Photodynamic Therapy (PDT) is used clinically for the treatment of Actinic Kerasotis (AK) and non-melanoma skin cancers (NMSC). These treatments utilize the patient’s ability to convert the pro-drug aminolevulinic acid (ALA) to protoporphyrin IX (PpIX) as part of the heme cycle. Conventional PDT treatment requires a period of incubation to increase the concentration of PpIX at the affected site before a high fluence-rate narrow band light is used to activate the PpIX. Upon activation, the release of reactive oxygen species causes localized cell death, but has also been attributed to reports of pain during treatment. Broadband low fluence-rate light sources and shorter incubation times have been shown to reduce the reported pain while still providing similar efficacy. To compare the light dose provided by these various narrowband and broadband sources, a PpIX absorbance weighted light dose is used. Previous work using a murine skin model has shown this metric to be correlated with epidermal damage and STAT3 cross-linking. However, when comparing light sources at different wavelengths it is important to consider the penetration depth of both the PpIX and the light. Monte Carlo simulations have been implemented to better estimate the impact of tissue optical properties and biodistribution of PpIX. These results are compared with in vivo bioassays with the aim of providing a more accurate tool for light-dose estimation in clinical practice.
Ethan P. LaRochelle, Kayla A. Marra, Karina E Lukovits, M. Shane Chapman, Edward V. Maytin, Tayyaba Hasan, and Brian W. Pogue, "A comparison of low fluence-rate light sources for ALA-PpIX based photodynamic therapy of skin
(Conference Presentation)," Proc. SPIE 10476, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXVII, 1047606 (Presented at SPIE BiOS: January 27, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2290805.5751476566001.
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