Advantages of fluorescence over diffuse reflectance measurements tested in phantom experiments with dynamic inflow of ICG

Time-resolved measurements of diffuse reflectance and fluorescence were carried out using phantom with dynamic inflow of indocyanine green (ICG) in tubes located at different depths. Better sensitivity of fluorescence signals related to the inflow of the dye was observed in comparison to simultaneously acquired diffuse reflectance. Obtained results can be referred to results of in-vivo measurements. We have observed much larger amplitude of changes in relative number of detected photons, mean time of flight and variance of the distributions of times of arrival of fluorescence photons than amplitudes of respective parameters measured from diffuse reflectance distributions of times of flight of photons. The constructed phantom allows us to study influence of concentration of the dye in the tube and the surrounding medium as well as temporal relation between appearance of the boli in deeper and superficial tube. Results of the study were used in optimization of the time-resolved multichannel system for simultaneous monitoring of fluorescence and reflectance.