Extraction of the vertebral foramen of the third lumbar vertebra with snakes

This paper describes a new method for extracting the vertebral foramen of the third lumbar vertebra which is used to assess bone structure non-invasively with X-ray CT images. Because the bone structure and bone mineral density give us important information for diagnosing osteoporosis or fracture, we have to extract this contour accurately. For extraction of the contour we propose a new method with a snake algorithm. In this method we used a distance function calculated with an edge image for a potential function. This method was tested with 57 images including those of patients with osteoporosis. The contour extraction was accomplished successfully. Then we evaluated three features calculated with X-ray CT images and examined them in normal volunteers and patients with osteoporosis.