In this work, a novel method for determining the principal directions (maxima) of the diffusion orientation distribution function (ODF) is proposed. We represent the ODF as a symmetric high-order Cartesian tensor restricted to the unit sphere and show that the extrema of the ODF are solutions to a system of polynomial equations whose coefficients are polynomial functions of the tensor elements....

Due the well-known limitations of diffusion tensor imaging (DTI), high angular resolution diffusion imaging is currently of great interest to characterize voxels containing multiple fiber crossings. In particular, Q-ball imaging (QBI) is now a popular reconstruction method to obtain the orientation distribution function (ODF) of these multiple fiber distributions. The latter captures all import...

Compared with Diffusion Tensor Imaging (DTI), High Angular Resolution Imaging (HARDI) can better explore the complex microstructure of white matter. Orientation Distribution Function (ODF) is used to describe the probability of the fiber direction. Fisher information metric has been constructed for probability density family in Information Geometry theory and it has been successfully applied fo...

High Angular Resolution Diffusion Imaging (HARDI) demands a higher amount of data measurements compared to Diffusion Tensor Imaging (DTI), restricting its use in practice. We propose to represent the probabilistic Orientation Distribution Function (ODF) in the frame of Spherical Wavelets (SW), where it is highly sparse. From a reduced subset of measurements (nearly four times less than the stan...

Introduction: Q-ball imaging (Tuch 2004) is a high angular resolution diffusion MR imaging technique proven successful in resolving multiple intravoxel fiber orientations. Standard computations of the orientation distribution function (ODF, the probability of diffusion in a given direction) from q-ball use radial projections and do not consider the solid angle, resulting in distributions differ...

Hydroxyapatite (HA) whisker reinforced polyetheretherketone (PEEK) composites have been investigated as bioactive materials for load-bearing orthopedic implants with tailored mechanical properties governed by the volume fraction, morphology, and preferred orientation of the HA whisker reinforcements. Therefore, the objective of this study was to establish key structure-property relationships an...

It's well known that in diffusion MRI (dMRI), fibre crossing is an important problem for most existing diffusion tensor imaging (DTI) based tractography algorithms. To overcome these limitations, High Angular Resolution Diffusion Imaging (HARDI) based tractography has been proposed with a particular emphasis on the the Orientation Distribution Function (ODF). In this paper, we advocate the use ...

Recent advances in diffusion MRI have allowed for improved understanding of the white matter connectivity. Models like the Diffusion Tensor, diffusion Orientation Distribution Function (ODF) with a monoexponential signal decay have shown good fiber reconstruction accuracies. More complex radial signal decay models, like the bi-exponential model, have been shown to better approximate the in-vivo...

In this paper we study the impact of denoising the raw high angular resolution diffusion imaging (HARDI) data with the Non-Local Means filter adapted to Rician noise (NLMr). We first show that NLMr filtering improves robustness of apparent diffusion coefficient (ADC) and orientation distribution function (ODF) reconstructions from synthetic HARDI datasets. Our results suggest that the NLMr filt...

INTRODUCTION: To remove noise artifacts and enhance SNR, diffusion-weighted (DW) measurements are often repeated multiple times (NEX) along each gradient direction (typically, from 2 to 4 measurements) and each DW image is averaged. This averaging increases acquisition time considerably. It is also not clear what effects it has on the reconstructed diffusion profiles such as the orientation dis...