Instrumental, optical and geometrical parameters affecting time-gated diffuse optical measurements: a systematic study.

In time-domain diffuse optics the sensitivity to localized absorption changes buried inside a diffusive medium depends strongly on the interplay between instrumental, optical and geometrical parameters, which can hinder the theoretical advantages of novel measurement strategies like the short source-detector distance approach. Here, we present a study based on experimental measurements and simulations to comprehensively evaluate the effect of all different parameters. Results are evaluated exploiting standardized figures of merit, like contrast and contrast-to-noise ratio, to quantify the system sensitivity to deep localized absorption perturbations. Key findings show that the most critical hardware parameter is the memory effect which ultimately limits the dynamic range. Further, a choice of the source-detector distance around 10 mm seems to be a good compromise to compensate non-idealities in practical systems still preserving the advantages of short distances. This work provides both indications for users about the best measurement conditions and strategies, and for technology developers to identify the most crucial hardware features in view of next generation diffuse optics systems.