Tensor Distribution Function in Multiple Shell High Angular Resolution Diffusion Imaging

Introduction: DTI reveals white matter microstructure and fiber pathways in the living brain by examining the 3D diffusion profile of water molecules in brain tissue. Even so, DTI-derived measures will be incorrect where fibers cross or mix, as the single tensor model cannot resolve these more complicated white matter configurations. This issue can be addressed using the model-free diffusion spectrum imaging (DSI), which exploits the direct Fourier inversion of the diffusion signal. This technique is time intensive, as it measures the signal on a 3D Cartesian lattice [1]. An alternative approach based on sampling only on one or multiple spherical shells in q-space has been proposed, referred to as high angular resolution diffusion imaging[2]. Each spherical shell, being a 2D manifold with a specific b value [3], includes a number of measurement points which grows quadratically with the desired angular resolution, as opposed to cubically with the spatial resolution in the entire 3D lattice of DSI.