Kamri Clarke

Purpose: 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. Methods: 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. In 19 glioma cases with significant peritumoral vasogenic edema, 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 ODF‐FP on subsampled single‐shell diffusion‐weighted images, which contemporary clinical scanners can acquire within a few minutes. Results: Our approach produces high volumes of streamlines traversing vasogenic edema and reaches high overlap with the cortical regions activated at task‐based fMRI, significantly outperforming common fiber reconstruction methods in the clinically feasible data set. Conclusion: ODF‐FP proves effective on research and clinical quality dMRI, which offers an opportunity for application in neurosurgery.

In diffusion MRI, vasogenic edema manifests as a major fraction of isotropic water that dilutes the anisotropic intraaxonal 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.

Peritumoral vasogenic edema of the brain is a major confounding factor for diffusion MRI tractography. Excessive fluids accumulated in edematous white matter decrease anisotropy of water self-diffusion which affects tracking algorithms. 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 boost diffusion anisotropy to improve white matter fiber identification in edematous regions.

Purpose: The accuracy of diffusion MRI tractography reconstruction decreases in the white matter regions with crossing fibers. The optic pathways in rodents provide a challenging structure to test new diffusion tractography approaches because of the small crossing volume within the optic chiasm and the unbalanced 9:1 proportion between the contra‐ and ipsilateral neural projections from the retina to the lateral geniculate nucleus, respectively.Methods: Common approaches based on Orientation Distribution Function (ODF) peak finding or statistical inference were compared qualitatively and quantitatively to ODF Fingerprinting (ODF‐FP) for reconstruction of crossing fibers within the optic chiasm using in vivo diffusion MRI ( healthy C57BL/6 mice). Manganese‐Enhanced MRI (MEMRI) was obtained after intravitreal injection of manganese chloride and used as a reference standard for the optic pathway anatomy.Results: ODF‐FP outperformed by over 100% all the tested methods in terms of the ratios between the contra‐ and ipsilateral segments of the reconstructed optic pathways as well as the spatial overlap between tractography and MEMRI.Conclusion: In this challenging model system, ODF‐Fingerprinting reduced uncertainty of diffusion tractography for complex structural formations of fiber bundles.