Projects/Structural/2007 Project Week Nonrigid Groupwise Registration

Affine registration on synthetic data

<img src="serdarAffineOrig.jpg" alt="The central slice of the mean of the synthetic data" width="256" height="256">	<img src="serdarAffineRegister.jpg" alt="The central slice of the mean of the affine registered data" width="256" height="256">
<img src="serdarAffineOrig.jpg" alt="The central slice of the mean of the synthetic data" width="256" height="256">	<img src="serdarAffineRegister.jpg" alt="The central slice of the mean of the affine registered data" width="256" height="256">
Left: The central slice of the mean of the synthetic data is shown on left. The images were created by 30 random affine transformations. Right: The central slice of the mean of the registered images.

Key Investigators

• MIT: Serdar K Balci, Polina Golland, Lilla Zollei, Sandy Wells
• Kitware: Luis Ibanez

Objective

We extended a previously demonstrated entropy based groupwise registration method to include a free-form deformation model based on B-splines.

The objective in groupwise registration is to bring subjects in a population into joint alignment in order to establish correspondences among anatomical structures.

Approach, Plan

We implemented a non-rigid groupwise registration method using sum of pixelwise entropies as a joint alignment criterion. We have chosen B-splines as our non-rigid deformation model and optimized ITK's B-Spline implementation by computing jacobian field locally. We extended ITK's pairwise registration framework to include groupwise registration methods. We provide an efficient implementation of the objective function using multi-threaded classes. To compare our registration framework to a pairwise approach we implemented a template based method where we register every subject to the mean image using sum of squared differences.

Our plan is to incorporate our implementation into ITK and to provide test cases for validation.

Progress

We implemented the project in ITK and submitted the code to ITK's Namic SANDBOX repositories.