Snake head boundary extraction using global and local energy minimisation

Snakes are now a very popular technique for shape extraction by minimising a suitably formulated energy functional. A dual snake configuration using dynamic programming has been developed to locate a global energy minimum. This complements recent approaches to global energy minimisation via simulated annealing and genetic algorithms. These differ from a conventional evolutionary snake approach, where an energy function is minimised according to a local optimisation strategy and may not converge to extract the target shape, in contrast with the guaranteed convergence of a global approach. The new technique employing dynamic programming is deployed to extract the inner face boundary, along with a conventional normal-driven technique to extract the outer face boundary. Application to a database of 75 subjects showed that the outer contour was extracted successfully for 96% of the subjects and the inner contour was successful for 82%. The results demonstrated the benefits that could accrue from inclusion of face features, giving an appropriate avenue for future research.