Novel Single and Multiple Shell Gradient Sampling Schemes for Diffusion MRI Using Spherical Codes

Jian Cheng (1) , Dinggang Shen (2) , Pew-Thian Yap (2) , Peter J. Basser (1)

1 STBB - Section on Tissue Biophysics and Biomimetics [Bethesda]
2 BRIC - Biomedical Research Imaging Center [North Carolina]

Data sampling schemes are for diffusion MR acquisition and reconstruction. Diffusion weighted (DW) data is normally acquired on single or multiple shells in q-space. The samples in different shells are typically distributed uniformly, because they should be invariant to the orientation of structures in tissue, or the laboratory coordinate frame. The Electrostatic Energy Minimization (EEM) method was originally proposed for single shell sampling scheme in dMRI [1], and was recently generalized to the multi-shell case, called generalized EEM (gEEM) [2], which has been successfully used in the Human Connectome Project (HCP). Three algorithms based on the Spherical Code (SC) concept were proposed in [3] to maximize the minimal angle between different samples in single or multiple shells, which demonstrated better angular separation and rotational invariance than the gEEM method. In this abstract, we propose two novel algorithms based on the SC concept, i.e., Iterative Maximum Overlap Construction (IMOC) to generate a sampling scheme from discretized sphere, and a constrained non-linear optimization (CNLO) method to update a given initial scheme on a continuous sphere. Compared with Incremental Spherical Code (ISC) and Mixed Integer Linear Programming (MILP) methods in [3] which were developed for a discretized sphere, IMOC obtains a larger angular separation than ISC and is more efficient than MILP that is known to be NP hard. Compared with the RGD method that relies on taking the gradient of a discontinuous function, the optimization in CNLO is more robust because the cost function and constraints are all continuous. Experiments demonstrated that the proposed two methods both provide larger separation angles and better rotational invariance than the methods in [2].

Mots clés: sampling scheme; diffusion MRI; spherical code

Domaines: Imagerie médicale

Jian Cheng, Dinggang Shen, Pew-Thian Yap, Peter J. Basser. Novel Single and Multiple Shell Gradient Sampling Schemes for Diffusion MRI Using Spherical Codes. 23rd Scientific Meeting and Exhibition of the ISMRM, May 2015, Toronto, Canada. ⟨hal-01154773⟩