic, homogeneous calibrated phantoms of distinct elasticity representing the spectrum of liver fibrosis severity was mechanically characterized. The repeatability of the measurements and the reproducibility between the two platforms were found to be excellent with mean coefficients of variations of 1.62% for the shear velocity mean values and 1.95% for the associated standard deviations. MRE velocities were robust to the amplitude and pattern variations of the displacement field with virtually no difference between outcomes from both magnets at identical excitation frequencies even when the displacement field amplitude was 6 times smaller. However, MRE outcomes were very sensitive to the number of voxels per wavelength, s, of the recorded displacement field, with relative biases reaching 62% and precision losing up to a factor 23.5. For both magnetic field strengths, MRE accuracy and precision were largely degraded outside of established conditions of validity ($6 \lesssim s \lesssim 9$) resulting in estimated shear velocity values not significantly different between phantoms of increasing elasticity. When fulfilling the spatial sampling conditions, either prospectively in the acquisition or retrospectively before the reconstruction, MRE produced quantitative measurements that allowed to unambiguously discriminate, with infinitesimal p-values, between the phantoms mimicking increasing severity of liver fibrosis.
