Surgical simulator reconstructs the deformation and the elasticity of the organs by software algorithm. As this calculation is complicated, phase-lags or the sudden elasticity would arise when we press the surface of the organ models with our fingertips. In this paper, we propose a method to solve these problems by correcting the computing time delay using the nonlinear estimation of the finger position and smoothing the elasticity value using the cubic spline interpolation. Further, experiments by simulation carried out to ensure the validity of this method.

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In this paper, we represent a virtual rheology object as the Mass-Spring-Damper (MSD) model. One is the original model whose structure is voxel-lattice. The model consists of many small and uniform voxels. The other is the octree hiearchical model in positioning. The model consists of larger and smaller voxels. All voxels include many MSD basic elements. If a human pushes or pulls such virtual MSD rheology models, both are deformed each other by propagating forces along basic elements. The numbers of masses and basic elements in the octree model are extremely smaller than these in the original model. Therefore, the octree-based model can save the time to calculate force propagation along all the basic elements. Nevertheless, shape deformation of rheology object represented by the octree model is better than or similar to that represented by the original voxel-lattice model. As a result, the octree-based MSD rheology model is quite useful. These properties are ascertained by several experiment and simulation results.

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In this paper, a haptic system for realizing the work by both hands in a virtual environment was proposed. It is desired that the simulation of work by both of hands can be realized in a virtual environment as if we were in real space. Visual and Haptic sense are indispensable to simulate a work in a virtual environment.A haptic device, which can provide haptic sense to the thumb, the index finger and the middle finger of the operator's both hands, was developed to perform cooperative works of both hands. As for the visual information, the operator's hand is modeled exactly and displayed on the screen. By these functions, the operator can perform exactly the simulation of the work.

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We reconstructed the fusion image of FIESTA and magnetic resonance angiography (MRA) to allow clear visualization of the spatial relationship between the arteries and facial nerve in the cerebellopontine cistern. Methods. 10 patients with hemifacial spasm were studied. We compared their preoperative two-dimensional image (MRA and FIESTA) and three-dimensional reconstructed image with actual operative view. We reconstructed the fusion image by using computer visualization software (Amira, Maxnet, Tokyo, Japan). Results. In 5 patients (50%), the predicted offending arteries from two-dimensional images accorded with them in operation. In 8 patients (80%), the offending arteries from three-dimensional images accorded with them in operation. Conclusion. Three-dimensional reconstructed images of the fusion between MRA and FIESTA may prove a useful in the operative assesment of microvascular decompression in patients with hemifacial spasm.

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We propose a deformable model for elastic organ based on structural mechanics under the consideration of multi-point-contact for medical training systems using Virtual Reality (VR) technology. In a previous paper, we proposed an organ deformation model which approximates a liver deformation by a single-beam deformation based on the structural mechanics. The calculation cost of the single-beam model is much less than that of the 3D Finite element method (FEM) since the beam consists of one-dimensional elements. In this paper, we propose a multi-beam model under the consideration of multi-point-contact by extending the single-beam model. A real-time deformation can be realized and the proposed model was implemented in the laparoscopic surgery training system.

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We have been developing a virtual human body using haptic devices for endoscopic surgery training simulator. This system is composed of two 3-DOF haptic devices and a control board with USB 2.0 interface. This system is connected to a host computer through Ethernet. Two operational tools are connected to haptic devices each through holes on the virtual body, and an operator is able to feel the sense of touch with virtual organs. Furthermore we proposed a new method to calculate a reaction force fast, and we constructed two types of examinations to evaluate a validation of the proposed method. Experimental results show that the proposed method was valid to the faster of the haptic simulation.

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