Structured illumination enhances resolution and contrast in thick tissue fluorescence imaging

Area of Science:

• Biomedical Optics
• Medical Imaging
• Fluorescence Microscopy

Background:

• Thick, scattering tissues pose significant challenges for conventional imaging methods, limiting resolution and contrast of fluorescent molecular probes.
• Existing techniques often struggle to achieve sufficient depth penetration and signal-to-background ratio (SBR) in complex biological media.

Discussion:

• This study introduces a novel noncontact imaging method employing multifrequency structured illumination within the multiple-scattering regime.
• The technique utilizes spatially modulated scalar photon density waves, adapting principles from structured light microscopy for deep tissue imaging.
• By manipulating spatial frequencies of the structured light, selective suppression of deeper fluorescence and enhancement of superficial signals are achieved.

Key Insights:

• Demonstrated significant improvements in SBR (up to sevenfold) and resolution (33%) for buried fluorescent objects (1-mm) at depths of 3 mm in tissue phantoms.
• The method effectively reduces background noise by localizing signals through measurement of fluorescence spatial frequency dependence.
• Rapid implementation is possible using a spatial light modulator and a straightforward image demodulation scheme.

Outlook:

• Potential applications in preclinical research and diagnostics requiring deep-tissue optical imaging of molecular probes.
• Further optimization could extend capabilities to in vivo imaging scenarios with highly scattering biological tissues.
• This technique offers a promising avenue for advancing noninvasive molecular imaging in complex biological environments.