Joint inversion of electromagnetic and acoustic data with edge-preserving regularization for breast imaging

Joint inversion of microwave and ultrasonic data for breast imaging is investigated with deterministic edge-preserving regularization by introducing auxiliary variables indicating whether a pixel is on an edge or not. These edge markers are shared by dielectric and acoustic parameters and are the link to perform fusion between these two modalities. They can be jointly optimized from the last parameter profiles of microwave and ultrasonic cases and guide the next optimization as the coefficients of the regularization term. Alternate minimization is used to update acoustic contrast, edge markers and dielectric contrast. Comprehensive numerical experiments are carried out on three breast phantoms, a simple synthetic one and two extracted from a database. The results show that the joint inversion algorithm can gain from the high resolution of ultrasonic imaging and the high contrast of microwave imaging. The quality of microwave imaging is enhanced in clear fashion and small tumors can be detected.