Material ejection in nanosecond Er:YAG laser ablation of water, liver, and skin
Material ejection in nanosecond Er:YAG laser ablation of water, liver, and skin
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DOI：
10.1007/s00339-005-3213-5
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发表时间：
2005-07-01
影响因子：
2.7
通讯作者：
Vogel, A
中科院分区：
文献类型：
--
作者：
Apitz, I;Vogel, A
我们研究了Q开关Er：YAG激光组织消融（脉冲持续时间为70 ns）中的材料喷射机制，其中中等和大的辐射暴露与靶材料中的大体积能量密度相关。对于水，非平衡表面蒸发的初始阶段之后是表观液体体积从超临界状态的爆炸性蒸发。具有较低峰值温度的较深层的烧蚀作为相爆炸进行。对于机械强度强的组织，非平衡表面蒸发之后是蒸汽爆炸，伴随着生物分子热分解成挥发性产物。在更深层中，烧蚀以受限沸腾的形式进行，并通过蒸汽压机械撕裂组织基质。在5.4J/cm（2）的辐照量下产生的反冲应力在500-900 MPa的数量级。对于水和软组织，如肝脏，反冲导致强大的二次材料排出。对于更坚固的组织，如皮肤，即使回缩应力大大超过组织的静态拉伸强度，也没有观察到二次排出。烧蚀诱导的材料排出导致烧蚀效率和烧蚀的机械副作用两者的增加。在纳秒激光组织消融和反冲诱导的材料驱逐的相变序列的理论建模仍然是未来工作的一个重大挑战。
We investigated the mechanisms of material ejection in Q-switched Er:YAG laser tissue ablation (70-ns pulse duration) where moderate and large radiant exposures are associated with large volumetric energy densities in the target material. For water, an initial phase of non-equilibrium surface vaporization is followed by an explosive vaporization of the superficial liquid volume from a supercritical state. The ablation of deeper layers with lower peak temperatures proceeds as phase explosion. For mechanically strong tissues, non-equilibrium surface vaporization is followed by a vapour explosion coupled with thermal dissociation of the biomolecules into volatile products. In deeper layers, ablation proceeds as confined boiling with mechanical tearing of the tissue matrix by the vapour pressure. The recoil stress induced at a radiant exposure of 5.4J/cm(2) is in the order of 500-900 MPa. For water and soft tissues such as liver, the recoil causes a powerful secondary material expulsion. For stronger tissues such as skin, no secondary expulsion was observed even though the recoil stress largely exceeds the static tensile strength of the tissue. Recoil-induced material expulsion results in an increase of both ablation efficiency and mechanical side effects of ablation. Theoretical modelling of the succession of phase transitions in nanosecond-laser tissue ablation and of recoil-induced material expulsion remain a major challenge for future work.