Modified Fast Marching Tractography Algorithm and Its Ability to Detect Fibre Crossing

White matter fibre tractography is a non-invasive method for reconstructing three dimensional trajectories of fibre pathways. Fast Marching is one of fibre tracking methods in which co-linearity of principal eigenvectors determines the speed of front´s evolution. In this algorithm effect of tensor´s eigenvalues are not considered. In the current work, the speed function of standard fast marching was modified by considering the strength of tensor´s eigenvectors. The proposed speed function has an adaptive Fractional Anisotropy (FA) weighted factor which can be set by type of brain´s environments (i.e. isotropic and anisotropic regions). This modification was found to have high accuracy for detecting fibres by reducing false pathways. The proposed method has performed high accuracy in detection of fibre crossing.