Model-based 3D segmentation of the bones of the ankle and subtalar joints in MR images

摘要

Our ongoing project on the kinematic analysis of the joints of the foot and ankle via magnetic resonance (MR) imaging requires segmentation of bones in images acquired at different positions of the joint. This segmentation requires an extensive amount of operator time, especially for the current study involving 300 scenes and 4 bones to be segmented in each scene. A 3D model-based segmentation approach is developed wherein the model is generated from the segmentation of a specific bone from one scene and is used for segmenting the same bone in all other scenes. This method works in two sequential steps. In the first step, the patient- and bone-specific model is generated by segmenting the target bone from one scene using the live wire method. In the second step, the segmentation of the same bone for the same patient in a scene corresponding to another ankle position is obtained by finding an optimum rigid body transformation to minimize its fitting energy. The fitting energy utilized captures both boundary- and region-based information in a unified manner. This method has produced satisfactory results for the 30 pairs of images used for evaluation. The model-based segmentation method will significantly reduce the operator time required by our ongoing study.