About this Research Topic
The white matter region of the human brain is composed of neuronal axon bundles that transmit long range signals between the brain regions. As such, techniques that enable us to map and track fiber bundles will provide glimpses into the complexity of connections within the brain. Such information may be useful for identifying the neuropathology of mental illnesses and gaining insight into how the brain regions interact with each other.
The application of diffusion weighted magnetic resonance imaging (DW-MRI) for brain imaging relies upon the property that water molecules move faster along neural axons than against them. By measuring water diffusion in the brain, the location and trajectories of axons can be visualized and the axonal pathways can be reconstructed using DW-MRI. In addition, as more than two thirds of the human brain white matter are thought to contain multiple axonal bundles crossing each other, it is critical to have a technique that not only allows us to visualize the three-dimensional architecture of neural fiber pathways in the human brain, but at the same time, to reveal more than one dominant axonal orientation at each location.
High angular resolution diffusion imaging (HARDI) is a recently-developed advanced DW-MRI technique that precisely allows us to achieve the aforementioned aims. HARDI measures water diffusion along a large number of different directions on the sphere and has the ability to characterize more complex neural fiber geometries as compared to the classical method of diffusion tensor imaging. It has been shown that accurate fiber estimates can be obtained from HARDI data by quantitatively comparing fiber orientations retrieved from HARDI against histological measurements, therefore further validating its use in brain imaging studies. However, due to the rich information HARDI provides on the diffusion profile, it is often a challenge to process, analyze and understand such data in a rigorous manner.
The aim of this multidisciplinary research topic is to bring together the recent methodological advancements made in the development of fundamental mathematical tools for handling HARDI data and new data-driven biological discoveries brought about by such novel modeling and analysis methods, that are otherwise unattainable in vivo. A strong preference will be given to techniques that are used in population or longitudinal studies of the human brain, where such methods provide new insights into the description and prediction of the diffusion behavior in the different white matter regions of the human brain. In addition, new quantitative techniques assisting clinicians and neuroscientists to pathologically analyze neural pathways are welcomed. Finally, studies verifying the white matter integrity characterized by HARDI imaging with that found in histology are also highly encouraged. In order to encourage researchers to make use of the techniques/algorithms proposed in this Research Topic as well as to simplify the task of comparing future methods to the aforementioned, authors are highly encouraged to make available sample codes/programs.
We welcome both scientists and clinicians to contribute a variety of articles, including original research, methods, hypothesis and theory, and long and short reviews.
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