Acoustic estimation of thermal distribution in the vicinity of femtosecond laser-induced optical breakdown.
Acoustic estimation of thermal distribution in the vicinity of femtosecond laser-induced optical breakdown.
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飞秒激光引起的光学击穿附近热分布的声学估计。
DOI：
10.1109/tbme.2006.877111
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
O'Donnell,Matthew
中科院分区：
文献类型：
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作者：
Zohdy,MarwaJ;Tse,Christine;Ye,JingYong;O'Donnell,Matthew
激光诱导光击穿（LIOB）或光破坏可以在生物医学应用的组织中产生单个微泡。我们之前已经开发了一种共定位高频超声系统来检测和表征这些激光诱导的微泡。由于超声速度随温度变化，该系统也可用于直接估计光破坏附近的热效应。在这项研究中，使用脉冲频率为250 kHz的793 nm， 100 fs的Ti:Sapphire激光，在水箱底部产生了单个气泡（大小为60-100 mum）。击穿期间和击穿后，使用单元件85-MHz超声波换能器记录罐底气泡周围区域的脉冲回波，并使用相敏相关跟踪计算温度相关脉冲回波位移。然后将这些位移拟合到一个有限元传热模型中，以估计有效的热分布。在1.5和4 J/cm2的影响下，计算了激光曝光时间范围为6.25至312.5 ms（1600至78000激光脉冲）的估计值。结果表明，在1.5 J/cm2fluence条件下，当激光脉冲小于1600个时，产生的气泡在100 μ m内温度升高最小（<1℃）。这意味着在气泡附近，LIOB可以被控制为热无创
Laser-induced optical breakdown (LIOB), or photodisruption, can generate individual microbubbles in tissues for biomedical applications. We have previously developed a co-localized high-frequency ultrasound system to detect and characterize these laser-induced microbubbles. Because ultrasound speed varies with temperature, this system can also be used to directly estimate thermal effects in the vicinity of photodisruption. In this study, individual bubbles (sizes 60-100 mum) were created at the bottom of a water tank using a 793-nm, 100-fs Ti:Sapphire laser pulsed at 250 kHz. During and after breakdown, pulse-echoes from the tank bottom in the region surrounding a bubble were recorded with a single-element 85-MHz ultrasonic transducer, and temperature-dependent pulse-echo displacements were calculated using phase-sensitive correlation tracking. These displacements were then fit to a finite-element heat transfer model to estimate the effective thermal distribution. Estimates were calculated for laser exposure times ranging from 6.25 to 312.5 ms (1600 to 78 000 laser pulses), at 1.5 and 4 J/cm2fluences. Results suggest a minimal temperature increase (<1deg C) within 100 mum of a bubble created with <1600 laser pulses at 1.5 J/cm2fluence. This implies that LIOB can be controlled to be thermally noninvasive in the bubble vicinity