Development of ultra wideband antenna for dielectric profile imaging for breast tumour detection

Abstract

The rising prevalence of breast cancer in the younger female population has demanded the need for safer and cheaper diagnostic methods. Microwave imaging has emerged as a viable alternative to conventional methods of breast cancer detection. The difference in dielectric contrast between different type of breast tissue and the tumorous tissues is the basis for microwave imaging. The basic building blocks of a microwave imaging system are the transmitter and receiver antennas, the data acquisition system, the imaging algorithm and the object of interest. Antennas play a key role in acquiring the scattered data in any microwave imaging system. Microwave imaging in the UWB has the advantage of resolution and penetration into tissues, due to the wide range of frequencies involved. Compact UWB antennas have the advantages of conforming to tomographic configuration, with better resolution and capability to acquire multi frequency signals from the target under investigation. The work in the thesis focuses on the development of antennas in UWB, for use in microwave imaging for the detection of breast tumours. The work is carried out in two phases. The first part of the work deals with the development of UWB antennas and their characterization. The second part of the work deals with the performance validation of the antennas in an imaging system. The performance of antennas are analyzed and compared. newlineThree compact UWB antennas are developed for the dielectric profiling of breast tumour. First one is a keyhead shaped antenna, the second one is a modified circular monopole and the third one is an egg shaped antenna. The antennas are newlineiv newlineexperimentally tested and its characteristics, i.e., the impedance bandwidth, the radiation pattern, and gain were measured. All the three antennas have omnidirectional patterns in the UWB. newlineThe microwave imaging setup was implemented using the proposed three antennas as receiver in a bistatic tomographic configuration.A cylindrical phantom with and#949;r = 3.7 made of Delrin with three PVC inclusions (and#949;r = 4.4) mimicking the tumour is used as the phantom in the experiment. The antennas collect the signals in the near field by a VNA and the measured S12 is stored in a PC. The data is then converted into the corresponding image by using the Distorted Born Iteration method along with the Total Variation regularization technique. The reconstructed images are analyzed for the localization and permittivity profile and compared with the original profile of the cylindrical phantom. newlineThe reconstructed images from the data acquired using the three antennas are compared. All the three antennas were able to detect two out of three inclusions in different frequency ranges within UWB. The keyshaped antenna performed in the 8.895 - 10.4 GHz band, the circular monopole in the band 6.87 10.4 GHz and the egg shaped antenna in the 3.7 - 9.4 GHz band. Based on the accuracy of localization and estimated permittivity profile, the egg shape antenna has performed better which is supported by the uniform gain characteristic of the antenna in the UWB.