Name: Eberhard Gersing

Email: egersin@gwdg.de

CompanyName: University Hospital Goettingen

Country: Germany

Abstract: Cancer tissue monitoring during photodynamic treatment using bioimpedance spectroscopy

In earlier experiments we investigated the changes in tumor tissue during hyperthermia by impedance spectroscopy. The aim of the present investigation is the detection of the effects of photodynamic treatment (PDT) on tumor tissue without and with additional application of hyperthermia.
After administration of the photo-active drug, the tumors (DS sarcoma) grown on the hind feet of rats were irradiated with suitably filtered light of a halogen lamp during 60 min. Before, during and after the irradiation, the impedance was measured in the frequency range of 100 Hz to 3.7 MHz using a pair of titanium needle electrodes (with fractal surfaces) inserted into the tumor. Additionally, the temperatures of the tumor and the body as well as the mean arterial blood pressure were recorded.
In contrast to an exclusive hyperthermic treatment (producing an extracellular edema), the evaluation of the impedance spectra shows that the PDT causes an intracellular edema, beginning with the onset of the irradiation. The effect is increased by additional application of hyperthermia.
The method of impedance spectroscopy (and presumably multifrequency tomography as well) proves to be a helpful tool for immediate detection of the alterations in tissue during treatment.

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