评估水喷雾条件对脉冲激光辐照骨硬组织的消融速率、消融效率以及组织表面形态学变化的影响。实验样品为新鲜离体牛胫骨组织;光源为脉冲CO2激光(波长10.64 μm),脉冲频率60 Hz,能量密度26.5 J/cm2,光束经关节臂传输后聚焦在组织样品表面进行垂直点状照射,光斑尺寸为400 μm,辐照时间10 s。激光辐照时,水雾以45°角倾斜向组织表面喷射,喷水速率分别设置为0(无喷水),0.26,0.5,0.6,0.7和0.9 mL/s。辐照后,体式显微镜观察组织样品表面形貌变化,OCT技术测量弹坑深度,扫描电镜观察弹坑微结构变化。结果表明,水喷雾条件对脉冲CO2激光骨硬组织的消融速率,消融效率以及组织表面形态学变化具有重要影响:水喷雾不仅可以起到冷却和降低热损伤的作用,通过优化选择激光辐照参数和喷水速率,可以显著增大消融速率和消融效率,改善靶组织表面的形态结构。

We evaluate the influence of water spray′s flow rates on the rate,the efficiency of laser-hard tissue ablation and the resulting surface morphology. Fresh bovine shank bone in vitro was used in the experiment. Light emitted from a pulsed CO2 laser with a wavelength of 10.64 μm and a repetition rate of 60 Hz was transmitted through an articulated-mirror-arm system and focused to a spot of which the diameter is about 400 μm on the bone sample surface directly. The radiant energy density was 26.5 J/cm2 and irradiation time was 10 s. A water spray system applied spray on sample surface with an angle of 45°during irradiation at flow rates of 0(without a water spray),0.26,0.5,0.6,0.7 and 0.9 mL/s. After irradiation,the morphological changes and microstructure of ablation craters were examined by stereoscopic microscope and scanning electron microscope (SEM) respectively. The ablation depth was also measured by optical coherence tomography (OCT). The result shows that the water spray has a profoundly influence on laser ablation rate and efficiency for hard tissue removal and the resulting morphology. Water spray not only can cool the tissue and reduce the thermal damage,but also can augment ablation rate and efficiency,and alter the surface morphology by optimal selection of laser irradiation parameters and water spray flow rate.