The Kyorin infrared coagulator (KIRC) using an infrared halogen lamp is being developed for the surgical treatment of arrhythmia, infective endocarditis, and other disorders; however, no assessments have been conducted on the effects of the shape of its probe tip on irradiance distribution of the irradiation light on the tissue contact surface, or on thermal changes in the myocardial tissue. Therefore, in the present study we performed simulation (analysis of irradiance distribution on tissue contact surface and thermal analysis of myocardial tissue) with differing KIRC probe tip shapes, and assessed the thermal changes in tissue under the infrared irradiation.

In the simulation (using OpticStudio software) of irradiance of the tissue contact surface, we modelled two probe shapes (flat and tapered) and materials, and analyzed the irradiance distribution of the irradiation light (probe tip output 22W) on the tissue contact surface in a two-dimensional coordinate system (X, Y). The specific heat and other environment conditions in the thermal analysis simulation of myocardial tissue with a thermal analysis program (QuickTherm) were set and the tissue model was constructed. With the probe tip output as in OpticStudio, the thermal analysis was performed for the tissue surface (0mm) and depths of 2, 4, and 6mm.

The analysis using OpticStudio showed maximum irradiance values of 40W/cm² (X, Y=±1, ±1) with the flat tip and 50W/cm² (X=±1) and 48W/cm² (Y=±1) with the tapered tip. These findings were applied to the analysis of the tissue model with QuickTherm, which showed temperatures of 64℃ at the surface and 4℃ at 6mm depth with the flat tip and thus higher than those found with the tapered tip. This is presumably attributable to an area of the heat source on the tissue surface with the flat tip that was 2.63 times that with the tapered tip, and accordingly higher heat conduction to a deep region.

In this study, simulation was performed to analyze the irradiance distribution of irradiation light on the tissue contact surfaces with differing probe tip shapes, to elucidate its relation to the thermal effect in the myocardial tissue, and to assess the thermal change in the tissue. In the future, it will be necessary to analyze the relation between the myocardial optical absorption property (wavelength spectrum) and the heat source.

The purpose of this study is to develop a support software to place ultrasound transducer, which produces local acoustic radiation force, for active induction of a micro object, representing a thin catheter, through blood vessel network. First, based on the image analysis of 3D blood vessel network, which was obtained using echography, the system calculates the possible area of the ultrasound transducer to be able to induce a micro object to desired path in blood vessel network. Meanwhile, due to the shape of body surface and the position of the ribs, which was obtained by an optical position sensor, the common area with the body surface was derived. Then, considering the position and the movable area of the robot, which grasps and moves the ultrasound transducer, the system indicates the candidate commands for the robot. To verify the system performance, we have conducted a simulation for active induction experiment of thin catheter through blood vessel network of a normal volunteer subject. As the result, we confirmed the variation of the thin catheter induction according to both body posture and breathing condition.