title: SR-HARDI: Spatially Regularizing High Angular Resolution Diffusion Imaging.
abstract: High angular resolution diffusion imaging (HARDI) has recently been of great interest in mapping the orientation of intra-voxel crossing fibers, and such orientation information allows one to infer the connectivity patterns prevalent among different brain regions and possible changes in such connectivity over time for various neurodegenerative and neuropsychiatric diseases. The aim of this paper is to propose a penalized multi-scale adaptive regression model (PMARM) framework to spatially and adaptively infer the orientation distribution function (ODF) of water diffusion in regions with complex fiber configurations. In PMARM, we reformulate the HARDI imaging reconstruction as a weighted regularized least-squares regression (WRLSR) problem. Similarity and distance weights are introduced to account for spatial smoothness of HARDI, while preserving the unknown discontinuities (e.g., edges between white matter and grey matter) of HARDI. TheL1penalty function is introduced to ensure the sparse solutions of ODFs, while a scaledL1weighted estimator is calculated to correct the bias introduced by theL1penalty at each voxel. In PMARM, we integrate the multiscale adaptive regression models (Li et al., 2011), the propagation-separation method (Polzehl and Spokoiny, 2000), and Lasso (least absolute shrinkage and selection operator) (Tibshirani, 1996) to adaptively estimate ODFs across voxels. Experimental results indicate that PMARM can reduce the angle detection errors on fiber crossing area and provide more accurate reconstruction than standard voxel-wise methods.
authors.affiliation: Department of Biostatistics and Biomedical Research Imaging Center University of North Carolina at Chapel Hill Chapel Hill, NC 27599, USA.
authors.forename: Shangbang
authors.initials: S
authors.lastname: Rao
authors.affiliation: Department of Biostatistics and Biomedical Research Imaging Center University of North Carolina at Chapel Hill Chapel Hill, NC 27599, USA.
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Ibrahim
authors.affiliation: Department of Biostatistics and Biomedical Research Imaging Center University of North Carolina at Chapel Hill Chapel Hill, NC 27599, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Cheng
authors.affiliation: Department of Biostatistics and Biomedical Research Imaging Center University of North Carolina at Chapel Hill Chapel Hill, NC 27599, USA.
authors.forename: Pew-Thian
authors.initials: PT
authors.lastname: Yap
authors.affiliation: Department of Biostatistics and Biomedical Research Imaging Center University of North Carolina at Chapel Hill Chapel Hill, NC 27599, USA.
authors.forename: Hongtu
authors.initials: H
authors.lastname: Zhu
keywords: Ensemble Average Propagator; High angular resolution diffusion imaging; Orientation distribution function; Penalized multiscale adaptive regression model; Propagation-separation