Preliminary experimental results for imaging at millimetre-wave frequencies in breast phantoms

Breast cancer is one of the main causes of death among women worldwide. Microwave and millimetre wave imaging systems for breast cancer detection have been proposed as alternative or complementary techniques to the actual diagnostic devices. Several microwave prototypes and breast tissue-mimicking phantoms have been proposed to scan the breast in the low microwave regime; however, when cancers within very fat tissues are targeted the resolution at microwave frequencies is not satisfying for an early diagnosis. A possible solution to this problem could be the use of higher frequencies, at the cost of a relatively lower penetration depth. In this paper, for the first time, a preliminary image at mm-waves of a fatty breast phantom with an embedded 4-mm metallic target is presented. The recipe and the procedure for phantom preparation is explained, and dielectric properties are measured and compared to those of ex-vivo human tissues, in the [0.5-50] GHz frequency range. The proposed preliminary mm-wave system architecture is composed by two mono-modal truncated double-ridge waveguides), and a synthetic linear aperture is created by shifting these radiators with two microstep actuators in 10 different positions. Data were acquired in the [18]-[40] GHz frequency range and calibrated. The image was finally obtained through Delay and Sum beamforming with coherence-factor weighting.