title: Towards quantitative connectivity analysis: reducing tractography biases.
abstract: Diffusion MRI tractography is often used to estimate structural connections between brain areas and there is a fast-growing interest in quantifying these connections based on their position, shape, size and length. However, a portion of the connections reconstructed with tractography is biased by their position, shape, size and length. Thus, connections reconstructed are not equally distributed in all white matter bundles. Quantitative measures of connectivity based on the streamline distribution in the brain such as streamline count (density), average length and spatial extent (volume) are biased by erroneous streamlines produced by tractography algorithms. In this paper, solutions are proposed to reduce biases in the streamline distribution. First, we propose to optimize tractography parameters in terms of connectivity. Then, we propose to relax the tractography stopping criterion with a novel probabilistic stopping criterion and a particle filtering method, both based on tissue partial volume estimation maps calculated from a T1-weighted image. We show that optimizing tractography parameters, stopping and seeding strategies can reduce the biases in position, shape, size and length of the streamline distribution. These tractography biases are quantitatively reported using in-vivo and synthetic data. This is a critical step towards producing tractography results for quantitative structural connectivity analysis.
authors.affiliation: Sherbrooke Connectivity Imaging Lab (SCIL), Computer Science Department, Faculty of Science, Université de Sherbrooke, 2500 Boulevard Université, Sherbrooke, QC, Canada J1K 2R1; Project Team Athena, INRIA Sophia Antipolis Méditerranée, 2004 Route des Lucioles BP 93, 06902 Sophia Antipolis Cedex, France. Electronic address: gabriel.p.girard@usherbrooke.ca.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Girard
authors.affiliation: Department of Diagnostic Radiology, Faculty of Medicine and Health Science, Université de Sherbrooke, 12e Avenue Nord, Sherbrooke, QC, Canada J1H 5N4; Sherbrooke Molecular Imaging Center, Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Science, Université de Sherbrooke, 12e Avenue Nord, Sherbrooke, QC, Canada J1H 5N4.
authors.forename: Kevin
authors.initials: K
authors.lastname: Whittingstall
authors.affiliation: Project Team Athena, INRIA Sophia Antipolis Méditerranée, 2004 Route des Lucioles BP 93, 06902 Sophia Antipolis Cedex, France.
authors.forename: Rachid
authors.initials: R
authors.lastname: Deriche
authors.affiliation: Sherbrooke Connectivity Imaging Lab (SCIL), Computer Science Department, Faculty of Science, Université de Sherbrooke, 2500 Boulevard Université, Sherbrooke, QC, Canada J1K 2R1; Sherbrooke Molecular Imaging Center, Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Science, Université de Sherbrooke, 12e Avenue Nord, Sherbrooke, QC, Canada J1H 5N4.
authors.forename: Maxime
authors.initials: M
authors.lastname: Descoteaux
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D001931:Brain Mapping / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D066128:Gray Matter / Q000033:anatomy & histology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D066127:White Matter / Q000033:anatomy & histology*
keywords: anatomical MRI; connectivity analysis; diffusion MRI; particle filtering; white matter tractography