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签成像技术，通常基于照明扫描。然而，由于出现的锥缺失问题，低分辨率在轴向的结果。在第一个资助期，我们展示了一个多核光纤细胞旋转器（MCF-OCR）系统，该系统在全球范围内首次实现了双光束阱中所有轴的实时程控细胞旋转。MCF-OCR集成到一个芯片实验室系统中，由于光纤的高灵活性，该系统可以很容易地安装在市售显微镜中。事实证明，与传统的照明扫描断层扫描相比，MCF-OCR断层扫描可以实现更精确的重建，并提供三维各向同性分辨率。这在单细胞水平上是有效的，但是像细胞簇、类器官和胚胎这样的大型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，以及波恩多重散射算法的定制版本，是否能够对直径大于100微米的大型生物样品进行无标签高分辨率断层扫描。三维自适应阱提高了光阱的稳定性。MCF用于光场成像，测量电池的粗略折射率分布，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断层扫描也具有挑战性。因此，我们在自适应光学方面的经验将被用来建立一个用于断层扫描的扩展景深显微镜。目的是为强度图像的层析重建量身定制玻恩多重散射算法。高分辨率三维各向同性折射率的重建对于癌症和代谢研究等生物医学领域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.