INPRES, a system for Augmented Reality has been developed in the collaborative research center "Information Technology in Medicine - Computer- and Sensor-Aided Surgery". The system is based on see-through glasses. In extensive preclinical testing the system has proven its functionality and tests with volunteers had been performed successfully, based on MRI imaging. We report the surgeons view of the first use of the system for AR guided biopsy of a tumour near the skull base. Preoperative planning was performed based on CT image data. The information to be projected was the tumour volume and was segmented from image data. With the use of infrared cameras, the positions of patient and surgeon were tracked intraoperatively and the information on the glasses displays was updated accordingly. The systems proved its functionality under OR conditions in patient care: Augmented reality information could be visualized with sufficient accuracy for the surgical task. After intraoperative calibration by the surgeon, the biopsy was acquired successfully. The advantage of see through glasses is their flexibility. A virtual stereoscopic image can be set up wherever and whenever desired. A biopsy at a delicate location could be performed without the need for wide exposure. This means additional safety and lower operation related morbidity to the patient. The integration of the calibration-procedure of the glasses into the intraoperative workflow is of importance to the surgeon.
This paper is going to present a summary of our technical experience with the INPRES System -- an augmented reality system based upon a tracked see-through head-mounted display. With INPRES a complete augmented reality solution has been developed that has crucial advantages when compared with previous navigation systems. Using these techniques the surgeon does not need to turn his head from the patient to the computer monitor and vice versa. The system's purpose is to display virtual objects, e.g. cutting trajectories, tumours and risk-areas from computer-based surgical planning systems directly in the surgical site. The INPRES system was evaluated in several patient experiments in craniofacial surgery at the Department of Oral and Maxillofacial Surgery/University of Heidelberg. We will discuss the technical advantages as well as the limitations of INPRES and present two strategies as a result. On the one hand we will improve the existing and successful INPRES system with new hardware and a new calibration method to compensate for the stated disadvantage. On the other hand we will focus on miniaturized augmented reality systems and present a new concept based on fibre optics. This new system should be easily adaptable at surgical instruments and capable of projecting small structures. It consists of a source of light, a miniature TFT display, a fibre optic cable and a tool grip. Compared to established projection systems it has the capability of projecting into areas that are only accessible by a narrow path. No wide surgical exposure of the region is necessary for the use of augmented reality.
In this paper we present recent developments and pre-clinical validation results of our approach for augmented reality (AR, for short) in craniofacial surgery. A commercial Sony Glasstron display is used for optical see-through overlay of surgical planning and simulation results with a patient inside the operation room (OR). For the tracking of the glasses, of the patient and of various medical instruments an NDI Polaris system is used as standard solution. A complementary inside-out navigation approach has been realized with a panoramic camera. This device is mounted on the head of the surgeon for tracking of fiducials placed on the walls of the OR. Further tasks described include the calibration of the head-mounted display (HMD), the registration of virtual objects with the real world and the detection of occlusions in the object overlay with help of two miniature CCD cameras. The evaluation of our work took place in the laboratory environment and showed promising results. Future work will concentrate on the optimization of the technical features of the prototype and on the development of a system for everyday clinical use.
While many tools for preoperative planning and simulation of surgical interventions are available, the surgical procedure itself still lacks the computer based assistance. In this paper we present an approach for closing this gap using Augmented Reality techniques. The idea is to use a see- through head-mounted display for the superimposition of a patient with virtual dat. This technique enables surgeons to visualize and to re-use preoperatively calculated data directly in the operation field. At the Institute for Process Control and Robotics (IPR) at Universitaet Karlsruhe (TH) an experimental hardware setup for the Intraoperative Presentation of image data causes hard accuracy challenges. Main steps in the technical area are calibration, tracking and registration. We present our solutions for these machine vision related tasks. Afterwards we describe the way data is supplied and prepared for superimposition, and we also describe the presentation process. At the end of the paper clinical evaluation and future work will be discussed.
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