Barakovic, MuhamedGirard, GabrielSchiavi, SimonaRomascano, DavidDescoteaux, MaximeGranziera, CristinaJones, Derek K.Innocenti, Giorgio M.Thiran, Jean-PhilippeDaducci, Alessandro2021-08-092021-08-092021-08-092021-06-1510.3389/fnins.2021.646034https://infoscience.epfl.ch/handle/20.500.14299/180490In the central nervous system of primates, several pathways are characterized by different spectra of axon diameters. In vivo methods, based on diffusion-weighted magnetic resonance imaging, can provide axon diameter index estimates non-invasively. However, such methods report voxel-wise estimates, which vary from voxel-to-voxel for the same white matter bundle due to partial volume contributions from other pathways having different microstructure properties. Here, we propose a novel microstructure-informed tractography approach, COMMITAxSize, to resolve axon diameter index estimates at the streamline level, thus making the estimates invariant along trajectories. Compared to previously proposed voxel-wise methods, our formulation allows the estimation of a distinct axon diameter index value for each streamline, directly, furnishing a complementary measure to the existing calculation of the mean value along the bundle. We demonstrate the favourable performance of our approach comparing our estimates with existing histologically-derived measurements performed in the corpus callosum and the posterior limb of the internal capsule. Overall, our method provides a more robust estimation of the axon diameter index of pathways by jointly estimating the microstructure properties of the tissue and the macroscopic organisation of the white matter connectivity.text::journal::journal article::research article