A robust comparison approach of velocity data between MRI and CFD based on divergence-free space projection

Recent achievements in 4D flow MRI increased the interest of CFD-MRI studies, which require comparison of velocity fields from both approaches for validation purposes. A novel flow regularization approach is proposed to provide a ground truth and to perform robust, mathematically reasonable comparisons between CFD and MRI. Our suggested method projects the measured and denoised data into the same space as the computational domain and applies the Helmholtz-Hodge theorem to recover the divergence-free property of the flow field by decomposing the velocity field into its divergence-free, curl-free and harmonic components. Furthermore, an aortic phantom study has been set-up under fully controlled laminar flow conditions with helical flow patterns to validate the proposed method using phase-contrast MRI measurements, whereas a dynamic stenosed case was used under turbulent flow conditions to analyse the robustness of applied pre-processings including the denoising of MRI data and the decomposition of velocity vector field.