RT Journal Article
SR Electronic
T1 Prevalence of white matter pathways coming into a single diffusion MRI voxel orientation: the bottleneck issue in tractography
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.06.22.449454
DO 10.1101/2021.06.22.449454
A1 Kurt G Schilling
A1 Chantal M.W. Tax
A1 Francois Rheault
A1 Bennett Landman
A1 Adam Anderson
A1 Maxime Descoteaux
A1 Laurent Petit
YR 2021
UL http://biorxiv.org/content/early/2021/06/22/2021.06.22.449454.abstract
AB Characterizing and understanding the limitations of diffusion MRI fiber tractography is a prerequisite for methodological advances and innovations which will allow these techniques to accurately map the connections of the human brain. The so-called “crossing fiber problem” has received tremendous attention and has continuously triggered the community to develop novel approaches for disentangling distinctly oriented fiber populations. Perhaps an even greater challenge occurs when multiple white matter bundles converge within a single voxel, or throughout a single brain region, and share the same parallel orientation, before diverging and continuing towards their final cortical or sub-cortical terminations. These so-called “bottleneck” regions contribute to the ill-posed nature of the tractography process, and lead to both false positive and false negative estimated connections. Yet, as opposed to the extent of crossing fibers, a thorough characterization of bottleneck regions has not been performed. The aim of this study is to quantify the prevalence of bottleneck regions. To do this, we use diffusion tractography to segment known white matter bundles of the brain, and assign each bundle to voxels they pass through and to specific orientations within those voxels (i.e. fixels). We demonstrate that bottlenecks occur in greater than 50-70% of fixels in the white matter of the human brain. We find that all projection, association, and commissural fibers contribute to, and are affected by, this phenomenon, and show that even regions traditionally considered “single fiber voxels” often contain multiple fiber populations. Together, this study shows that a majority of white matter presents bottlenecks for tractography which may lead to incorrect or erroneous estimates of brain connectivity or quantitative tractography (i.e., tractometry), and underscores the need for a paradigm shift in the process of tractography and bundle segmentation for studying the fiber pathways of the human brain.Competing Interest StatementThe authors have declared no competing interest.