Tractography of White Matter Fibers in Presence of Astrocytoma

Abstract

Diffusion Magnetic Resonance Imaging (dMRI), a technique that maps the axonal mi- crostructure of the brain, is often used nowadays to investigate white matter alterations. Clinicians have gained useful insights from these studies for surgical planning and demon- strating subtle abnormalities in a variety of diseases. Our work aims to identify the effects of astrocytoma, a type of tumor that affects the brain, on white matter (WM) tracts. For this purpose, three patients with different grades of astrocytomas, acquired by the UK Data Archive, are used. Constrained Spherical De- convolution (CSD)-based deterministic tractography is applied on these datasets in order to assess the tumor-induced alterations on WM tracts. Three types of these alterations were observed: displacement of fibers around the tumor, destruction of the intralesional fibers, and destruction with displacement of the fibers within the tumoral region. A comparison is also performed between the results obtained using different reconstruction methods: Diffu- sion Tensor Imaging (DTI) and CSD. Although both methods confirm the existence of the tumor and its associated alterations, CSD-based tractography is most appropriate to use when dealing with tasks sensitive to intravoxel fiber connections such as the planning of a surgical procedure. Finally, a comparison between the left and right hemispheres reveals that the number of streamlines can be used to predict the existence of a tumor. The results were validated by a group of doctors and researchers in the field. The main contributions of this work reside in determining a pattern to the effects of astrocytomas on WM tracts. While monitoring the field, we found that, among the re- searches investigating brain pathologies, none were particularly focused on this type of tumor. In addition, the use of CSD-based deterministic tractography while investigating brain pathologies is new in the literature, where most published articles use DTI as the only local reconstruction technique. Another contribution of this work is the comparison between the left and right hemispheres of both normal and brain tumor patients.