Holographic optical coherence tomography (OCT) for functional retina imaging

全息术可以记录和评估光波场的相位和幅度。全息光学相干层析成像(OCT)提供了散射体中额外的深度分辨的相位和幅度测量。利用相位信息对散焦和其他成像误差进行纯数字补偿，以及对散射组织内的变化进行高精度干涉测量成为可能。全场扫描源OCT使用高速摄像机来并行OCT成像，提供对人类视网膜的锁相成像。局部和全局运动限制了可以确定相位变化的精度。在第一个资助期，运动校正和新算法显著改善了阶段评估。在光刺激后，光感受器细胞外节和内丛状层的形态变化可观察到8秒以上。在人类中，第一次对最内层神经元层的光感受器和神经节细胞之间的功能关系进行了成像。通过将全息OCT和多普勒测量相结合，可以在5 mm×14 mm的图像范围内同时测量动脉血流和脉动引起的动脉和视网膜组织的机械变化，时间分辨率超过180 Hz。在第二个资助期，这些研究将继续，通过抑制多重散射光来提高分辨率和改善对比度，多重散射光强烈影响成像，特别是在视网膜色素上皮下。单个神经细胞组的功能将被选择性地成像；单细胞成像将通过改进像差校正和通过分钟长的体积平均来提高信噪比来实现。其目标是对从光感受器到神经节细胞的所有神经层进行全面的功能成像。为了确定视网膜的生物力学参数，脉动血管引起的变形将与局部血流相关。由于细胞或细胞器的自发局部运动而产生的细胞特异性或代谢对比的可能性将被调查。全息OCT为活体相敏成像提供了独特的机会。该研究项目为全面的功能视网膜成像奠定了基础，这将提供对生理过程的更好理解，并可能为临床诊断开辟新的途径。

Holography allows to record and evaluate phase and amplitude of a light wave field. Holographic optical coherence tomography (OCT) provides additionally depth-resolved measurements of phase and amplitude in scattering volumes. Using the phase information a purely numerical compensation of defocus and other imaging errors, as well as high-precision interferometric measurements of changes within scattering tissues become possible. Full-field swept-source OCT, which uses high-speed cameras to parallelize OCT imaging, provides phase-locked imaging of human retina. Local and global motion limits the accuracy with which changes in phase can be determined. In the first funding period, motion correction and new algorithms significantly improved the phase evaluation. It was possible to visualize for more than 8 seconds morphological changes in the outer segments of photoreceptor cells and in the inner plexiform layer after an optical stimulation. For the first time in humans, the functional relationship between photoreceptors and ganglion cells in the innermost neuronal layer was imaged. By combining holographic OCT with Doppler measurements, it was possible to simultaneously measure arterial blood flow and pulsation-induced mechanical changes of arteries and retinal tissue in image fields of 5 mm x 14 mm with a time resolution of more than 180 Hz. In the second funding period, these studies will be continued with increased resolution and improved contrast by suppression of multiple scattered light, which strongly affects imaging especially below the retinal pigment epithelium. The function of individual groups of neuronal cells will be selectively imaged; single-cell imaging will be enabled by improving aberration correction and by minute-long volume averaging for improving SNR. The goal is comprehensive functional imaging of all neuronal layers from photoreceptors to ganglion cells. To determine biomechanical parameters of the retina, deformations due to pulsatile vessels will be correlated with local blood flow. The possibility of cell-specific or metabolic contrast due to spontaneous local movement of cells or cell organelles will be investigated. Holographic OCT offers unique opportunities for phase-sensitive imaging in vivo. The research project lays the foundation for comprehensive functional retinal imaging, which will provide a better understanding of physiological processes and may open new avenues for clinical diagnostics.