Development of fluorescent materials for Diffuse Fluorescence Tomography standards and phantoms

The availability of fluorescence standards is necessary in the development of systems and methods for fluorescence imaging. In this study, two approaches for developing diffuse fluorescence materials to be used as standards or phantoms in diffuse fluorescent tomography applications were investigated. Specifically, silicone rubber and polyester casting resin were used as base materials, and silicone pigments or TiO₂ / India Ink were added respectively to vary the optical properties. Characterization of the optical properties achieved was performed using time-resolved methods. Subsequently, different near-infrared fluorochromes were examined for imparting controlled and stable fluorescence properties. It was determined that hydrophobic fluorophores (IR 676 and IR 780 Iodide) suspended in dichloromethane and hydrophilic fluorophores (Cy5.5 and AF 750) suspended in methanol produced diffusive silicone and resin fluorescent materials, respectively. However only the hydrophobic fluorophores embedded within silicone resulted in the construction of a material with the characteristics of a standard, i.e. stability of fluorescence intensity with time and a linear dependence of normalized fluorescence intensity to fluorophore concentration.