An Improved Forward Scattering Simulation Technique for Microwave Breast Imaging

Microwave imaging is a promising alternative to conventional mammography methods. At microwave frequencies, normal and malignant tissues show high contrasts in their electrical properties. Microwave Imaging (MWI) systems can be used to construct three-dimensional profiles of the electrical properties of the body part that is being examined. MWI systems illuminate the body part with electromagnetic radiation of a suitable frequency. Using the measured scattered field at the surface of the body, inverse scattering algorithms reconstruct profiles of the electrical properties of the target. It is therefore of the uttermost importance that the forward scattering set-up is correct so that an inversion algorithm can create accurate profiles of electrical properties. We propose an improvement over the existing integral equation based forward scattering simulation techniques for microwave breast cancer imaging. Early detection of breast cancer is crucial. At this stage, the size of malignant tissue can be in the order of millimeters. For imaging involving such a small malignancy, one must use high-frequency radiation. At such frequencies, in order to overcome the relaxation effect of complex permittivity, we use the Debye model. For solving the forward scattering problem, we use the stabilized bi-conjugate gradient fast Fourier transform method (BI-CGSTAB-FFT). For the scattering domain, we apply the socalled cyclic boundary condition. This reduces the number of FFTs involved thus saving time and memory. For the BI-CGSTAB-FFT iteration method, we choose the initial value of the total field to be the incident electric field. This choice yields better convergence than a random selection of initial condition.