Oxygen microelectrode measurements in R3230Ac Tumors during photodynamic therapy with verteporfin

Measurements of tissue oxygen partial pressure (pO2), blood flow and blood pressure were recorded in rat mammary R323OAc tumors during treatment with verteporfin-based photodynamic therapy. Microelectrodes of 12 micron tip diameter were used in a fixed position throughout the measurements to provide data on the temporal changes at a single location within the tissue. The microelectrode signal changes in P°2 indicated an overall trend to acute loss of P°2 after treatment, but with some notable exceptions where the P02 did not decrease either during the treatment or after treatment. These regions which showed little change in P02 were correlated with locations in which the P°2 was high to begin with before the initiation of treatment. Blood flow decreased during treatment, with the dominant effect immediately upon the initiation of treatment.

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