Model-Based Approach for Extracting Femur Contours in X-ray Images

Extraction of bone contours from x-ray images is an important first step in computer analysis of medical images. It is more complex than the segmentation of CT and MR images because the regions delineated by bone contours are highly nonuniform in intensity and texture. Classical segmentation algorithms based on homogeneity criteria are not applicable. This thesis presents a model-based approach for either semi-automatically or automatically extracting femur contours from hip x-ray images. The semi-automatic method requires users to manually align the model to the femur in the image while the automatic method works by first detecting prominent features, followed by registration of the model to the x-ray image according to these features. Then the model is refined using active contour algorithm to get the accurate result. Experiments show that the semiautomatic method can always accurately extract the femur contours and the automatic method can extract the contours of the femurs with regular shapes, despite variations in size, shape and orientation.