| Pain is an unpleasant experience and corresponding emotion of fear and positive feeling of human.Pain stimulation has been widely used in brain science,the diagnose of neuropathy,chonic pain study and research of analgesic research.lt is a very important experimental tool in mechanism study,and also a significant method in clinical application.An effective pain stimulation is necessary in pain study,and the laser evoked potentials(LEPs) is one of the most valuable pain stimulating experimental mode by its character of non-contacting,specially eliciting nociceptors and great synchronism.Nowadays,this method has been applied in scientific study and clinical diagnosis,and shown its indispensable in pain study.However,LEPs also has some shortages which includes can not accomplish baseline control and eliciting tonic pain. And these shortages limit its further application.Based on the demands of pain mechanism study and clinical application,this study presented a new kind LEPs technique,method and instrument which could both elicit traditional transient pain and tonic pain,baseline control and irradiating area control.Considering that most of the LEPs only use pulse laser as stimulator and thus the tonic pain can be hardly elicited,this study designed a new work mode for pain stimulation:assembling both pulse980nm diode laser and continue waveform1940nm Tm:YAG laser together.Based on this design,this study developed the special designed programmed circuit and corresponding upper computer software,and finally assembled the whole dual wavelength laser stimulating system.For achieving the research target mentioned above,three key techiques had been invented:pain stimulating area control,the feedback control of irradiated surface and laser absorbed heat layer.By using the simple optical system composed by collimating lens and filters,the shape and size control of irradiated region on target skin was realized,therefore,the pain stimulating area control was achieved.By designed and accomplished the temperature control method and corresponding closed feedback control system which composed by temperature measured module,upper computer and the precise voltage control module of programmed circuit,the feedback temperature control of irradiated surface was accomplished.Thus,the dual wavelength laser owned the ability of baseline temperature control and tonic pain stimulation.For generating ideal transient eliciting effects and reducing the danger of cutaneous damage,the laser absorb heat layer which based on the mechanism of photothermal effect and absorption coefficient of980nm and1940nm lasers had been studied and used.By the laser absorb heat layer technique,the mechanism of laser heat pain had been changed from photothermal effect to heat cutaneous conduction.For testing the real effects of these techiques mentioned above,the in vitro experiments had been applied.The temperature records of these experiments showed that the aim of this study had been certified successfully accomplished.In addition,for understanding the temperature distribution and guiding pain study and clinical application,we established the cutaneous temperature distribution model of dual wavelength laser:First we measured the parameter of dual wavelength laser system,and then built an accurate FEM-2temporal and spital temperature distribution model by1940nm laser irradiation which benefit by the high water absorption coefficient and the low reflectance and emission in the skin;we built the temperature distribution model of hemoglobin absorb heat layer brushing skin after980nm pulse laser irradiation which benefit by the high hemoglobin absorption coefficient.The reasonableness of these models were certified by in vitro experiments.The dual wavelength laser pain stimulator presented in this study own the advantage of eliciting both transient pain and tonic pain in the same organism by synchronous or modulation stimulation.And the character of specially eliciting nociceptors can be reserved.In addition,several nociceptors in certain area can be elicited by pain region control,which is an advantage in IENF detection.Baseline temperature control can avoid the detection of LEPs by different baseline and enhance the LEPs quantity. In conclusion,this system presents great application prospect and value in pain study,clinical diagnosis and medicine research. |
