Influence of the boundary conditions on the accuracy of diffusion theory in frequency-resolved spectroscopy

摘要

A detailed investigation of the use of time-resolved reflectance and frequency-resolved reflectance for the optical characterization of scattering medium such as breast tissues based on the diffusion equation has been performed. Two different boundary conditions were imposed at the air-tissue interface : the first use the" zero real surface" (ZRS), the second refers to the " zero extrapolated surface" (ZES). To simplify the preliminary analysis, the tissues have been assimilated to a semi-infinite geometry or a slab sufficiently thick. Among the results, the computation showed that at low frequency approximation, the determination of the phase angle shift is independent of whatever boundary conditions is applied. Consequently breast tissue optical properties would be retrieved by means of frequency resolved data (modulation and phase) recorded at two different radial distances. For modulated light at f≈20 MHz, and using a model accounting for simple ZRS formulation. Under thes approximations discrepancies are within 3% for μ_a and 0.5% for μ'_s.