FOD Restoration for Enhanced Mapping of White Matter Lesion Connectivity.

To achieve improved understanding of white matter (WM) lesions and their effect on brain functions, it is important to obtain a comprehensive map of their connectivity. However, changes of the cellular environment in WM lesions attenuate diffusion MRI (dMRI) signals and make the robust estimation of fiber orientation distributions (FODs) difficult. In this work, we integrate techniques from image inpainting and compartment modeling to develop a novel method for enhancing FOD estimation in WM lesions from multi-shell dMRI, which is becoming increasingly popular with the success of the Human Connectome Project (HCP). By using FODs estimated from normal WM as the boundary condition, our method iteratively cycles through two key steps: diffusion-based inpainting and FOD reconstruction with compartment modeling for the successful restoration of FODs in WM lesions. In our experiments, we carry out extensive simulations to quantitatively demonstrate that our method outperforms a state-of-the-art method in angular accuracy and compartment parameter estimation. We also apply our method to multi-shell imaging data from 23 multiple sclerosis (MS) patients and one LifeSpan subject of HCP with WM lesion. We show that our method achieves superior performance in mapping the connectivity of WM lesions with FOD-based tractography.