Safety assessment of microwave radar breast imaging in the 0.434-9 GHz range

In recent years, microwave imaging has become a possible candidate for the early detection of breast cancer. Due to the different water content, there exists a dielectric contrast between malignant and healthy breast tissue at microwave frequencies. In addition, breast tumours appear relatively close to the skin surface, allowing low-power microwaves to penetrate through the tissue with a loss that is acceptably low to permit for a radar-like detection approach. While this imaging modality is relatively new, and a few prototypes have been reported, not many publications consider its safety.;This work studies the exposure of a breast in the far field of radiofrequency sources operating in the 0.434-9-GHz range to assess the safety of a basic radar microwave imaging system. The electromagnetic fields inside a realistic MRI-derived 3-D numerical breast model has been computed using the finite-difference time-domain (FDTD) method with the help of SEMCAD-X (Schmid & Partner Engineering AG), a 3-D FDTD solver. It was used to model the resulting Specific Absorption Rate (SAR) of the breast tissue exposed to a plane wave. Experimental results are presented and discussed to determine whether they comply with exposure limits from Health's Canada Safety Code 6.