Photon absorption remote sensing (PARS): comprehensive absorption imaging enabling label-free biomolecule...

Area of Science:

• Biomedical Optics
• Microscopy
• Histopathology

Background:

• Label-free optical absorption microscopy faces challenges in specificity and contrast for histopathological imaging.
• Current methods often require staining or complex processing, limiting adoption.

Purpose of the Study:

• Introduce Photon Absorption Remote Sensing (PARS), a novel absorption microscopy modality.
• Demonstrate PARS's capability to simultaneously capture radiative and non-radiative de-excitation processes for enhanced biomolecule specificity.
• Validate PARS for label-free characterization and unmixing of clinically relevant biomolecules in complex tissues.

Main Methods:

• Developed a multiwavelength PARS system with UV (266 nm) and visible (532 nm) excitation.
• Applied PARS to image human skin and murine brain tissue samples.
• Utilized Gaussian mixture models (GMM) for biomolecule characterization and non-negative least squares (NNLS) for abundance mapping, validated against stained images and deep learning methods.

Main Results:

• PARS simultaneously captures auto-fluorescence, photothermal, and photoacoustic signals for richer contrast.
• Successfully characterized, differentiated, and unmixed clinically relevant biomolecules in human skin and murine brain tissues.
• PARS unmixing and abundance estimates showed strong agreement with established ground truth methods.

Conclusions:

• PARS provides unique, comprehensive, and previously inaccessible label-free contrast for molecular pathology.
• The rich data from PARS can serve as a foundation for developing AI and machine learning tools for diagnostics and visualization.
• PARS represents a significant advancement in label-free histopathological imaging, addressing current limitations in specificity and contrast.