Open AccessTissue microstructure features derived from anomalous diffusion measurements in magnetic resonance imaging
Author(s) -
Yu Qiang,
Reutens David,
O'Brien Kieran,
Vegh Viktor
Publication year - 2017
Publication title -
human brain mapping
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.005
H-Index - 191
eISSN - 1097-0193
pISSN - 1065-9471
DOI - 10.1002/hbm.23441
Subject(s) - white matter , corpus callosum , axon , diffusion mri , magnetic resonance imaging , voxel , tractography , nuclear magnetic resonance , radius , microscale chemistry , neuroscience , physics , biology , psychology , medicine , radiology , mathematics education , computer security , computer science
Objectives : Tissue microstructure features, namely axon radius and volume fraction, provide important information on the function of white matter pathways. These parameters vary on the scale much smaller than imaging voxels (microscale) yet influence the magnetic resonance imaging diffusion signal at the image voxel scale (macroscale) in an anomalous manner. Researchers have already mapped anomalous diffusion parameters from magnetic resonance imaging data, but macroscopic variations have not been related to microscale influences. With the aid of a tissue model, we aimed to connect anomalous diffusion parameters to axon radius and volume fraction using diffusion‐weighted magnetic resonance imaging measurements. Experimental design : An ex vivo human brain experiment was performed to directly validate axon radius and volume fraction measurements in the human brain. These findings were validated using electron microscopy. Additionally, we performed an in vivo study on nine healthy participants to map axon radius and volume fraction along different regions of the corpus callosum projecting into various cortical areas identified using tractography. Principal observations : We found a clear relationship between anomalous diffusion parameters and axon radius and volume fraction. We were also able to map accurately the trend in axon radius along the corpus callosum, and in vivo findings resembled the low‐high‐low‐high behaviour in axon radius demonstrated previously. Conclusions : Axon radius and volume fraction measurements can potentially be used in brain connectivity studies and to understand the implications of white matter structure in brain diseases and disorders. Hum Brain Mapp 38:1068–1081, 2017 . © 2016 Wiley Periodicals, Inc.