AbstractID: 7828 Title: Tracking Small Volume Radiation-Induced Effects in Soft Tissue using
Electrical Impedance Spectroscopy
Optimal use of ionizing radiation in cancer and other medical treatments depends on a detailed understanding of non-targeted normal tissue response. In the
future, non-invasive biologically based imaging techniques, such as electrical impedance spectroscopy (EIS) may be used to determine radiation-response
distributions in each patient. This may allow response-tailored treatment plans and lead to accurate prediction of latent tissue reaction, before clinical
symptoms appear. Electrical impedance spectroscopy (EIS) is sensitive to histological change and we have previously demonstrated its capability in
detecting dose responses in muscle after large single X-ray doses of 70Gy–150Gy1. In this extension of earlier studies, smaller volumes (~0.5 cm3) are
irradiated to lower doses (26 and 52Gy at 5mm) by employing a high-dose-rate technique. Measurements were performed on thirty rats at one, two, and
three months post-irradiation, employing 31 frequencies in the 1kHz to 1MHz range. Our newly implemented 4-electrode impedance probe measures the
target tissue independent of the highly variable skin impedance, increasing measurement robustness. Mean low frequency conductivity values increased
from a baseline value of 0.23 Siemens/m (0.22-0.25 range) to 0.34 Siemen/m (0.31-0.38 range) in the high dose group and correlate with histologically
assessed injury progression. Our success in detecting responses at these greatly reduced doses and early time points is encouraging, yet conductivity values
overlapped between the two dose groups, indicating some limitation in sensitivity. Later time points should be included in future studies as these will
undoubtedly show greater electrical contrast and should be truer indicators of late damage.
1
Paulsen, et al. Rad. Res. 152(1),(1999)
Supported by NIH and NCI.