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首页> 外文会议>Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-Optics >Subsurface photodisruption in pig skin as monitored by high-frequency ultrasound
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Subsurface photodisruption in pig skin as monitored by high-frequency ultrasound

机译：高频超声监测猪皮肤的地下光探测

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For diagnostic or therapeutic technologies using femtosecond laser-induced optical breakdown (LIOB) in turbid biological tissues, pulses of sufficient fluence must be delivered to the site of interest. As light attenuates and diffuses rapidly due to wavelength-dependent absorption and scattering, it is important to develop penetration optimization schemes. In this study, we use a high frequency (50MHz) ultrasonic technique to investigate the precision and penetration depth limitations of infrared femtosecond laser-induced photodisruption in excised pig skin. Optical parameters varied include laser fluence (energy density in J/cm2) and focusing numerical aperture. Our ultrasonic method uses sensitive detection of laser-induced bubbles to measure breakdown extent. Using a geometrically focused Nd:Glass laser (1053 nm, 800 fs) source, we show that acoustically detectable bubbles can be produced as deep as 900 um into excised porcine skin. As penetration exceeds several hundred microns, however, multiple bubbles stacked at different depths can be produced with a single laser excitation. Secondary bubble creation is more likely at supra-threshold fluences or with low NA (≤ 0.4) focusing, where optical self-focusing may occur near threshold fluences. However, as the numerical aperture is increased (> 0.4) for deeper focusing, aberrations can severely distort the beam, increasing the perceived LIOB-threshold with maximal penetrations of less than 500um. Using an index matching fluid (i.e. aqueous glycerol solutions) to help reduce scattering, we are able to improve penetration. However, multiple breakdown sites and the corresponding reduction in precision is still likely in skin even with glycerol treatment.
机译：对于使用Femtosecond激光诱导的光学击穿（Liob）在浑浊的生物组织中的诊断或治疗技术，必须向感兴趣部位提供足够的流量的脉冲。随着光衰减和扩散由于波长依赖性吸收和散射而迅速地扩散，重要的是开发穿透优化方案。在这项研究中，我们使用高频（50MHz）超声波技术来研究红外飞秒激光诱导的切除猪皮肤的精度和穿透深度局限。光学参数变化包括激光流量（J / CM2中的能量密度）和聚焦数值孔径。我们的超声波方法使用激光诱导气泡的敏感检测来测量击穿程度。使用几何聚焦的ND：玻璃激光器（1053nm，800 fs）来源，我们表明声学可检测的气泡可以像900μm一样深入生产成低烧的猪皮。然而，由于渗透超过数百微米，可以通过单一激光激发产生在不同深度处堆叠的多个气泡。二次泡沫创建更有可能在Supra阈值流量或低Na（≤0.4）聚焦，其中光学自聚焦可能发生接近阈值流量。然而，随着数字孔径增加（> 0.4），对于更深的聚焦，像差可能会严重扭曲光束，从而增加具有小于500um的最大渗透的感知的LioB阈值。使用指数匹配的液体（即甘油溶液水溶液）以帮助减少散射，我们能够改善渗透。然而，即使使用甘油处理，也可能在皮肤上进行多次击穿位点和相应的抑制性。

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