University of Basel, Department of Biomedical Engineering, Faculty of Medicine, Biomedical Laser and, Switzerland.
University of Zürich, Musculoskeletal Research Unit, Zürich, Switzerland.
J Biomed Opt. 2021 Sep;26(9). doi: 10.1117/1.JBO.26.9.095002.
The highest absorption peaks of the main components of bone are in the mid-infrared region, making Er:YAG and CO2 lasers the most efficient lasers for cutting bone. Yet, studies of deep bone ablation in minimally invasive settings are very limited, as finding suitable materials for coupling high-power laser light with low attenuation beyond 2 μm is not trivial.
The first aim of this study was to compare the performance of different optical fibers in terms of transmitting Er:YAG laser light with a 2.94-μm wavelength at high pulse energy close to 1 J. The second aim was to achieve deep bone ablation using the best-performing fiber, as determined by our experiments.
In our study, various optical fibers with low attenuation (λ = 2.94 μm) were used to couple the Er:YAG laser. The fibers were made of germanium oxide, sapphire, zirconium fluoride, and hollow-core silica, respectively. We compared the fibers in terms of transmission efficiency, resistance to high Er:YAG laser energy, and bending flexibility. The best-performing fiber was used to achieve deep bone ablation in a minimally invasive setting. To do this, we adapted the optimal settings for free-space deep bone ablation with an Er:YAG laser found in a previous study.
Three of the fibers endured energy per pulse as high as 820 mJ at a repetition rate of 10 Hz. The best-performing fiber, made of germanium oxide, provided higher transmission efficiency and greater bending flexibility than the other fibers. With an output energy of 370 mJ per pulse at 10 Hz repetition rate, we reached a cutting depth of 6.82 ± 0.99 mm in sheep bone. Histology image analysis was performed on the bone tissue adjacent to the laser ablation crater; the images did not show any structural damage.
The findings suggest that our prototype could be used in future generations of endoscopic devices for minimally invasive laserosteotomy.
骨骼主要成分的最高吸收峰位于中红外区域，这使得铒：钇铝石榴石（Er:YAG）和二氧化碳（CO2）激光成为切割骨骼最有效的激光。然而，在微创环境下进行深入骨消融的研究非常有限，因为要找到合适的材料来耦合高功率激光光，并且在 2 μm 以上的衰减较低并不简单。
本研究的首要目的是比较不同光纤在传输近 1 J 高脉冲能量的 2.94 μm 波长铒：YAG 激光时的性能。第二个目的是使用我们实验确定的性能最佳的光纤实现深骨消融。
在我们的研究中，使用具有低衰减（λ=2.94 μm）的各种光纤来耦合 Er:YAG 激光。光纤分别由氧化锗、蓝宝石、氟化锆和中空芯二氧化硅制成。我们比较了光纤的传输效率、对高 Er:YAG 激光能量的阻力和弯曲灵活性。使用性能最佳的光纤在微创环境下实现深骨消融。为此，我们采用了先前研究中发现的自由空间深骨消融的最佳 Er:YAG 激光设置。
三种光纤在重复率为 10 Hz 时能承受高达 820 mJ 的脉冲能量。性能最佳的光纤由氧化锗制成，与其他光纤相比，提供了更高的传输效率和更大的弯曲灵活性。在重复率为 10 Hz 时，输出能量为 370 mJ/脉冲，我们在绵羊骨中达到了 6.82±0.99 mm 的切割深度。对激光烧蚀坑附近的骨组织进行了组织学图像分析；图像未显示任何结构损伤。
研究结果表明，我们的原型可用于未来微创激光截骨术的内窥镜设备。
