Magnetic contrast-enhanced microwave biomedical imaging using discontinuous Galerkin contrast source inversion

Microwave imaging (MWI) continues to steadily progress towards clinical application as a low-cost complementary imaging tool for breast cancer detection and treatment monitoring. Contrast-enhanced MWI is a relatively new extension to the research field which employs exogenous agents to improve resulting reconstructions by artificially accentuating the complex dielectric or magnetic property variation between healthy and cancerous tissues. Although a handful of microwave contrast agent studies have been carried out focusing primarily on modifying the permittivity of the targeted tissue (S.C. Hagness et al., IEEE Trans. BME, 57, 8, 1831–1834, 2010), recent investigations of magnetic nano-particles (MNP) have been of particular interest, since they augment the magnetic permeability of the region in which they accumulate. As a dearth of magnetic material exists naturally in the human body, MNP-enhanced MWI allows the detection of targeted induced magnetic anomalies within otherwise purely dielectric biological tissues, using the electromagnetic response produced by clusters of retained MNPs (O.M. Bucci et al., IEEE Trans. Biomed. Eng., 58, 9, 2528–2536, 2011). To the authors´ knowledge the only published work reporting quantitative images of magnetic polarizability has used synthetic breast data, with inversions based on the truncated singular value decomposition (TSVD) scheme (R. Scapaticci et al., IEEE Trans. Biomed. Eng., 61, 4, 1071–1079, 2014).