Study Of Medical Infrared Imaging Technology Based On Bioheat Transfer

The heat effect of biology has brought the research of medical application of infrared technology and bioheat transfer, which causes a new subject called medical infrared thermograph. It can realize the early and nondestructive diagnosis of the human diseases. The medical infrared imaging technology is a result of what is combined with medical technologies, infrared imaging technologies, and computer multimedia technologies. It is an imaging instrument to record the thermal field of human body and to complement the modern medical imaging technology mainly constituted by X-CT, MRI and so on.The medical infrared imaging technology passively receives the infrared radiation of human body by the infrared thermal imager, which can only get the surface temperature distribution. It is hard to directly reflect the correlative information of the inner heat source and to get the abnormal interior temperature distribution. It is necessary to do fundamental theoretic research to confirm the relationship between the inner heat source and surface temperature distribution. It can be said that the most medical infrared imaging technology can only realize the qualitative diagnosis according to the infrared images of surface temperature distribution, and has not achieved the quantitative diagnosis.In order to solve the above problems of the medical infrared imaging technology, the bioheat transfer mechanism of biology is further studied and the reasonable models of bioheat transfer are built based on the bioheat transfer theory. The invisible surface temperature distribution is transformed to visible infrared image by the infrared imaging system. Combined with the bioheat transfer model and the infrared image, the particular information of interior temperature distribution and inner heat source can be got by the computer processing.In order to analyze the surface temperature distribution affected by the inner heat source, the relationship between the surface temperature distribution and inner heat source is studied from the bioheat transfer theory and the simple heat transfer model. Combined with the thermodynamics knowledge, the bioheat transfer equation is deduced based on the study of bioheat transfer mechanism. The models of the surface temperature distribution affected by two kinds of inner heat sources are built to analyze the effect for surface temperature distribution of different parameters of inner heat source.In order to get the particular information of inner heat source, the heat conduction differential equation of the isotropy tissue with inner heat source is established based on the Fourier law and the law of energy conservation. By the solution of the equation, the expression of the relationship between the surface temperature distribution and the abnormal inner heat source is deduced. By means of the results of the finite element analysis, the model is simulated and numerically analysed. The situation of heat exchange with the environment is also considered. On this basis, the modified model which can be applied in the research of biology is proposed. By the clinical examples this modified model is better than the original one.In order to nondestructively obtain the interior temperature distribution, the Pennes bioheat transfer equation is solved to obtain the temperature changes with the depth variation under the different boundary conditions. Combined with the Pennes'experiment data and Wissler's research results, the solved results are analyzed and calculated, and the best boundary condition is also acquired. According to the solved result under this best boundary condition, the effects of thermal parameters on the temperature distribution in biologic tissues are discussed.Based on the above theory analysis and method research, a new infrared imaging system is designed. The relevant image preprocessing of nonuniformity correction and image contrast enhancement are achieved. The software-hardware element of this system proposed. According to theory research of the fourth chapter, the layered algorithm is realized to obtain the interior temperature distribution of different layers from the surface infrared image. The reasonable experiments results are achieved by this system.