Probabilistic white matter and fiber tract atlas construction

In this paper we describe a framework for creating a probabilistic white matter atlas from diffusion MR images. The approach is based on sampling from the posterior distributions of the parameters of the local model of diffusion and transforming them to a common coordinate space using non-rigid registration. These transformed distributions are then combined to form population distributions of the local fibre direction at each voxel from which a large number of samples are drawn to create an atlas. Next a fibre tract atlas is created by performing probabilistic tractography, between 83 anatomical regions of interest, where the resulting tracts represent the most likely trajectory of pathways for the population. The atlas is created for an entire population 171 subjects ranging from 20–90 years. Statistical comparison of FA in the atlas co-ordinate space allows comparison of diffusion properties across the population without bias from differences in the anatomy. We perform permutation testing of FA within tracts propagated from the temporal lobe and demonstrate significant differences between male and female populations.