Quantitative fluorescence spectroscopy in turbid media using fluorescence differential path length spectroscopy

We have developed a new technique, fluorescence differential path length spectroscopy (FDPS), that enables the quantitative investigation of fluorophores in turbid media. FDPS measurements are made with the same probe geometry as differential path length spectroscopy (DPS) measurements. Phantom measurements are performed for two fiber diameters (400 mu m and 800 mu m) and for a wide range of optical properties (mu(s)': 0 to 10 mm(-1); mu(a): 0 to 2 mm(-1)) to investigate the influence of the optical properties on the measured differential fluorescence signal. The differential fluorescence signal varies by a factor of 1.4 and 2.2 over the biologically relevant scattering range (0.5 to 5 mm(-1)) for a given fluorophore concentration for 400 mu m and 800 mu m fibers, respectively. The differential fluorescence signal is attenuated due to absorption at the excitation wavelength following Lambert-Beer's law with a path length equal to the differential path length. (C) 2008 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.2992132]