Search

In this paper, we propose a novel method to product biological models using polyurethane elastomer, which has high photoelastic coefficient and a method to analyze stress states on the model by photoelastic method. With this method, stress condition on vascular wall represented by two principal stresses is clearly visualized on vascular fringe as rainbow-colored photoelastic stress pattern, and the quantitative stress is analyzed from that pattern. For analysis of stress states by photoelastic method, retardation and path length of penetration light through the model must be observed. Proposed method is possible to observe these two parameters simultaneously. Retardation is decided from RGB value of rainbow-colored photoelastic stress pattern and path length is decided from permeability of light. The accuracy of stress analysis is evaluated by tensile test using artery-like cylindrical model. Lastly using the model produced by new method, we analyze stress states quantitatively on the model of cerebral artery. Consequently, it should be valuable for various applications not only surgical simulations but also hemodynamic studies and pathological studies.

In this paper, we propose an in vitro patient-tailored anatomical model of human cerebral artery, a hardware platform for simulating intravascular neurosurgery for making diagnosis and surgical trainings. Proposed vessel model hollowly reproduces 3-dimensional configuration of vessel lumens within an elastic transparent silicone cube, using fluoroscopic information which is obtained with CT (Computed Tomography), MRI (Magnetic Resonance Imaging) and other imaging modalities. It also reproduces the physical characteristics of artery tissue, such as elastic modulus, Poisson's ratio and friction coefficient, within respectively 10% of errors. Consequently, it allows simulating neurovascular procedures, which is accompanied by the realistic feel of operating catheters, and the realistic behavior of surgical instruments (e. g. slip/stick motion and unwinding motion). Presented vasculature model should provide an innovative platform for interventionalists to make preliminary surgical simulation, for young trainees to practice intervention procedures and for developers to evaluate surgical robots, device and other various medical instruments.

In this paper, we focus on the problem of safety and operability which is involved in a teleoperation system (master slave system) for medical application, and propose a new control strategy to improve performance of safety and operability by two force display methods. One is a multiple sensor information display method which display several force information that are measured by several force sensors on one master device. The another one is a variable impedance characterization of master device which changes the impedance parameter of the master device according to the situation of the medical operation. We also apply this method to the neurosurgical telemedicine system, and perform an experiment to evaluate our method.

Nowadays, minimum invasive surgery using intravascular surgical tools is getting greater attention in the medical field. This technique allows us to reduce physical pain and sequelae from patients. For example, a catheter is one of the medical tools which is used in endovascular surgeries. The catheter is frequently used for neurosurgical operations. We propose a new type of force sensor for intravascular neurosurgery. This micro force sensor can be installed in the tip of the catheter. We developed a prototype micro force sensor whose diameter is 1.6 mm and length is 12 mm. Using this micro force sensor, we can measure the contact force between the catheter and blood vessels. This is quite important to reduce the unnecessary contact force between the catheter and blood vessels. In this paper, we show the structure of the micro force sensor and its characteristics, and we also show the results of in vivo experiment.

In this paper, we propose a new prototype model of the active guide wire microcatheter whose bending has two degrees of freedom. The design and fabrication methods of this active microcatheter are described. It is 3Fr, 4Fr, 6Fr (1Fr=1/3mm)in diameter and consists of catheter tube and active guide wire with ICPF on its front end as the servo actuator. The bending motion and bending angle of the active guide wire microcatheter have been measured by application of electricity in water and in physiological saline solution. We also modeled this active microcatheter. Experimental results show that the model of the active catheter is reasonable for practical applications. By using simulators (conditions similar to those of a body cavity), we also carried out simulation experiments in vitro. The experimental results indicate that the proposed active guide wire catheter is applicable to intracavity operations.

Recently, the catheter has been down-sized and has become functional, and it has begun to be used for practical medical operations. Nowadays intravascular neurosurgery using the catheter is carried out for an aneurysm or cerebral thrombosis. However, it is quite difficult to select the direction at a divergence point because brain blood vessels are narrow and complex. For this reason, an active catheter whose tip can be actuated by a microactuator is studied and developed. Even if the active catheter is realized, its control is very difficult. Therefore we investigate an assistance system for the doctor operating the active catheter. In this paper, we propose the concept of an intelligent medical assistance system for operation of the active catheter. To realize this medical assistance system, we built a prototype of a virtual simulator system consisting of an active joystick, which has force feedback capability, and a 3D-computer graphics display. Using this simulator system, we evaluated the effectiveness of the proposed visual and operation assistance methods through extensive experiments.