Determination of in-vivo tissue optical properties for anal photodynamic therapy

Determination of in-vivo tissue optical properties for anal photodynamic therapy (PDT) is challenging due to the light integrating-sphere effect in an enclosed cylindrical cavity. We developed a model for optical properties determination for anal PDT from measurements of light fluence rate inside a cylindrical cavity submerged in tissue-mimicking liquid phantoms. Measurements are performed in a set of phantoms with known optical properties (μa = 0.1-0.9 cm-1) and (μs’ = 5.5-16.5 cm-1) and the primary and scatter light fluence rates are determined. We developed a forward empirical model to relate scatter light fluence rate measured in an enclosed cylindrical geometry to the surrounding tissue optical properties in tissue-simulating liquid phantoms.