A multi-structural Fiber Crossing Anisotropic Diffusion Phantom for HARDI reconstruction techniques validation

Introduction There is significant interest in evaluating the performance and reliability of white matter fiber tractography algorithms. Diffusion tensor imaging (DTI) approach [1] is a powerful tool for non-invasive investigation of microstructure and has been successfully applied to detect different white matter diseases [2]. DTI-based fiber tracking gives insights into the complex architecture of the brain. However, it is well known that it presents a number of limitations, especially in presence of fiber crossing, suggesting the development of new algorithms based on non-parametric reconstruction techniques (HARDI [3-7]). The validation of fiber reconstruction by these different approaches remains challenging and requires suitable test phantoms. For isotropic diffusion, the ADC can be well verified on pure spherical water phantoms, whilst the use of simulated data is limited by the fact that no real MRI data are considered, with particular regard to the presence of normal imaging artifacts, noise characteristics, and voxel size limitations. These aspects have suggested the realization of an experimental model with different fiber crossing configurations (PIVOH, Phantom with Intra-Voxel Orientation Heterogeneity), able to simulate the structural complexity of the white matter, in correspondence of fiber intersection.