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题名	复频域光学相干层析成像技术的研究
作者	步鹏
学位类别	博士
答辩日期	2007
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 频域光学相干层析成像 正弦相位调制 空间载波 多普勒效应
其他题名	Research on complex Fourier domain optical coherence tomography
中文摘要	光学相干层析成像（Optical Coherence Tomography, OCT）是一种非侵入、高分辨率、可在体检测生物组织内部微结构的生物医学光学成像技术。最近发展起来的频域OCT技术与传统时域OCT技术相比，由于具有高速度、高灵敏度的优点更适合生物组织的在体成像，代表着光学相干层析成像技术的发展趋势。然而，频域OCT由于直接对采集的实数频域干涉条纹（干涉谱）进行逆傅里叶变换，受到固有寄生像的困扰。这些寄生像分别是复共轭镜像、自相干噪声和直流背景。复共轭镜像的存在，导致频域OCT成像深度范围减半，同时，直流背景和自相干噪声的存在，降低了系统信噪比。复频域OCT，通过重建复频域干涉条纹，可以消除以上寄生像，实现频域OCT的全深度成像。目前主要采用移相干涉术实现复频域OCT，但是由于移相干涉术需要连续采集多幅移相干涉图，并在它们之间保持固定的相位关系，不仅降低了成像速度，而且对样品运动和环境扰动造成的移相误差敏感，从而限制了该技术在在体成像领域的应用。 针对上述问题，本论文将两种外差干涉术与频域OCT相结合，提出两种新型快速复频域OCT技术，分别为： 一种基于正弦相位调制的复频域OCT。将正弦相位调制干涉术引入频域OCT，利用压电陶瓷（PZT）带动参考镜作正弦振动，在频域干涉条纹中引入正弦相位调制，通过探测正弦相位调制的频域干涉条纹的时间频谱获得频域干涉条纹的相位和幅度信息，重建了复频域干涉条纹，消除了复共轭镜像、直流背景，和自相干噪声，实现了全深度探测。该方法与移相法相比，不需要精确的移相，抗环境干扰能力较好，可应用于动态物体的成像。 一种基于空间载波的复频域OCT。将空间载波外差干涉术引入频域OCT，利用倾斜的参考波在二维频域干涉条纹的横向方向引入空间载波，通过探测包含空间载波的二维频域干涉条纹的空间频谱获得频域干涉条纹的相位和幅度信息，重建了复频域干涉条纹，消除了复共轭镜像、直流背景，和自相干噪声，实现了全深度探测。该方法无需横向和深度方向的机械扫描，只需利用面阵CCD采集一幅含有空间载波的二维频域干涉条纹，即可重建一幅全深度的二维层析图像，对物体的运动模糊不敏感，在在体成像领域有很好的应用前景。 从传统的结构成像向功能成像扩展，是光学相干层析成像技术的另一个发展趋势。如提供样品深度分辨的偏振信息的偏振OCT，提供样品深度分辨的光谱信息的光谱OCT等。由于多普勒效应，样品内部散射介质的微小运动导致干涉条纹的多普勒频移，基于此效应，在复频域OCT工作的基础上，本文提出一种多普勒复频域OCT技术。基于正弦相位调制干涉术探测得到时变的复频域干涉条纹，该时变条纹的相位包含了样品内运动介质产生的多普勒频移信息，对其沿光谱方向作逆傅里叶变换后，分别取其幅度和相位，同时获得了样品内部深度分辨的结构图像和位移信息，实现了复频域OCT的多普勒功能成像。该方法实现了复频域OCT信号的准外差探测，具有成像深度范围大、成像速度快、信噪比高的优点，在血流流速测量、组织弹性测量、以及细胞三维动态行为观察等领域有很好的应用前景。
英文摘要	Optical coherence tomography (OCT) is a promising interferometric imaging technique that can provide micron-scale cross-sectional images of biological tissue in a noninvasive and noncontact way. Fourier domain OCT (FDOCT) has attracted great attentions in the past decade due to its high speed and high sensitivity as compared with the conventional time domain OCT (TDOCT). However, FDOCT suffers from the complex conjugate ambiguity due to straightforward Fourier transform of the real-valued spectral interferogram, as well as dc and autocorrelation noise, which reduce the available imaging depth range to half the original area. This problem can be resolve by complex FDOCT by reconstructing the complex spectral interferogram. At present phase-shifing interferometry is mainly used to achieve complex FDOCT, however, this method is difficult to be applied to in vivo imaging because it requires high stability of the interferometer and the sample to keep a defined phase relation between the phase-shifted interferograms. In this thesis, two kinds of novel high-speed complex FDOCT are realized by introducing heterodyne interferometry into the FDOCT. First, a complex FDOCT using sinusoidal phase-modulating interferometry is proposed, where a sinusoidal phase modulation is introduced into the spectral interferogram by vibrating a reference mirror mounted on a PZT. A complex spectral interferomgram is obtained to achieve full range imaging by detecting the temporal frequency spectrum of the sinusoidal phase-moulated interferometric signal. This mehod is free of the phase-shifting error and relatively insensitive to the environmental disturbance, which is useful for in vivo imaging of a dynamic object. Second, a one-shot parallel complex FDOCT using spatial carrier frequency is proposed, in which a spatial carrier frequency is introduced into the two-dimensional (2D) spectral interferogram in the lateral direction by using a tilted reference wavefront. This spatial-carrier-contained 2D spectral interferogram is recorded with one shot of a 2D-CCD camera, and is Fourier-transformed in the lateral direction to obtain a 2D complex spectral interferogram by spatial carrier technique. This method is very suitable for in vivo imaging because it is free of the sample motion artifact due to the one-shot characteristic. Recent development of OCT has seen its shift from structural imaging to functional imaging, such as polarization-sensitive OCT and spectroscopic OCT. In this thesis a complex FDOCT for Doppler functional imaging is proposed. A time-varying complex spectral interferogram is reconstructed by using sinusoidal phase-modulated complex FDOCT. This time-varying complex spectral interferogram is inverse Fourier-transformed along the spectral direction, and by taking its amplitude and phase the depth-resolved structure and displacement information are both obtained. This method may be applied to blood flow imaging, tissue elasticity measurement, and cellular 3D dynamics measurement.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15516]
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	步鹏. 复频域光学相干层析成像技术的研究[D]. 中国科学院上海光学精密机械研究所. 2007.

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