Multi-Scale Label-free Human Brain Imaging with Integrated Serial Sectioning Polarization Sensitive Optical Coherence Tomography and Two-Photon Microscopy

Abstract

The study of neurodegenerative processes in the human brain requires a comprehensive understanding of cytoarchitectonic, myeloarchitectonic, and vascular structures. Recent computational advances have enabled volumetric reconstruction of the human brain using thousands of stained slices, however, tissue distortions and loss resulting from standard histological processing have hindered deformation-free reconstruction of the human brain. The development of a multi-scale and volumetric human brain imaging technique that can measure intact brain structure would be a major technical advance. Here, we describe the development of integrated serial sectioning Polarization Sensitive Optical Coherence Tomography (PSOCT) and Two Photon Microscopy (2PM) to provide label-free multi-contrast imaging, including scattering, birefringence and autofluorescence of human brain tissue. We demonstrate that high-throughput reconstruction of 4x4x2cm3 sample blocks and simple registration of PSOCT and 2PM images enable comprehensive analysis of myelin content, vascular structure, and cellular information. We show that 2 μm in-plane resolution 2PM images provide microscopic validation and enrichment of the cellular information provided by the PSOCT optical property maps on the same sample, revealing the sophisticated capillary networks and lipofuscin filled cell bodies across the cortical layers. Our method is applicable to the study of a variety of pathological processes, including demyelination, cell loss, and microvascular changes in neurodegenerative diseases such as Alzheimer's disease (AD) and Chronic Traumatic Encephalopathy (CTE).

Enhanced Multiscale Human Brain Imaging by Semi-supervised Digital Staining and Serial Sectioning Optical Coherence Tomography

“…Additionally, we plan to incorporate multimodality input, such as polarization information, into our DS model to increase the imaging sensitivity to birefringence structures, including myelin fibers (17,19). Another promising modality we aim to integrate with the S-OCT is two photon microscopy, which allows imaging of small vessels and myelin fibers based on autofluorescence contrast with reduced noise and improved resolution (34).…”

“…The S-OCT microscope was described previously (34). We used a swept light source (AxsunTech) with 100 kHz swept rate, a central wavelength of 1310 nm, and a spectral full width half maximum (FWHM) of 110nm, yielding an axial resolution of 5.6 µm in brain tissue (n=1.4).…”

“…Although our technique is sensitive to fiber structures in the gray matter, the speckle noise and limited resolution resulted in discontinuities and grainy artifacts in the DS results. We expect that these issues will likely be overcome by future generations of high-resolution S-OCT systems (34,35) and improved processing algorithms. Despite current limitations, we believe that our semi-supervised learning-based DS framework is broadly useful to other bioimaging modalities and DS applications.…”