DETECTING OSTEOPOROSIS FROM DENTAL RADIOGRAPHS USING ACTIVE SHAPE MODELS P. D. Allen 1 , J. Graham 1 , D. J. J. Farnell 1 , E. J. Marjanovic 1 , J. Adams 1 , R. Jacobs 2 K. Karayianni 3 , C. Lindh 4 , P. F. van der Stelt 5 , K. Horner 6 , H. Devlin 6 . 1 ISBE, University of Manchester, UK. 2 Oral Imaging Centre, Katholieke Universiteit Leuven, Belgium. 3 Dental School, University of Athens, Greece. 4 Faculty of Odontology, Malm¨ o University, Sweden. 5 Academic Centre for Dentistry, Amsterdam, The Netherlands. 6 School of Dentistry, University of Manchester, UK. ABSTRACT We describe a novel method of estimating reduced bone min- eral density (BMD) from dental panoramic tomograms (DPTs) which show the entire mandible. Careful expert width mea- surement of the inferior mandibular cortex has been shown to be predictive of BMD in hip and spine osteopenia and osteo- porosis. We have implemented a method of automatic mea- surement of the width by active shape model search, using as training data 132 DPTs of female subjects and tested on a test data set of 606 DPTs of female subjects whose BMD has been established by dual-energy X-ray absorptiometry. We demonstrate that the sensitivity of the automatic method to osteoporosis is equivalent to that of expert manual measure- ment. Index Terms— Osteoporosis, Dental Radiographs, Bone Mineral Density, Active Shape Model, Image Segmentation. 1. INTRODUCTION Osteoporosis is a general loss of bone mineral density and can lead to an increased risk of fracture. Based on factors such as previous fracture, family history, and height loss, pa- tients deemed to be at risk are referred for bone mineral den- sity (BMD) assessment using dual-energy X-ray absorptiom- etry (DXA). However, there has recently been great inter- est among dental researchers in the possibility of identifying those at risk of reduced BMD from dental radiographs since mandibular BMD is related to systemic BMD [1]. Figure 1 shows an example of a dental panoramic tomo- gram (DPT) of a normal patient and figure 2 shows a schematic close up of the right mandible. The cortical region in this di- agram is referred to as the inferior mandibular cortex (IMC), and there is evidence from careful manual measurements by experts that the thickness of this cortex is correlated with sys- temic BMD and hence osteoporosis [2]. In particular, the This work was supported by a research and technological development project grant from the European Commission Fifth Framework Programme ‘Quality of Life and Management of Living Resources’ (QLK6-2002-02243). Mental Foramen Ante−Gonion Gonion Fig. 1. An example of a panoramic dental tomogram of a normal (non-osteoporotic) patient. The positions of anatom- ical points key to manual annotation are shown. The mental foramen is a hole in the mandible through which the men- tal nerve passes, and which is faintly discernible on the DPT. The Gonion and Ante-Gonion are recognisable points where the curvature of the mandible changes. Fig. 2. Schematic diagram of the right mandible, showing the point at which the inferior mandibular cortex thickness is measured by dentists (Mental Index MI). 1256 1424406722/07/$20.00 ©2007 IEEE ISBI 2007