Development of Label-Free Optical Imaging Modality for Quantitative Multi-Scale Histopathology

Department of Biomedical EngineeringLabelling-based imaging technique has taken many attentions for the many decades since the first fluorescence confocal imaging overcome the limitation of traditional bright field microscopes. The dramatic contrast scattered from the immune-tagging molecules with required excitation beam shed light on the numerous scientific findings. However, the difficulties of handling tagging molecules and required many steps may lead to hamper the frequent use of fluorescence microscope. Thus, the label-free imaging technique has emerged as a new alterative tool overcoming the limitations illustrated in labeling-based imaging technique. In my doctoral course, I have built up three different types of imaging modalities that enable to label-free imaging, quantitative imaging and deep tissue whole mount imaging with tissue clearing techniques. First, in order to make it possible for large-scale imaging in biological tissues, we developed a home built serial sectioning optical coherence tomography (S-OCT). Previously, in terms of enabling whole-mount imaging like reconstruction of 3D neuronal network, the physical sectioning method has been spotlighted. With the depth limitation, however, previously used serial-sectioning method encountered some pitfalls such as laboring-intensive, ultrathin-section wrinkle formation, surface scratches, time consuming, etc. As an alternative tool beyond the disadvantages explained in previous physical sectioning system, this newly developed serial sectioning optical coherence tomography provides label free imaging of ex-vivo mouse organs in comfortable settings. Throughout the serial sectioning study, whole mouse brain and kidney with micro-vessel networks was reconstructed by a series of image stacks. Second, diffraction phase microscopy (DPM) was developed as disease screening tool for histopathology study in tissue level. The main advantage of using this label-free microscopy is to provide quantitative phase information which can be used for evaluation of optical properties. Using retrieved optical properties such as scattering coefficient and anisotropy, histopathological screening would be possible with quantitative information. Third, deep tissue imaging has always attracted the attention from many biologists studying murine development. Previously, analysis of mammalian embryos has been proceeded by traditional sectioning histological mechanism using like Hematoxylin and Eosin (H&E) staining. However, entire morphological and phenotypic information was hardly acquired using this technique. Thus, we built optical projection tomography (OPT) to provide label-free and quantitative volumetric information for murine developmental study. More detailed system explanation would be followed in each technical chapter. Label-free imaging techniques have many potentials to be used from the optical bench to bedside in clinics. Since it has ease of use and high access of imaging sample compared to the imaging way of immune-molecule tagging basis, I believe that this type of imaging modality would be used as a mainstay both in research basis and clinical facilities.clos