Point-of-care breast imaging for monitoring neoadjuvant treatment: case studies with transmission-based microwave imaging

Objective: This study aims to track changes in tissues due to neoadjuvant chemotherapy with a transmission-based microwave imaging system that scans the entire breast and is fast, comfortable and suited to point-of-care implementation. Methods: Microwave scans are collected with patients undergoing chemotherapy treatment. Specifically, both breasts are scanned prior to each cycle of chemotherapy. The microwave scanner consists of planar transmit and receive arrays that are placed in contact with the breast. Signals with frequency content from 0.1 to 8 GHz are transmitted through the tissue, and the travel time of these signals is used to estimate the microwave frequency properties (permittivity). Property estimates at each sensor pair are mapped to the imaging plane. Results: Case studies are presented for 6 patients. Comparison of the scans of left and right breasts suggests increased properties related to the presence of the tumor at the initial scan. Consistent properties are observed for the contralateral breast at different time points, while changes in the breast with the tumor are noted. In addition, differences between the breasts are more clearly depicted in dense breasts. Conclusions: This study demonstrates the potential for a transmission-based microwave scanner to provide feedback on treatment progress. Significance: Point-of-care microwave imaging has the potential to offer regular, quantitative feedback on treatment progress as an alternative to palpation.