System for Bulk Dielectric Permittivity Estimation of Breast Tissues at Microwave Frequencies

This paper presents an apparatus capable of measuring the average dielectric properties of the human breast. It is composed of two arrays between which the breast is placed. Each array is fitted with five ultra-wideband (UWB) sensors operating from 1.5 to 10 GHz. Direct contact is made between the breast skin and the sensor arrays, avoiding any matching liquid. The transmission coefficients for all possible sensor pairs in the two arrays are measured in 15 s. The data are then transformed to the time domain, and a time delay spectroscopy technique is used to estimate permittivity. The system was tested using phantoms with known properties and showed accurate estimations. Tests on human subjects resulted in dielectric property estimates in line with published data, while variation between scans of the same volunteer is as small as 2%.