The Fundamental And Animal Experimental Study Of Ultrasound Guided Endovenous Laser Treatment

Objective：to investigate the mechanism of temperature rise of venous wall induced byendovenous laser treatment (EVLT); to investigate the effects of various laserparameters and operation methods on the effectiveness and safety of EVLT.Material and Methods: the first part: the experimental study of the law ofpost-irradiation temperature rise of fresh coagulated caprine blood. Different laserpower and pullback speed were used in the ablation of fresh coagulated caprine venousblood, and the highest temperature as well as the duration of temperature higher than60℃were measured when thermocouples were placed at different distances from thefiber tip (to simulate different venous diameter). The second part: the experimentalstudy of the law of temperature rise of caprine saphenous venous wall in hindlimb afterlaser ablation. EVLT was performed with corresponded experimental parameters(power and pullback speed) selected due to the first part of the study, and the highesttemperature as well as the duration of temperature higher than60℃were measured.The experimental settings which can achieve the time-temperature thresholds forthermocoagulation of biological tissue induced by laser ablation were investigated tobe applied in the third part of this study. The third part: the comparative pathologicalstudy of effects on EVLT when target vein was treated with or without pressure. EVLTwas performed with or without pressure under corresponded experimental settingswhich can achieve the time-temperature thresholds in various diameters of vein provedby the second part. The pathological samples of target veins were taken to compare thedegree of the cellular necrosis of venous intima and venous perforation.Results: The first part: the temperature of venous blood rised after laser irradiation, suggesting that the temperature rise of venous blood induced by laser irradiation wasone factor related to the mechanism of temperature rise of venous wall after EVLT. Thedegree of temperature rise was affected by laser power, distance from fiber tip andpullback speed. Under certain settings of laser power, distance from fiber tip andpullback speed, the degree of temperature rise and duration time could achieve thetime-temperation threshold for thermocoagulation of biological tissue induced by laserablation. The second part: the degree of temperature rise was higher in vivo than invitro under the same laser power, distance from fiber tip and pullback speed,suggesting both the direct irradiation of laser on venous wall and the direct contact offiber tip to venous wall were factors related to the mechanism of temperature rise ofvenous wall in EVLT. Time-temperation threshold for thermocoagulation of biologicaltissue induced by laser ablation could be achieved when proper parameters wereselected according to venous diameter. The third part: there was a significantdifference of cellular necrosis rate of venous intima and venous perforation ratebetween groups in which treatment was performed with or without pressure afterEVLT in caprine saphenous venous wall in hindlimb. The cellular necrosis rate ofvenous intima was88.6%and96.8%in groups with and without pressure respectively(P<0.05), and venous perforation rate was65.6%and21.1%respectively (P<0.05).Conclusion:1. the temperature rise of venous blood induced by laser irradiation, thedirect irradiation of laser on venous wall and the direct contact of fiber tip to venouswall were all factors related to the mechanism of temperature rise of venous wall afterEVLT;2. time-temperation threshold for thermocoagulation could be achieved toinduce cellular necrosis when proper parameters (laser power, pullback speed) wereselected according to venous diameter;3. the cellular necrosis rate of venous intimawas significantly higher and venous perforation rate was significantly lower in groupswithout pressure compared to groups in which pressure was applied, suggestingpressure should not be applied during EVLT was performed.