In the Laboratory for Medical Imaging Research (ESAT) at the University of Leuven, Professor Verstreken and his team are designing a system for oral implant surgery planning. The initial input consists of Computer Tomographies (CT) of the jaws, combined with three-dimensional surface rendered models of the bone. These images are integrated in a specific kind of Computer Aided Design (CAD) implant models. The thus obtained views are exported to an HTML format in order to be shown in the operating theatre, with use of netscape as an HTML browser. The final step to be taken includes the interactive guidance during surgery, which is currently being investigated.
The current applied procedure in oral implant surgery consists in mounting a fixed prosthesis on titanium cylinders. These are inserted into pre-drilled holes in the jaw. The patient is guaranteed a far better oral rehabilitation, using this method than with the more traditional removable prosthesis. The long term cumulative success rate indeed amounts to more than 95%. Within the Medical Imaging Research Group at Leuven University, the idea has been launched to develop a planning system for this delicate surgical intervention, offering the surgeon some excellent pre-operative visualisation opportunities in order to position and aim the drill with utmost care.
Last autumn, the researchers have presented their concept at the Fourth International Workshop on Rapid Prototyping in Medicine and Computer-Assisted Surgery, which took place at the University of Erlangen in Germany. There, they showed how the Computer Tomographies of the jaws that are routinely made for clinical evaluation of patients needing oral implant, are taken as a starting point for the computation of two-dimensional reslices. These are shown together with three-dimensional surface rendered models of the bone. To the thus created views, CAD-like implant models can be added, allowing the structure to be inspected from every possible viewpoint and angle.
The majority of the patients concerned, already received a removable prosthesis, which means an enormous help to determine the position of the teeth in the final fixed superstructure. Therefore, the research team has developed a technique to scan and segment this radiolucent prosthesis in order to predict the resulting aesthetics for a certain implant configuration. Both periodontologist and prosthodontist are able to benefit from the enhanced visualisation potential at a very early stage in their operation design.
Next, the detailed views are exported to an HTML format to be displayed in the operating theatre, together with the traditional 2D CT films, by means of netscape as an HTML browser. There is absolutely no extremely expensive hardware needed in this way to preserve a satisfying degree of interactivity. The three-dimensional bone surface, which has been extracted from the CT, corresponds marvellously to what the surgeon actually sees when exposing the bone. The drilling subsequently can be performed up to the highest level of precision.
Still, Dr. Verstreken and his colleagues are searching to provide effective interactive guidance during surgery. For that purpose, several navigation and tracking technologies have been investigated till finally, a conceptual model has been designed, comprising a phantom head with jaw models and a Polhemus magnetic tracker. Soon, this tracker has been replaced by an optical one, offering the necessary robustness and accuracy. At present, the team studies the possibilities for instrument design, patient registration and integration of the interactive guidance in the existing surgical protocol. Read more about their research at the University of Leuven web site of the Laboratory for Medical Imaging Research.