基于散斑方差和多普勒算法的光学相干层析术血流成像

Blood Flow Imaging by Optical Coherence Tomography Based on Speckle Variance and Doppler Algorithm

提出了一种基于扫频光学相干层析术的散斑方差(SV)和多普勒算法结合的方法来提取人体皮肤毛细血管的血流信号。这种方法利用了SV算法获取血流信号强度和多普勒算法获取相位信息的优势。SV算法对两幅结构图同一位置的强度进行方差运算。多普勒算法可以通过测量相邻A扫之间的相位变化来获取多普勒频移,进而获取血流流速信息,但这种方法中扫频光源的相位和采样信号随时间存在漂移,导致触发信号和采集卡模数转换之间的延迟时间在一个取样时钟周期中变化。为了校正这部分相位变化,实验系统中采用双参考镜,通过校正两参考镜相邻A扫之间的相位变化来对相应血流部分进行相位校正。进行了样本模拟实验和人体皮肤成像实验,SV算法获取血流强度和经标准平面镜校正的多普勒频移来获取血流方向,综合运用两种方法得到具有方向信息的血流强度图。

For extracting the blood flow signal of the human skin blood capillary, a combination method of speckle variance （SV） based on the swept source optical coherence tomography, and Doppler algorithm is proposed. This method takes advantage of SV algorithm to get the blood flow signal intensity and advantage of Doppler algorithm to obtain phase. SV algorithm calculates the variance of intensity at the same location of two frames. Doppler algorithm calculates the phase shift between adjacent A scans in order to obtain frequency shift. However, the phase of the swept source output and the sampled signal drift slowly over time, causing the delay between the trigger signal and the subsequent analog to digital conversion to vary within a sample clock cycle. To correct the change in phase, double reference mirrors are used in the experimental system. We adjust the phase shift between adiacent A scans of the two reference mirrors to correct the phase of the corresponding blood flow. Sample simulation experiment and human skin imaging experiment are carried out. SV algorithm is used to obtain the intensity of blood and Doppler phase shift after correction is used to obtain the direction of blood. Blood flow intensity with direction information is obtained by combination of the two methods.