Monitoring the Effect of PDT on in Vivo Oxygen Saturation and Microvascular Circulation
Photodynamic therapy (PDT) is a treatment for various malignant and benign lesions using light-activated photosensitising drugs in the presence of molecular oxygen. PDT causes tissue damage by a combination of processes involving the production of reactive oxygen species (in particular singlet oxygen), which can directly induce cell killing1, or indirectly via disruption of the tissue microvasculature2. Since the cytotoxic effect relies on the presence of oxygen, monitoring of tissue oxygenation both during and after PDT is important for understanding the basic physiological mechanisms and dosimetry of PDT3,4. Furthermore, it is known that the tumour destruction can be limited by the amount of available oxygen5, 6. During irradiation, changes in tissue oxygenation occur due to PDT-induced vasoconstriction and oxygen consumption in photodynamic reactions. Thereby tissue oxygenation can be reduced to levels insufficient for any further tumour destruction7, 8. In order to prevent a significant reduction in available oxygen levels, online real time monitoring could be useful during treatment.
KeywordsPhotodynamic Therapy Fluorescein Angiography Tissue Oxygen Saturation Porfimer Sodium Exposed Liver
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