Signal degradation by coherence tomography multiple scattering in optical of dense tissue: a Monte Carlo study towards optical clearing of biotissues
Signal degradation by coherence tomography multiple scattering in optical of dense tissue: a Monte Carlo study towards optical clearing of biotissues
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DOI：
10.1088/0031-9155/47/13/307
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发表时间：
2002-07-07
影响因子：
3.5
通讯作者：
Wang, RKK
中科院分区：
文献类型：
--
作者：
Wang, RKK
多重散射是限制光穿透生物组织的主要来源，从而阻碍了高分辨率光学成像技术对深层微结构的可视化。光学清除方法是生物医学光学中用于控制组织光学特性的一项新探索；例如，散射系数和光子的前向散射程度，通过使用化学给药方法来提高光学成像深度，特别是最近发展的光学相干层析成像（OCT）。本文系统地研究了多重散射如何影响信号衰减和定位，以及组织光学性质的改变如何增强光学成像深度和信号定位，特别是通过最小散射光子（LSP）和多散射光子（MSP）的单独考虑，利用蒙特卡罗模拟。LSP是那些贡献精确OCT信号的光子，即局部化，而MSP是那些降低OCT信号的光子。结果表明，不论是降低散射系数还是增加前向散射程度，OCT的信号定位和成像深度都得到增强。虽然介质各向异性因子的增加在改善信号定位方面更有效，但它为LSP和MSP在组织内传播的光子引入了更多的散射事件，还发现OCT成像分辨率几乎随着探测深度的增加而呈指数下降，而不是声称的系统分辨率。我们证明了当光逐渐穿透高散射介质时，光学清除可以成为提高成像分辨率的有用工具。实验结果也直观地显示了多次散射对脂肪内溶液和健康人全血（分别为中等和高度散射介质）OCT信号分布的影响。
Multiple scattering is a major source that limits light penetration into biotissues, thereby preventing visualization of the deep microstructures for high-resolution optical imaging techniques. The optical clearing approach is a new adventure in biomedical optics for manipulating the optical properties of tissue; for example, the scattering coefficient and the degree of forward scattering of photons, by the use of the chemical administration method in order to improve the optical imaging depth, particularly for the recently developed optical coherence tomography (OCT). This paper investigates systematically how the multiple scattering affects signal attenuation and localization in general, and how the alterations of optical properties of tissue enhance the optical imaging depth and signal localization in particular, by the use of Monte Carlo simulations through the separate considerations of the least scattered photons (LSP) and multiple scattered photons (MSP). The LSP are those photons that contribute to the precise OCT signal, i.e. localization, and the MSP are those that degrade the OCT signal. It is shown that with either the reduction of the scattering coefficient or the increase of the degree of forward scattering, signal localization and imaging depth for OCT is enhanced. Whilst the increase of the anisotropic factor of the medium is more efficient in improving signal localization, it introduces more scattering events for the photons travelling within the tissue for both the LSP and MSP, It is also found that the OCT imaging resolution is almost reduced exponentially with the increase of the probing depth as opposed to the claimed system resolution. We demonstrate that optical clearing could be a useful tool to improve the imaging resolution when the light progressively penetrates the high scattering medium. Experimental results are also presented to show intuitively how multiple scattering affects OCT signal profiles by the use of intralipid solution and healthy human whole blood, representing moderately and highly scattering media respectively.