Mackanos Mark A, Simanovskii Dmitrii, Joos Karen M, Schwettman H Alan, Jansen E Duco
Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA.
Lasers Surg Med. 2007 Mar;39(3):230-6. doi: 10.1002/lsm.20461.
Investigations with a Mark-III free electron laser, tuned to 6.45 microm in wavelength have demonstrated minimal collateral damage and high ablation yield in ocular and neural tissues. While the use of mid-IR light produced by the free electron laser (FEL) has shown much promise for surgical applications, further advances are limited due the high costs of its use. Further investigation and widespread clinical use of six-micron radiation requires the development of an alternative laser source. In this research, we compared a Mark-III FEL and an Er:YAG pumped ZGP-OPO with respect to the effect of pulse duration on ablation efficiency and thermal damage on porcine cornea.
STUDY DESIGN/MATERIALS AND METHODS: A five by seven grid of craters was made about the center of each cornea. Craters were made with a 60-microm spotsize with a 500-microm spacing. Ablation craters were made using 50 pulses per crater at approximately three times the ablation threshold (for water). Histological analysis was used to determine crater depth and thermal damage.
The average zone of thermal damage at 6.1 microm was found to be 4.1 microm for the optical parametric oscillator (OPO) and 5.4 microm for the FEL. At 6.45 microm, the damaged zone was 7.2 microm for the OPO and 7.2 microm for the FEL. At 6.73 microm, the damaged zone was 6.3 microm for the OPO and 7.6 microm+/-0.3 microm for the FEL.
The OPO caused similar or significantly less thermal damage in porcine cornea when compared with the FEL while generating significantly deeper craters. We determined that the ZGP-OPO has much promise as a bench-top replacement for the FEL for soft tissue ablation.
使用波长调谐至6.45微米的Mark-III自由电子激光进行的研究表明，在眼部和神经组织中，附带损伤最小且消融率高。虽然自由电子激光（FEL）产生的中红外光在手术应用中显示出很大前景，但由于使用成本高昂，进一步的进展受到限制。六微米辐射的进一步研究和广泛临床应用需要开发替代激光源。在本研究中，我们比较了Mark-III自由电子激光和掺铒钇铝石榴石泵浦的ZGP光参量振荡器（OPO）在脉冲持续时间对猪角膜消融效率和热损伤的影响方面的差异。
研究设计/材料与方法：在每个角膜中心周围制作一个5×7的弹坑网格。弹坑采用60微米光斑尺寸，间距为500微米。每个弹坑使用50个脉冲进行消融，能量约为消融阈值（针对水）的三倍。采用组织学分析来确定弹坑深度和热损伤。
发现对于光参量振荡器（OPO），在6.1微米处热损伤的平均区域为4.1微米，对于自由电子激光（FEL）为5.4微米。在6.45微米处，OPO的损伤区域为7.2微米，FEL为7.2微米。在6.73微米处，OPO的损伤区域为6.3微米，FEL为7.6±0.3微米。
与自由电子激光相比，光参量振荡器在猪角膜中造成的热损伤相似或显著更小，同时产生的弹坑明显更深。我们确定ZGP光参量振荡器作为自由电子激光用于软组织消融的台式替代品具有很大前景。
