Bone segmentation using multiple communicating snakes

Skeletal age assessment is a frequently performed procedure which requires high expertise and a considerable amount of time. Several methods are being developed to assist radiologists in this task by automating the various steps of the process. In this work we describe a method to perform the segmentation step, by means of a modified active contour approach. A set of separate active contours models each bone in a portion of the radiogram. Due to the complexity of the contour, and to the presence of multiple adjacent contours, we add to the commonly used energy terms a first-order derivative energy which allow to take into account the direction of the contour. Moreover, anatomical relationships among bones are modeled as additional internal elastic forces which couple together the contours. Contour energy is optimized using a genetic algorithm. Chromosomes are used to encode positions of snake points, using a polar representation. The genetic optimization overcomes the difficulties related to local minima and to the initialization criterium, and conveniently allows the addition of new energy terms. Experimental results show the method allows to achieve an accurate segmentation of the bone complexes in the region of interest