The Research Of Temperature Control And Field Distribution Model Under The Pain Stimulus Of Near Infrared Laser

Pain is a damage or danger alarm signal to the organism.In both medical research and clinical diagnosis,pain detection has very important significance.As the most effective tool for pain detection research, the non-contact stimulus mode of laser pain stimulus can ensure the activation of damaging sensor without the interference of mechanoreceptors,thus the laser evoked potentials (LEPs) are more likely to be detected;In addition,the high speed of transient temperature rise makes the synchronization of the LEPs signal better.At present,the most of LEPs studies are about the CO2 laser. The research of the near infrared laser,especially the temperature of tonic pain and skin temperature field distribution, is relatively small.Based on the above discussion,the study is designed to promote the progress of near infrared laser pain stimulus.Objective:Taking the research of near infrared laser stimulus as background,the pain stimulus system is built.Besides, a new temperature control system in tonic pain and skin temperature field distribution model can be established under the light of near infrared laser.In the end,some relevant ex-vivo experiments are designed to explore the relationship between the above two technologies and pain,thus promoting the application of near infrared pain stimulus.Methods:Firstly,using the Tm:YAG laser to built the near infrared laser pain stimulus system; Secondly, according to the needs of clinical and scientific research, two kinds of temperature control system,contact and non-contact, were established. Besides,we designed ex-vivo experiments to evaluate temperature control effect; Finally, the stimulation study will complete two kinds of experiments after finishing building the model of FEM-2:time-dependent temperature responses in different sub-skin depths and space-dependent surface temperature.Each experiment will use the following two cases to verify temperature distribution on ex-vivo pig skin pieces:the case that the laser beam waist spot size is constantly 3.5 mm and four groups of different power (P=0.25 W,0.5 W,0.75 W and 1 W),and the case that the laser power is constantly 1 W and three groups of different waist spot size (R= 2 mm,3 mm,3.5 mm).Results:The in-vitro experimental results of the temperature control system show that the above two kinds of temperature control system can achieve a certain time pain;In the practical control of tonic pain, laser output with high average power density should be used to make skin surface temperature rise quickly to the pain threshold, and then, lower power density irradiation should be applied to maintain a constant thermal stimulation;The time-dependent temperature responses in different sub-skin depths and space-dependent surface temperature that recorded in ex-vivo experiments are accorded with the results that the FEM-2 model predicted. The FEM-2 model can be used to guide the actual pain research;When it comes to tonic pain, the condition of R=3.5 mm(P=1W) without thermal damage has bigger pain area than the condition of R=2 mm(P=1W).In other words,the former condition can produce tonic pain is a more ideal way in the research of tonic pain.Conclusion:The near infrared laser pain stimulus system can well realize the temperature control of tonic pain and the building and analysis of skin temperature field model.The above two kinds of technologies can contribute to the near near infrared laser pain research.