Enabling technology for precision, image-guided photodynamic therapy of oral lesions: monitoring protoporphyrin IX photoproduct accumulation as a dosimetry reporter

Photodynamic therapy (PDT) using aminolevulinic acid (ALA) induced protoporphyrin IX (PpIX) has been shown to be effective for early stage cancers and pre-malignant lesions of the oral cavity. Nevertheless, adoption remains limited to a few practitioners with expertise in laser medicine. We have developed intraoral PDT hardware with a dental camera form factor which integrates PDT light delivery with multichannel fluorescence imaging for treatment guidance and monitoring. In this proceedings article we specifically investigate the role of fluorescence quantification of PpIX photoproduct (PP) accumulation as an optical reporter of dose deposited. Using tissue phantoms we show that PpIX fluorescence signal decreases while PP fluorescence increases with increasing PDT light dose, corresponding to increased production of reactive molecular species. Going forward the combined PP/photobleaching optical signature could serve as a real time reporter of dose deposited during ALA-PDT of oral lesions.