The use of active shape models for locating structures in medical images

Abstract

This paper describes a technique for building compact models of the shape and appearance of flexible objects (such as organs) seen in 2-D images. The models are derived from the statistics of sets of labelled images of examples of the objects. Each model consists of a flexible shape template, describing how important points of the object can vary, and a statistical model of the expected grey levels in regions around each model point. The shape models are parameterised in such a way as to allow 'legal' configurations. Such models have proved useful in a wide variety of applications. We describe how the models can be used in local image search and give examples of their application to medical images. We also describe how the method can be simply extended to segment 3-D objects in volume images and to track structures in image sequences.