Fiber-optic bundle design for quantitative fluorescence measurement from tissue

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Abstract
We demonstrate a new design for a fiber-optic bundle to measure fluorescence signals from tissue. In this design, the intensity of the signal is not significantly affected by the medium’s absorption and scattering coefficients and hence depends only on the fluorophore’s properties. Monte Carlo simulations of light scattering were used for designing and verifying the results obtained. The fiber-optic bundle was tested on tissue-simulating phantoms and compared with a standard nonimaging fiber-optic bundle. The new bundle was composed of 30 individual 100-μm fibers. Fibers on the end of the bundle that touch the tissue surface were separated from one another by approximately 1 mm. This design permits integration of the signal over several locations while maintaining localized sampling from regions smaller than the average mean free scattering path of the tissue. The bundle was tested by measurement of the fluorescence signals from tissue-simulating solutions containing fluorescent compounds. These studies demonstrate that the new bundle reduces the effect of the intrinsic absorption in the medium, permitting detection of fluorescence that is linearly proportional to the fluorophore concentration.