中红外医用光纤激光的研制及其与生物组织作用的研究

发布时间：2018-08-20 13:44

【摘要】：近年来,2.0μm激光手术治疗系统相比于传统开放式外科手术和经尿道电切术,在治疗前列腺等泌尿系统疾病方面,具有出血量少、作用创口小以及手术安全性高等优势。这是由于水分子在1.94μm波长处有一个吸收峰,组织受激光照射,内部的水分会迅速吸收激光能量,瞬间达到气化所需的温度条件并受热分解。在此过程中,组织的气化分解能快速带走大量的热能量,减小其在邻近组织中的热传导作用,降低对目标组织周围的热损伤。然而目前市场上商用化的铥激光手术刀的光源大多采用连续二极管端面抽运的Tm:YAG激光系统和Tm:YLF激光系统。掺Tm~(3+)光纤激光器相较于传统铥固体激光器具有较好的光束质量、良好的集成性和较高的紧凑性,完全具有替代传统固体激光手术刀的潜在应用价值。因此,研究掺铥光纤激光系统与新鲜生物组织的相互作用,开展定量分析和定性讨论是非常有必要的。本文基于2.0μm波段掺铥光纤激光器的各种优点,开发和研制了一款连续/准连续全光纤铥激光治疗系统和搭建了基于全光纤主振荡功率放大(MOPA)结构的高功率铥激光手术实验系统,并且重点研究了2.0μm波段掺铥光纤激光与生物软组织的相互作用。主要研究成果有以下几点:(1)基于Tm~(3+)对793 nm泵浦的吸收能级建立了掺铥光纤激光器的速率方程,并结合边界条件对激光器的输出功率特性进行了数值模拟,并计算了达到预期输出功率所需的光纤长度和输出激光的斜率效率。数值仿真结果表明掺铥增益光纤长度为6 m时,在12 W泵浦功率下可以实现3.4 W的激光输出。我们通过调节边界条件参数,同时对掺铥光纤激光器的MOPA放大输出特性进行了数值分析。当种子源功率为3 W时,采用10 m的掺铥增益光纤并设置泵浦功率为160 W时可以实现81.75 W激光输出,此时放大器的斜率效率为48.9%。(2)基于掺铥光纤激光输出功率的数值模拟结果、泵浦参数以及增益光纤参数,对低功率铥光纤激光治疗仪的连续激光源系统进行搭建,并封装实现了2μm全光纤激光治疗仪的整机系统。该系统可以输出中心波长为1981.53 nm,光谱宽度为0.07 nm的窄带连续激光。在连续工作模式下可以实现最高2.0 W,在占空比为50%的准连续工作模式下可以实现平均功率为1.0 W的输出。其次我们应用低功率全光纤铥激光治疗仪对新鲜小猪皮肤进行单点消融实验研究,定量分析在激光作用下,组织热穿透深度始终控制在2.5 mm以下。当1 Hz的激光作用下,组织消融深度相对于连续激光将会大幅提高,皮肤组织也能达到相同消融时间和激光平均功率下的最大消融深度和最小凝固深度。在与3μm铒激光对皮肤组织的作用深度对比中,3μm激光具有更浅的穿透深度,但我们依然可以调节铥激光的参数来适应于铒激光的组织作用情况。(3)开展了2μm全光纤MOPA结构的铥激光实验系统搭建和研究。系统的主振荡级可以输出中心波长为1980.4 nm,光谱宽度(FWHM)为0.05 nm的窄带连续激光。实验中,我们测试了大模场掺铥光纤激光放大器的输出功率最高可以达到78.1 W,此时的泵浦功率为138.8 W,放大斜率效率为57%。于此同时,我们也开展了30 W量级的高功率掺铥光纤激光器切割新鲜猪肾脏的实验研究,在具有切割效应情况下,我们将切割速度从3 mm/s提高到5 mm/s,组织凝固宽度和深度会降低50%左右。综合所有数据表明,肾脏组织热作用深度在3 mm以内,最大凝固深度在1 mm左右,进一步验证了2μm高功率掺铥光纤激光器在中红外激光医疗领域的发展可能性。
[Abstract]:In recent years, compared with traditional open surgery and transurethral resection, 2.0 micron laser surgery system has the advantages of less bleeding, less wound and higher safety in the treatment of urinary system diseases, such as prostate. This is because water molecules have an absorption peak at 1.94 micron wavelength, and the tissues are irradiated by laser, so the internal part of the system is safe. In this process, tissue gasification can quickly take away a large amount of heat energy, reduce its heat conduction in adjacent tissues, and reduce the thermal damage around the target tissue. However, commercialized thulium laser surgery is currently on the market. Tm:YAG laser system and Tm:YLF laser system are mostly used as the light source of the knife. Compared with traditional thulium solid-state laser, Tm~ (3+) doped fiber laser has better beam quality, better integration and higher compactness, so it has the potential application value to replace the traditional solid-state laser scalpel. Quantitative analysis and qualitative discussion are very necessary to study the interaction between thulium-doped fiber laser system and fresh biological tissue. Based on the advantages of 2.0 micron-band thulium-doped fiber laser, a continuous/quasi-continuous all-fiber thulium laser treatment system and an all-fiber main oscillator power amplification system are developed. The experimental system of high-power thulium-doped fiber laser with MOPA structure is studied. The interaction between thulium-doped fiber laser and biological soft tissue at 2.0 micron band is studied. The main results are as follows: (1) Based on the absorption level pumped by Tm~ (3+) at 793 nm, the rate equation of the thulium-doped fiber laser is established, and the boundary conditions are combined with the laser. The output power characteristics are numerically simulated and the fiber length and the slope efficiency of the output laser required to achieve the desired output power are calculated. The numerical simulation results show that the laser output can reach 3.4 W at 12 W pumping power when the length of the Tb-doped gain fiber is 6 m. We adjust the boundary condition parameters and simultaneously treat the Tb-doped fiber. The output characteristics of the amplifier are analyzed numerically. When the seeding power is 3 W, 81.75 W laser output can be achieved with 10 m Tb-doped gain fiber and 160 W pump power. The slope efficiency of the amplifier is 48.9%. (2) Based on the numerical simulation results of the output power of the Tb-doped fiber laser, the pump parameters and the pump power Gain fiber parameters, build the continuous laser source system of low power Thulium fiber laser therapeutic instrument, and package the whole system of 2 micron all fiber laser therapeutic instrument. The system can output a narrow-band continuous laser with a central wavelength of 1981.53 nm and a spectral width of 0.07 nm. The average power of 1.0 W can be achieved in the quasi-continuous mode with 50% air-to-air ratio. Secondly, the single-point Ablation Experiment of fresh piglet skin was carried out with low-power all-fiber thulium laser therapeutic apparatus. The thermal penetration depth of tissue was always controlled below 2.5 mm under the action of laser. Under the action of 1 Hz laser, the tissue was ablated quantitatively. The ablation depth will be greatly increased compared with CW laser, and the maximum ablation depth and minimum coagulation depth of skin tissue can be achieved at the same ablation time and laser average power. The main oscillation stage of the system can output a narrow-band CW laser with a central wavelength of 1980.4 nm and a spectral width of 0.05 nm. In the experiment, we measured the transmission of a large-mode field Tb-doped fiber laser amplifier. The maximum output power can reach 78.1 W, when the pump power is 138.8 W and the amplification slope efficiency is 57%.. At the same time, we have also carried out an experimental research on the high power TM * fiber laser cutting the fresh pig kidney at 30 W level. Under the condition of cutting effect, we will increase the cutting speed from 3 mm/s to 5 mm/s, and the width of the tissue solidification. All the data show that the thermal depth of kidney tissue is less than 3 mm and the maximum coagulation depth is about 1 mm. This further verifies the development possibility of 2 micron high power Tb-doped fiber laser in the field of mid-infrared laser medical treatment.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R312;TN24

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