Laloš Jernej, Gregorčič Peter, Jezeršek Matija
Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva cesta 6, 1000 Ljubljana, Slovenia.
Biomed Opt Express. 2018 Mar 26;9(4):1893-1905. doi: 10.1364/BOE.9.001893. eCollection 2018 Apr 1.
We present an optical study of elastic wave propagation inside skin phantoms consisting of agar gel as induced by an Er:YAG (wavelength of 2.94 μm) laser pulse. A laser-beam-deflection probe is used to measure ultrasonic propagation and a high-speed camera is used to record displacements in ablation-induced elastic transients. These measurements are further analyzed with a custom developed image recognition algorithm utilizing the methods of particle image velocimetry and spline interpolation to determine point trajectories, material displacement and strain during the passing of the transients. The results indicate that the ablation-induced elastic waves propagate with a velocity of 1 m/s and amplitudes of 0.1 mm. Compared to them, the measured velocities of ultrasonic waves are much higher, within the range of 1.42-1.51 km/s, while their amplitudes are three orders of magnitude smaller. This proves that the agar gel may be used as a rudimental skin and soft tissue substitute in biomedical research, since its polymeric structure reproduces adequate soft-solid properties and its transparency for visible light makes it convenient to study with optical instruments. The results presented provide an insight into the distribution of laser-induced elastic transients in soft tissue phantoms, while the experimental approach serves as a foundation for further research of laser-induced mechanical effects deeper in the tissue.
我们展示了一项光学研究，该研究针对由掺铒钇铝石榴石（波长为2.94μm）激光脉冲诱导产生的、在由琼脂凝胶构成的皮肤模型内部的弹性波传播。使用激光束偏转探头来测量超声波传播，并使用高速相机记录消融诱导的弹性瞬变中的位移。利用粒子图像测速法和样条插值法的方法，通过定制开发的图像识别算法对这些测量结果进行进一步分析，以确定瞬变过程中的点轨迹、材料位移和应变。结果表明，消融诱导的弹性波以1m/s的速度传播，振幅为0.1mm。与之相比，所测量的超声波速度要高得多，在1.42 - 1.51km/s范围内，而其振幅则小三个数量级。这证明琼脂凝胶可作为生物医学研究中一种基本的皮肤和软组织替代物，因为其聚合物结构再现了足够的软固体特性，并且其对可见光的透明度使得使用光学仪器进行研究很方便。所呈现的结果提供了对软组织模型中激光诱导弹性瞬变分布的深入了解，而该实验方法为进一步研究组织更深层的激光诱导机械效应奠定了基础。
