title: Bound pool fractions complement diffusion measures to describe white matter micro and macrostructure.
abstract: Diffusion imaging and bound pool fraction (BPF) mapping are two quantitative magnetic resonance imaging techniques that measure microstructural features of the white matter of the brain. Diffusion imaging provides a quantitative measure of the diffusivity of water in tissue. BPF mapping is a quantitative magnetization transfer (qMT) technique that estimates the proportion of exchanging protons bound to macromolecules, such as those found in myelin, and is thus a more direct measure of myelin content than diffusion. In this work, we combined BPF estimates of macromolecular content with measurements of diffusivity within human white matter tracts. Within the white matter, the correlation between BPFs and diffusivity measures such as fractional anisotropy and radial diffusivity was modest, suggesting that diffusion tensor imaging and bound pool fractions are complementary techniques. We found that several major tracts have high BPF, suggesting a higher density of myelin in these tracts. We interpret these results in the context of a quantitative tissue model.
authors.affiliation: Electrical Engineering, Stanford University, Stanford, CA, USA. nikola@mrsrl.stanford.edu
authors.forename: Nikola
authors.initials: N
authors.lastname: Stikov
authors.forename: Lee M
authors.initials: LM
authors.lastname: Perry
authors.forename: Aviv
authors.initials: A
authors.lastname: Mezer
authors.forename: Elena
authors.initials: E
authors.lastname: Rykhlevskaia
authors.forename: Brian A
authors.initials: BA
authors.lastname: Wandell
authors.forename: John M
authors.initials: JM
authors.lastname: Pauly
authors.forename: Robert F
authors.initials: RF
authors.lastname: Dougherty
mesh_terms: D016880:Anisotropy; D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism; D001931:Brain Mapping / Q000379:methods*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D009413:Nerve Fibers, Myelinated / Q000378:metabolism / Q000648:ultrastructure; D009434:Neural Pathways / Q000033:anatomy & histology* / Q000378:metabolism