MRI Diffusion Indices Sampled Along Streamline Trajectories: Quantitative Tractography Mapping

Abstract Several useful tractography-derived maps have recently been introduced, such as track density imaging (TDI) and the average pathlength map (APM). Here, an extension to these techniques is introduced by sampling diffusion indices along streamline trajectories (DIST). With this approach, voxels contain summary information of diffusivity measures within streamlines. The diffusion metrics can also be used as weighting factors for streamline number or length, generating DIST-weighted TDI and DIST-weighted APM, respectively. Furthermore, when higher-order models of diffusion are used to estimate the fiber orientation distribution within each voxel, it is possible to obtain directional TDI, APM, DIST, and DIST-weighted TDI and APM. The reproducibility of this approach using two b-values (1000 and 3000 s/mm(2)) and the effect of pathologic abnormalities are demonstrated.