Review of the Dielectric Properties of Animal and Human Tumors Determined from In Vivo Measurements

In this article, we combine a review of the wide range of tissue dielectric studies and applications (e.g., safety, imaging, therapy) being pursued by the bioelectromagnetics community with a description of one specific application of dielectric measurements (in vivo tumor classification). The tumor measurements were acquired over a frequency range of 0.01-4.0 GHz using a technique based on the impedance change recorded by a short antenna when placed near or in a lossy dielectric. Substantial differences (up to 300%) were found between the dielectric properties of tumors (mammary adenocarcinoma, melanoma, lung carcinoma, glioblastoma and ependymoblastoma) and normal host tissues. Such differences reflect the known heterogeneity of abnormal cell growth in cancer. In addition, in vivo human measurements of breast carcinoma, normal skin and breast tissue indicate that a maximum differential power absorption (30% higher in tumor) occurs between 1.0 and 2.0 GHz. This information, when combined with tumor size, geometry, and anatomical location, enable the design and development of effective systems for the detection of tumors and for electromagnetically induced differential hyperthermia treatment. Finally, we also discuss these results in the context of other impedance and dielectric approaches used to characterize normal and neoplastic cells and tissues.