Near-Field Radar Microwave Imaging as an Add-on Modality to Mammography

According to global statistics, there is a high incidence of cancer in western countries; and, due to the limited resources available in most health care systems, it seems like one of the most feasible options to fight against cancer might be strict prevention policies—such as eliminating carcinogens in people’s daily lives. Nevertheless, early cancer detection and effective treatment are still necessary, and understanding their efficacy and limitations are important issues that need to be addressed in order to ultimately enhance patients’ survival rate. In the case of breast cancer, some of the problems faced by conventional mammography have been addressed in the literature; they include high rate of false-positive and false-negative results, as well as the possibility of overdiagnosis. New technologies, such as digital breast tomosynthesis (DBT), have been able to improve the sensitivity and specificity by using 3D imaging. However, the low contrast (1%) existing between tumors and healthy fibroglandular tissue at X-ray frequencies has been identified as one of the main causes of misdiagnosis in both conventional 2D mammography and DBT. Near-field radar imaging (NRI) provides a unique opportunity to overcome this problem, since the contrast existing between the aforementioned tissues is intrinsically higher (10%) at microwave frequencies. Moreover, the low resolution and highly complex scattering patterns of microwave systems can be enhanced by using prior information from other modalities, such as the DBT. Therefore, a multimodal DBT/NRI imaging system is proposed to exploit their individual strengths while minimizing their weaknesses. In this work, the foundation of this idea is reviewed, and a preliminary design and experimental validation of the NRI system, used as a DBT complement, is introduced

Microwave Breast Imaging Techniques and Measurement Systems

Electromagnetic waves at microwave frequencies allow penetration into many optically non-transparent mediums such as biological tissues. Over the past 30 years, researchers have extensively investigated microwave imaging (MI) approaches including imaging algorithms, measurement systems and applications in biomedical fields, such as breast tumor detection, brain stroke detection, heart imaging and bone imaging. Successful clinical trials of MI for breast imaging brought worldwide excitation, and this achievement further confirmed that the MI has potential to become a low-risk and cost-effective alternative to existing medical imaging tools such as X-ray mammography for early breast cancer detection. This chapter offers comprehensive descriptions of the most important MI approaches for early breast cancer detection, including reconstruction procedures and measurement systems as well as apparatus

Multi-antenna multi-frequency microwave imaging systems for biomedical applications

Medical imaging refers to several different technologies that are used to view the human body in order to diagnose, monitor, or treat medical conditions. Each type of technology gives different information about the area of the body being studied depending on the radiation used to illuminate de body. Nowadays there are still several lesions that cannot be detected with the current methods in a curable stage of the disease. Moreover they present some drawbacks that limit its use, such as health risk, high price, patient discomfort, etc. In the last decades, active microwave imaging systems are being considered for the internal inspection of light-opaque materials thanks to its capacity to penetrate and differentiate their constituents based on the contrast in dielectric properties with a sub-centimeter resolution. Moreover, they are safe, relatively low-cost and portable. Driven by the promising precedents of microwaves in other fields, an active electromagnetic research branch was focused to medical microwave imaging. The potential in breast cancer detection, or even in the more challenging brain stroke detection application, were recently identified. Both applications will be treated in this Thesis. Intensive research in tomographic methods is now devoted to develop quantitative iterative algorithms based on optimizing schemes. These algorithms face a number of problems when dealing with experimental data due to noise, multi-path or modeling inaccuracies. Primarily focused in robustness, the tomographic algorithm developed and assessed in this thesis proposes a non-iterative and non-quantitative implementation based on a modified Born method. Taking as a reference the efficient, real-time and robust 2D circular tomographic method developed in our department in the late 80s, this thesis proposes a novel implementation providing an update to the current state-of-the-art. The two main contributions of this work are the 3D formulation and the multi-frequency extension, leading to the so-called Magnitude Combined (MC) Tomographic algorithm. First of all, 2D algorithms were only applicable to the reconstruction of objects that can be assumed uniform in the third dimension, such as forearms. For the rest of the cases, a 3D algorithm was required. Secondly, multi-frequency information tends to stabilize the reconstruction removing the frequency selective artifacts while maintaining the resolution of the higher frequency of the band. This thesis covers the formulation of the MC tomographic algorithm and its assessment with medically relevant scenarios in the framework of breast cancer and brain stroke detection. In the numerical validation, realistic models from magnetic resonances performed to real patients have been used. These models are currently the most realistic ones available to the scientific community. Special attention is devoted to the experimental validation, which constitutes the main challenge of the microwave imaging systems. For this reason, breast phantoms using mixtures of chemicals to mimic the dielectric properties of real tissues have been manufactured and an acquisition system to measure these phantoms has been created. The results show that the proposed algorithm is able to provide robust images of medically realistic scenarios and detect a malignant breast lesion and a brain hemorrhage, both at an initial stage

Ultra-Wideband (UWB) Antenna Sensor Based Microwave Breast Imaging: A Review

Globally, breast cancer is reported as a primary cause of death in women. More than 1.8 million new breast cancer cases are diagnosed every year. Because of the current limitations on clinical imaging, researchers are motivated to investigate complementary tools and alternatives to available techniques for detecting breast cancer in earlier stages. This article presents a review of concepts and electromagnetic techniques for microwave breast imaging. More specifically, this work reviews ultra-wideband (UWB) antenna sensors and their current applications in medical imaging, leading to breast imaging. We review the use of UWB sensor based microwave energy in various imaging applications for breast tumor related diseases, tumor detection, and breast tumor detection. In microwave imaging, the back-scattered signals radiating by sensors from a human body are analyzed for changes in the electrical properties of tissues. Tumorous cells exhibit higher dielectric constants because of their high water content. The goal of this article is to provide microwave researchers with in-depth information on electromagnetic techniques for microwave imaging sensors and describe recent developments in these techniques

Miniaturized UWB elliptical patch antenna for skin cancer diagnosis imaging

The biomedical imaging shows promising results in many applications such as protein characterization and cancer detection using non-ionizing radiation. Skin cancer is one of the most common types of cancer because it is exposed by sun rays during the day. Many techniques have been offered to detect the tumor in the early stage such as ultrasonic and MW imaging. However, most of these studies showed a large printing area with lower BW so as the low resolution. To overcome these drawbacks, a new low profile UWB elliptical patch antenna with high performance is designed on PTFE as a substrate. Then a layer of Indium Tin Oxide (ITO) applies to improve the antenna radiation characteristics. The proposed antenna has a broad BW from 3.9 GHz to 30 GHz along with a resonance at 2.4 GHz. Furthermore, the antenna presents a maximum gain of 7.3 dB, maximum directivity of 7.78 dBi, the maximum radiation efficiency of 92 %, and consistent, stable radiation pattern throughout the frequency band. Besides, the time-domain characteristics show that the antenna can be a suitable candidate for microwave imaging of skin cancer

Design and characterisation of wideband antennas for microwave imaging applications

Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) are well known equipments used to generate images to aid in diagnostic procedure. However, the imaging equipments have some limitations whereby the equipments are very expensive and therefore, they are not always accessible in many medical centres. Besides, the equipments are bulky and less mobility. Moreover, existing CT cannot be used frequently on the human body because the scanner exposes patients to more radiations of ionised frequency. The limitations of the equipment create a need to design an alternative imaging method which is relatively low cost, small in size, has high mobility, and non-ionise frequency. This research is to design an antenna for microwave imaging, namely corrugated u-slot antenna at 1.17-5.13 GHz with the reference of S11 less than -10 dB. Two corrugated u-slot antennas; namely antenna 1 and antenna 2 are placed on a mirror side of skull phantom to examine their ability to detect an object inside the skull. VeroClear-RGD810 skull phantom containing water is used, and the obtained results are verified using ZCorp zp-150 skull phantom which has approximately similar permittivity. Both the antennas are tested to detect the object which is located at 40 mm and 80 mm from the respective examined antenna. An Inverse Fast Fourier Transform (IFFT) technique is used to analyse the time domain reflection pulse according to the dielectric properties difference, as the electromagnetic wave propagates through the skull. The results show that the antenna 1 is able to detect the object faster than the antenna 2 for both skulls, due to inconsistent thickness of the phantoms. Furthermore, the antennas are fabricated in adjacent to measure decomposition and superposition specific absorption rate (SAR) in Specific Anthropomorphic Mannequin (SAM) head phantom at 1800 MHz and 2600 MHz. The maximum allowable SAR in head is 2 W/kg at 10 g contiguous tissue which is referred to International Commission on Non-Ionizing Radiation Protection (ICNIRP) guideline. Based on the measured results, superposition SAR of the antenna can reach up to ±12% of the maximum decomposition SAR. This research forms a significant contribution to medical engineering field in designing a corrugated u-slot antenna that serves to detect an abnormality inside human head at 1.17-5.13 GHz. The designed antenna satisfies the SAR standard, which is required in microwave imaging applications

Design and characterisation of wideband antennas for microwave imaging applications

Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) are well known equipments used to generate images to aid in diagnostic procedure. However, the imaging equipments have some limitations whereby the equipments are very expensive and therefore, they are not always accessible in many medical centres. Besides, the equipments are bulky and less mobility. Moreover, existing CT cannot be used frequently on the human body because the scanner exposes patients to more radiations of ionised frequency. The limitations of the equipment create a need to design an alternative imaging method which is relatively low cost, small in size, has high mobility, and non-ionise frequency. This research is to design an antenna for microwave imaging, namely corrugated u-slot antenna at 1.17-5.13 GHz with the reference of S11 less than -10 dB. Two corrugated u-slot antennas; namely antenna 1 and antenna 2 are placed on a mirror side of skull phantom to examine their ability to detect an object inside the skull. VeroClear-RGD810 skull phantom containing water is used, and the obtained results are verified using ZCorp zp-150 skull phantom which has approximately similar permittivity. Both the antennas are tested to detect the object which is located at 40 mm and 80 mm from the respective examined antenna. An Inverse Fast Fourier Transform (IFFT) technique is used to analyse the time domain reflection pulse according to the dielectric properties difference, as the electromagnetic wave propagates through the skull. The results show that the antenna 1 is able to detect the object faster than the antenna 2 for both skulls, due to inconsistent thickness of the phantoms. Furthermore, the antennas are fabricated in adjacent to measure decomposition and superposition specific absorption rate (SAR) in Specific Anthropomorphic Mannequin (SAM) head phantom at 1800 MHz and 2600 MHz. The maximum allowable SAR in head is 2 W/kg at 10 g contiguous tissue which is referred to International Commission on Non-Ionizing Radiation Protection (ICNIRP) guideline. Based on the measured results, superposition SAR of the antenna can reach up to ±12% of the maximum decomposition SAR. This research forms a significant contribution to medical engineering field in designing a corrugated u-slot antenna that serves to detect an abnormality inside human head at 1.17-5.13 GHz. The designed antenna satisfies the SAR standard, which is required in microwave imaging applications