Spatial mapping of fluorophore quantum yield in diffusive media.

Area of Science:

• Biophotonics
• Optical Imaging
• Fluorescence Spectroscopy

Background:

• Fluorescence quantum yield (QY) quantifies fluorescence efficiency.
• QY is sensitive to microenvironmental factors like pH and temperature.
• Current QY measurement methods are limited to non-scattering media.

Purpose of the Study:

• To develop and demonstrate a new imaging method, quantum yield imaging (QYI), for mapping QY in optically diffusive media.
• To enable spatially resolved QY measurements in complex biological tissues.
• To assess the feasibility of QY as a sensitive indicator of local tissue parameters.

Main Methods:

• QYI combines wide-field diffuse optical techniques, specifically spatial frequency domain imaging (SFDI), with planar fluorescence imaging.
• SFDI measures background optical properties and fluorophore absorption.
• QY is calculated by integrating data from SFDI and fluorescence imaging, with instrument response corrected using a known QY standard.

Main Results:

• The study successfully demonstrated QYI in liquid phantoms using rhodamine B and SNARF-5.
• QY measurements showed high agreement with known values, with errors of 0.021 for rhodamine B and 0.012 for SNARF-5.
• The method accurately mapped QY across a range of methanol:water ratios and pH levels, demonstrating sensitivity to environmental changes.

Conclusions:

• Quantum Yield Imaging (QYI) is a viable technique for spatially mapping fluorescence quantum yield in optically diffusive media.
• This method overcomes limitations of traditional QY measurements in scattering environments.
• QYI holds potential for non-invasive monitoring of physiological parameters in biological tissues.