Quantifying spatial localization of optical mapping using Monte Carlo simulations

Optical mapping techniques used to study spatial distributions of cardiac activity can be divided into two categories. 1) Broad-field excitation method, in which hearts stained with voltage or calcium sensitive dyes are illuminated with broad-field excitation light and fluorescence is collected by image or photodiode arrays. 2) Laser scanning method, in which illumination uses a scanning laser and fluorescence is collected with a photomultiplier tube. The spatial localization of the fluorescence signal for these two methods is unknown and may depend upon light absorption and scattering at both excitation and emission wavelengths. We measured the absorption coefficients (micro a), scattering coefficients (micro s), and scattering anisotropy coefficients (g) at representative excitation and emission wavelengths in rabbit heart tissue stained with di-4-ANEPPS or co-stained with both Rh237 and Oregon Green 488 BAPTA 1. Monte Carlo models were then used to simulate absorption and scattering of excitation light and fluorescence emission light for both broad-field and laser methods in three-dimensional tissue. Contributions of local emissions throughout the tissue to fluorescence collected from the tissue surface were determined for both methods. Our results show that spatial localization depends on the light absorption and scattering in tissue and on the optical mapping method that is used. A tissue region larger than the laser beam or collecting area of the array element contributes to the optical recordings.     

KubelkaMunk 模型下的人动脉组织对氦氖激光的光学特性

本文测量了人动脉对He-Ne激光的反射和透射传输特性。实验采用两积分球系统及波长为632.8nm的He-Ne激光器,并根据测量数据采用Kubelka-Munk模型分析和计算了人动脉组织对该波长激光的吸收系数、散射系数及总的光强I(x)及前向散射通量i(x)和后向散射通量j(x)的变化情况。结果表明,不同的动脉组织的漫反射率和透射率有明显差别,而且,不同的动脉组织对激光的吸收系数和散射系数也有明显的不同,不同的动脉组织中总的光强I(x)及前向散射通量i(x)和后向散射通量j(x)的变化情况也有明显的区别。     

Kubelka—Munk模型下的人血管对632．8nm氦—氖激光的散射与吸收特性

本文测量了人动脉和静脉对He-Ne激光的反射和透射传输特性。实验采用两积分球系统及波长为632．8nm的He-Ne激光器,并根据测量数据及采用Kubelka-Munk模型分析和计算了人动脉和静脉组织对该波长激光的吸收系数、散射系统及总的光强I（x)及前向散射通量i(x)和后向散射通量j(x)的变化情况。结果表明,人动脉和静脉内外侧的漫反射率和透射率有明显差别,而且,动脉对激光的吸收系数明显较静脉的要小,而动脉对激光的散射系数却明显较静脉的要大,在动脉和静脉组织中总的光强I（x）及前向散射通量i(x)和后向散射通量j(x)的变化情况也有明显的区别。     

Dynamics of temperature dependent optical properties of tissue:dependence on thermally induced alteration

Thermal damage in heated bovine myocardial tissue is assessed from measured changes in total reflection and transmission of light. Mathematical expressions, based on random walk analysis of light propagation within tissue slabs, are used to relate the diffuse reflection and transmittance to the absorption coefficient, μ_a , and effective scattering coefficient, μ'_s for samples of myocardial tissue which were subjected to rapid step changes in temperature. Time-dependent changes in μ'_s indicate two processes, one with a fast and temperature-dependent rate the other with a slow and apparently temperature-independent rate. For final temperatures above 56.8°C and for the first 500 s after the temperature change, the optical parameters are well fit by exponential forms that exhibit temperature-dependent time constants as predicted by Arrhenius reaction rate theory of thermal damage. The scattering changes are associated with an apparent activation energy, ΔE, of 162 kJ/mole and a frequency constant, A, of 3×10²³ s^-1 . This method provides a means for estimating optical coefficients which are needed to assess laser tissue dosimetry     

Kubelka-Munk模型下人血管对He-Ne激光的散射与吸收特性

测量了人动脉和静脉对He Ne激光的反射和透射传输特性。实验采用两积分球系统及波长为 6 32 8nm的He Ne激光器 ,并根据测量数据及采用Kubelka Munk模型分析和计算了人动脉和静脉组织对该波长激光的吸收系数、散射系数及总的光强I(x)及前向散射通量i(x)和后向散射通量 j(x)随厚度的变化情况。结果表明 ,人动脉和静脉的漫反射率和透射率有明显差别 ,而且 ,动脉对激光的吸收系数和散射系数明显较静脉的大 ,在动脉和静脉组织中I(x) ,i(x)和 j(x) 随厚度的变化情况也有明显的区别。     

随机分布反馈光纤激光器研究进展

随机分布反馈光纤激光器(RDFFL)是近几年才发展起来的一种新型光纤激光器。它在结构上区别于传统激光器,即无反射镜,激光的反馈通过光纤中随机分布的背向瑞利散射效应实现,因此是一种随机激光器。RDFFL通过光纤中的分布式拉曼散射效应获得增益,可实现稳定的、空间不相干的连续激光输出,被认为是一种重要的新光源,可用于非线性光学、光通信和传感等领域。对RDFFL的研究进展进行了综述,阐明了其工作原理,从理论上分析了其工作特性,并分析了其应用与发展前景。     

Kubelka—Munk模型下的兔血管对496．5nmAr^＋激光的散射与吸收特性

本文测量了兔动脉和静脉对Ar^ 激光的反射和透射传输特性。实验采用两积分球系统及波长为496．5nm的Ar^ 激光器,并根据测量数据及采用Kubelka-Munk模型分析和计算了兔动脉和静脉组织对该波长激光的吸收系数、散射系数及总的光强I（x)、前后散射通量i(x)和后向散射能量j(x)随厚度的变化情况。结果表明,兔动脉和静脉的漫反射率和透射率有明显差别,动脉对激光的吸收系数明显较静脉的要小,而动脉对激光的散射系数却明显较静脉的要大。在动脉和静脉组织中总的光强I（x)及前向散射通量i(x)和后向散射通量j(x)随厚度的变化情况也有明显的区别。     

基于激光散射图像小麦叶片叶绿素检测研究

为了实现叶绿素含量的无损检测研究,采用激光后向散射图像技术来测量小麦叶片光学特性参量的方法,进行了理论分析和实验验证。利用670nm和970nm的半导体激光器和视频成像系统获得了小麦叶片的激光后向散射图像,通过漫反射理论分析了叶片组织表面的漫射光分布和在这两个波长下绿叶、黄叶、干叶的激光后向散射图像的变化特征,取得了其光学特性参量数据(约化散射系数和吸收系数),并与叶片的叶绿素相对含量值建立对应的函数关系。结果表明,小麦叶片的光学特性参量与叶绿素相对含量值呈现线性相关,其中利用约化散射系数建立的叶绿素相对含量值预测模型中,预测集样本的相关系数为0.9095,预测均方根误差为5.9;利用吸收系数建立的叶绿素相对含量值预测模型中,预测集样本的相关系数为0.8366,预测均方根误差为7.5,说明激光后向散射图像技术测定植物叶绿素含量是可行的。这一结果对激光散射图像实现农作物长势诊断是有帮助的。     

Kubelka Munk模型上人静脉组织的光学特性

本文测量了人静脉对He-Ne激光的反射和透射传输特性，实验采用两积分球系统和波长为632.8nm的He-Ne激光器，并根据测量数据及采用Kubelka-Munk（K-M）模型分析和计算了人静脉组织对该波长激光器的吸收系数，散射系数及总的光强I（x）及前向散射通量i（x)和后向散射通量j(x)的变化情况，结果表明，不同的静脉组织的漫反射率和透射率有明显差别，对激光的吸收系数和散射系数也有明显的不同：I(x）、i(x）和j(x)的变化情况也有明显的区别。     

A Note on the Theory of Backscattering of Light by Living Tissue

A set of equations derived to describe the optics of highly scattering materials are explained, extended, and applied to the problem of in vitro and in vivo measurement of the relative oxygen saturation of nonhemolyzed blood. Fundamental absorption and scattering coefficients are described and related to the absorption coefficient of hemolyzed blood. Diffusion equations for light photons are used to solve the scattering problem in a three-dimensional system that may be useful for in vivo oxyhemoglobin measurements. Crude application to published data from in vitro measurements on nonhemolyzed blood indicates that the scattering coefficient of whole blood is probably not very wavelength-dependent.     

Kubelka-Munk模型下的兔血管对Ar+激光的散射与吸收特性

测量了兔动脉和静脉对Ar+激光的反射和透射传输特性.实验采用两积分球系统及Ar+激光器,并根据测量数据和采用Kubelka-Munk模型分析、计算了兔动脉与静脉组织对该波长激光的吸收系数、散射系数、总光强I(x)及前向散射通量i(x)和后向散射通量j(x)随厚度的变化情况.结果表明,兔动脉与静脉的漫反射率和透射率有明显差别,且动脉对激光的吸收系数明显较静脉的小,而动脉对激光的散射系数却明显较静脉的大,在动脉和静脉组织中总光强I(x)、前向散射通量i(x)和后向散射通量j(x)随厚度的变化情况也有明显的区别.     

K-M模型下的兔血管对Ar~+激光的散射与吸收特性

本文测量了兔动脉和静脉对 Ar+ 激光的反射和透射传输特性。实验采用两积分球系统及波长为476 .5 nm的 Ar+激光器 ,并根据测量数据采用 Kubelka- Munk模型分析了兔动脉和静脉组织对该波长激光的吸收系数、散射系数及总光强 I(x)及前向散射通量 i(x)和后向散射通量 j(x)随厚度的变化情况。结果表明 ,兔动脉和静脉的漫反射率和透射率有明显差别 ;动脉对激光的吸收系数明显较静脉的要小 ;而动脉对激光的散射系数却明显较静脉的要大 ;在动脉和静脉组织中 I(x)及 i(x)和 j(x)随厚度的变化也有明显的区别     

K—M模型下的兔血管对Ar＋激光的散射与吸收特性

本文测量了兔动脉和静脉对Ar 激光的反射和透射传输特性,实验采用两积分球系统及波长为476．5nm的Ar 激光器,并根据测量数据采用Kubelka-Munjk模型分析了兔动脉和静脉组织对该波长激光的吸收系数,。散射系数及总光强I（x)及前向散射通量i(x)和后向散射通量j(x) 随厚度的变化情况,结果表明;兔动脉和静脉的漫反射率和透射率有明显判别,动脉对的吸收系数明显较静脉的要小,而动脉对激光的散射系数对明显较静脉的要大,在动脉和静脉组织中I（x)及i(x)和j(x)随厚度的变化也有明显的区别。     

饱和线性吸收情况下克尔介质中的激光相移研究

研究强场激光入射时饱和吸收效应对非线性激光相移的影响,由量子光学出发,进行推导,对线性吸收系数进行修正,应用克尔介质的动力学方程,根据薄介质近似,得到非线性相移在介质出射面处的横向分布。     

Reducing shadowing losses with femtosecond‐laser‐written deflective optical elements in the bulk of EVA encapsulation

A new approach on decreasing the optical shadowing of the solar cell grid fingers is presented. The approach relies on a local change of the optical properties in the bulk of the photovoltaic module encapsulation material ethylene vinyl acetate (EVA). In particular, scattering and diffractive optical elements are locally generated within the volume of cross‐linked EVA encapsulation material by applying a femtosecond‐laser‐writing process. When these optical elements are located above the metal grid fingers, the optical shadowing of these grid fingers can be decreased. In an experimental proof of concept, the optical performance of this approach is demonstrated. The best results obtained so far indicate a decrease in optical shadowing by 17%. The material characteristics of the volume optics were investigated by applying confocal Raman microscopic characterisation, which indicates that the EVA material partially degraded upon the impact of the laser beam and is partly carbonised. Supplementary optical simulations show that the light deflection is caused by diffraction. However, parasitic absorption substantially deteriorates the optical performance of the deflective volume optics. Copyright © 2014 John Wiley & Sons, Ltd.     

中国人血液的组织光学参数

本文介绍了血液组织光学特性的测量原理与方法，并测量获得了不同血型的中国人血液的组织光学参数，包括血液吸收系数、散射系数、全衰减系数、平均散射余弦、有效衰减系数和穿透深度等。本研究对激光照射血液疗法以及其它激光照射人体组织的诊断与治疗，具有重要的实用或参考价值。     

采用空间分辨漫反射测定胃组织光学特性

研究了人正常胃黏膜及黏膜下层组织对488 nm,514.5 nm,532 nm,630 nm和632.8 nm的激光的光学特性及其差异,实验采用空间分辨反射光和CCD探测器以及非线性拟合确定组织光学特性。结果表明,人正常胃黏膜及黏膜下层组织对五个波长的激光的吸收系数、约化散射系数、光学穿透深度、漫射系数、漫反射率和漫反射率的位移都是随着激光波长的变化而变化的。其吸收系数的最大值在532 nm,其值为0.482 mm-1,最小值在632.8 nm,其值为0.224 mm-1,最大差异在532 nm和632.8 nm之间,其值为115%,最小差异在488 nm和532 nm之间,其值为1.90%。其约化散射系数的最大值在488 nm,其值为5.93 mm-1,最小值在632.8 nm,其值为3.87 mm-1,最大差异在488 nm和632.8 nm之间,其值为53.2%,最小差异在514.5 nm和532 nm之间,其值为3.25%。其光学穿透深度的最大值在632.8 nm,其值为0.612 mm,最小值在488 nm,其值为0.341 mm。其漫射系数的最大值在632.8 nm,其值为0.084 mm,最小值在488 nm,其值为0.055 mm。其漫反射率的最大值在630 nm,其值为0.356,最小值在532 nm,其值为0.271。其Δx的最大值在632.8 nm,其值为0.153 mm,最小值在488 nm,其值为0.100 mm。可见,人正常胃黏膜/黏膜下层组织对五个波长的激光的光学特性参数存在明显的差异。     

人肝组织病变及热凝固导致组织光学特性的变化

研究了人肝的病变及热凝固的肝组织对532 nm和1064 nm激光的光学特性的变化。实验采用双积分球测量系统以及运用生物组织的反向倍增(IAD)光学模型。结果表明,正常肝组织对532 nm和1064 nm的吸收系数显著地较肝肿瘤组织要大;正常肝和肝肿瘤组织热凝固后对532 nm的吸收系数都显著地增大,正常肝组织热凝固后对1064 nm的吸收系数显著减小。而肝肿瘤组织热凝固后对1064 nm的吸收系数却显著地增大。正常肝组织对532 nm和1064 nm的散射系数都显著地较肝肿瘤组织要小,正常肝和肝肿瘤组织热凝固后散射系数都显著地增大。正常肝组织对532 nm和1064 nm的各向异性因子都明显地较肝肿瘤组织要大,正常肝和肝肿瘤组织热凝固后其各向异性因子都明显地减小。     

混浊介质参数对超短脉冲激光透射强度与形状的影响

以扩散近似理论为基础,考虑输入超短激光脉冲之后,研究了介质厚度ｄ,吸收系数μａ,散射系数μｓ及各向异性系数ｇ分别对脉冲透射的定量影响。