FDTD-based time reversal for microwave breast cancer Detection-localization in three dimensions

In a previous study, a novel time-reversal (TR) algorithm based on the finite-difference time-domain (FDTD) method for ultra-wideband microwave breast cancer detection was presented. The system properties and performance were originally studied for two-dimensional (2-D) simplified models and geometries and, more recently, for a realistic breast model based on magnetic resonance imaging measured data. This paper extends this FDTD TR algorithm to a three-dimensional (3-D) case in order to study localization of the tumor target in 3-D. The FDTD TR algorithm solves the full 3-D wave equation and, thus, takes into account polarization effects. In order to compare the new images with previous results, we consider a 2-D planar receiver array, which is an extension of the line of receivers introduced in the 2-D model. A direct comparison from 3-D to 2-D reconstructions illustrates the advantages of using the fully 3-D algorithm, which counterbalances its additional computational cost.