Optimization of the phantom parameters for diffuse optical fluorescence tomography of biotissues <i>in vivo</i>
The paper presents the results obtained in studies of the conditions ensuring correct recording of the concentration of the photosensitizer based on a new indotricarbocyanine dye in biotissues in vivo with the use of a diffuse fluorescence tomograph. When the dye concentration in 50 % blood serum is 4 mmol/l, the fluorescence lifetime is τ<sub>f</sub> = 1.44 ns and in 5 % bovine serum albumin it comes to τ<sub>f</sub> = 1.41 ns, and the kinetics of fluorescence decay are single-exponential. It is demonstrated that, when a concentration of the dye is 40 mmol/l, in the solution one can observe not only monomers but also nonluminescent H-aggregates, with the absorption band overlapping the fluorescence spectrum of monomers. As a result, there is a possibility for nonradiative transfer of the electronic excitation energy from monomers to the nonluminescent associates leading to a decrease of the molecular fluorescence lifetime down to 1.18 ns. It has been found that an ideal medium to prepare a solution for the phantom is blood serum with the dye concentration below 4 mmol/l.