Abstract: There is described herein an image segmentation technique using an iterative process. A contour, which begins with a single point that expands into a hollow shape, is iteratively deformed into a defined structure. As the contour is deformed, various constraints are applied to points along the contour to dictate its rate of change and direction of change are modified dynamically. The constraints may be modified after one or more iterations, at each point along the contour, in accordance with newly measured or determined data.