Level Set Segmentation with Shape Priors

1. Level Set Segmentation with Shape Priors Jue Wang and Jiun-Hung Chen CSE/EE 577 Spring 2004

2. Notes on Level Set • Steps for implementation • Define your own energy functional • Initialize the curve and surface • Evolve according to the numerical solution: • Continue until stopping criteria is reached

3. Notes on Level Set • So the key is • Defining a good energy function according to your application • For basic image segmentation, the energy functional is usually defined as:

4. Notes on Level Set • Numerical Implementation • Not easy to figure out but they’re in books, for example • Numerical stability should be also considered when you design your own energy function

5. Segmentation with Shape Prior Reference shape Level set seg. w/o shape prior Level set seg. w/ shape prior Input image D. Cremers and S. Soatto. A pseudo-distance for shape priors in level set segmentation. IEEE Workshop on Variational, Geometric and Leve Set Methods in Computer Vision, 2003.

6. Segmentation with Shape Prior • Basic Idea • Shape prior can be represented as another implicit function • The evolution of current is influenced by the distance between and . • Problem: how to define the distance

7. Segmentation with Shape Prior • A Pseudo-distance • Shape energy: • Evolution function:

8. Segmentation with Shape Prior • Pose parameters • Numerical solution help needed for this 

9. Results • An image’s worth of thousands of words • An EXE is worth more

10. Future Work • How to incorporate statistical shape models? • Have a bunch of reference shapes instead of one • X.M. et al. Integrating prior shape models into level-set approaches. Pattern Recognition Letters, April 2004.