Micro surgery needs adequate navigation by using virtual reality technology. This paper proposes method of haptic representation of non-invasive area fo r support system of micro surgery. An operator of our system holds 6 DOF force display and sees volume graphics. In case the virtual treatment tool approaches non-invasive area, force is applied to the operator's hand in order not to invade the area. Generated force is determined by volume data of CT image. Through the evaluation of the basic performance of this method, we applied our algorithm to experiment of navigation in human gullet.

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The spatial perceptions with the naked eye and under the surgical microscope were analyzed in a group of experienced and a group of inexperienced neurosurgeons. The phantom surgical field contained a start point, a virtual gate, and a target point. The virtual gate was an invisible zone arbitrarily set in the phantom. The examinees were first instructed the position of the invisible virtual gate. Then they were asked to point consecutively to the three points with a suction tube with the naked eye, under the microscope, and by watching a navigation monitor. A surgical navigator was used to record the three-dimensional position of the suction tip. The pointing deviation from the suction tip to the center of the virtual gate was evaluated. The pointing accuracy with the naked eye did not differ between the two groups, but that under the microscope was significantly better in the experienced group than in the inexperienced group. Fluctuations in pointing deviation were significantly greater in the inexperienced group, especially with the microscope. Further analysis demonstrated these differences were attributable to poorer depth perception of the phantom surgical space among the inexperienced neurosurgeons.

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The lack of depth perception and the sense of distance with 2-D video displays are drawback for endoscopic surgery. A stereoscopic 3-D endoscope and a BiVIS (Binocular Vision by Image Shifting) endoscope have been developed to solve these problems. We compared conventional 2-D, 3-D and BiVIS endoscopes in terms of performance for depth perception, manipulation and sensory scores of a three-dimensional effect. Although the BiVIS display system did not show superiority in depth perception and sense of distance, the result, indicated that it gave operators a stronger sensation of depth and reality than a 2-D system. The stereoscopic 3-D display system had superiority in depth perception, and gave operators a stronger sensation of being solid and powerful than a 2-D system. It, however, gave operators a stronger impression of motion sickness, and thus was not preferred over the other systems.

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This paper discusses the possibility of applying Virtual Reality (VR) techniques to the mental care of patients. It describes the results of a basic study and the development of a system for implementing a new concept we call "bedside wellness". The system aims at improving the quality of life for bedridden patients. A prototype system intended to reduce stress and facilitate movement was proposed and developed based on a basic study. It provides a virtual walk through a forest by using VR technology and foot devices installed on the bed. The system was evaluated by an experiment with healthy subjects. The data suggested positive effects of the system; however, points for improvement were also learned. After making some of these improvements, clinical use of the system has begun.

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This paper presents a performance evaluation of two kinds of surgical navigation display systems for endoscopic sinus surgery. Conventional surgical navigation systems with a triplanar display lack information of endoscope viewing direction. Our new system shows a single perspective view of the patient and the endoscope model that has a viewing cone with a simulated light to indicate the viewing direction and visual field. A performance experiment with a dummy skull revealed characteristics of these two navigation systems: the perspective display navigation with a coronal clipping plane showed better performance in the case of difficult tasks, while the triplanar display navigation was almost ignored by the subjects.

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A computer-aided surgical simulator using virtual reality (VR) technique is developed on a high-speed graphical computer. By using the VR devices of the simulator such as a "virtual knife"-typed position sensor, data globes and a head-mounted display, one can virtually operate on the three-dimensionally displayed patient images which are reconstructed from their CT or MRI. Our simulation software is featured with its modularity where surgical simulation in the various disciples can be developed by combining the program modules which perform specific 3D image processing or VR device control. We applied this system to a neurosurgery to enucleate brain tumors. It was found this system provides good pre-operative estimations about positional relations between the skull and tumors.

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We have developed a virtual surgery system capable of performing surgical maneuvers on the elastic organs. In this system it is able to handle organs as elastic models and obtain a value for force feedback in real time. Furthermore, by connecting to the force feedback device we tried to manipulate the elastic organ model with a sense of touch. We tried to devise a system that would allow us to push, pinch, or incise these soft tissue models in virtual space, with a sense of touch.

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We developed a system that makes viscous sensation to the human legs in mud like wet rice field. In the first half of this paper , we mentioned a structure and a system of the force display device to the legs and its motion. In the latter half part, we mentioned some results of the experiment to evaluate comparative with real mud rice field. As the experimental results , we confirmed that the result next to real thing and almost subjects could fell it as (environment of) mud rice field.

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