Quasi-real-time fluorescence imaging with lifetime dependent contrast

Area of Science:

• Biomedical Optics
• Fluorescence Imaging
• Biophotonics

Background:

• Conventional fluorescence lifetime imaging (FLI) is complex, requiring intricate algorithms and multiple data points.
• Signal-to-noise ratios diminish at longer delay times in traditional FLI, limiting tissue characterization.
• Existing methods face challenges in accurately quantifying fluorophore lifetimes for biomedical applications.

Purpose of the Study:

• To develop a simplified time-resolved fluorescence imaging method that bypasses lifetime extraction.
• To introduce normalized fluorescence yield imaging for enhanced contrast in distinguishing fluorophores and tissues.
• To demonstrate a potential clinical tool for noninvasive, real-time imaging applications.

Main Methods:

• Utilized normalized fluorescence yield imaging, a novel technique converting decay time differences into intensity differences.
• Employed a gated intensified charge-coupled device (iCCD) camera and an ultraviolet light-emitting diode (LED) light source for experimental verification.
• Applied simple mathematical algorithms to extract contrast rather than absolute lifetime values.

Main Results:

• Successfully distinguished between chemical dyes (Fluorescein, Rhodamine-B) and biomedical samples (elastin, collagen powders).
• Achieved good contrast for fluorophores with less than 6% difference in fluorescence lifetime.
• Demonstrated that extended gate times (up to 16 ns) can yield effective contrast depending on the sample.

Conclusions:

• Normalized fluorescence yield imaging offers a feasible alternative to conventional FLI by eliminating the need for lifetime extraction.
• The method's ability to generate contrast from fluorescence decay times shows promise for simplified biomedical imaging.
• This technique has potential for clinical translation in noninvasive, real-time tissue characterization and imaging.