computer methods and programs in biomedicine 91 ( 2 0 0 8 ) 13–21 journal homepage: www.intl.elsevierhealth.com/journals/cmpb Towards an integrated system for planning and assisting maxillofacial orthognathic surgery Raphael Olszewski a , Marta B. Villamil b,c , Daniela G. Trevisan b,c , Luciana P. Nedel b,c,* , Carla M.D.S. Freitas b , Herv´ e Reychler a , Benoit Macq c a Universit´ e catholique de Louvain, Saint Luc University Clinics, Department of Oral and Maxillofacial Surgery, Brussels, Belgium b Universidade Federal do Rio Grande do Sul, Instituto de Inform´ atica, Porto Alegre, Brazil c Universit´ e catholique de Louvain, Communication and Remote Sensing Laboratory, Louvain-la-Neuve, Belgium article info Article history: Received 3 October 2007 Received in revised form 10 January 2008 Accepted 19 February 2008 Keywords: 3D cephalometry TMJ simulators Virtual planning Mixed reality Maxillofacial surgery abstract Computer-assisted maxillofacial orthognathic surgery is an emerging and interdisciplinary field linking orthognathic surgery, remote signal engineering and three-dimensional (3D) medical imaging. Most of the computational solutions already developed make use of dif- ferent specialized systems which introduce difficulties both in the information transfer from one stage to the others and in the use of such systems by surgeons. Trying to address such issue, in this work we present a common computer-based system that integrates pro- posed modules for planning and assisting the maxillofacial surgery. With that we propose to replace the current standard orthognathic preoperative planning, and to bring information from a virtual planning to the real operative field. The system prototype, including three- dimensional cephalometric analysis, static and dynamic virtual orthognathic planning, and mixed reality transfer of information to the operation room, is described and the first results obtained are presented. © 2008 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Maxillofacial dysmorphoses can be corrected with orthog- nathic surgeries, an important field of maxillofacial surgery, which standard procedure can be subdivided into five steps (see Fig. 1): diagnosis (A); treatment planning (B); model simu- lation of the surgery (C); information transfer to the operating room (D); bone fixation (E). The diagnosis of a dysmorphosis is based on anamnesis, clinical examination, and comple- mentary exams (A). In the classical procedure, the most frequently used complementary examination consists in the cephalometric analysis. This analysis is usually performed on the lateral and sometimes on the frontal radiography of the ∗ Corresponding author at: Universidade Federal do Rio Grande do Sul, Instituto de Inform ´ atica, Caixa Postal 15.064, 91501-970 Porto Alegre, RS, Brazil. Tel.: +55 51 33087037. E-mail addresses: raphael.olszewski@stom.ucl.ac.be (R. Olszewski), mbvillamil@inf.ufrgs.br (M.B. Villamil), nedel@inf.ufrgs.br (L.P. Nedel), carla@inf.ufrgs.br (C.M.D.S. Freitas), reychler@stom.ucl.ac.be (H. Reychler), macq@tele.ucl.ac.be (B. Macq). skull and face. Cephalometric analyses can be divided into two main analytic procedures. The dimensional (quantita- tive) analyses consist in measurements of distances between cephalometric landmarks and comparison of these distances to the normative data. The topological (qualitative) analyses consist in finding proportions inside diverse craniofacial dys- morphoses. The treatment planning (B) is then established depending on the clinical examination, on the expectancy of the patient, and on the results from the cephalometric analy- sis. The planning is simulated on plaster casts of the maxilla and the mandible teeth (C). The surgeon defines the direction and magnitude of the displacement of the bones. The trans- fer of this information from the preoperative planning to the 0169-2607/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.cmpb.2008.02.007