Tommy Henriksson

Quantitative Microwave Imaging for Breast Cancer Detection Using a Planar 2.45 GHz System

Microwave imaging is recognized as a potential candidate for biomedical applications, such as breast tumor detection. In this context, the capability of a planar microwave camera to produce quantitative imaging of high-contrast inhomogeneous objects is investigated. The image reconstruction is achieved by means of an iterative Newton-Kantorovich algorithm. Promising numerical simulation results indicate that the planar geometry is suitable for quantitative imaging, as long as the signal-to-noise ratio is higher than 40 dB. Such a requirement is satisfied with the camera due to appropriate data averaging. Furthermore, different calibration techniques are discussed, aiming to reduce the model error, which results from the limitations of the numerical model involved in the reconstruction to accurately reproduce the experimental setup. The experimental work also includes the development of a phantom using a new fluid tissue equivalent mixture based on Triton X-100. As a final result, this paper shows the first reconstructed quantitative images of a high-contrast inhomogeneous 2-D object obtained by using experimental data from the camera.

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.

Breast Phantoms for Microwave Imaging

Herein, we study the dielectric properties of various mixtures susceptible to be used in manufacturing of reference inhomogeneous breast phantoms dedicated to the experimental validation of microwave breast imaging systems in the 0.5-6-GHz frequency range. Particularly, we investigate the stability over time and temperature of these properties and their reproducibility for a given mixture, as well as the ability of some mixtures to mimic the various breast tissues, i.e., to show dielectric properties close to that given by one-pole Debye models that describe the mean relative dielectric permittivity of various tissue types.

Towards Enhancing Skin Reflection Removal and Image Focusing Using a 3-D Breast Surface Reconstruction Algorithm

Suppressing skin reflection is vital for successful tumor detection in radar breast imaging systems. In this communication, a novel skin reflection removal (SRR) algorithm is presented based on a previously-proposed breast surface reconstruction algorithm. This skin reflection removal algorithm is validated using numerical MRI-derived breast models. This communication also investigates how the same skin location information can be used to enhance the delay-and-sum algorithm.

Towards a planar Microwave Tomography system for early stage breast cancer detection

In this paper, the advantages of planar Microwave Tomography (MT) applied to early stage breast cancer detection are presented. In the proposed planar configuration, the breast is compressed between two dielectric plates in a configuration similar to that of X-ray mammography. This approach would allow the future implementation of a dual modality imaging system where the advantages of both techniques can be exploited. The research efforts made both at DRÉ/L2S (Supelec) and Poly-grames (École Polytechnique de Montréal), for the development of a planar MT system are described, as well as, the key features of the latter. A numerical validation is used to show how the breast compression can lead to an enhancement of the reconstructed images.

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.

A Numerical Study of Debye and Conductive Dispersion in High-Dielectric Materials Using a General ADE-FDTD Algorithm

A new formulation of the auxiliary difference equation (ADE) finite-difference time-domain (FDTD) algorithm for the simulation of dispersive materials has been presented in the literature. Although flexible and efficient, this algorithm suffers from instability when modeling lossy high contrast dielectrics. In this paper, we adapt this ADE-FDTD formulation and present alternative algorithms for modeling static conductivity and Debye dispersion. The stability of these algorithms is assessed by numerical simulation in a wide variety of dielectric media, and their performance is compared to the existing algorithm by means of a simulation of the reflection of a plane wave from a dielectric boundary. Results and comparison with theory demonstrate the stability and accuracy of the new methods. The flexibility, computational efficiency, and ability to model a wide range of materials make these new methods highly attractive compared to other dispersive FDTD algorithms, particularly for modeling materials with multiple dispersion models.