Automatic measurement of vertebral shape using active shape models

The authors describe how active shape models (ASMs) have been used to accurately and robustly locate vertebrae in lateral dual energy X-ray absorptiometry (DXA) images of the spine. DXA images are of low spatial resolution, and contain significant random and structural noise, providing a difficult challenge for object location methods. All vertebrae in the image were searched for simultaneously, improving robustness in location of individual vertebrae by making use of constraints on shape provided by the position of other vertebrae. They show that the use of ASMs with minimal user interaction allows accuracy to be obtained which is as good as that achievable by human operators using a standard manual method.