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单纤维反射光谱的蒙特卡罗分析:光子路径长度和采样深度。

Monte Carlo analysis of single fiber reflectance spectroscopy: photon path length and sampling depth.

机构信息

Center for Optical Diagnostics and Therapy, Department of Radiation Oncology, Erasmus Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands.

出版信息

Phys Med Biol. 2009 Nov 21;54(22):6991-7008. doi: 10.1088/0031-9155/54/22/016. Epub 2009 Nov 4.

Abstract

Single fiber reflectance spectroscopy is a method to noninvasively quantitate tissue absorption and scattering properties. This study utilizes a Monte Carlo (MC) model to investigate the effect that optical properties have on the propagation of photons that are collected during the single fiber reflectance measurement. MC model estimates of the single fiber photon path length (L(SF)) show excellent agreement with experimental measurements and predictions of a mathematical model over a wide range of optical properties and fiber diameters. Simulation results show that L(SF) is unaffected by changes in anisotropy (g epsilon [0.8, 0.9, 0.95]), but is sensitive to changes in phase function (Henyey-Greenstein versus modified Henyey-Greenstein). A 20% decrease in L(SF) was observed for the modified Henyey-Greenstein compared with the Henyey-Greenstein phase function; an effect that is independent of optical properties and fiber diameter and is approximated with a simple linear offset. The MC model also returns depth-resolved absorption profiles that are used to estimate the mean sampling depth (Z(SF)) of the single fiber reflectance measurement. Simulated data are used to define a novel mathematical expression for Z(SF) that is expressed in terms of optical properties, fiber diameter and L(SF). The model of sampling depth indicates that the single fiber reflectance measurement is dominated by shallow scattering events, even for large fibers; a result that suggests that the utility of single fiber reflectance measurements of tissue in vivo will be in the quantification of the optical properties of superficial tissues.

摘要

单纤维反射光谱是一种无创定量组织吸收和散射特性的方法。本研究利用蒙特卡罗(MC)模型研究了在单纤维反射测量过程中收集的光子传播过程中光学性质的影响。MC 模型对单纤维光子路径长度(L(SF))的估计与实验测量和数学模型的预测在广泛的光学性质和纤维直径范围内非常吻合。模拟结果表明,L(SF)不受各向异性变化的影响(g epsilon [0.8, 0.9, 0.95]),但对相位函数的变化敏感(Henyey-Greenstein 与修正 Henyey-Greenstein)。与 Henyey-Greenstein 相位函数相比,修正的 Henyey-Greenstein 相位函数导致 L(SF)减少 20%;这种效应与光学性质和纤维直径无关,可以用简单的线性偏移来近似。MC 模型还返回深度分辨的吸收分布,用于估计单纤维反射测量的平均采样深度(Z(SF))。模拟数据用于定义一个新的数学表达式,用于表示 Z(SF),它与光学性质、纤维直径和 L(SF)有关。采样深度模型表明,即使对于大纤维,单纤维反射测量也主要由浅层散射事件主导;这一结果表明,单纤维反射测量组织在体内的应用将在于对浅层组织的光学性质进行定量分析。

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