Development and evaluation of a sensor and antenna array for a portable microwave-based breast cancer detection system

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Rana, Muhammad Masud
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Breast microwave sensing (BMS) is a novel breast screening technique for detecting breast cancer based on detecting the dielectric contrast between cancer and breast healthy tissue. The current BMS systems are designed for use in clinical environments and are not suited for use in remote locations due to the hardware setup. This dissertation describes research conducted as part of developing a prototype portable breast microwave sensing (BMS) system for early breast cancer detection. The portable BMS system includes a scanning chamber, transmitter and receiver sensors on a semi-circular platform and the data measurement software used to control it. The portable system uses a horn antenna to transmit frequencies from 1.5 GHz to 6 GHz. A single receiver antenna was characterized at different distances from the transmitter. The symmetry of the semicircular receiver platform was investigated with respect to a reference antenna directly in line with the beam axis of the horn antenna, and with a 20 cm spacing. Another receiver antenna was placed at 0 cm and 1 cm horizontal separation from the reference antenna's immediate to its left or right side. This thesis investigated the response of the antenna sensor array to a point scatterer, using simulation and experiment. This study compares the E-field characteristics and DC voltages for each sensor, using simulation in CST Microwave Studio version 2019 and experimental results for both a free air system and with an Aluminum rod placed at 83 positions in the scanning plane. From the symmetrical analysis, the percentage of differences in the signal strength between the antenna placed to the left or right side of the reference antenna in the receiver were determined to be (0.22±1.63)% and (-0.17±1.74)% respectively, for 0 cm and 1 cm distance from the reference antenna. Each antenna element experienced mutual coupling with the antenna's on its immediate left and right in the receiver array. The optimal separation of each antenna in the receiver array was calculated to be 4 mm based on an envelope correlation coefficient of 0.37. The semi-circular receiver sensor array was built using thirteen patch antennas with a 4 mm separation between antennas. The portable BMS system was calibrated using a 13×10 array of geometric correction constants, which were calculated from the simulated E-field. The differences between the simulated and experimental results ranged from -4% to 3% for open space conditions and ±15% when an Aluminum rod was placed at different positions in the scanning plane. The receiver antenna array's measured power ranged from 10.3 dBm to 9.3 dBm at a 95% CI under open space conditions. The maximum value of the average relative power (ARP) was 1.63, and the minimum value of the average relative power was -0.65 in the receiver antenna array. The experimental ARP results agreed with calculated results from the derived mathematical model of the portable BMS system, by 80% when considering the phase angle and by 85% without the phase angle. The preliminary results are promising and provide some insight as to where improvements must be made to enhance the detection ability and to reduce the differences between simulation and experiment results of the portable system.
Breast microwave sensing , Breast cancer, Sensor array, horn antenna, E-field, DC voltage, geometric constant
Muhammad Masud Rana, Debarati Nath, Stephen Pistorius, "Sensitivity Analysis of a Portable Microwave Breast Cancer Detection System," 7th International Conference on Biomedical Engineering and Systems (ICBES'20), Czech Republic.