Computer Assisted Quantitative Analysis of Deformities of the Human Spine B. Verdonck 1, R. Nijlunsing 1, F. A. Gerritsen 1, J. Cheung 2, D. J. Wever2, A. Veldhuizen 2, S. Devillers 3, S. Makram-Ebeid 3 1 Philips Medical Systems Nederland B.V., EO.Box 10.000, NL-5680 DA Best, The Netherlands, Bert.Verdonck@best.ms.philips.com http://www.medical.philips.com 2 Academic Hospital Groningen, P.O. Box 30.001, NL-9700 RB Groningen, The Netherlands 3 Laboratoires d'Electronique Philips S.A.S., P.O. Box 15, F-94453 Limeil-Brevannes cedex, France Abstract. Nowadays, conventional X-ray radiographs are still the images of choice for evaluating spinal deformaties such as scoliosis. However, digital trans- lation reconstruction gives easy access to high quality, digital overview images of the entire spine. This work aims at improving the description of the scoliotic deformity by developing semi-automated tools to assist the extraction of anatom- ical landmarks (on vertebral bodies and pedicles) and the calculation of deformity quantifying parameters. These tools are currently validated in a clinical setting. 1 Introduction The interest in three dimensional (3D) analyses of spinal deformities is increasing over the last decades. This evolution is partially due to the progress of digital imaging tech- nology and automated image processing. The description and quantification of the geometry of scoliosis, a complex 3D deformity of the spine, is essential and will assist the clinician in the accurate and reliable follow up of natural history, brace and operative treatment. Computer Tomography (CT) imaging could give immediate access to 3D informa- tion. However, it does not allow the patient to be in a natural standing posture and it would expose him to higher X-ray dose. Optical and opto-electronic image capture is without any risk for the patient but yields limited accuracy and gives only indirect infor- mation about the deformity of the vertebral column. Large focus, long film X-ray radio- graphs are still the images of choice for evaluating deformities of the entire spine in gen- eral and scoliosis more specifically. We have developed a digital method for creating complete overview images of the human vertebral column [1]. The image is reconstructed from a series of overlapping X-ray images acquired with a dedicated protocol on a conventional image intensifier based digital X-ray system (with constant translation speed and frame acquisition rate). Successive images are matched and merged into one overview image. These overviews have demonstrated improved image quality for equivalent X-ray dose as compared to