title: Improved Framework for Tractography Reconstruction of the Optic Radiation.
abstract: The optic radiation (OR) is one of the major components of the visual system and a key structure at risk in white matter diseases such as multiple sclerosis (MS). However, it is challenging to perform track reconstruction of the OR using diffusion MRI due to a sharp change of direction in the Meyer's loop and the presence of kissing and crossing fibers along the pathway. As such, we aimed to provide a highly precise and reproducible framework for tracking the OR from thalamic and visual cortex masks. The framework combined the generation of probabilistic streamlines by high order fiber orientation distributions estimated with constrained spherical deconvolution and an automatic post-processing based on anatomical exclusion criteria (AEC) to compensate for the presence of anatomically implausible streamlines. Specifically, those ending in the contralateral hemisphere, cerebrospinal fluid or grey matter outside the visual cortex were automatically excluded. We applied the framework to two distinct high angular resolution diffusion-weighted imaging (HARDI) acquisition protocols on one cohort, comprised of ten healthy volunteers and five MS patients. The OR was successfully delineated in both HARDI acquisitions in the healthy volunteers and MS patients. Quantitative evaluation of the OR position was done by comparing the results with histological reference data. Compared with histological mask, the OR reconstruction into a template (OR-TCT) was highly precise (percentage of voxels within the OR-TCT correctly defined as OR), ranging from 0.71 to 0.83. The sensitivity (percentage of voxels in histological reference mask correctly defined as OR in OR-TCT) ranged from 0.65 to 0.81 and the accuracy (measured by F1 score) was 0.73 to 0.77 in healthy volunteers. When AEC was not applied the precision and accuracy decreased. The absolute agreement between both HARDI datasets measured by the intraclass correlation coefficient was 0.73. This improved framework allowed us to reconstruct the OR with high reliability and accuracy independently of the acquisition parameters. Moreover, the reconstruction was possible even in the presence of tissue damage due to MS. This framework could also be applied to other tracts with complex configuration.
authors.affiliation: Center of Neuroimmunology, Service of Neurology, Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.
authors.forename: Eloy
authors.initials: E
authors.lastname: Martínez-Heras
authors.affiliation: Laboratory of Surgical NeuroAnatomy (LSNA). Facultat de Medicina. Universitat de Barcelona, Barcelona, Spain.
authors.forename: Federico
authors.initials: F
authors.lastname: Varriano
authors.affiliation: Center of Neuroimmunology, Service of Neurology, Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.
authors.forename: Vesna
authors.initials: V
authors.lastname: Prčkovska
authors.affiliation: Comprehensive Stroke Center, Department of Neuroscience. Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Laredo
authors.affiliation: Center of Neuroimmunology, Service of Neurology, Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.
authors.forename: Magí
authors.initials: M
authors.lastname: Andorrà
authors.affiliation: Center of Neuroimmunology, Service of Neurology, Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.
authors.forename: Elena H
authors.initials: EH
authors.lastname: Martínez-Lapiscina
authors.affiliation: Medical Imaging Platform, Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Calvo
authors.affiliation: Center of Neuroimmunology, Service of Neurology, Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.
authors.forename: Erika
authors.initials: E
authors.lastname: Lampert
authors.affiliation: Center of Neuroimmunology, Service of Neurology, Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Villoslada
authors.affiliation: Center of Neuroimmunology, Service of Neurology, Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.
authors.forename: Albert
authors.initials: A
authors.lastname: Saiz
authors.affiliation: Laboratory of Surgical NeuroAnatomy (LSNA). Facultat de Medicina. Universitat de Barcelona, Barcelona, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Prats-Galino
authors.affiliation: Center of Neuroimmunology, Service of Neurology, Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Llufriu
mesh_terms: D000328:Adult; D001369:Axons / Q000473:pathology*; D016022:Case-Control Studies; D038524:Diffusion Magnetic Resonance Imaging; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D009103:Multiple Sclerosis / Q000175:diagnosis / Q000473:pathology; D014793:Visual Cortex / Q000473:pathology*