MWI – MicroWave Imaging

Microwave Imaging (MWI) has been extensively used to analyze dielectric bodies due to the fact that microwave radiation can penetrate into many optically opaque mediums such as living systems. Recently, MWI has developed into a promising technique for breast cancer detection where electrical permittivity and conductivity are well known to differ significantly in benign and in malignant breast tissues for a wide range of frequencies, including microwaves. The ability of non-invasively mapping these properties is therefore desirable and constitutes a way of detecting cancer. A possible technique to be used is the Microwave tomography (MWT). In this, a number of antennas (e.g. 8 to 16), are arranged on a circle which surrounds the breast. One antenna is used for emitting an electromagnetic (EM) wave, which propagates through the breast, and the other antennas measure the received field intensity and phase. This allows collecting a dataset which contains information about the distribution of electrical properties in the volume of the breast. To handle the data an electromagnetic model of the whole-system is required (phase one: forward modeling), and some algorithms (inverse problems) must be considered in order to reconstruct the value of electrical properties (phase two: inverse problem solution).

The Antenna and EMC Lab (LACE) is involved in both phases of the described MWI approach. In particular we focus on modeling the whole-system (without any approximation) by using advanced Finite Element Method (FEM), and Method of Moment (MoM). To compare our simulations with measured data, some algorithms based on inverse problem formulation are used. By acting on the distribution of electrical properties in the model it is possible to fit simulated measurements to real measurements, and to estimate hence the true distribution of electrical properties of the breast. We mostly employ a formulation based on the least squares problem, with Tikhonov regularization as the inversion is ill-posed. Also, we take care of designing and implementing the wideband antennas to be used as transmitter/receiver in the MWI tomographic system.

Advanced Computing and Electromagnetics