In diffusion MRI, simultaneous multi-slice single-shot EPI acquisitions have the potential to increase the number of diffusion directions obtained per unit time, allowing more diffusion encoding in high angular resolution diffusion imaging (HARDI) acquisitions. Nonetheless, unaliasing simultaneously acquired, closely spaced slices with parallel imaging methods can be difficult, leading to high ...

Due to the well-known limitations of diffusion tensor imaging (DTI), high angular resolution diffusion imaging (HARDI) is used to characterize non-Gaussian diffusion processes. One approach to analyze HARDI data is to model the apparent diffusion coefficient (ADC) with higher order diffusion tensors (HODT). The diffusivity function is positive semi-definite. In the literature, some methods have...

Introduction The structure of the optic chiasm varies widely between the primate and the rodent [1]. The fiber architecture of the marmoset (Callithrix jacchus), a New World primate, is close to that of humans [2]; therefore, the marmoset has been used to study the development of the optic chiasm. Further, the body weight of the marmoset (around 300 g) is similar to that of the rat, but its bra...

Two canonical representations for regularization of unit sphere functions encountered in the context of high angular resolution diffusion imaging (HARDI) are discussed. One of these is based on spherical harmonic decomposition, and its one-parameter extension via Tikhonov regularization. This case is well-established, and is mainly reviewed for the sake of completeness. The second one is new, a...

Diffusion weighted imaging (DWI) is widely used to study microstructural characteristics of the brain. Diffusion tensor imaging (DTI) and high-angular resolution imaging (HARDI) are frequently used in radiology and neuroscience research but can be limited in describing the signal behavior in composite nerve fiber structures. Here, we developed and assessed the benefit of a comprehensive diffusi...

INTRODUCTION: The quest of diffusion-weighted (DW) imaging is to non-invasively obtain information about the average diffusion of water molecules in biological tissue. Many recent high angular resolution diffusion imaging (HARDI) [1, and references therein] techniques are proposed to infer the diffusion or fiber orientation distribution function (ODF), but this ODF only captures the angular str...

Since the advent of high angular resolution diffusion imaging (HARDI) techniques in diffusion MRI great efforts have been taken in order to reconstruct complex white-matter structures, such as crossing, branching and kissing fibers. However, even highly sophisticated fiber tracking schemes, such as probabilistic tracking, suffer from the data’s poor signal-to-noise (SNR) ratio. In this paper we...

Current methods in high angular resolution diffusion imaging (HARDI) estimate the probability density function of water diffusion as a continuous-valued orientation distribution function (ODF) on the sphere. However, such methods could produce an ODF with negative values, because they enforce non-negativity only at finitely many directions. In this paper, we propose to enforce non-negativity on...

High Angular Resolution Diffusion Imaging (HARDI) can characterize complex white matter micro-structure, avoiding the Gaussian diffusion assumption inherent in Diffusion Tensor Imaging (DTI). However, HARDI methods normally require significantly more signal measurements and a longer scan time than DTI, which limits its clinical utility. By considering sparsity of the diffusion signal, Compresse...

We introduce a framework for population analysis of white matter tracts based on diffusion-weighted images of the brain. The framework enables extraction of fibers from high angular resolution diffusion images (HARDI); clustering of the fibers based partly on prior knowledge from an atlas; representation of the fiber bundles compactly using a path following points of highest density (maximum de...