1 March 2016 Optical spectroscopy of radiotherapy and photodynamic therapy responses in normal rat skin shows vascular breakdown products
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Abstract
Photodynamic therapy (PDT) and radiotherapy are non-systemic cancer treatment options with different mechanisms of damage. So combining these techniques has been shown to have some synergy, and can mitigate their limitations such as low PDT light penetration or radiotherapy side effects. The present study monitored the induced tissue changes after PDT, radiotherapy, and a combination protocol in normal rat skin, using an optical spectroscopy system to track the observed biophysical changes. The Wistar rats were treated with one of the protocols: PDT followed by radiotherapy, PDT, radiotherapy and radiotherapy followed by PDT. Reflectance spectra were collected in order to observe the effects of these combined therapies, especially targeting vascular response. From the reflectance, information about oxygen saturation, met-hemoglobin and bilirubin concentration, blood volume fraction (BVF) and vessel radius were extracted from model fitting of the spectra. The rats were monitored for 24 hours after treatment. Results showed that there was no significant variation in the vessel size or BVF after the treatments. However, the PDT caused a significant increase in the met-hemoglobin and bilirubin concentrations, indicating an important blood breakdown. These results may provide an important clue on how the damage establishment takes place, helping to understand the effect of the combination of those techniques in order to verify the existence of a known synergistic effect.
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Cintia Teles de Andrade, Marcelo Saito Nogueira, Stephen Chad Kanick, Kayla Marra, Jason Gunn, Jacqueline Andreozzi, Kimberley S. Samkoe, Cristina Kurachi, Brian W. Pogue, "Optical spectroscopy of radiotherapy and photodynamic therapy responses in normal rat skin shows vascular breakdown products", Proc. SPIE 9694, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXV, 969410 (1 March 2016); doi: 10.1117/12.2210988; https://doi.org/10.1117/12.2210988
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