title: Validation of q-ball imaging with a diffusion fibre-crossing phantom on a clinical scanner.
abstract: Magnetic resonance (MR) diffusion imaging provides a valuable tool used for inferring structural anisotropy of brain white matter connectivity from diffusion tensor imaging. Recently, several high angular resolution diffusion models were introduced in order to overcome the inadequacy of the tensor model for describing fibre crossing within a single voxel. Among them, q-ball imaging (QBI), inherited from the q-space method, relies on a spherical Radon transform providing a direct relationship between the diffusion-weighted MR signal and the orientation distribution function (ODF). Experimental validation of these methods in a model system is necessary to determine the accuracy of the methods and to optimize them. A diffusion phantom made up of two textile rayon fibre (comparable in diameter to axons) bundles, crossing at 90 degrees , was designed and dedicated to ex vivo q-ball validation on a clinical scanner. Normalized ODFs were calculated inside regions of interest corresponding to monomodal and bimodal configurations of underlying structures. Three-dimensional renderings of ODFs revealed monomodal shapes for voxels containing single-fibre population and bimodal patterns for voxels located within the crossing area. Principal orientations were estimated from ODFs and were compared with a priori structural fibre directions, validating efficiency of QBI for depicting fibre crossing. In the homogeneous regions, QBI detected the fibre angle with an accuracy of 19 degrees and in the fibre-crossing region with an accuracy of 30 degrees .
authors.affiliation: Unité de Neuroradiologie Anatomique et Fonctionnelle, Service Hospitalier Frédéric Joliot, CEA SHFJ UNAF. cpoupon@shfj.cea.fr
authors.forename: Muriel
authors.initials: M
authors.lastname: Perrin
authors.forename: Cyril
authors.initials: C
authors.lastname: Poupon
authors.forename: Bernard
authors.initials: B
authors.lastname: Rieul
authors.forename: Patrick
authors.initials: P
authors.lastname: Leroux
authors.forename: André
authors.initials: A
authors.lastname: Constantinesco
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Mangin
authors.forename: Denis
authors.initials: D
authors.lastname: Lebihan
mesh_terms: D016880:Anisotropy; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D001931:Brain Mapping / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008959:Models, Neurological; D009412:Nerve Fibers / Q000502:physiology*