Bio-tissue temperature measuring for laser medicine

摘要

Temperature is an intuitionistic indicator of laser and tissue thermal interaction. It can be used as verification of theory prediction as well as online clinic indicator. Temperature measuring is an indispensable tool in laser and tissue photo-thermal theory research. A computer-assistant noninvasive or minimally invasive temperature measuring system, which can be used in laser medicine, was introduced. Combined infrared radiation thermometer and miniature thermocouple, the surface irradiating point and inner temperature can be monitored synchronously. This system has some necessary advantages for in vivo tissue temperature measuring. The infrared radiation thermometer temperature range is 0～200°C and 1mV/°C analog voltage output signal can be tntered to computer. Inside LED red light and aiming sound can assure the distance between thermometer and measuring point to be the focus distance of 25mm and measuring circle has the least diameter of 2.5mm. The mini K-thermocouples were made by ourselves, their temperature range is 25～500 °C, the diameter of 0.4mm, and the response time is rapid up to 0.1s. They are convenient for precision orientation in the organisms. Multichannel temperature measuring can reduce the measurement error and be able for distribution measuring. Integrated temperature sensor LM35 and numerical computation is used to compensate the cold port temperature of the thermocouples. The numerical computation can also revise the nonlinearity error with the least squares method quintic polynomial fitting, which excels to the circuit method. Calibration results with glycerin and mercury thermometer showed the absolute error value is less than 0.45°C within 26-98°C. The real time temperatures of murine skin tissue irradiated by CO_2 and Nd:YAG laser were measured. Such a system is suitable to high precision, large range, minute point, rapid response and real time tissue temperature measuring in laser applications. The saved data can be used for later analysis and compared with the thermal transferring theory model and calculation.