Anisotropic modeling for IR navigation-based PDT dosimetry.

An infrared (IR) camera system has been developed for use in pleural photodynamic therapy (PDT). This system was introduced to pleural PDT to provide uniform light dose distribution to ensure predictable PDT outcome. Light is delivered through a fiber that is in an endotracheal (ET) tube filled with Intralipid as scattering media. A tracking tool is attached to the ET tube to monitor the position of the optical fiber based point source. An anisotropic light distribution model is introduced to correct the angle dependent light distribution due to a capped end by design of the ET tube, which scatters light differently than the sides. In this study, the anisotropic nature of the balloon was characterized and incorporated into the calculation for light fluence during treatment. This model is verified by the light dose calculation from a phantom study. Furthermore, a new tracking tool was designed with multiple faces to increase the angular field of view and thus collect more viable data during treatment. The new tracking tool is directly entered into the ET tube with the light delivering fiber, thus eliminating the need to calibrate the laser source position prior to treatment via an optimization method. With this improved system, the calculated light fluence and the measured isotropic detector readings are more accurately matched.