Generating fiber crossing phantoms out of experimental DWIs

In Diffusion Tensor Imaging (DTI), differently oriented fiber bundles inside one voxel are incorrectly modeled by a single tensor. High Angular Resolution Diffusion Imaging (HARDI) aims at using more complex models, such as a two-tensor model, for estimating two fiber bundles. We propose a new method for creating experimental phantom data of fiber crossings, by mixing the DWI-signals from high FA-regions with different orientation. The properties of these experimental phantoms approach the conditions of real data. These phantoms can thus serve as a 'ground truth' in validating crossing reconstruction algorithms. The angular resolution of a dual tensor model is determined using series of crossings, generated under different angles. An angular resolution of 0.67pi was found in data scanned with a diffusion weighting parameter b = 1000 s/mm2. This resolution did not change significantly in experiments with b = 3000 and 5000 s/mm2, keeping the scanning time constant.