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利用高速摄像技术检测脉冲CO2激光诱导液体气穴通道形成、发展和坍塌的动态过程,考察不同聚焦辐照条件对气穴效应的影响。实验获得了气穴通道脉动过程的序列图像,得到了表征气穴通道特性的参数(如最大穿透深度等)。实验结果表明,不同聚焦条件对气穴通道的动力学过程有显著影响。正离焦及焦点位置条件下,气穴通道在最大纵深时,整体形态类似于漏斗状,而负离焦条件下,则呈U形。研究结果对激光医疗、激光水下加工、能源等领域的研究具有一定的参考价值。  相似文献   
2.
We evaluate the ablation thresholds of Er:YAG and Er,Cr:YSGG laser for enamel and dentin.A total of 140 dental slices is evenly divided into two groups:the dentin group and the enamel group.Dental tissues are irradiated with either an Er:YAG laser or an Er,Cr:YSGG laser with pulse widths in the order of 100 μs.The laser fluence is increased gradually until the ablation crater is formed.The laser ablation threshold is calculated using probit analysis.The ablation thresholds of the Er:YAG laser for dentin and enamel range from 2.88 to 3.36 J/cm2 and from 2.94 to 3.8 J/cm2,respectively,and the ablation thresholds of the Er,Cr:YSGG laser for dentin and enamel range from 2.92 to 4.2 J/cm2 and from 4.93 to 5.66 J/cm2,respectively.  相似文献   
3.
The influence of scanning speed on hard bone tissue ablation is studied with a 10.6-μm laser. The groove morphology and the thermal damage created in bovine shank bone by pulsed CO2 laser are examined as a function of incident fluence by optical microscope following standard histological processing. The results show that ablation groove width, depth and ablation volume, as well as the zone of thermal injury, increase gradually with incident fluence. As compared to the result for high scanning speed, the lower scanning speed always produces larger ablation volume but thicker zone of thermal injury. It is evident that scanning speed plays an important role in the ablation process. In clinical applications, it is important to select appropriate scanning speed to obtain both high ablation rates and minimal thermal injury.  相似文献   
4.
The feasibility of fenestration operation in middle ear bone with pulsed infrared laser is evaluated. Healthy male New Zealand rabbits in vivo are used in the experiment. Middle ear mastoid bone of animal model is completely exposed with conventional methods, and then a pulsed CO2 laser (10.6 μm) and an Er:YAG laser (2.94 μm) are used to perform the fenestration operation. Diamond drill is also used as a control group. The total operation time and light irradiation time are recorded and the opening efficiency is assessed. The morphological changes and thermal damage around the opening window on the middle ear bone are examined. It is shown that both laser systems are suitable for the fenestration operation in middle ear bone, and this no-touch technique has a lot of benefits compared with traditional methods. The bleeding during operation has an important effect on operation time and thermal injury and needs to be controlled efficiently in further study.  相似文献   
5.
Wavelength dependence of soft tissue ablation by using pulsed lasers   总被引:3,自引:0,他引:3  
Pulsed laser ablation of soft biological tissue was studied at 10.6-,2.94-,and 2.08-μm wavelengths.The ablation effects were assessed by means of optical microscope,the ablation crater depths were measured with reading microscope.It was shown that Er:YAG laser produced the highest quality ablation with clear, sharp cuts following closely the spatial contour of the incident beam and the lowest fluence threshold.The pulsed CO_2 laser presented the moderate quality ablation with the highest ablation efficiency.The craters drilled with Ho:YAG laser were generally larger than the incident laser beam spot,irregular in shape,and clearly dependent on the local morphology of biotissue.The ablation characteristics,including fluence threshold and ablation efficiency,varied substantially with wavelength.It is not evident that water is the only dominant chromophore in tissue.  相似文献   
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