Implementation of a portable diffraction phase microscope for digital histopathology.

Quantitative phase imaging (QPI) has a significant advantage in histopathology as it helps in differentiating biological tissue structures and cells without the need for staining. To make this capability more accessible, it is crucial to develop compact and portable systems. In this study, we introduce a portable diffraction phase microscopy (DPM) system that allows the acquisition of phase map images from various organs in mice using a low-NA objective lens. Our findings indicate that the cell and tissue structures observed in portable DPM images are similar to those seen in conventional histology microscope images. We confirmed that the developed system's performance is comparable to the benchtop DPM system. Additionally, we investigate the potential utility of digital histopathology by applying deep learning technology to create virtual staining of DPM images.

Multi-contrast digital histopathology of mouse organs using quantitative phase imaging and virtual staining.

Quantitative phase imaging (QPI) has emerged as a new digital histopathologic tool as it provides structural information of conventional slide without staining process. It is also capable of imaging biological tissue sections with sub-nanometer sensitivity and classifying them using light scattering properties. Here we extend its capability further by using optical scattering properties as imaging contrast in a wide-field QPI. In our first step towards validation, QPI images of 10 major organs of a wild-type mouse have been obtained followed by H&E-stained images of the corresponding tissue sections. Furthermore, we utilized deep learning model based on generative adversarial network (GAN) architecture for virtual staining of phase delay images to a H&E-equivalent brightfield (BF) image analogues. Using the structural similarity index, we demonstrate similarities between virtually stained and H&E histology images. Whereas the scattering-based maps look rather similar to QPI phase maps in the kidney, the brain images show significant improvement over QPI with clear demarcation of features across all regions. Since our technology provides not only structural information but also unique optical property maps, it could potentially become a fast and contrast-enriched histopathology technique.

Serial optical coherence microscopy for label-free volumetric histopathology.

The observation of histopathology using optical microscope is an essential procedure for examination of tissue biopsies or surgically excised specimens in biological and clinical laboratories. However, slide-based microscopic pathology is not suitable for visualizing the large-scale tissue and native 3D organ structure due to its sampling limitation and shallow imaging depth. Here, we demonstrate serial optical coherence microscopy (SOCM) technique that offers label-free, high-throughput, and large-volume imaging of ex vivo mouse organs. A 3D histopathology of whole mouse brain and kidney including blood vessel structure is reconstructed by deep tissue optical imaging in serial sectioning techniques. Our results demonstrate that SOCM has unique advantages as it can visualize both native 3D structures and quantitative regional volume without introduction of any contrast agents.

Label-free optical projection tomography for quantitative three-dimensional anatomy of mouse embryo.

Recent progress in three-dimensional optical imaging techniques allows visualization of many comprehensive biological specimens. Optical clearing methods provide volumetric and quantitative information by overcoming the limited depth of light due to scattering. However, current imaging technologies mostly rely on the synthetic or genetic fluorescent labels, thus limits its application to whole-body visualization of generic mouse models. Here, we report a label-free optical projection tomography (LF-OPT) technique for quantitative whole mouse embryo imaging. LF-OPT is based on the attenuation contrast of light rather than fluorescence, and it utilizes projection imaging technique similar to computed tomography for visualizing the volumetric structure. We demonstrate this with a collection of mouse embryo morphologies in different stages using LF-OPT. Additionally, we extract quantitative organ information applicable toward high-throughput phenotype screening. Our results indicate that LF-OPT can provide multi-scale morphological information in various tissues including bone, which can be difficult in conventional optical imaging technique.

Effect of tissue staining in quantitative phase imaging.

Quantitative phase imaging (QPI) is an emerging modality, which enables the identification of abnormalities in tissue based on optical properties. QPI can be applied to any biological specimen due to its label-free imaging capability, but its use in stained tissue is unclear. Here, we study the variability of QPI with the staining dye. Several tissues such as brain, heart and lung were stained with hematoxylin and eosin, and their optical properties compared at 550 and 730 nm. Our results showed that phase and scattering coefficients varied when QPI was used at the absorption wavelength of the staining dye. We also found that the variation of optical properties was dependent on tissue morphology.

Optical properties of acute kidney injury measured by quantitative phase imaging.

The diagnosis of acute kidney disease (AKI) has been examined mainly by histology, immunohistochemistry and western blot. Though these approaches are widely accepted in the field, it has an inherent limitation due to the lack of high-throughput and quantitative information. For a better understanding of prognosis in AKI, we present a new approach using quantitative phase imaging combined with a wide-field scanning platform. Through the phase-delay information from the tissue, we were able to predict a stage of AKI based on various optical properties such as light scattering coefficient and anisotropy. These optical parameters quantify the deterioration process of the AKI model of tissue. Our device would be a very useful tool when it is required to deliver fast feedback of tissue pathology or when diseases are related to mechanical properties such as fibrosis.

Measurement of multispectral scattering properties in mouse brain tissue.

We present the scattering properties of mouse brain using multispectral diffraction phase microscopy. Typical diffraction phase microscopy was incorporated with the broadband light source which offers the measurement of the scattering coefficient and anisotropy in the spectral range of 550-900 nm. The regional analysis was performed for both the myeloarchitecture and cytoarchitecture of the brain tissue. Our results clearly evaluate the multispectral scattering properties in the olfactory bulb and corpus callosum. The scattering coefficient measured in the corpus callosum is about four times higher than in the olfactory bulb. It also indicates that it is feasible to realize the quantitative phase microscope in near infrared region for thick brain tissue imaging.