复频域多普勒光学相干层析成像技术研究
文献类型：学位论文
| 作者 | 南楠 |
| 学位类别 | 博士 |
| 答辩日期 | 2014 |
| 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 复共轭镜像 多普勒 正弦相位调制 |
| 其他题名 | Research on complex Fourier domain Doppler 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。多普勒OCT是OCT技术的功能性扩展，可同时获得生物样品内组织结构与血流的层析图像。与时域多普勒OCT技术相比，频域多普勒OCT技术具有成像速度与灵敏度高的优点，更适合生物组织的在体成像。然而，频域多普勒OCT存在复共轭镜像的问题，导致系统的成像深度范围减半，同时无法利用信噪比和速度探测灵敏度最高的零光程差位置附近区域。本论文针对复共轭镜像问题提出一种正弦相位调制复频域多普勒OCT技术，对该技术进行理论分析和实验研究。主要工作包括以下几个方面： 1．提出一种基于正弦相位调制B-M扫描的复频域OCT技术。通过在不同横向位置获取的干涉谱信号中引入正弦相位调制，利用傅里叶变换结合带通滤波的方法重建复干涉谱信号。该技术消除复共轭镜像、自相干噪声以及直流背景的影响，将有效成像深度范围扩大到原来的两倍；同时完成相位调制与横向扫描，缩短了数据采集时间。与线性B-M扫描技术相比，该技术中零光程差的位置不随横向扫描点变化，避免了横向扫描过程中信噪比的降低。对人体皮肤的在体三维全深度成像实验表明，基于该技术的复频域OCT系统的复共轭镜像消除比达到36dB，图像中角质层、表皮层及真皮乳突层等皮肤层状结构清晰可见。 2．提出一种基于正弦相位调制的复频域多普勒OCT技术。该技术将正弦相位调制B-M扫描与多普勒技术相结合，消除复共轭镜像影响的同时，利用速度探测灵敏度最高的零光程差位置附近区域获得比普通多普勒OCT更高的速度探测灵敏度。全深度成像实验表明，复频域多普勒OCT系统的复共轭镜像消除比达到45dB，镜像消除数据处理使系统信噪比提高7dB；系统相位稳定性实验表明，复频域多普勒OCT系统的速度探测灵敏度高于普通多普勒OCT，达到2×10-3mm/s；流体层析成像实验表明，提出的复频域多普勒OCT技术可以实现生物样品的在体全深度多普勒与结构层析成像。 3．提出一种相位差分复频域多普勒OCT技术。该技术针对复频域多普勒OCT镜像消除效果易受样品运动影响的问题，采用相邻的相位差分信号代替原层析信号的相位构成新的复层析信号，并分别对新信号的实部与虚部进行相位解调以重建全深度层析信号，消除运动对相位解调的影响，恢复出全深度结构与全深度多普勒层析图像。该技术不增加系统的复杂性，能够消除频域光学相干层析图像中的复共轭镜像、直流背景和自相关噪声，有效减小样品内部高速运动对镜像消除效果的影响，系统的信噪比与速度探测灵敏度不随横向扫描距离增加而降低。仿真分析表明，应用本论文提出的技术可以有效抑制样品运动的影响，获得与静止样品相同的镜像消除效果。 |
| 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 way. Doppler optical coherence tomography (DOCT) is a functional extension of OCT to obtain high-resolution tomographic images of tissue structure and blood flow simultaneously. Fourier domain DOCT has attracted great attention due to its high speed and high signal-to-noise ratio (SNR) compared with conventional time domain DOCT. However, Fourier domain DOCT suffers from the problem of the complex conjugate ambiguity, which reduces the available imaging depth range to half of the original area. The problem also makes high SNR and velocity sensitivity region around the zero optical path difference (OPD) position unavailable. In view of this problem, a novel complex Fourier domain DOCT with sinusoidal phase modulation is presented in this dissertation. This technique is validated both theoretically and experimentally. The main researches of this dissertation are as follows. 1．A complex Fourier domain OCT using sinusoidal phase modulation for B-M scan is proposed. The sinusoidal phase modulation is introduced to the interference spectrums while lateral scan is performing. Compared with the linear B-M scan, the sinusoidal B-M scan has the obvious advantage. The zero OPD position does not move along lateral scanning and the SNR degrading with the lateral scanning is avoided. The technique is validated experimentally. Human finger skin is imaged in vivo. In the images, the stratum corneum, the epidermis and the upper dermis can be clearly identified. The complex conjugate rejection ratio reaches to 36 dB. 2．A complex Fourier domain Doppler OCT is proposed by combining sinusoidal B-M scan technique and DOCT. Because the phase around the zero OPD position is stable and the complex conjugate ambiguity is removed, the velocity sensitivity of the proposed technique is improved greatly. The results of full-range imaging experiment indicate that in the proposed technique the complex conjugate artifact rejection ratio can reach to 45 dB, and the SNR is 7 dB higher than that in the conventional DOCT. The results of phase stability experiment indicate the velocity sensitivity obtained using the proposed technique reaches to 2×10-3mm/s, which is higher than the velocity sensitivity obtained using conventional DOCT. Full-range OCT and Doppler imaging are demonstrated using the flow phantom and in vivo mouse ear. 3．A phase-difference complex Fourier domain DOCT is proposed for imaging samples with high axial motion. In the technique, a new A-line signal is obtained by replacing the phase of A-line signal with phase difference of two consecutive A-lines. The real and imaginary parts of the new A-line signal are phase-demodulated separately to obtain the full-range A-line signal. The simulation results indicate that for moving structures with large velocities, the proposed technique shows better performance in complex conjugate artifact elimination than sinusoidal phase modulation complex Fourier domain DOCT. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15873]  |
| 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 | 南楠. 复频域多普勒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. 2014. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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