Clinical evaluation of microwave breast imaging using scattering tomography

Microwave imaging has attracted increasing attention as a breast tumor detection modality because it is non-ionizing and poses minimal risk to the human body. In particular, microwave tomography, which is based on solving the inverse scattering problem, enables visualization of the internal structure of tissues and is therefore expected to have a significant clinical potential. However, the practical implementation of microwave tomography has been hindered by the extremely small scattered-field variations produced by small malignant lesions within lossy breast tissue, as well as unavoidable modeling errors in numerical simulations of the human body and the imaging system. In this study, we introduce a clinically operable microwave breast imaging device that incorporates two key innovations: (i) A highly sensitive dual-polarized antenna array designed to enhance the detectability of weak scattered fields, and (ii) a robust inversion algorithm capable of reconstructing permittivity distributions under substantial modeling and measurement uncertainties. After outlining the relevant electromagnetic properties of breast tissue, we describe how these integrated hardware and software innovations overcome the limitations that have prevented earlier systems from achieving clinical performance. Finally, we summarize clinical results obtained from 24 breast tumor patients. The prototype achieved a sensitivity of 58%, surpassing that of X-ray mammography (40%) in the same cohort, demonstrating the practical potential of our innovation-driven approach to microwave breast imaging.