Investigation into detection of malignant tumor using Singularity Expansion Method (SEM)

摘要

Due to the advent of short-pulse technology (UWB), there has been a considerable amount of interest shown in the application of the transient or impulse response of a radar target. A typical application for such a system is the use of a UWB illuminating pulse in ground penetrating radar (GPR). However, the detection and identification of buried and subsurface objects still remains a difficult problem, as there is no single sensor or diagnostic tool which can provide sufficient information about the object. The singularity expansion method (SEM) has been used for a long time in the detection and recognition of targets in free space. This method is usually used to represent the scattered signal from the object in terms of a sum of complex exponentials. A similar methodology is very popular in GPR systems in tracking and identification of buried landmines. Currently X-ray mammography and ultrasound are the primary screening tools used in the identification of certain types of breast cancer but recently microwave imaging has been explored as an alternate tool in identification of malignant breast cancer tumors [1-2]. In this work, we would like to explore the use of SEM to detect cancerous growth in breast tissue. An SEM approach requires aspect independent poles to be extracted first and then uses this information to determine, for example, the E-pulse for discrimination. Although the resonance behavior of the target occurs in the late time portion of the transient signal, both early and late time portions of the signature are useful for extracting the features of the target [3-6]. In this work, we primarily concentrate on the late time response of the target as it contains the target resonances. The primary objective of this research work is to detect and identify a malignant tumor embedded in breast tissue from the scattered (forward or backscattered) signals. It is well known that the transient scattering of electromagnetic waves from a conducting or dielectric target contains information about the resonance behavior of the target itself as quantified by the complex poles or complex natural resonances (CNR) of the target [6]. The CNRs are theoretically aspect independent, depending only on the shape and electrical properties of the target such as permittivity and conductivity. The extracted CNRs will be used to identify the malignant cancerous tissue from the normal tissues.