Spatial Resolution Evaluation of a Microwave System for Breast Cancer Screening

The ability of microwave breast imaging to achieve sub-centimeter spatial resolution has been proven before in simulation and simple experimental studies. However, detecting sub-centimeter tumours depends not only on the theoretical spatial resolution limit, but also on the level of background clutter and measurement uncertainty. Therefore, estimating the actual limit of the smallest detectable object in a specific measurement setup is critical before the setup can be deployed in a clinical scenario. Here, we present a method of such evaluation on a planar microwave imaging setup for breast cancer imaging. The method utilizes the measurement of a small scattering probe of known size and permittivity in a uniform embedding medium. The contrast-to-noise ratio (CNR) of the generated point spread function can then be evaluated to determine the system-specific spatial resolution. The effectiveness of this approach is demonstrated in an experimental study of a compressed-breast phantom. This method can be applied to evaluate the limit of the size of detectable objects for other acquisitions systems, e.g. hemispherical or cylindrical antenna configurations.