Clinically-feasible white matter fiber tractography in peritumoral zones with cerebral vasogenic edema

In diffusion MRI, vasogenic edema manifests as a major fraction of isotropic water that dilutes the anisotropic intra-axonal portion of the signal. Many tractography algorithms mistake vasogenic edema for the white matter boundary and terminate tracking to prevent producing spurious streamlines. As a result, visual representations of fascicles traversing edema are often compromised, limiting the clinical utility of tractography in neurosurgery. We address this hurdle with ODF-Fingerprinting (ODF-FP) -- a dictionary-based fiber reconstruction algorithm that accommodates variability of neural tissue. By adding a regularization term to the ODF-FP matching formula, we counterbalance the drop of diffusion anisotropy in edematous regions to improve white matter fiber identification. We test our approach in 19 glioma cases with significant peritumoral vasogenic edema. For each case, we quantify the volume of the reconstructed white matter tracts immersed in edema, then we use the cortical regions activated during task-based functional MRI as validation for tractography. To assess the potential for clinical translation, we additionally test the performance of our reconstruction method on subsampled single-shell diffusion-weighted images, which contemporary clinical scanners can acquire within a few minutes.