Fast 3D Breast Imaging With a Transmission-Based Microwave System.

Microwave breast imaging has recently been explored for tumor detection, treatment monitoring, and estimating breast density. Only one prior work has presented quantitative three-dimensional (3D) breast imaging based on a full-wave inverse scattering approach applied to experimental data collected from human subjects; most other works rely on quantitative 2D images or qualitative reconstructions. This paper introduces a fast and efficient 3D quantitative reconstruction approach for microwave breast imaging without the need for prior information or iterative algorithms typically used in solving full-wave equations. The method assumes wave propagation in straight lines, similar to the ray tracing method used in ultrasound imaging, and formulates the algorithm based on this assumption. The algorithm is applied to data collected at multiple antennas over a wideband frequency range with a novel microwave transmission system. This system is designed to be in direct contact with the breast, eliminating the need for a matching medium. We experimentally demonstrate quantitative 3D permittivity reconstruction for graphite phantoms with various sizes and numbers of inclusions, comparing the results with available 3D CT scans of these phantoms. Next, we test this algorithm for 3D quantitative permittivity reconstruction in four healthy participants with different breast density categories and compare the images with their mammograms. Finally, the stability of the 3D permittivity reconstruction over three time points for the participants is demonstrated.