基于谱域光学相干层析术的人体皮肤三维血流成像研究

发布时间：2018-04-24 06:55

本文选题：医学成像 + 光学相干层析术　；参考：《南京理工大学》2016年博士论文

【摘要】：光学相干层析术(Optical Coherence Tomography,OCT)是20世纪90年代提出的一种可对生物组织活体断层成像的方法,具有分辨率高、成像速度快和对样品无损伤等优点。该技术利用生物组织的后向散射光与参考光的干涉信号来提取生物组织深度方向上的信息,在横向上则利用两个扫描振镜进行二维扫描,经过数据处理来重构样品的三维图像。该成像技术的分辨率为微米量级,在组织中的最大成像深度能够达到2 mm。人体所需的营养物质和氧气都是通过血液循环输送到全身各组织,并且在毛细血管中发生物质交换。当组织发生病变时,血管的分布也会发生相应的变化。因此在临床医学中,组织中的血管分布图像可以辅助疾病诊断,如癌症,牛皮癣和酒色斑等疾病。本文首先设计并搭建了一台谱域OCT系统(Spectral Domain OCT,SDOCT),然后主要对基于OCT的血流成像技术进行了研究。主要内容包括下面几个方面:首先设计并搭建了一台SDOCT系统。为了优化系统性能,搭建了一套快速扫描延迟线系统来补偿该系统色散。为了提高色散补偿精度,提出通过测量参考臂和样品臂色散不匹配值的方法来评定色散补偿效果;同时提出基于该系统的测量透射样品色散值和折射率的方法。为了抑制活体成像过程中环境抖动和系统不稳定等在相位差图像中引入的随机噪声,提出基于谱域互相关的相位分辨多普勒OCT技术来计算组织中的血流速度。该方法中,对连续两次A扫的干涉条纹信号通过互相关运算来去除噪声。在血流模拟实验中,新方法将速度信号的信噪比由53 dB提高到56 dB;在对老鼠耳朵上血流成像的实验中,该方法将速度信号的信噪比由45 dB提高到49 dB。为了解决相关成像OCT方法中血流图像分辨率和血流图像信噪比之间的矛盾,提出…基于体数据的相关成像OCT方法来重构血流图像,实现在不减小XZ 载面内图像分辨率的情况下提高血流图像的质量。实验结果证明窗口为3×3×3像素时基于体数据的相关成像OCT方法所得血流信号的信噪比比窗口为7×7像素时传统相关成像OCT方法所得血流信号的信噪比高2 dB,并且血流图像的分辨率高了近一倍。为了去除相关成像OCT方法中由呼吸和心跳等引起的抖动噪声,提出利用补零技术和图像配准技术来对结构图像进行配准,再通过计算相关系数的方法提取血流信号。为了提高提取血流信号的灵敏度,提出利用OCT图像中的虚部信号来计算相关系数。实验结果证明在人体皮肤的血流图像中,补零技术和图像配准技术能够有效地去除抖动噪声;在老鼠耳朵血流成像实验中,基于虚部相关的方法能够提取出更多的血流信号,包括传统相关成像OCT方法未能提取的小血管信号。为了提高血流图像质量,提出利用多光束扫描方法来抑制血流图像中的噪声,分析了样品位于测量光束焦点之外时对多普勒相位和散斑方差的影响并通过血流模拟实验来验证了理论;最后,通过人体皮肤成像实验来证明了多光束扫描方法能够应用在相位分辨多普勒OCT,相位分辨多普勒方差OCT和散斑方差OCT方法中来提高所得血流图像的质量。
[Abstract]:Optical Coherence Tomography (OCT) is a method of imaging of living tissue in biological tissue in 1990s. It has the advantages of high resolution, fast imaging speed and no damage to the sample. This technique uses the backscatter light of biological tissue and the interference signal of reference light to extract biological tissue depth. In the direction of information, two scanning mirrors are scanned horizontally, and the three-dimensional image of the sample is reconstructed through data processing. The resolution of the imaging technique is micron. The nutrients and oxygen required for the maximum imaging depth of the tissue to reach 2 mm. human body are circularly transported through the blood to the whole body. Tissue, and material exchange in capillaries. When tissue changes, the distribution of blood vessels also changes. Therefore, in clinical medicine, the distribution of blood vessels in the tissue can assist the diagnosis of disease, such as cancer, psoriasis and wine stains. In this paper, a spectral domain OCT system (Spectral) is designed and built in this paper. Domain OCT, SDOCT), and then mainly study the blood flow imaging technology based on OCT. The main contents include the following aspects: first design and build a SDOCT system. In order to optimize the system performance, a set of fast scanning delay line system is set up to compensate the dispersion of the system. In order to improve the dispersion compensation precision, the measurement is proposed. In order to suppress the random noise introduced in the phase difference image such as environment jitter and system instability, a method based on the system is proposed to measure the dispersion value and the refractive index of the transmitted sample. The phase resolution Doppler OCT technique is used to calculate the blood flow velocity in the tissue. In this method, the interference stripe signal of two consecutive A scans is removed by intercorrelation. In the flow simulation experiment, the signal to noise ratio of the velocity signal is increased from 53 dB to 56 dB; in the experiment on the blood flow imaging on the old rat ears, this method will speed up The signal-to-noise ratio of the signal is increased from 45 dB to 49 dB.. In order to solve the contradiction between the resolution of the blood flow image and the SNR of the blood flow image in the correlation imaging OCT method, it is proposed that the signal to noise ratio (SNR) of the blood flow image should be resolved. The correlation imaging OCT method based on body data is used to reconstruct the blood flow image to improve the quality of the blood flow image without reducing the image resolution in the XZ plane. The experimental results show that the signal to noise ratio of the blood flow signal obtained by the correlation imaging OCT method based on body data is 3 x 3 x 3 pixels, and the traditional correlation is compared with the window of 7 x 7 pixels. The signal to noise ratio of the blood flow signal obtained by the OCT method is 2 dB, and the resolution of the blood flow image is nearly doubled. In order to remove the jitter noise caused by the respiration and the heartbeat in the related imaging OCT method, this paper uses the technology of zero filling and image registration to register the structure image, and then extracts the blood flow by calculating the correlation coefficient. In order to improve the sensitivity of the extracted blood flow signal, we propose to use the virtual part signal in the OCT image to calculate the correlation coefficient. The experimental results show that in the blood flow image of the human skin, the technology of zero filling and image registration can effectively remove the jitter noise. In the experiment of mouse ear blood flow imaging, the method based on the virtual part can be used in the rat ear blood flow imaging experiment. More blood flow signals are extracted, including the small vascular signals that are not extracted by the traditional correlation imaging OCT method. In order to improve the quality of the blood flow image, a multi beam scanning method is proposed to suppress the noise in the blood flow image. The effects of the sample on the Doppler phase and speckle variance are analyzed and the blood is passed through the blood. The flow simulation experiment is used to verify the theory. Finally, through the human skin imaging experiment, it is proved that the multi beam scanning method can be applied to improve the quality of the blood flow image in phase resolved Doppler OCT, phase resolved Doppler variance OCT and speckle variance OCT.

【学位授予单位】：南京理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：R445.9;TP391.41

【参考文献】