Ultra-wideband (UWB) microwave radar imaging techniques provide a non-invasive means to extract information related to an object's internal structure. For these applications, a short-duration electromagnetic wave is transmitted into an object of interest and the backscattered fields that arise due to dielectric contrasts at interfaces are measured. In this paper, we present a method that may be used to estimate the time-of-arrival (TOA) parameter associated with each reflection that arises due to a dielectric property discontinuity (or dielectric interface). A second method uses this information to identify the locations of points on these interfaces. When data are collected at a number of sensor locations surrounding the object, the collection of points may be used to estimate the shape of contours that segregate and enclose dissimilar regions within the object. The algorithm is tested with data generated when a cylindrical wave is applied to a number of numerical 2D models of increasing complexity. Moreover, the algorithm's feasibility is evaluated using data generated from breast models constructed from magnetic resonance (MR) breast scans. Results show that this is a promising approach to identifying regions and the internal structure within the breast.
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