Abstract
Metasurface Technology for Electromagnetic Medical DevicesOver the last two decades, metamaterials and metasurfaces have been used to fabricate innovative antenna designs, offering advanced and cost-effective solutions compared to conventional radiating systems. This thesis investigates the feasibility of combining metasurface design concepts and imaging techniques to create innovative microwave imaging systems.
Microwave imaging is a valid alternative to the current imaging techniques because it is non-invasive and uses non-ionising radiation. Furthermore, it can be a portable and ergonomic technology. Stroke detection and differentiation is one of the most promising microwave imaging applications and has drawn the interest of many groups worldwide. Stroke is a neurological disorder which occurs when blood supply to a part of the brain is interrupted or reduced (ischemic stroke), or when a blood vessel breaks and bleeds into the brain (hemorrhagic stroke). Stroke is a medical emergency and prompt treatment is crucial. Thus, patients’ survival depends on a quick diagnosis through the use of an efficient imaging method. Therefore, there is increasing interest in developing new diagnostic tools, such as microwave brain imaging scanners, to supplement the current imaging modalities. Developing these devices requires designing systems with increasing number of sensors (i.e., antennas). Using advanced materials can not only improve the characteristics of these antennas, but also enhance detection by tackling the impedance mismatch problem that electromagnetic waves encounter when probing human tissue.
This research work presents an approach to enhance the hardware of a custom made brain imaging scanner with an innovative metasurface film based on a Jerusalem cross resonator. This metasurface design has been tested through full-wave simulations and experiments, using several setups and antenna types. The results presented in this thesis suggest that the proposed metasurface enhances the “weak” signal scattered by a stroke-mimicking target placed in a brain phantom volume. This translates into more accurate tomographic and radar image reconstructions. As a further analysis, the feasibility of developing a more compact and ergonomic microwave brain imaging scanner was investigated. To this end, a new array based on metasurface enhanced antennas was proposed. Even in this case, the results suggest that the metasurface antenna loading increases the signal difference due to the presence of a stroke mimicking target and improves the quality of the reconstructed images. The last part of this thesis is focused on other clinical applications of metasurface technology, including cerebrovascular imaging, breast cancer detection, hyperthermia monitoring and microwave thermal ablation monitoring.
All the metasurface designs proposed in this thesis are tailored to fulfill specific requirements and achieve the desired goals (e.g., impedance-matching, improved field penetration into the human tissue, enhanced antenna designs), depending on the microwave imaging prototype and its application. In conclusion, this research work suggests that incorporating metasurface structures into the hardware of microwave imaging systems might lead towards the development of innovative, compact and ergonomic medical devices with the desired clinical accuracy.
| Date of Award | 1 Jun 2023 |
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| Original language | English |
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| Supervisor | Panos Kosmas (Supervisor) & Efthymios Kallos (Supervisor) |