Realtime Tracking of the Photobleaching Trajectory During Photodynamic Therapy

Objective: Photodynamic therapy (PDT) is an alternative treatment for cancer, which involves the administration of a photosensitizing agent that is activated by light at a specific wavelength. This illumination causes after a sequence of photoreactions, the production of reactive oxygen species responsible for the death of the tumor cells but also the degradation of the photosensitizing agent, which then loose the fluorescence properties. The phenomenon is commonly known as the photobleaching process and can be considered as a therapy efficiency indicator. Methods: This paper presents the design and validation of a real-time controller able to track a preset photobleaching trajectory by modulating the light impulses width during the treatment sessions. Results: This innovative solution was validated by in vivo experiments that have shown a significantly improvement of reproducibility of the interindividual photobleaching kinetic. Conclusion: We believe that this approach could lead to personalized PDT modalities. Significance: This work may open new perspectives in the control and optimization of photodynamic treatments.