title: Neurite density from magnetic resonance diffusion measurements at ultrahigh field: comparison with light microscopy and electron microscopy.
abstract: Due to its unique sensitivity to tissue microstructure, diffusion-weighted magnetic resonance imaging (MRI) has found many applications in clinical and fundamental science. With few exceptions, a more precise correspondence between physiological or biophysical properties and the obtained diffusion parameters remain uncertain due to lack of specificity. In this work, we address this problem by comparing diffusion parameters of a recently introduced model for water diffusion in brain matter to light microscopy and quantitative electron microscopy. Specifically, we compare diffusion model predictions of neurite density in rats to optical myelin staining intensity and stereological estimation of neurite volume fraction using electron microscopy. We find that the diffusion model describes data better and that its parameters show stronger correlation with optical and electron microscopy, and thus reflect myelinated neurite density better than the more frequently used diffusion tensor imaging (DTI) and cumulant expansion methods. Furthermore, the estimated neurite orientations capture dendritic architecture more faithfully than DTI diffusion ellipsoids.
authors.affiliation: Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Nørrebrogade 44, Arhus C, Denmark. sune@pet.auh.dk
authors.forename: Sune N
authors.initials: SN
authors.lastname: Jespersen
authors.forename: Carsten R
authors.initials: CR
authors.lastname: Bjarkam
authors.forename: Jens R
authors.initials: JR
authors.lastname: Nyengaard
authors.forename: M Mallar
authors.initials: MM
authors.lastname: Chakravarty
authors.forename: Brian
authors.initials: B
authors.lastname: Hansen
authors.forename: Thomas
authors.initials: T
authors.lastname: Vosegaard
authors.forename: Leif
authors.initials: L
authors.lastname: Østergaard
authors.forename: Dmitriy
authors.initials: D
authors.lastname: Yablonskiy
authors.forename: Niels Chr
authors.initials: NC
authors.lastname: Nielsen
authors.forename: Peter
authors.initials: P
authors.lastname: Vestergaard-Poulsen
mesh_terms: D000465:Algorithms; D000818:Animals; D001921:Brain / Q000166:cytology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004574:Electromagnetic Fields; D005110:Extracellular Space / Q000502:physiology; D006624:Hippocampus / Q000166:cytology; D008297:Male; D008854:Microscopy, Electron; D015233:Models, Statistical; D009412:Nerve Fibers / Q000648:ultrastructure; D016501:Neurites / Q000502:physiology*; D010296:Parietal Lobe / Q000166:cytology; D051381:Rats; D017208:Rats, Wistar