Suitability of using far-infrared imaging system for noncontact evaluation on working state of implantable medical devices

摘要

The far-infrared thermal imaging is a promising noncontact way to assess the working state of an implantable medical device (IMD). The unique merit of this method lies in its direct detection of the unusual skin surface temperature distribution caused by the implanted IMD. This paper is dedicated to present a comprehensive investigation on the suitability of using far-infrared system to evaluate the thermal state at the skin surface above the implantation location of the IMD under various working, physiological, or environmental thermal conditions. It was found that an evident variation in temperature as disclosed on the skin surface is beneficial for the far-infrared thermal imaging detection. In addition, numerical simulations were also performed on three dimensional bioheat transfer problems in human bodies embedded with IMD by different implantation depth and physical characteristics. Both theoretical analysis and numerical simulation indicated that for a specific image system with fixed temperature resolution, when the IMD is embedded as close as possible to the superficial skin, the abnormal region of temperature on skin surface can be much more visible. Conceptual experiments either in vitro or in vivo are implemented to preliminarily demonstrate the theoretical predictions. To further improve the detection of an implanted IMD, intentional cooling by the alcohol was proposed and evaluated. Given the fact that several information of an implanted IMD can be revealed through the infrared thermograph, such noncontact imaging method could serve well as an assessment approach without causing any wound and radiation to human body.