Experimental Research And Device Design Of Laser-induced Thermal Damage To Biological Tissues

Laser hyperthermia is a technology that locally irradiating the target area with a laser to raise the temperature to the ablation temperature of the tumor tissue which makes it necrotic.As a new method for the treatment of malignant tumors at the present stage,laser hyperthermia has the advantages of high accuracy and high energy density.However,there are still technical difficulties in this method that have not been overcome,such as localized overheating causing tissue vaporization,which greatly hindered the pace of laser thermotherapy entering the clinical field.This paper aims to analyze the thermal damage distribution of biological tissue caused by laser hyperthermia based on the results of in vitro tissueexperimentand numerical simulation.Furthermore,according to the preferred laser hyperthermia treatment parameters,combined with the design of the heat dissipation structure and the laser-targeted constant temperature system,the laser hyperthermia device is designed and constructed.With the help of the established experimental platform for laser hyperthermia in vitro tissue,the effects ofdifferent parameters on the temperature field of tissue are studied.The results show that the laser power P,the laser probe length LP and the laser-targeted constant temperature TL all haveapositive correlation with the area of the heat-affected area of the tissue.In order to satisfy the temperature range of laser hyperthermia treatment,the preferred laser power P is 0.2-1W.The change of laser probe length LP has less effect on the transverse temperature field of the tissue,but effectively increases the longitudinal thermal influence area of the tissue.When the laser-targeted constant temperature TL is 50-90℃,it has an effect on lateral heat influence distance of 4-14 mm.The change of the in vitro tissue volume VT has little effect on the change of the tissue temperature field and can be ignored.In this paper,a simplified three-dimensional model of human liver tissue is established.Based on the model,the temperature field change of the tumor under different treatment conditions is studied,and furthermore,the corresponding optimal treatment parameters and treatment plan are analyzed.The results show thatthe preferred laser power P is 0.2-1.3W due to satisfy the temperature range of laser hyperthermia treatment.In the single probe model,when the laser-targeted constant temperature TL is 45-90℃,it has an effect on lateral heat influence distance of 3-20 mm,and the cross-sectional area of the effective heat-affected area rises in a slow down velocity as the laser-targeted constant temperature TL increases.For a tumor with a diameter of 4 cm,the preferred treatment plan is to select a laser probe with a length of 30 mm for bilaterally symmetrical treatment.This paper uses finite element numerical simulation methods to compare and analyze the heat dissipation effects of different heat dissipation schemes of laser hyperthermia device.Based on the consideration of heat dissipation effectiveness and feasibility,the heat dissipation scheme of using a single air duct combined with heat dissipation fins is preferred.The operation of the laser-targeted constant temperature system is realized by designing and coding.Based on the selection of the above-mentioned preferred treatment parameters,heat dissipation scheme and laser-targeted constant temperature system,a laser hyperthermia device is successfully designed and constructed in this paper.