Photodynamic therapy (PDT) involves interactions between the three main components of light fluence,
photosensitizer concentration, and oxygenation. Currently, singlet oxygen explicit dosimetry (SOED) has focused on
the first two of these components. The macroscopic model to calculate reacted singlet oxygen has previously
involved a fixed initial ground state oxygen concentration. A phosphorescence-based oxygen probe was used to
measure ground state oxygen concentration throughout treatments for mice bearing radioactively induced
fibroscarcoma tumors. Photofrin-, BPD-, and HPPH-mediated PDT was performed on mice. Model-calculated
oxygen and measured oxygen was compared to evaluate the macroscopic model as well as the photochemical
parameters involved. Oxygen measurements at various depths were compared to calculated values. Furthermore, we
explored the use of noninvasive diffuse correlation spectroscopy (DCS) to measure tumor blood flow changes in
response to PDT to improve the model calculation of reacted singlet oxygen. Mice were monitored after treatment to
see the effect of oxygenation on long-term recurrence-free survival as well as the efficacy of using reacted singlet
oxygen as a predictive measure of outcome. Measurement of oxygenation during treatment helps to improve SOED
as well as confirm the photochemical parameters involved in the macroscopic model. Use of DCS in predicting
oxygenation changes was also investigated.
Michele M. Kim, Rozhin Penjweini, Yi Hong Ong, Jarod C. Finlay, and Timothy C. Zhu, "Oxygen measurements to improve singlet oxygen dosimetry," Proc. SPIE 10047, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXVI, 100470A (Presented at SPIE BiOS: January 28, 2017; Published: 13 February 2017); https://doi.org/10.1117/12.2250432.
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