Dielectric properties of breast tissues: Experimental results up to 50 GHz

Nowadays, breast cancer is the most diffused disease among women around the word. Statistics indicate an increase in incident rate, especially in Europe, North America, and Oceania. Currently, the set of diagnostic tools for breast cancer detection is wide. Nevertheless, these tools exhibit limitations, especially when aiming at cost-effective periodical mass screenings. Therefore, there is a growing interest toward microwave imaging systems for biomedical applications, and several microwave prototypes have been proposed worldwide. However, in order to have a satisfying resolution for early-diagnosis, microwaves may be not sufficient, and a crucial point is the utilization of higher frequencies. To this aim, as the physical principle of all imaging techniques at these frequencies is based on the detection of the dielectric discontinuities between materials, the characterization of all breast tissues in the mm-wave spectrum becomes fundamental. No experimental data were available beyond 20 GHz before the two extensive experimental campaigns performed at the European Institute of Oncology in 2014 and 2016. In this paper, the results concerning the full database (given by the fusion of the two datasets) of ex-vivo samples, are presented. In particular, a huge amount of data is considered, involving more than 330 samples, of which 237 healthy and 99 malignant, taken from around 100 women with an age spanning from 28 years up to 85 years.