From Local Q-Ball Estimation to Fibre Crossing Tractography

Abstract

Fibre crossing is an important problem for most existing diffusion tensor imaging (DTI) based tractography algorithms. To overcome limitations of DTI, high angular resolution diffusion imaging (HARDI) techniques such as q-ball imaging (QBI) have been introduced. The purpose of this chapter is to first give state of the art review of the existing local HARDI reconstruction techniques as well as the existing HARDI-based tractography algorithms. Then, we describe our analytical QBI solution to reconstruct the diffusion orientation distribution function (ODF) of water molecules and we propose a spherical deconvolution method to transform the diffusion ODF into a sharper fibre ODF. Finally, we propose a new deterministic and a new probabilistic algorithm based on this fibre ODF. We show that the diffusion ODF and fibre ODF can recover fibre crossing in simulated data, in a biological phantom and in real datasets. The fibre ODF improves angular resolution of QBI by more than 15∘ and greatly improves tractography results in regions of complex fibre crossing, fanning and branching.