근적외선 형광영상시스템의 PWM 제어에 관한 연구

Abstract

Near infrared fluorescence imaging systems have been developed for image guided surgery. Fluorescent images using near infrared rays have no worry about radioactivity and it is easy to observe tissues that are difficult to identify with eyes because tissue transparency is better than visible light band. Especially, since it can confirm the image in real time and can perform the operation, it helps to precisely ablate cancerous area. However, research on fluorescence imaging in Korea is focused on the development of contrast agent, and development of fluorescence imaging equipment is insufficient. Fluorescent imaging equipment has been developed in Korea, but its size is bigger than that of overseas equivalent products, resulting in poor competitiveness. In this thesis, we aim to reduce the size of the equipment by using a fluorescence imaging system using PWM control. In the proposed fluorescence imaging system, the liquid cooling system, which occupies a large volume in the existing system, is eliminated. Instead, the LED output was changed to PWM mode as a means of controlling the heat generation. The proposed method could reduce the size of the system because the liquid cooling equipment was deleted. Using the proposed fluorescence imaging system, we measured LED and probe internal/external temperature according to PWM Duty Ratio and also NIR fluorescence images were taken and compared with the CW method. Fluorescent images obtained from the experiment were sampled and compared with the least amount of external components, and compared with CW and PWM images using difference images and PSNR. Experimental results show that the proposed system has no problems in LED and camera operation for a long time, but CW system has two LEDs fail during the experiment. In addition, the CW method in the early stage of the experiment showed a brighter and better image than the PWM method. However, the quality of the image deteriorated over time, which is lower than that of the PWM method. This was confirmed by the change in PSNR value. The fluorescence imaging system using PWM control enabled the miniaturization of the equipment. It is also confirmed that the proposed thermal suppression method can obtain a stable image. In order to make the near-infrared fluorescence imaging system more compact, we will carry out research on the light source such as the bio-transmittance, the penetration depth, the minimum amount of light required for ICG excitation, and the embedding of the fluorescence imaging system.