Automatic measurement of vertebral shape using active shape models

Abstract

In this paper, we describe how Active Shape Models (ASMs) have been used to accurately and robustly locate vertebrae in noisy lateral Dual Energy X-ray Absorptiometry (DXA) images of the spine. Vertebrae were located using either separate models for each vertebra, or a combined model of the whole spine. The combined model was found to be more robust. We show that ASMs allow normal vertebrae to be located as accurately as by human operators. We measure the performance of ASMs in locating fractured vertebrae of osteoporotic patients. We also describe how model parameters may be used to estimate how accurately a vertebra had been locatated, in order to detect vertebrae for which search had failed.