A DESIGN FOR A STABLE AND REPRODUCIBLE PHANTOM FOR USE IN NEAR-INFRARED IMAGING AND SPECTROSCOPY

This note describes a stable, reproducible phantom which replicates the optical properties of tissue, for use in near infra-red spectroscopy and imaging. The base material is a clear, unpolymerized liquid resin, which forms a polyester on addition of a catalyst. The polyester has a low intrinsic absorption coefficient for infra-red light and is non-scattering. Before the resin is set, measured quantities of scattering particle suspensions and absorbing dyes can be added. The scattering-phase function of these particles has been measured, and the mean cosine of the scattering angle, g, calculated. Knowing this, by varying the concentration of scattering particles a range of materials with known transport scattering coefficients can be produced. By varying the concentration and mix of dyes, the absorption coefficient of the resin can be easily controlled. The resin can be easily machined or cast into arbitrary shapes, with regions of differing optical properties. Once set the polyester is stable, in terms of both physical and optical properties.