Quality Control of Microwave Equipment for Tissue Imaging

While the development of microwave imaging technology for biomedical applications has been ongoing for many years, no clinical devices are currently in use. A major challenge is achieving data quality that would ensure adequate image resolution for the specific diagnostic application. Imaging systems are typically designed with a theoretical resolution limit in mind, which is rarely achieved in practice due to measurement uncertainties, background clutter, and system noise. Uncertainties and background clutter are particularly prominent in medical diagnostic imaging. This paper proposes a method for data quality assessment of an experimental imaging system that aims at a specific image resolution. It utilizes two measurements, one of a uniform background medium and one of the same medium with a small scattering probe embedded within it. The probe's size and permittivity reflect the desired application-specific resolution. The method extracts the system point-spread function (PSF) from the two measurements and computes the PSF contrast-to-noise ratio. A case study is presented, demonstrating the quality control protocol and its ability to identify datasets of inadequate quality and provide an evaluation metric. The protocol also highlights possible sources of error and enables data filtering that increases significantly the reconstructed image quality.