A real-time surgical navigation system that superimposes the real, intuitive 3D image for medical diagnosis and operation was developed.This system creates 3D image based on the principle of integral photography, named “Integral Videography”, which can be observed following the operator's movement of the field of vision via a half-mirror as if they could be seen through the body.Moreover, a real-time IV algorithm for calculating the 3D image of surgical instruments was used for registration between the location of surgical instruments and the organ during the operation.The experimental results of sticking a point location and avoiding dangerous area show the errors of this navigation system were in the range of 2-3mm.Because of the simplicity and the accuracy of real-time projected point location, this system will be practically usable in the medical field.

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Using a patient's 3D dataset obtained from CT or MRI, our virtual reality system can perform surgical simulations in 3D virtual space. Many researchers utilized more costly organ models which used a finite element method (FEM) or the spring-damper model. However, in order to adapt this system to a PC, we employed the more economical method which created the realtime organ transformations necessary for an authentic simulation.As a result our system can perform incisions on a 3D image of a patient's body surface and internal organs in the manner of realtime simulation.

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We proposed and developed the prototype of a master-slave-type 4 D.O.F. pair of surgical forceps with force sensors. By using two types of servo forceps, the smooth control of the forceps was verified experimentally.Moreover feasibility for clinical application was made clear byin vivoexperiment.

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Most malformed ears of neonates can be treated by mounting a suitably shaped orthosis. However, it needs much experience to make a orthosis that produces adequate corrective force. Especially, excessive force may cause a decubituslike inflammation on the auricle. We are studying computer aided treatment system to support the orthosis design. And we have already developed fundamental design and manufacturing system.This paper describes automatic orthosis shape modification method to prevent the excessive contact force using three dimensional finite element analysis.In each insertion step of incremental method, contact force of every nodal point of the orthosis is calculated.The shape is modified by canceling the insertion of nodal point where excessive contact force is produced.The result of the simulation shows that the maximum contact force was reduced to one third by the modified shape. Orthoses of original shape and the modified shape by the method are manufactured. Also, two types of force sensor systems using silicon tube and strain gage are constructed.They use phenomena that air flow in the tube decreases and the strain gage is deformed when they are pressed.The thickness of tube sensor is 0.5mm and that of strain gage sensor is 0.2mm. Orthoses on which sensors are mounted are inserted into a testee's auricle and the contact force is measured.The results of both sensors showed that the force produced by the orthosis of modified shape was approximately half of original shape.

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