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Use of DTI Tractography to Define Target Regions for Radiotherapy for Glioblastoma


Glioblastoma (GBM) is a progressive and malignant form of glioma with very poor prognosis. Treatment options for GBM include surgery, chemotherapy, and radiotherapy, with radiotherapy being the focus of this study. GBM is especially hard to treat with radiotherapy due to the fact that the disease often extends microscopically beyond the visible tumor on MRI, leading to high recurrence rates.

The widely accepted method of radiotherapy uses a 2cm isotropic expansion from the MRI indicated tumor region in order to capture the microscopic glial cells that protrude beyond the apparent tumor margin. This method, however, is nonspecific as the radiation volume often radiates grey matter regions that not only have a lower probability of tumor growth, but is also responsible for important cognitive functions associated with motor and sensory neuronal cells.

Studies have shown that GBM grows preferentially along the white matter tracts of the brain, which plays an integral role in our method of predicting tumor growth. Using patient data from 3 individuals with GBM, we utilized a diffusion tensor imaging (DTI) technique, tractography, to predict tumor growth along white matter tracts. DTI is very quantitative in capturing the anisotropic nature of the diffusion of water molecules in white matter tracts, which will allow us to model the tumor growth using tractography.

Ours results were compared against the clinical planned radiation treatment for each of the 3 patients, which showed significantly greater coverage of white matter tracts, areas of high probable tumor recurrence.

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