Thomas Lee
University of California, Davis

Fiber Direction Estimation in Diffusion MRI

Diffusion magnetic resonance imaging is a medical imaging technology to probe anatomical architectures of biological samples in an in vivo and non-invasive manner through measuring water diffusion. It is widely used to reconstruct white matter fiber tracts in brains. This can be done with the following steps. First, one estimates the diffusion direction(s) for each voxel of the biological sample. As it is reasonable to assume that the diffusion directions from neighboring voxels are similar, a local smoothing may be applied to the estimated tensors or directions to improve the estimation of diffusion directions. Finally, a tracking algorithm is used to reconstruct fiber tracts based on (estimated) diffusion directions.

Most commonly used tensor estimation methods assume a single tensor and do not work well when multiple principal diffusion directions are within a single voxel. The first part of this talk reports our work on identifying and estimating multiple diffusion directions within a voxel. The second part describes a direction smoothing method that greatly improves diffusion direction estimation in regions with crossing fibers. This smoothing method is shown to have excellent theoretical and empirical properties. Lastly, this talk presents a fiber tracking algorithm that takes (estimated) diffusion directions as input and accommodates multiple directions within a voxel.

This is joint work with Seungyong Hwang, Debashis Paul, Jie Peng, and Raymond Wong.

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