AxTract: Toward microstructure informed tractography

Abstract

Diffusion-weighted (DW) magnetic resonance imaging (MRI) tractography has become the tool of choice to probe the human brain's white matter in vivo. However, tractography algorithms produce a large number of erroneous streamlines (false positives), largely due to complex ambiguous tissue configurations. Moreover, the relationship between the resulting streamlines and the underlying white matter microstructure characteristics remains poorly understood. In this work, we introduce a new approach to simultaneously reconstruct white matter fascicles and characterize the apparent distribution of axon diameters within fascicles. To achieve this, our method, AxTract, takes full advantage of the recent development DW-MRI microstructure acquisition, modelling and reconstruction techniques. This enables AxTract to separate parallel fascicles with different microstructure characteristics, hence reducing ambiguities in areas of complex tissue configuration.We report a decrease in the incidence of erroneous streamlines compared to the conventional deterministic tractography algorithms on simulated data. We also report an average increase in streamline density over 15 known fascicles of the 34 healthy subjects. Our results suggest that microstructure information improves tractography in crossing areas of the white matter. Moreover, AxTract provides additional microstructure information along the fascicle that can be studied alongside other streamline-based indices. Overall, AxTract provides the means to distinguish and follow white matter fascicles using their microstructure characteristics, bringing new insights into the white matter organization. This is a step forward in microstructure informed tractography, paving the way to a new generation of algorithms able to deal with intricate configurations of white matter fibres and providing quantitative brain connectivity analysis.

The architecture of functional lateralisation and its relationship to callosal connectivity in the human brain

“…brainstem) 74 . The advent of new diffusion imaging methods 75 , as well as post-mortem investigations 76 , might circumvent this bias in the future.…”

Brain networks and their relevance for stroke rehabilitation

“…This implies the need for validation of different tractography algorithms based on ground truth datasets. Further models of elevating the accuracy of fibre tractography have been recently introduced to e.g., include microstructural information in the processing and reconstruction of fibres -microstructural informed tractography (Daducci et al, 2015, Girard et al, 2017.…”

Topological principles and developmental algorithms might refine diffusion tractography

“…Such methods have the potential to reduce the false positives problem of tractography but remain exploratory and preliminary. Also, since axon diameters remain constant along tracts (Innocenti et al 2018 ), implementing biologically inspired tractography algorithm using diffusion MRI methods sensitive to axonal diameters (Assaf et al 2008 ; Alexander et al 2010 ; NODDI), will help us produce more accurate brain connectomes (Girard et al 2017 ). The limitations of axonal diameter measurements using diffusion MRI are the source of heated debates beyond the aims of the present paper.…”