Biomedical imaging at microwave frequencies has shown potential for breast cancer detection and monitoring. The advantages of microwave imaging over current imaging techniques are that it is relatively inexpensive, and uses low-energy, non-ionizing radiation. It also provides a quantitative measurement of the dielectric properties of tissues, which offers the ability to characterize tissue types. Microwave imaging also comes with significant drawbacks. The resolution is poor compared to other imaging modalities, which presents challenges when trying to resolve fine structures. It is also not very sensitive to low contrast objects, and the accuracy of recovered tissue properties can be poor. This thesis shows that the use of prior information in microwave imaging inversion algorithms greatly improves the resulting images by minimizing mathematical difficulties in reconstruction that are due to the ill-posed nature of the inverse problem. The focus of this work is to explore novel methods to obtain and use prior information in the microwave breast imaging problem. We make use of finite element contrast source inversion (FEM-CSI) software formulated in two and three dimensions (2D, 3D). This software has the ability to incorporate prior information as an inhomogeneous numerical background medium. We motivate the usefulness of prior information by developing a simulated annealing technique that segments experimental human forearm images into tissue regions. Tissue types are identified and the resulting map of dielectric properties is used as prior information for the 2D FEM-CSI code. This results in improvements to the reconstructions, demonstrating the ability of prior information to improve breast images. We develop a combined microwave tomography/radar algorithm, and demonstrate that it is able to reconstruct images of superior quality, compared to either technique used alone. The algorithm is applied to data from phantoms containing tumours of decreasing size and can accurately monitor the changes. The combined algorithm is shown to be robust to the choice of immersion medium. This property allows us to design an immersion medium-independent algorithm, in which a numerical background can be used to reduce the contrast. We also develop a novel march-on-background technique that reconstructs high quality images using data collected in multiple immersion media. / October 2016

<p>Microwave imaging is an efficient diagnostic modality for non-invasively visualizing dielectric contrasts of non-metallic bodies. An increasing interest of this field has been observed during the last decades. Many application areas in biomedicine have been issued, recently the breast tumor detection application using microwave imaging.</p><p>Many groups are working in the field at the moment for several reasons. Breast cancer is a major health problem globally for women, while it is the second most common cancer form for women causing 0.3 % of the yearly female death in Sweden. Medical imaging is considered as the most effective way of diagnostic breast tumors, where X-ray mammography is the dominating technique. However, this imaging modality still suffers from some limitations. Many women, mostly young ones, have radiographically dense breasts, which means that the breast tissues containing high rates of fibroglandular tissues. In this case the density is very similar to the breast tumor and the diagnosis is very difficult. In this case alternative modalities like Magnetic Resonance Imaging (MRI) with contrast enhancement and Ultrasound imaging are used, however those are not suitable for large scale screening program.Another limitation is the false-negative and false-positive rate using mammography, in general 5–15 % of the tumors are not detected and many cases have to go though a breast biopsy to verify a tumor diagnosis. At last the mammography using breast compression sometimes painful, and utilizing ionizing X-rays. The big potential in microwave imaging is the reported high contrast of complex permittivity between fibroglandular tissues and tumor tissues in breasts and that it is a non-ionizing method which probably will be rather inexpensive.</p><p>The goal with this work is to develop a microwave imaging system able to reconstruct quantitative images of a female breast. In the frame of this goal this Licentiate thesis contains a brief review of the ongoing research in the field of microwave imaging of biological tissues, with the major focus on the breast tumor application. Both imaging algorithms and experimental setups are included. A feasibility study is performed to analyze what response levels could be expected, in signal properties, in a breast tumor detection application. Also, the usability of a 3D microwave propagation simulator, (QW3D), in the setup development is investigated. This is done by using a simple antenna setup with a breast phantom with different tumor positions. From those results it is clear that strong responses are obtained by a tumor presence and the diffracted responses gives strong information about inhomogeneities inside the breast. The second part of this Licentiate thesis is done in collaboration between Mälardalen University and Supélec. Using the existing planar 2.45 GHz microwave camera and the iterative non-linear Newton Kantorovich code, developed at Département de Recherches en Electromagnétisme (DRE) at Supélec, as a starting point, a new platform for both real-time qualitative imaging and quantitative images of inhomogeneous objects are investigated. The focusing is related to breast tumor detection. For the moment the tomographic performance of the planar camera is verified in simulations through a comparison with other setups. Good calibration is observed, but still experimental work concerning phantom development etc. is needed before experimental results on breast tumor detection may be obtained.</p>

Microwave imaging is an efficient diagnostic modality for non-invasively visualizing dielectric contrasts of non-metallic bodies. An increasing interest of this field has been observed during the last decades. Many application areas in biomedicine have been issued, recently the breast tumor detection application using microwave imaging. Many groups are working in the field at the moment for several reasons. Breast cancer is a major health problem globally for women, while it is the second most common cancer form for women causing 0.3 % of the yearly female death in Sweden. Medical imaging is considered as the most effective way of diagnostic breast tumors, where X-ray mammography is the dominating technique. However, this imaging modality still suffers from some limitations. Many women, mostly young ones, have radiographically dense breasts, which means that the breast tissues containing high rates of fibroglandular tissues. In this case the density is very similar to the breast tumor and the diagnosis is very difficult. In this case alternative modalities like Magnetic Resonance Imaging (MRI) with contrast enhancement and Ultrasound imaging are used, however those are not suitable for large scale screening program.Another limitation is the false-negative and false-positive rate using mammography, in general 5–15 % of the tumors are not detected and many cases have to go though a breast biopsy to verify a tumor diagnosis. At last the mammography using breast compression sometimes painful, and utilizing ionizing X-rays. The big potential in microwave imaging is the reported high contrast of complex permittivity between fibroglandular tissues and tumor tissues in breasts and that it is a non-ionizing method which probably will be rather inexpensive. The goal with this work is to develop a microwave imaging system able to reconstruct quantitative images of a female breast. In the frame of this goal this Licentiate thesis contains a brief review of the ongoing research in the field of microwave imaging of biological tissues, with the major focus on the breast tumor application. Both imaging algorithms and experimental setups are included. A feasibility study is performed to analyze what response levels could be expected, in signal properties, in a breast tumor detection application. Also, the usability of a 3D microwave propagation simulator, (QW3D), in the setup development is investigated. This is done by using a simple antenna setup with a breast phantom with different tumor positions. From those results it is clear that strong responses are obtained by a tumor presence and the diffracted responses gives strong information about inhomogeneities inside the breast. The second part of this Licentiate thesis is done in collaboration between Mälardalen University and Supélec. Using the existing planar 2.45 GHz microwave camera and the iterative non-linear Newton Kantorovich code, developed at Département de Recherches en Electromagnétisme (DRE) at Supélec, as a starting point, a new platform for both real-time qualitative imaging and quantitative images of inhomogeneous objects are investigated. The focusing is related to breast tumor detection. For the moment the tomographic performance of the planar camera is verified in simulations through a comparison with other setups. Good calibration is observed, but still experimental work concerning phantom development etc. is needed before experimental results on breast tumor detection may be obtained.

Microwave imaging techniques have shown excellent capabilities in various fields such as civil engineering, nondestructive testing, industrial applications, and have in recent decades experienced strong growth as a research topic in biomedical diagnostics. Many research groups throughout the world work on prototype systems for producing images of human tissues in different biomedical applications, particularly breast tumor detection. However, the research community faces many challenges and in order to be competitive to other imaging modalities one of the means is to put emphasis on experimental work. Consequently, the use of flexible and accurate measurement systems, together with the design and fabrication of suitable antennas, are essential to the development of efficient microwave imaging systems. The first part of this thesis focuses on measurement systems for microwave imaging in terms of antenna design and development, robot controlled synthetic array geometries, permittivity measurements, and calibration. The aim was to investigate the feasibility of a flexible system for measuring the fields around an inhomogeneous object and to create quantitative images. Hence, such an aim requires solving of a nonlinear inverse scattering problem, which in turn requires accurate measurements for producing good quality experimental data. The presented solution by design of a flexible measurement system is validated by examination of microwave imaging from experimental data with a breast phantom. The second part of the thesis deals with the research challenges of designing high performance antennas to be placed in direct contact with or in close proximity to the imaged object. The need for novel antenna applicators is envisaged in the framework of the Mamacell measurement system, where the antenna applicators have to be designed and constructed to effectively couple the energy into the imaging object. For this purpose the main constraints and design requirements are a narrow lobe of the antenna, very small near-field effects, and small size. Numerical simulations and modeling shows that the proposed ridged waveguide antenna is capable of fulfilling the design requirements and the performance goals, demonstrating the potential for the future microwave imaging system called Mamacell.

Lic.-avh. (sammanfattning) Västerås : Mälardalens högskola, 2007. / Härtill 3 uppsatser. S. 45-53: Bibliografi.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 86-94). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--Oregon State University, 2011. / Printout. Includes bibliographical references (leaves 182-187). Also available on the World Wide Web.

A microwave imaging system processes scattered electromagnetic fields in the microwave region to create images. It is an alternative or complementary imaging tool that can be used in breast cancer imaging. It employs non-ionising radiation and during measurement, compression of the scanned body part is avoided. These benefits potentially lead to safer and more comfortable examinations. It also has the potential to be both sensitive and specific to detect small tumors, whilst being much lower cost than current methods, such as magnetic resonant imaging, mammography and ultrasound. This thesis reports a multi-layer active antenna array for breast imaging using microwaves from 3 GHz to 8 GHz. The proposed structure resolves the outstanding problem in the design of large active antenna arrays for tissue imaging, namely, the isolation of the antennas from the electronic circuits. A ground plane within the multi-layer design separates the antenna array from the electronics array while providing shielding to the antennas from the back and improved power coupling into the tissue. The possibility of a high-speed vertical connector to provide interconnection between the antenna array and the mixer array is investigated and measurements show that it could be utilized for the frequency range from 3 GHz to 8 GHz. / Thesis / Master of Applied Science (MASc)

Commercial concealed weapon detection systems are large and expensive and are not suitable to be used as a portable system. Currently, new methods of concealed weapon detection are being developed to build small and compact systems. One such method is based upon the natural resonances of objects; however, no such system has made it to the market due to the low quality of the signals used in the detection algorithms. In this thesis, a prototype concealed weapon detection system is developed and tested for operation in a cluttered environment. This system utilizes the late-time portion of a radar return to extract the resonance information of an unknown target. After proper signal processing and clutter suppression, the signals are classified to determine if the object is a threat. Multiple measurements with frequency-sweep and time-domain systems are used to verify the algorithm. Microwave tissue imaging techniques aim to reconstruct the internal dielectric distribution of the tissue and rely on the dielectric contrast between healthy and malignant tissues. This contrast has been shown to be weak, and therefore, the signals are easily susceptible to noise. This thesis proposes and validates a method for signal-to-noise ratio analysis of complex S-parameter data sets that are used for microwave imaging. A study of de-noising and artifact reduction techniques for microwave holographic imaging is also presented. / Thesis / Master of Applied Science (MASc)

Yes / This article presented a novel compact multi-input-multi-output (MIMO) hexagonal monopole antenna with a uniplanar compact frequency-selective-surface (FSS) array for microwave imaging (MWI). The ultra-wideband (UWB) dual-element linear MIMO antenna was designed on the FR4 substrate with 50 Ω coplanar waveguide feed, T-strip isolation, novel numerical calculation, and equivalent circuit analyses. The main issues of realising high-resolution images based on planer UWB antenna for MWI are the low gain, omnidirectional pattern, design size, and mutual coupling of MIMO design. A novel technique was proposed to solve a hybrid issue (mutual coupling) of the MIMO reflected-waves from the FSS array and direct-wave. The uniplanar UWB-FSS unit cell was compacted by combining a square-loop and cross-dipole with a size of 0.095λ×0.095λ. The novel isolated UWB-MIMO antenna and UWB-FSS array (IMAF) were integrated, after investigating the distance between the antenna and FSS. The fabricated IMAF with a stable gain improvement of 4.5 dBi higher than the antenna without FSS, directional radiation pattern, size of 30×73.8×21.6 mm3 observed that a low mutual coupling of -27 dB, and operation bandwidth of 3.0-11.7 GHz. Moreover, a handbag was scanned experimentally via the bi-static approach to detect a small concealed object. The MWI system based on the MIMO antenna with FSS was displayed image resolution of 55% higher than that of MIMO antenna without FSS. The new baggage-scanner approach confirmed that the proposed MIMO antenna with FSS array can lead the humanity for healthy MWI applications.