漫射光子密度波在生物组织内部传输特性的模拟和实验研究

【作者】 虞勇坚；

【导师】 倪晓武； 朱拓；

【作者基本信息】 南京理工大学 ， 生物医学工程， 2004， 硕士

【摘要】 本文从模拟和实验这两个角度详细地研究了在连续光源照射下漫射光子密度波在生物组织内部的传输特性，以及组织内部含有异物时对漫射光子密度波传输的影响。 根据漫射光子密度波的理论，编制了可以动态显示光子在组织内部的传输过程、可以在程序界面上直接输入组织的光学参数和光源参数、可以用灰度图像和数据方式给出运算结果的Monte Carlo程序，结果直观且便于分析。 利用编制的程序，进行了大量的模拟，得到了在改变生物组织光学参数时对光子在组织体内部传输的影响，发现了一些新的现象，并作了解释。讨论了多层组织的情况，特别是对单层组织内部含有异物的情景也作了模拟和分析。结果显示，用Monte Carlo模拟的方法可以探测到具有一定大小和位置的异物。 实验上首先用650nm的半导体激光定性的研究了650nm的半导体激光在穿透稀牛奶溶液(质量比约10^-5量级)时，隐藏在溶液内的异物的可见度变化以及透射面上光斑的变化情况。结果表明，随着溶液中散射粒子浓度的增大，原先隐藏在溶液中的异物逐渐变得清晰，但同时透射面上的光斑也逐渐变小直至消失，而溶液却逐渐显得明亮起来。 本文分析了在生物组织诊断中应该选用的最佳波长，设计了激光发射系统和偏压式光电探测器。用幅度探测的方式，对0.3cm厚单层猪肉组织和（0.2cm+0.4cm）厚双层猪肉组织的透射光强分布以及组织体内部含有异物时透射光强分布的变化进行了探测，从由实验数据还原以后光强分布图上可以明显看到较大异物（如直径2.5mm的石墨棒）的存在，但是对较小的异物（如直径0.5mm的石墨棒）却无法识别，一方面是由于异物的大小和所处的位置的原因，另一方面是由于探测器分辨率的不足的原因故无法探测到。文章最后选用同样的组织参数进行了模拟，实验结果和模拟吻合较好。 本文的工作一方面说明Monte Carlo方法是模拟光子在生物组织内部传输的有效方法，另一方面也从模拟和实验的角度证明了漫射光子密度波技术是可以探测到组织内部的隐藏异物的。本文的研究可为组织光学、光子医学生物学、医疗诊断等领域提供实验依据和参考价值。更多还原

【Abstract】 In this article the property of DPDW transmitting through Bio-Tissue produced by illuminating of continuous waves was studied in simulations and experiments. The effect to the transmittance of DPDW when an abnormal object was contained in tissue was also discussed.On the basics of DPDW’s theory, a program that could show the process when a photon walk through the tissue and the parameters of source and tissue could be inputted on the interface and the result can be given with gray pictures and TXT documents was programmed. The result was simple and could be analyzed easily.By making full use of the program to simulate the spread of photons when changing the parameters of tissue, some new phenomena was found and explained. The situation of multiplayer and abnormal objects contained in monolayer tissue was also discussed. As a result, the position and size of abnormal objects could be detected by Monte Carlo simulate.The rarely milk solution (the concentration of quality is about 1E-5) was studied qualitatively with 650nm LD. The visibility of abnormal objects hidden in the solution and the variety of speckle in the surface of transmission were investigated too. From the result, with the acceleration of concentration of scattering particle, the abnormal objects embedding in the solution could be see clearly, but the speckle in the surface of transmission was diminished, and the solution became brightly.In this article, the best wavelength used to diagnose those changes in tissues was analyzed. The 808nm laser emission system and the photoelectric detector working under reversed voltage were designed. The distributing of intensity of transmitted light with and without abnormal objects was tested in monolayer and double-layers of pork tissue with the thickness were 0.3cm and 0.6cm. From the distribution of intensity of transmitted light that was inversed from the data of experiments, the biggish abnormal object ( F2.5mm) can be see obviously. But the lesser abnormal object (F0.5mm) cannot be founded. One the one hand the reason was the position and size of abnormal object; on the other hand was the lower resolving power of detector. In the last part of this paper, the Monte Carlo simulation was processed with the same parameters. The experiment and simulation were fit well.It can be conclude that the Monte Carlo simulation is an effective method to simulate the transmittance of photons walk in tissues. And the fact that the embedded abnormal object can be detected form the experiments and the simulations with DPDW. The research result will provide theoretical and experimental reference to Tissue Optics, Biomedical Photonics, Medical Diagnose and corresponding fields.更多还原