Region-based approach for the spectral clustering Nyström approximation with an application to burn depth assessment

Image segmentation methods based on spectral graph theory, although capable of overcoming some of the drawbacks of the so-called "central"-grouping methods, are computationally expensive and quickly become infeasible to solve as the size of the image grows. As a counter measure, the Nystrom approximation allows to extrapolate the complete grouping solution for these methods using only a proportionally smaller set of samples instead of the whole pixels that compose the image. In this correspondence, we further explore the Nystrom approximation by taking the concept of "regions", pixels of the image previously grouped by a central method, to both reduce the computational resources required and provide a finer segmentation of the image by combining the strengths of both methods. We apply the proposed approach to the segmentation of images of burns where we attempt to extract regions that would roughly correspond to the different degrees of the lesion.