Feasibility study of tumor morphology classification via contrast-enhanced UWB breast imaging — A pole-zero analysis

Classifying lesions by ultra-wideband (UWB) microwave imaging is challenged by the possibly low contrast in the dielectric properties of tumors and healthy breast tissues. One possible solution to this problem is to use a microwave contrast agent such as microbubbles to acquire the differential backscatter response before and after administration of the contrast medium. This eliminates the clutter interference caused by dense tissue heterogeneities. In this paper, we study a contrast-agent-aided imaging method for lesion morphology classification by analyzing the received signals in the complex domain. A finite-difference time-domain (FDTD) numerical phantom is employed to simulate electromagnetic wave propagation inside the breast and extract the reflected waveforms with and without a contrast agent in the tumor site. The complex-domain transfer function of the differential response is then used to draw the pole-zero plots (PZPs), whose patterns are dependent on the lesion morphologies. The analysis is of potential use for discrimination between benign and malignant masses, where the former usually possesses a better-defined shape as opposed to the latter.