A novel microwave tomography system for breast imaging based on the modulated scattering technique

Summary form only given. Biomedical microwave tomography (BMWT) is a soft-tissue imaging modality that uses microwave radiation for reconstructing permittivity and conductivity profile of biological targets, also referred to as the complex dielectric profile. In BMWT an array of antennas surround the tissue and illuminate it successively, while the remaining antennas collect the field scattered by the tissue. The collected field data are then calibrated and processed using a nonlinear inverse scattering optimization algorithm. The outcome is a collection of quantitative images that represents the complex dielectric profile of the tissue.Our existing BMWT system at the University of Manitoba uses 24 dipole antennas for imaging limb tissues. We have successfully reconstructed images of human forearm and animal tissues using this system (M. OstadRahimi, et.al. IEEE Trans. Microw. Theory Techn., 2013). This two-dimensional (2D) BMWT system only provides images of the tissue on the transverseplane, thus it is not suitable for 3D breast imaging. In this work we study the feasibility of a novel 3D MWT approach to breast imaging. Note that the only reported BMWT clinical prototype for breast imaging is a 2D system that uses 16 monopole antennas (P. Meaney et.al. Acad. Radiol., 2007). The new system uses a fixed co-resident waveguide slot-antenna system that attaches under a clinical bed. Each multiplexed transmitting or collecting waveguide has a series of slots, equipped with at least one p-i-n diode which acts as a near-field probe. These are implemented using printed-circuit-boards. The waveguide-probe system is configured so as to create a 3D chamber. The p-i-n diodes are utilized to implement the modulated scattering technique (M. OstadRahimi et.al. IEEE Trans. Instrum. Meas., 2012). A matching fluid is usually required for imaging biological tissues, which reduces the mismatch between antennas and the tissue, as well as the dielectric contrast of the object to be rec- nstructed (C. Gilmore et.al. AAPM Med. Physics, 2013). The waveguide array is designed to operate inside such matching fluid i.e. water in this implementation. The same matching fluid fills the waveguide antennas. The collected field data are then calibrated and processed by our finite element contrast source inversion algorithm (A. Zakaria et.al. PIER, 2013). Here we present an analysis of the system as well as preliminary images that have been reconstructed from data obtained using this system.