An Integrated Microwave-Ultrasound Breast Imaging System: Initial Phantom Results

A novel, integrated microwave-ultrasound breast imaging system that requires minimal or no movement of the breast between scans has been developed. In this work, we present initial imaging results using a tissue-mimicking phantom, with experimental data obtained from the dual-mode system. The breast phantom is composed of four regions: skin, fat, fibrog-landular and tumour, each with complex-valued permittivity and acoustic speed designed to approximate those of real breast tissue. Quantitative 3-D ultrasound imaging is performed using a ray-based sound-speed reconstruction algorithm. Prior information is extracted from the sound-speed image and incorporated into the microwave finite-element method contrast-source inversion algorithm either as an initial guess or as a numerical inhomogeneous background. Although the resolution of the ultrasound imaging system itself is insufficient to detect the tumour, the low-resolution sound-speed reconstructions are used to improve tumour detection via microwave imaging. Resultant images with and without the ultrasound-derived prior information are presented. A simple thresholding technique is employed to assess the system's ability for tumour-detection. Preliminary findings are indicative of the potential of ultrasound-derived prior information in enhancing microwave imaging of the breast.