Photothermal Interaction Model Of Bio-tissue And Its Application On The Temperature Sensor

Photo-thermal response that result from interaction of laser irradiates on the bio-tissues is an important part of laser medical research. The photo-thermal therapy, which have been applied on clinical medicine at present was based on the thermal effects results from interaction between laser and bio-tissue. The light distribution were limited on the lesion tissue during the process of photo-thermal therapy, and then the light fluence were converted into heat energy, which were absorbed by tissue resulted in the increased temperature. But the heat energy will be spread to the around of lesion tissue through the heat conduction, which will lead to damage normal tissue, not only destroyed the lesion tissue. In order to avoid the phenomenon, it is necessary to monitor tissue temperature in the process of photothermal therapy and then adjust the treatment parameters. This thesis aims at the opt-thermal response that result from the interaction of laser irradiated the bio-tissues. The key points are optical transmission of bio-tissues, heat transfer of bio-tissues and new temperature measurement method. The research contents are including:Firstly, the light distributions of tissue were studied. The Monte Carlo method was presented to study the effects on light distribution of different laser incident angle irradiated tissue; the effects of light distribution caused by irradiated on the concave and convex tissues surface when laser irradiated vertically on tissue; the light distribution of complex tissue when laser irradiation vertically.And the results of simulation between diffusion equation and monte carlo method were compared to further illustrated the light distribution problem.Secondly, the temperature distributions of tissue were studied. The finite element analysis method was presented to study the temperature distribution of liver and skin tissue in different laser parmeters. Then the laser emitting modes and the external conditions were obtained.Thirdly, the light and temperature distribution of tissue were studied with dynamically photo-thermal parameters. The physical field of optical transmission and heat transfer in bio-tissue were coupled to study the light and temperature distribution of tissue changes with irradiated time with dynamically photothermal parameters through finite element analysis method. And then, the complex tissue model contained large vessels were constructed to study the effects that large vessels have on fraction of necrotic tissue.Fourthly, the applicaitons on photoacoustic imaging technology was used for monitoring temperature were studied in this thesis. The changes of temperature and photoacoustic signal with heating time,the relationship between photoacoustic signal and temperature with different power laser were studied.The photoacoustic imaging system with or without cylindrical lens have on was also studied to recover the effect of cylindrical lens in photoacoustic system.