Determining the optical properties of a gelatin‑TiO2 phantom at 780 nm

Tissue phantoms play a central role in validating biomedical imaging techniques. Here we employ a series of methods that aim to fully determine the optical properties, i.e., the refractive index n, absorption coefficient μ(a), transport mean free path [Formula: see text], and scattering coefficient μ(s) of a TiO(2) in gelatin phantom intended for use in optoacoustic imaging. For the determination of the key parameters μ(a) and [Formula: see text], we employ a variant of time of flight measurements, where fiber optodes are immersed into the phantom to minimize the influence of boundaries. The robustness of the method was verified with Monte Carlo simulations, where the experimentally obtained values served as input parameters for the simulations. The excellent agreement between simulations and experiments confirmed the reliability of the results. The parameters determined at 780 nm are [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]The asymmetry parameter g obtained from the parameters [Formula: see text] and [Formula: see text] is 0.93, which indicates that the scattering entities are not bare TiO(2) particles but large sparse clusters. The interaction between the scattering particles and the gelatin matrix should be taken into account when developing such phantoms.