Mitigating thermal mechanical damage potential during two-photon dermal imaging
Mitigating thermal mechanical damage potential during two-photon dermal imaging
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DOI：
10.1117/1.1806135
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发表时间：
2004-11-01
影响因子：
3.5
通讯作者：
Gratton, E
中科院分区：
文献类型：
--
作者：
Masters, BR;So, PTC;Gratton, E
双光子激发荧光显微镜可以对人体皮肤结构和生物化学进行体内高分辨率成像，穿透深度超过 100 μm。双光子皮肤成像过程中的主要损伤机制与表皮-真皮交界处空化的形成有关，从而导致组织的热机械损伤。在本报告中，我们验证了这种损伤机制是热起源的，并且与表皮-真皮交界处存在的黑色素颗粒对红外激发光的单光子吸收有关。已确定从皮肤库中选定的白种人皮肤样本的热机械损伤阈值，作为激光脉冲能量和重复率的函数。实验建立的热机械损伤阈值与飞秒脉冲激光照射下皮肤的简单热扩散模型一致。最大限度地减少热机械损伤对于双光子成像在人体皮肤体内无创光学活检中的潜在应用至关重要。我们描述了一种基于使用激光脉冲选择器来减轻样品热机械损伤的技术，该技术通过从激光脉冲串中选择一部分脉冲来降低激光重复率。由于激光脉冲选择器在保持激光脉冲峰值功率的同时降低了激光平均功率，因此可以最大限度地减少热机械损伤，同时最大限度地提高双光子荧光激发效率。
Two-photon excitation fluorescence microscopy allows in vivo high-resolution imaging of human skin structure and biochemistry with a penetration depth over 100 mum. The major damage mechanism during two-photon skin imaging is associated with the formation of cavitation at the epidermal-dermal junction, which results in thermal mechanical damage of the tissue. In this report, we verify that this damage mechanism is of thermal origin and is associated with one-photon absorption of infrared excitation light by melanin granules present in the epidermal-dermal junction. The thermal mechanical damage threshold for selected Caucasian skin specimens from a skin bank as a function of laser pulse energy and repetition rate has been determined. The experimentally established thermal mechanical damage threshold is consistent with a simple heat diffusion model for skin under femtosecond pulse laser illumination. Minimizing thermal mechanical damage is vital for the potential use of two-photon imaging in noninvasive optical biopsy of human skin in vivo. We describe a technique to mitigate specimen thermal mechanical damage based on the use of a laser pulse picker that reduces the laser repetition rate by selecting a fraction of pulses from a laser pulse train. Since the laser pulse picker decreases laser average power while maintaining laser pulse peak power, thermal mechanical damage can be minimized while two-photon fluorescence excitation efficiency is maximized.