Biomedical Laser and Optics Group (BLOG), Department of Biomedical Engineering, University of Basel, CH-4123, Allschwil, Switzerland.
Digital Dermatology, Department of Biomedical Engineering, University of Basel, CH-4123, Allschwil, Switzerland.
Lasers Med Sci. 2023 Sep 26;38(1):222. doi: 10.1007/s10103-023-03886-z.
Thermal effects during bone surgery pose a common challenge, whether using mechanical tools or lasers. An irrigation system is a standard solution to cool the tissue and reduce collateral thermal damage. In bone surgery using Er:YAG laser, insufficient irrigation raises the risk of thermal damage, while excessive water lowers ablation efficiency. This study investigated the potential of optical coherence tomography to provide feedback by relating the temperature rise with the photo-thermal expansion of the tissue. A phase-sensitive optical coherence tomography system (central wavelength of λ=1.288 μm, a bandwidth of 60.9 nm and a sweep rate of 104.17 kHz) was integrated with an Er:YAG laser using a custom-made dichromatic mirror. Phase calibration was performed by monitoring the temperature changes (thermal camera) and corresponding cumulative phase changes using the phase-sensitive optical coherence tomography system during laser ablation. In this experiment, we used an Er:YAG laser with 230 mJ per pulse at 10 Hz for ablation. Calibration coefficients were determined by fitting the temperature values to phase later and used to predict the temperature rise for subsequent laser ablations. Following the phase calibration step, we used the acquired values to predict the temperature rise of three different laser-induced cuts with the same parameters of the ablative laser. The average root-mean-square error for the three experiments was measured to be around 4 °C. In addition to single-point prediction, we evaluated this method's performance to predict the tissue's two-dimensional temperature rise during laser osteotomy. The findings suggest that the proposed principle could be used in the future to provide temperature feedback for minimally invasive laser osteotomy.
在进行骨外科手术时，无论是使用机械工具还是激光，热效应都是一个常见的挑战。冲洗系统是冷却组织和减少热损伤的标准解决方案。在使用铒：YAG 激光进行骨外科手术时，冲洗不足会增加热损伤的风险，而过度的水会降低消融效率。本研究通过将组织的温升与光热膨胀相关联，探讨了光相干断层扫描技术提供反馈的潜力。一个相敏光相干断层扫描系统（中心波长为 λ=1.288 μm，带宽为 60.9nm，扫描速率为 104.17 kHz）与一个定制的二向色镜一起集成到 Er:YAG 激光中。通过在激光烧蚀过程中使用热像仪监测温度变化（热像仪）和使用相敏光相干断层扫描系统相应的累积相位变化，进行相位校准。在这个实验中，我们使用了一个 Er:YAG 激光，每个脉冲 230mJ，频率为 10Hz 进行烧蚀。通过将温度值拟合到相位后期，确定校准系数，并用于预测随后的激光烧蚀的温升。在相位校准步骤之后，我们使用所获得的值来预测三个具有相同消融激光参数的不同激光诱导切割的温升。三个实验的平均均方根误差被测量为约 4°C。除了单点预测外，我们还评估了这种方法在预测激光截骨术中组织二维温升方面的性能。研究结果表明，所提出的原理将来可用于为微创激光截骨术提供温度反馈。
