Bioimpedance and treatment response monitoring in cancer research
Bioimpedance monitoring in vivo is an non-invasive technique to examine changes in electrical conductivity. The electrical properties of tissue depend upon the structural organization of cells, cell shape, structure and orientation, integrity of cell membranes, relative proportions of intra- and extra-cellular fluids and ionic composition within the tissue. Non-invasive bioimpedance monitoring techniques, correlated with pathology, may be used to predict radiosensitivity of tumours. The aim of this study is to evaluate the ability of bioimpedance monitoring to describe morphology and physiology of non-treated cancerous tissue and mapping radiosensitivity of tumors with different type, size and pathobiology.
A model with xenografts established from the human colorectal cell line HT29 were grown from implanted tumor tissue into immune-deficient GBNIH nude mice. Laboratory animals of male sex were anaesthetized with katte-zoletilmix and tumor size monitoried continuously. The mice were divided into three dose groups each given 0, 5, and 15 Gy with an 60Co source, respectively. Impedance measurements were performed with a 4-electrode probe. Tumor was compressed between the two electrodes to get full contact with surfaces. Impedances were recorded at frequencies between 1Hz and 1 MHz with a Solartron 1260 gain-phase analyzer and Solartron 1294 impedance unit.
Electrical impedance monitoring, as applied in this study, was evaluated as a measurement technique for radiation response prediction. The preclinical study, conducted on nude mice implanted with a human colorectal cancer, revealed the ability of bioimpedance monitoring method to detect radiation-induced electrical changes of growing tumors on an individual subject basis. There are two components of our study, electrical impedance monitoring and histological assessment. Impedance results are presented as a function of time. Impedans and phase data for irradiated and non-irradiated tumour are plotted as a function of necrosis fraction and tumor volume.
Impedance and phase values at low frequencies show some response to radiation injury. There was found to be correlation in both cases: between impedance and necrosis fraction and between impedance and tumor volume. Our results suggest that non-invasive impedance monitoring technique is able to provide information useful in predicting radiosensitivity of tumors.