New augmented reality concepts for craniofacial surgical procedures.
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Biomedical subjects
Publications and source records attributed to Harald Hoppe.
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Augmented Reality (AR) is a promising tool for intraoperative visualization. Two different AR systems, one projector based, one based on see-through glasses were used on patients. The task was the transfer of preoperative planning into the intraoperative reality, or the visualization of space occupying lesions, respectively. The intraoperative application of both systems is discussed from the surgeons point of view.
For visualizing surgical information (operation plans) directly onto the patient a projector-based augmented reality system is used for cranio-maxillofacial surgery. A prototype is introduced which has been evaluated in the first clinical cases. In a new setup with a second video projector it is now possible to give additionally 3D information for localization and orientation (6DoF). With this method the repositioning of a bone segment is intuitive and exact applicable.
Computer- and robot-based systems to support interventions become more and more important in modem surgery. In general these systems provide methods to plan an intervention pre-operatively and to execute it with support from a autonomous robot-system. Due to the principle restriction of a robot to comparatively simple work steps, there are some complex work steps which the surgeon may plan but which he/she has to execute manually. In craniofacial surgery osteotomised bone segments are deformed by hand to a shape given by the planning system. We support the execution of pre-planned deformation by comparison of the actual shape of an object with the target shape. The actual shape is obtained intra-operatively with a surface scanning device, the deviation from the target shape are visualised by projecting colour-coded error values directly on the object to be deformed. The surgeon uses these projections to adjust further deformation steps. The system is therefore able to validate the correct execution of planned deformations, especially of bony structures.
In 2000, the Institute for Process Control and Robotics/Universität Karlsruhe (TH) has developed a prototype system for projector based augmented reality consisting of a state-of-the-art PC, two CCD cameras and a video projector which is used for registration and projection of surgical planning data. Tracking, registration as well as projection require an accurate calibration process for cameras and video projectors. We have developed a new, flexible, plain and easy to implement model, which can both be used for calibration of cameras and video projectors.