三维高分辨率生物组织流场检测与成像技术

发布时间：2018-07-31 18:14

【摘要】：光学相干层析成像(Optical Coherence tomography,OCT)技术是一种非侵入、高分辨率的成像技术,能获取生物组织断层信息的医学成像技术。其中以扫频激光器为光源的扫频光学相干层析成像技术(Swept source OCT,SS-OCT)具有成像速度快、信噪比和灵敏度高的特点,是目前研究和生物医学成像的主要OCT形式。OCT和包括多普勒技术等在内的流场技术相结合可以获取样品内部流速信息,扩展了OCT的成像功能。对于生物组织,很多疾病与血流流速状况和血管形态相关。皮肤的病变,畸形和烧伤等都会引起皮肤表层毛细血管形态上的变化和病变。在眼科学方面,人类视网膜的血管分布却较为稀疏,但是视网膜是人体中单位重量耗氧量最高的组织。这一矛盾体被公认为是视网膜容易产生各种血管类疾病的原因。因此,对血液循环系统提供高分辨率的三维成像将成为这类疾病预防、诊断和治疗的关键。本文对扫频光学相干层析成像系统中影响流场检测的若干问题进行了研究,并致力于流场图像质量的提高,主要内容包括:搭建了中心波长1310 nm的扫频光学相干层析成像系统,对两个多面转镜扫频激光器不稳定性问题进行了测量与分析。其中输出功率波动和光谱错位会导致干涉信号强度和相位的不稳定,进而影响到OCT结构与流场成像效果。扫频范围的波动则会降低信号利用率,从而降低图像分辨率和信噪比。针对以上问题提出了一种基于马赫曾德干涉仪的相位、强度矫正方法,该方法可以在不截取信号的情况下对相位进行矫正,消除了干扰竖条纹,提高了流场检测效果以及图像的分辨率和信噪比。在处理过程中,干涉信号在时域就完成了对齐,因此获取一次马赫曾德干涉信号的相位信息,即可完成所有干涉信号的重采样过程,提高了成像速度。对流体网络模型进行了三维成像,验证了矫正方法的有效性;同时对兔耳部血管、人手指皮肤血管进行了在体流场检测,获得了良好的图像效果;其间还利用GPU对相位矫正算法进行了加速,能够对样品进行实时多普勒流速成像。
[Abstract]:Optical coherence tomography (Optical Coherence tomographic Oct) is a non-invasive, high-resolution imaging technique, which can obtain the information of biological tissue fault. The scanning optical coherence tomography (Swept source OCTS- Oct), which uses the scanning laser as the light source, has the advantages of fast imaging speed, high signal-to-noise ratio and high sensitivity. It is the main OCT form of biomedical imaging. Oct and flow field technology, including Doppler technology, can obtain the flow velocity information of the sample, and expand the imaging function of OCT. For biological tissue, many diseases are associated with blood flow velocity and vascular morphology. Skin lesions, deformities and burns can cause morphological changes in the surface capillaries. In ophthalmology, the blood vessels of human retina are sparsely distributed, but the retina is the tissue with the highest oxygen consumption per unit weight. This contradiction is recognized as the cause of various vascular diseases in the retina. Therefore, high resolution 3D imaging of the circulatory system will be the key to the prevention, diagnosis and treatment of these diseases. In this paper, some problems affecting the detection of flow field in the optical coherence tomography system are studied, and the quality of the flow field image is improved. The main contents are as follows: the scanning optical coherent tomography system with the center wavelength of 1310 nm is built. The instability of two multi-mirror scanning lasers is measured and analyzed. The fluctuation of output power and the misalignment of spectrum will lead to the instability of the intensity and phase of the interference signal, which will affect the OCT structure and the imaging effect of the flow field. The fluctuation of sweep range will reduce the signal utilization ratio and thus reduce the image resolution and signal-to-noise ratio (SNR). In order to solve the above problems, a phase and intensity correction method based on Mach Zende interferometer is proposed. This method can correct the phase without intercepting the signal and eliminate the interference of vertical stripes. The detection effect of the flow field and the resolution and signal-to-noise ratio of the image are improved. In the process of processing, the interference signal is aligned in the time domain, so if the phase information of the Mach Zende interference signal is obtained once, the resampling process of all the interference signals can be completed and the imaging speed can be improved. Three-dimensional imaging of the fluid network model was performed to verify the effectiveness of the correction method, and in vivo flow field detection of rabbit ear vessels and human finger skin vessels was carried out, and a good image effect was obtained. Meanwhile, the phase correction algorithm is accelerated by GPU, and the real time Doppler velocity imaging of the sample can be carried out.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R445

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