Novel technique gives quicker and more exact diagnostics in histopathology
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- Source: SPIE--International Society for Optics and Photonics
- Date: 01 May,2021
Histology is the study of biological cells at a microscopic level. Also called microscopic anatomy, histology is widely used to offer identification of cancer and other diseases. For instance, tissue samples obtained during surgery might help to ascertain whether additional surgical action is needed, and additional surgery may be avoided if a diagnosis can be rapidly obtained during an operation.
Conventional methods in histopathology are usually restricted to thin specimens and require chemical processing of the tissue to provide sufficiently substantial contrast for imaging, which slows the procedure. A recent progress in histopathology eliminates the need for chemical staining and empowers high-resolution imaging of thick tissue sections. As mentioned in Advanced Photonics, an international research team recently demonstrated a 3D label-free quantitative phase imaging technique which uses optical diffraction tomography to obtain volumetric imaging details. Automated stitching simplifies the image acquisition and analysis.
Optical diffraction tomography
Optical diffraction tomography is a microscopy method for reconstructing the refractive index of a tissue sample from its scattered field images obtained with different illumination angles. It enables label-free high contrast visualization of transparent samples. The complex scattered field transmitted through the sample is first recovered using off-axis holography, then the scattered fields obtained with various angle of illuminations are mapped in the Fourier space enabling the reconstruction of the sample refractive index.
A recognized limitation of optical diffraction tomography is due to the complex distribution of refractive indexes, which causes significant optical aberration in the imaging of thick tissue. To overcome this restriction, the team used digital refocusing and automatic stitching, allowing volumetric imaging of 100-m-thick cells over a lateral field of view of 2 mm 1.75 mm while maintaining a high resolution of 170 nm 170 nm 1400 nm.
Quick, accurate histopathology
The researchers demonstrated the capacity of their novel method by imaging an assortment of different cancer pathologies: pancreatic neuroendocrine tumor, intraepithelial neoplasia, and intraductal papillary neoplasm of bile duct. They imaged millimeter-scale, unstained, 100-μm-thick cells at a subcellular 3D resolution, which enabled the visualization of individual cells and multicellular tissue architectures, comparable to images obtained with traditional chemically processed tissues.
According to YongKuen Park, researcher at the Korea Advanced Institute of Science and Technology and senior author on the study,”The images obtained with the proposed method enabled clear visualization of distinct morphological features in the respective cells allowing for recognition and analysis of precursor lesions and pathologies.”
For the purpose of comparison, adjacent tissues were prepared in lean tissue slides with conventional H&E staining method. (the fifth row, 400x magnification). Picture credit: Hugonnet et al., doi 10.1117/1 ). AP.3.2.026004.
Park notes that additional research is needed, but the results suggest great potential for rapid, accurate histopathology during surgery:”More research is required on sample prep, reconstruction speed, and mitigation of multiple scattering. We anticipate optical diffraction tomography to provide quicker and more precise diagnostics in histopathology and intraoperative pathology consultations.”
Hugonnet, H., et al. (2021) Multiscale label-free volumetric holographic histopathology of thick-tissue slides with subcellular resolution. Advanced Photonics. doi.org/10.1117/1.AP.3.2.026004.