MEASUREMENT OF DIELECTRIC-PROPERTIES OF SUBCUTANEOUS FAT WITH OPEN-ENDED COAXIAL SENSORS

A three-layer model of stratum corneum, epidermis/dermis and subcutane ous fat has been developed for the capacitance of an open-ended coaxia l line in contact with human skin. Applying the model, the electrical properties of subcutaneous fat can be calculated from skin dielectric measurements with three probes of different sizes. The three-layer mod el is based on a variational formula for the capacitance of the coaxia l probe. An accurate approximation for the dielectric constant of the multilayer cutaneous structure is presented for the inverse problem of solving the dielectric constants of various layers. The method was te sted at 300 MHz with breast cancer patients who often have radiotherap y-induced late alterations in the structure of subcutaneous fat due to the development of subcutaneous fibrosis. Measurements from 206 sites yielded a good agreement between the dielectric constant of subcutane ous fat and the clinical score for subcutaneous fibrosis.