Abstract
Traditional single-grid and pyramidal B-spline parameterizations used in deformable image registration require
users to specify control point spacing configurations capable of accurately capturing both global and complex local
deformations. In many cases, such grid configurations are
non-obvious and largely selected based on user experience.
Recent regularization methods imposing sparsity upon the
B-spline coefficients throughout simultaneous multi-grid
optimization, however, have provided a promising means
of determining suitable configurations automatically. Unfortunately, imposing sparsity on over-parameterized Bspline models is computationally expensive and introduces
additional difficulties such as undesirable local minima in
the B-spline coefficient optimization process. To overcome
these difficulties in determining B-spline grid configurations, this paper investigates the use of convolutional neural networks (CNNs) to learn and infer expressive sparse
multi-grid configurations prior to B-spline coefficient optimization. Experimental results show that multi-grid con-
figurations produced in this fashion using our CNN based
approach provide registration quality comparable to L1-
norm constrained over-parameterizations in terms of exactness, while exhibiting significantly reduced computational
requirements