Finite Element Analysis to Compare the Accuracy of the Direct and MDEV Inversion Algorithms in MR Elastography

Magnetic resonance elastography (MRE) utilises an inversion algorithm to create maps of material properties (elastograms) from displacements caused by mechanically in- duced shear waves. This study aimed to assess the accuracy of measurements from multi-dual elasto-visco (MDEV) inversion in comparison to direct inversion (DI) in simplistic geometries. Finite element analysis (FEA) was used to simulate wave propagation in cuboid geometries with embedded cylindrical inserts. Accuracy of both algorithms was dependent upon insert length, diameter and shear modulus. Whilst MDEV reduced artefacts in the elastograms in comparison to DI it was unable to improve accuracy of the measurements. imply that in reality, measurements using DI are also depen- dent upon the geometry of the medium under investigation (14). An extension of DI more recently introduced is the multi-frequency dual elasto-visco (MDEV) inversion (15). Again this utilises the Laplacian but combines information acquired at multiple frequencies to reduce frequency de- pendent artefacts and achieve increased spatial resolution. This approach has been shown to improve image quality (16), however the ability of the technique to accurately resolve material properties in comparison to DI has not been assessed. This paper aims to investigate whether MDEV is able to achieve greater accuracy of material property measurements than DI in a variety of simplistic geometries. To achieve this finite element analysis (FEA), a commonly used technique in the field (17)-(19), has been employed. Since the methods of assessing newly developed software varies across the litera- ture, the 3-D datasets from the models used in this study have been made publicly available with the intention that future developers can utilise these and compare the performance of their software with the other available techniques.