Dielectric properties of the normal and malignant breast tissues in xenograft mice at low frequencies (100 Hz–1 MHz)

Abstract

Abstract Previous studies have shown that dielectric properties of biological tissues can be imaged at high frequencies (50 MHz–20 GHz) to detect abnormalities such as tumors. While evidence suggests that imaging these properties at low frequencies (e.g. below 1 MHz) holds a good potential in medical applications, less research efforts have been dedicated to explore these properties at such frequencies for medical imaging. This study uses a recently developed technique to measure tissue dielectric properties of normal and corresponding cancerous tissue at low frequencies. This was accomplished by using a preclinical animal tumor model. To develop this animal model, human breast cancer cell line (MDA-MB-231) was injected into hind legs of severely compromised immunodeficient (SCID) mice. As a result, tumors were developed while they were permitted to grow to the size of 8–10 mm in 8 weeks. The electrical conductivity and permittivity (EC and EP) of the grown xenograft tumors and their surrounding normal tissue were measured at 100 Hz–1 MHz frequency using a measurement method which includes using a custom-made experimental setup in conjunction with an inverse finite element framework. Histological analysis was performed on the tumor and normal tissue specimens to assess differences in their micro-structure. Results indicated that both conductivity and permittivity of the tumors have significantly greater values than those of the surrounding normal tissue with average ratio values of 3.5:1 and 10.9:1 for the EC and EP, respectively. Results obtained in this study are consistent with micro-structural changes observed by histological assessment. The substantially high EP ratios measured in this study suggests that electrical permittivity at low frequencies can potentially be used as a powerful biomarker for the detection of breast malignancies.