Design of illumination devices for delivery of photodynamic therapy in the oral cavity

We present three designs for delivery of light in the oral cavity for photodynamic therapy (PDT) under the requirements of average irradiance of 50 mW/cm2 and spatial non-uniformities well under 10% over a square area of 25 mm2. The main goal is to design a device that avoids having to shield the oral cavity prior to irradiation for PDT. Illumination theory is instrumental in identifying an effective geometry for the device. The designs proposed build upon the technology that is already available for PDT and use illumination theory concepts to maximize the efficiency of the light delivery. One design combines a cylindrical diffusing fiber with a reflector derived from the edge-ray theorem while a second consists of a fiber illuminator coupled to a lightpipe device. Both designs are successful in delivering the light reducing the need of shielding and in providing the desired irradiance and uniformity. The two approaches performed comparably and provided a higher irradiance than needed, thus inspiring the design of a third, simpler design based on an off-axis cylinder reflector.