David Gibbins

Microwave Radar-Based Differential Breast Cancer Imaging: Imaging in Homogeneous Breast Phantoms and Low Contrast Scenarios

This paper presents an improved antenna array for radar-based breast cancer imaging. The improvement was achieved by increasing the number of antennas in the array to 31 elements, as well as by improving the antenna design itself. Using an experimental setup, with homogeneous curved breast phantoms, we have demonstrated substantial imaging improvement with the new antenna array. The new system is also able to detect 7 mm-diameter tumor phantoms in any location within the breast, even as close as 4 mm from the skin layer. Additionally, we have shown good imaging results in low-contrast scenarios, where the dielectric contrast between tumor and normal tissue was reduced to 2:1. Presented results clearly demonstrate the large impact of antennas characteristics on imaging performance.

A Comparison of a Wide-Slot and a Stacked Patch Antenna for the Purpose of Breast Cancer Detection

A wide-slot UWB antenna is presented for intended use in the detection scheme being developed at the University of Bristol, based on the principle of synthetically focused UWB radar using a fully populated static array. The antennas measured and simulated, input and radiation characteristics are presented and compared to an existing, stacked patch antenna that has been designed for the same purpose. The results of this study show that the wide-slot antenna has excellent performance across the required frequency range. Compared to the stacked-patch antenna used in our previous array, the wide-slot antenna can be 3 times smaller (in terms of front surface). The compact nature of the slot antenna means that the detection array can be densely populated. Additionally, this new antenna offers better radiation coverage of the breast. For angles up to 60° away from bore-sight radiated pulses are almost identical (fidelity >95%), whereas for the patch antenna fidelity falls to 58% at the angular extremes. This uniform radiation into the breast should result in focused images with low levels of clutter.

Microwave Radar-Based Breast Cancer Detection: Imaging in Inhomogeneous Breast Phantoms

This letter presents, for the first time, experimental work on microwave breast cancer imaging using inhomogeneous breast phantoms. A recently designed 31-antenna array is used in imaging experiments. The imaging system operates in the full ultrawideband frequency range, between 3 and 10 GHz. To verify imaging performance of our system, new breast phantoms with inhomogeneous interior were developed. For three different breast phantoms presented in this work, the contrast between spherical phantom tumors and surrounding materials ranges from 5:1 to 1.6:1. Our results show that the biggest challenge in radar microwave imaging is the inhomogeneity of the volume being sensed, and not the contrast itself. In addition to experimental results, we also present the new image formation algorithm, which is a modified version of the delay-and-sum (DAS) algorithm. The new algorithm makes use of a new weighting factor, the coherence factor. The new algorithm is effective in reducing clutter, providing better images. For the most demanding imaging example presented herein, the new algorithm improves the peak clutter-to-target energy ratio by 3.1 dB.

Clinical trials of a multistatic UWB radar for breast imaging

This paper presents the development of a 60-element Ultra-WideBand (UWB) radar system for breast cancer detection and its use in clinical trials. The new system operates in the frequency range of 4–8GHz and is an improvement of the teams previous designs both in terms of the number of measurements made (which is increased by a factor of approximately 4) and in terms of acquisition speed. The 60-antenna radar system has undergone an extensive Clinical Trial in the Breast Care Centre at Frenchay Hospital, Bristol. The rapid data acquisition has improved the accuracy of images while also providing a clinical experience that is more convenient and acceptable to patients.

Towards contrast enhanced breast imaging using ultra-wideband microwave radar system

In this paper we present numerical results of contrast-enhanced breast imaging using ultra-wideband microwave radar system. Due to low contrast in electrical properties between dense breast tissues and malignant tissues, tumor detection using microwave might be extremely challenging. To overcome this problem, we propose here a radar imaging technique based on a localized contrast enhancement. Our results show that microwave contrast agents able of changing an effective dielectric constant of cancerous tissues by only 1% would greatly improve imaging performance.

Analysis of a UWB Hemispherical Antenna Array in FDTD With a Time Domain Huygens Method

Electromagnetic modeling is needed in a wide variety of large and complex situations. Existing numerical techniques such as finite difference time domain (FDTD) can, in principle, solve any problem no matter how large or complicated given a sufficiently powerful computer. However, in practice, there remain problems which require more computer power than is available. Recently, the time-domain Huygens (TDH) approach has been shown to be effective for enabling large problems such as propagation on body area networks (BANs) to be modeled in FDTD. In this paper, it is shown that the much larger problem of the conformal antenna array, which is used in the MARIA breast cancer tumor detection system, is also very amenable to this technique with even greater savings in computer resources. Accurate results are obtained using less that a tenth of the resources needed to solve the same problem using existing advanced FDTD tools. The details of how this method is applied, and the choices which need to be made, are discussed.

A novel 3-D breast surface reconstruction algorithm for a multi-static radar-based breast imaging system

The estimation of the skin reflection is a crucial step towards successful breast tumour detection. This paper investigates the two-dimensional improved version of an existing general purpose technique for estimating target objects of arbitrary shape. The ability of the proposed method in estimating the breast skin location is tested over a wide range of realistic FDTD-based scenarios with results demonstrating accurate estimation of the breast skin location.

Slot Antenna Performance and Signal Quality in a Smartphone Prototype

Antenna position and user grip on smartphone-like devices may lead to obstruction of radio signal paths and antenna detuning. A multiple-input-multiple-output (MIMO) outdoor propagation measurement campaign is presented, which collected data for slot antennas on a smartphone prototype. The antennas are in four positions, two polarizations, and one was obstructed due to operator grip. All MIMO links were measured within the channels coherence time while standing, walking, and driving. We show how signal levels change due to obstruction, position, and motion and that signal fluctuations increase significantly, thus tending to impair service quality. We also examine how proximity of the operators hand affects the antennas radiation and input characteristics.

Less Becomes More for Microwave Imaging: Design and Validation of an Ultrawide-Band Measurement Array.

A compact, enclosed, ultrawide-band (UWB) antenna array is presented to acquire data for a quantitative microwave imaging method. Compared to existing systems, the proposed array allows a UWB antenna to be placed close to a target object while, at the same time, minimizing the volume of the imaging array. The antennas and metallic enclosure are designed to easily integrate with an iterative threedimensional (3-D) nonlinear inverse scattering technique. The volume of the internal imaging domain has been minimized for this particular architecture to reduce the computational time spent on reconstructing the dielectrics within the domain. Each cavity-backed element radiates toward the target and presents stable transmission characteristics across the 1-4-GHz band.

An investigationo of a compact UWB antenna by measurement and FDTD simulation

The aim of the work described herein is to further investigate the design in [1] by means of both measurement and analysis, to determine if improvement could be made by careful optimisation of the design. Evaluation of the antenna¿s performance in terms of the excitation of particular current modes on its surface is made by means of an FDTD model.