Tomographic refractive index measurement using Adaptive fiber-optical cell Rotation

三维折射率层析成像是一种新兴的无标记成像技术，通常基于对照明的扫描。然而，由于存在漏锥问题，导致轴向分辨率较低。在第一个资助期，我们展示了多芯光纤单元旋转器(MCF-OCR)系统，实现了双光束陷阱中所有轴的实时程控单元旋转，这在全球范围内是第一次。MCF-OCR被集成到芯片实验室系统中，由于光纤的高度灵活性，该系统可以很容易地安装在商用显微镜中。事实证明，与传统的光照扫描层析成像相比，MCF-OCR层析成像可以实现更精确的重建，并提供各向同性的三维分辨率。这在单细胞水平上是有效的，但像细胞团、有机体和胚胎这样的大生物样本的光学断层扫描仍然具有挑战性。在该项目的第二阶段，我们将研究一种新的双光束陷阱设计，以及定制版本的Born多重散射算法，是否能够实现直径超过100微米的大生物样本的无标签高分辨率断层扫描。采用三维自适应陷阱可以提高光陷的稳定性。MCF用于光场成像，以测量单元的粗略折射率分布，从而为捕获光束产生空间优化的光场。此外，由于高分辨率显微镜的景深有限，将大样本的旋转应用于层析成像也是具有挑战性的。因此，我们在自适应光学方面的经验将被用来建造一种用于层析成像的扩展景深显微镜。其目的是定制Born多重散射算法，用于从强度图像进行层析重建。高分辨率三维各向同性折射率的重建对于癌症和新陈代谢研究等生物医学的广泛应用具有重要意义。

Three-dimensional refractive index tomography is an emerging label-free imaging technique that is commonly based on the scanning of the illumination. However, due to the occurring missing cone problem, a low resolutions in the axial direction results. In the first funding period, we demonstrated a multi-core fiber-optic cell rotator (MCF-OCR) system, enabling real-time program-controlled cell rotation about all axes in the dual-beam trap, for the first time worldwide. The MCF-OCR is integrated into a lab-on-a-chip system which can be easily installed in commercially available microscopes due to the high flexibility of optical fibers. It has been proven that MCF-OCR tomography can achieve more precise reconstruction compared to conventional illumination-scanning tomography and providing isotropic resolution in three dimensions. This is valid on the single cell level, but optical tomography of large biological samples like cell clusters, organoids, and embryos remains challenging. In the second phase of the project, we will investigate whether a new dual-beam trap design, together with a tailored version of the Born multiple scattering algorithm enables label-free high-resolution tomography of large biological samples with a diameter larger than 100 microns. The optical trapping stability will be improved by a three-dimensional adaptive trap. The MCF is used for light field imaging to measure the rough refractive index distribution of the cell for generating spatially optimized light fields for the trapping beams. Moreover, applying the rotation of large samples to tomography is also challenging due to the limited depth of field of high-resolution microscopes. Therefore, our experience in adaptive optics will be employed to build an extended depth-of-field microscope for tomography. The aim is to tailor the Born multiple scattering algorithm for tomographic reconstruction from the intensity images. The reconstruction of the high-resolution three-dimensional isotropic refractive index is important for a wide range of applications in biomedicine such as cancer and metabolism studies.