基于散射模型的光学相干层析成像技术研究
文献类型：学位论文
| 作者 | 郭昕 |
| 学位类别 | 博士 |
| 答辩日期 | 2015 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 王向朝 |
| 关键词 | 光学相干层析成像 散射性质 散射模型 分辨率 |
| 其他题名 | Research on Optical Coherence Tomography Based on Scattering Models |
| 中文摘要 | 光学相干层析成像（Optical Coherence Tomography，OCT）是一种基于低相干干涉术和扫描技术探测样品散射光的高分辨成像技术，是生物医学成像领域的研究热点。当前，更快的成像速度、更高的成像质量以及更丰富信息的获取，已经成为OCT技术的主要发展方向。OCT测量的散射光携带了样品散射性质信息，对这些信息进行提取可以增加由OCT获得的信息量，拓展OCT在组织成像和医学诊断等领域的应用。然而常规的OCT成像仅能提供反映样品结构变化的光强分布，不能直接获得样品的散射性质信息。此外，进入OCT测量系统的散射光还包含一部分多次散射光子，这些光子增加了图像噪声，也是图像信息来源的一部分。对多次散射进行研究有助于提高图像质量及获取多次散射光子携带的信息，而常规OCT成像不能单独获取多次散射信息并进行处理。另外，样品散射性质通过影响参与干涉的样品光，也会对成像质量产生影响。针对上述这些问题，为增加获取的信息量，提高成像质量，本论文开展基于散射模型的OCT技术研究，主要工作包含以下几个方面： 1.提出一种用于频域OCT的散射参数成像方法。该方法基于频域OCT原理和OCT散射模型，获得反映被测组织散射性质变化的F参数图像；然后应用泰勒定理和递推的方法，获得随深度和横向位置变化的散射系数图像。这两种散射参数图像不同于常规的结构图像，能够提供组织散射性质的分布信息。应用该方法获得在体人手掌皮肤组织的散射参数图像，图像显示了被测组织散射性质在深度和横向上的二维分布，从散射系数图像能够清楚地区分不同组织层的散射性质差异。 2.研究样品散射对频域OCT深度分辨率的影响。基于散射模型，研究样品散射对频域OCT干涉谱形状的改变，及这种改变进一步对空域信号深度分辨率产生的影响。理论分析和模拟结果表明，样品散射使探测的干涉谱信号发生形变，干涉谱强度分布向长波方向偏移，并进一步导致空域信号的分辨率降低。散射系数越大、深度越深，深度分辨率降低越多。 3.提出一种获得散射分解图像的方法。该方法依据基于EHF（extended Huygens–Fresnel）原理的OCT多次散射模型，通过对总强度信号进行分解，获得各散射分量的图像。这些图像能够提供不同散射分量的信息。各分量可被单独处理或进行信息提取，亦可对不同分量进行差异化处理后再重新合成；据此提出一种图像降噪方法，对噪声较强的分量单独进行滤波，再与其它分量合成，获得重建图像。应用提出的方法获得小鼠耳部皮肤的散射分解图像及重建图像，散射分解图像提供不同散射分量的信息，重建图像在噪声降低的同时，与直接滤波图像相比，有效减小了模糊效应。 4.提出一种基于光谱整形的频域OCT分辨率增强技术。该技术利用光源自身谱形构造整形因子，对频域OCT干涉谱信号进行整形，再利用整形后的干涉谱信号获得空域信号。模拟结果表明，该技术能够有效提高频域OCT的深度分辨率，对散射样品中深度相近的位置点有更强的分辨能力，且对高斯型或非高斯型光源的系统均适用。 |
| 英文摘要 | Optical coherence tomography (OCT) is an attractive imaging technology which detects scattered light based on low coherence interferometry and scanning technique. OCT can achieve high resolution and attracts increasing attention in the field of biomedical imaging technologies. At present, increasing imaging speed, enhancing image quality and acquiring more information have become the main research directions of OCT. Scattered light detected by OCT carries the information of scattering properties of sample. Extracting these properties is useful for increasing the amount of information acquired by OCT and extending the applications of OCT in the fields of tissue imaging and medical diagnosis. Moreover, there are some multiple scattered photons in the detected light. These multiple scattered photons increase the noise and also contribute some information to the image. Research on the effects of multiple scattering is useful for enhancing the image quality and extracting information. However, conventional OCT shows only the structure image, and cannot provide the information of scattering properties directly. And in conventional OCT, the information coming from multiple scattering cannot be acquired and processed independently. Furthermore, the scattering properties of sample can affect the image quality by affecting the sample light participating in the interference. In view of these problems, several OCT techniques are researched based on scattering models in this dissertation for increasing the amount of information acquired by OCT and enhancing the image quality. The main works of this dissertation are as follows. 1.A scattering parametric imaging method in Fourier domain OCT is proposed. In this method, based on the principle of Fourier domain OCT and the scattering model, the parameter F image which shows the change of scattering property of tissue can be obtained. Then, employing Taylor's theorem and recurrence method, the scattering coefficient image depending on the depth and transverse position can be obtained. These two kinds of scattering parametric images can provide the distribution information of the scattering property. The scattering parametric images of in vivo human palm skin are obtained by using the proposed method. The obtained images show the distributions of the scattering property of tissue along the depth and transverse direction. The scattering properties of different layers of tissue can be distinguished clearly in the scattering coefficient images. 2.The effect of scattering on depth resolution in Fourier domain OCT is researched. Based on the scattering model, the spectral shape affected by scattering of sample and the depth resolution affected by the spectral shape are researched. The results of theoretical analysis and simulations show that the scattering of sample changes the measured spectral shape, which tends toward longer wavelength, and further, decreases the depth resolution of the spatial signal. When the scattering coefficient is larger and the position measured is deeper, the depth resolution will decrease more. 3.A method for obtaining scattering decomposed images in OCT is proposed. In this method, based on the multiple scattering model of OCT, images of different scattering components can be obtained by decomposing the total intensity signal. These images show the information of different scattering components which can be processed or extracted separately. The components processed separately can also be recombined into a reconstructed total signal. Accordingly, a denoising method is proposed. The filtering is performed on only the multiple scattering component which contains more noise than other components. Then the total signal is constructed by combining the processed multiple scattering component with other components. Using the proposed method, the scattering decomposed images of mouse ear skin are obtained. They provide the information of different scattering components. Then the reconstructed image is obtained. The noise in the reconstructed image is depressed. And compared with the directly filtered image, the blurring effect in the reconstructed image is weaker. 4.A resolution enhancement technique in Fourier domain OCT based on spectral shaping is proposed. Employing the spectral shape of light source, a shaping factor is obtained. Then the interference spectral signal is reshaped to obtain the spatial signal with higher resolution. The results of simulations show that, for light sources with Gaussian and non-Gaussian spectra, the proposed technique can enhance the depth resolution and improve the capability to distinguish two near positions in scattering sample. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15941]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 郭昕. 基于散射模型的光学相干层析成像技术研究[D]. 中国科学院上海光学精密机械研究所. 2015. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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