Relation between fluorescence spectra of dilute and turbid samples

Area of Science:

• Biomedical Optics
• Spectroscopy
• Biophysics

Background:

• Analyzing fluorescence in turbid biological tissues presents challenges due to light scattering and absorption.
• Rank-annihilation-factor analysis (RAFA) is a powerful technique for spectral data analysis.
• Understanding fluorescence properties of biological media is crucial for diagnostics and research.

Purpose of the Study:

• To extend rank-annihilation-factor analysis (RAFA) for analyzing fluorescence from homogeneous turbid samples.
• To establish a fundamental relationship between fluorescence in dilute and turbid solutions.
• To validate the developed method using spectroscopic data from human aorta samples.

Main Methods:

• Derived a 'transfer function' for turbid materials using the two-flux Kubelka-Munk theory.
• Applied the transfer function to relate dilute and turbid solution fluorescence.
• Tested the method with fluorescence spectroscopy data from optically thin and turbid human aorta samples at 450-nm and 340-nm excitation.

Main Results:

• The extended RAFA method showed good agreement between measured and predicted dilute-solution fluorescence spectra for turbid samples.
• Agreement was within 5% at all emission wavelengths for 450-nm excitation.
• Agreement was within 20% for 340-nm excitation, with minor residual Soret-band absorption.
• Simulations indicated the transfer function is more sensitive to absorption than scattering properties.

Conclusions:

• The developed transfer function effectively extends RAFA for turbid sample fluorescence analysis.
• The method provides accurate predictions of fluorescence spectra in turbid biological media.
• The technique shows potential for applications in biomedical optics and material characterization where absorption is a key factor.