Integrated Optics Set-up for Photodynamic Therapy

Abstract: Interstitial photodynamic therapy is a local solid cancer treatment technique that relies on the simultaneous presence of light, photosensitizer and oxygen. SpectraCure AB has been developing a light delivery system for prostate cancer therapy. The use of this instrument is meant to be extended to other solid tumor treatments such as cancer in the pancreas or the ear, nose and throat tract. The connection between the eighteen light sources and the patient is based on a mechanical switch that enables the system to alternate between treatment mode and monitoring mode. This report presents the development of an all optical passive circuit aimed at replacing the complex mechanical switch. The core part of this alternative system is the possibility to perform measurements on all the eighteen channels during the treatment times, with clear advantages in terms of robustness of the measurements and positive treatment outcome. This feature has been obtained introducing a frequency encoding of each channel. Briefly, each channel is tagged with a characteristic modulation frequency, therefore distinguishable at each detection point from the other channels and from the treatment light. Satisfying results have been obtained with the new design, in terms of reliability for the evaluation of the effective attenuation coefficient, repeatability of the results and costs. A set of specifications has been proposed, to be used in the next generation of IPDT instruments.