Improving White Matter Tractography by Resolving the Challenges of Edema

In this paper, we present a paradigm for alleviating the challenge of fiber tracking through edematous brain regions. This new framework of fiber tracking is applied to the brain tumor datasets 1, 2 and 3 provided as part of the 3 MICCAI DTI Tractography Challenge. Although the data was single shell, b = 1000s/mm, we were able to successfully fit a two-compartment model to the data and extracted measures of free water in edema as well as corrected tensors. We subsequently used these corrected tensors for fiber tracking. Our tracking was initialized using regions of interest manually demarcated by the neurosurgeon, with streamline tracking being the adopted method. As part of the challenge, we tracked the corticospinal tracts of the three subjects in the presence of extensive edema. In addition, other peritumoral tracts in regions of edema were also tracked to evaluate the extent to which our technique was able improve tracking in edematous areas. Results of fiber tracking are presented for these tracts, before and after the correction of tensors and removal of the free water component. The evaluation criteria of the different tracts were based on the qualitative evaluation by the neurosurgeon and the anatomical knowledge of these tracts. Additionally, quantitative criteria, consisting of the change in the principal orientation of the tensors and the fractional anisotropy, both of which affect fiber tracking, were also used to evaluate our paradigm.