Median Filtering Methods in Diffusion Tensor Magnetic Resonance Imaging

DT-MRI(Diffusion Tenosr – Magnetic Resonance Imaging) tractography is a non-invasive method of tracing neuronal fiber bundles. DT-MRI measures anisotropy per pixel and provides the directional information of eigenvectors relevant for fiber tractography. Since eigenvectors in each voxel computed from DT-MRI usually contain noise, the calculated principal eigenvector direction may be different from the real direction in the voxel. As the propagation becomes longer, even very small differences in the voxels can make the whole computed fiber direction deviate far away from the real fiber direction [1]. Since in vivo field maps are usually corrupted by noise, the tractography problem turns out to be a mathematically “ill-posed” problem because the tracking results are very sensitive to perturbations by noise. The mathematical attempt to stabilize the solution is known as regularization [2].