Metamaterial Designs to Enhance Microwave Imaging Applications

Guo

et al. 2021

Diagnostics

Self Cite

Stroke is a very frequent disorder and one of the major leading causes of death and disability worldwide. Timely detection of stroke is essential in order to select and perform the correct treatment strategy. Thus, the use of an efficient imaging method for an early diagnosis of this syndrome could result in an increased survival’s rate. Nowadays, microwave imaging (MWI) for brain stroke detection and classification has attracted growing interest due to its non-invasive and non-ionising properties. In this paper, we present a feasibility study with the goal of enhancing MWI for stroke detection using metasurface (MTS) loaded antennas. In particular, three MTS-enhanced antennas integrated in different brain scanners are presented. For the first two antennas, which operate in a coupling medium, we show experimental measurements on an elliptical brain-mimicking gel phantom including cylindrical targets representing the bleeding in haemorrhagic stroke (h-stroke) and the not oxygenated tissue in ischaemic stroke (i-stroke). The reconstructed images and transmission and reflection parameter plots show that the MTS loadings improve the performance of our imaging prototype. Specifically, the signal transmitted across our head model is indeed increased by several dB‘s over the desired frequency range of 0.5–2.0 GHz, and an improvement in the quality of the reconstructed images is shown when the MTS is incorporated in the system. We also present a detailed simulation study on the performance of a new printed square monopole antenna (PSMA) operating in air, enhanced by a MTS superstrate loading. In particular, our previous developed brain scanner operating in an infinite lossy matching medium is compared to two tomographic systems operating in air: an 8-PSMA system and an 8-MTS-enhanced PSMA system. Our results show that our MTS superstrate enhances the antennas’ return loss by around 5 dB and increases the signal difference due to the presence of a blood-mimicking target up to 25 dB, which leads to more accurate reconstructions. In conclusion, MTS structures may be a significant hardware advancement towards the development of functional and ergonomic MWI scanners for stroke detection.

“…These two high dielectric substrates are bonded with with Rogers 3001 bonding film (

= 2.28, tan

= 0.003). In previous work [ 18 , 34 ], we have performed several simulation studies to optimize this geometry for operating in contact with the human skin when immersed in our coupling medium.…”

Section: Materials and Methodsmentioning

confidence: 99%

Metasurface-Enhanced Antennas for Microwave Brain Imaging

Guo

et al. 2021

Diagnostics

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“…This dielectric medium is required for our system's antennas to operate efficiently in the desired frequency range [44]. One of our previous studies has already presented the MM unit cell design and the periodic structure based on this pattern [43], but we review and expand this methodology further.…”

Section: Methodsmentioning

confidence: 99%

“…To this end, this paper presents experiments with simplified planar phantoms and a cylindrical target mimicking bleeding in the brain as well as numerical simulations with a tomographic scanner and a brain model with a target. Our SRR-based MM film is first proposed as an antireflection coating able to improve impedance matching and, thus, to reduce reflection and to enhance transmission of microwave energy into a body region such as the head [43]. However, aware that a slight increase in overall transmission may not necessarily improve an MWI system's ability to detect bleeding in the brain, this paper focuses on examining whether the MM can enhance the "weak" signal scattered from a blood-like target, which is relevant to our application of interest.…”

Section: Introductionmentioning

confidence: 99%

Feasibility Study of Enhancing Microwave Brain Imaging Using Metamaterials

Sotiriou

Cano-Garcia

et al. 2019

Sensors

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We present an approach to enhance microwave brain imaging with an innovative metamaterial (MM) planar design based on a cross-shaped split-ring resonator (SRR-CS). The proposed metasurface is incorporated in different setups, and its interaction with EM waves is studied both experimentally and by using CST Microwave Studio® and is compared to a “no MM” case scenario. We show that the MM can enhance the penetration of the transmitted signals into the human head when placed in contact with skin tissue, acting as an impedance-matching layer. In addition, we show that the MM can improve the transceivers’ ability to detect useful “weak” signals when incorporated in a headband scanner for brain imaging by increasing the signal difference from a blood-like dielectric target introduced into the brain volume. Our results suggest that the proposed MM film can be a powerful hardware advance towards the development of scanners for brain haemorrhage detection and monitoring.

“…The metallic pattern (thickness = 0.10 mm) is a variation of the Jerusalem Cross SRR. Our previous studies have already shown the MM unit cell design and the performance of MM layers based on this structure [13], [14].…”

Section: B Simulation Setupmentioning

confidence: 97%

“…In previous studies, we have examined various aspects of our work towards the design of a MWT scanner for brain imaging which incorporates a MM layer for signal enhancement and the DBIM-TwIST algorithm for recovering the unknown target of interest [13]- [15]. This paper examines in more details the potential of improving the quality of the reconstructed images for stroke detection and monitoring, by integrating MM technology in our MWT scanner.…”

Section: Introductionmentioning

confidence: 99%

Image Improvement Through Metamaterial Technology for Brain Stroke Detection

Karadima

2020 14th European Conference on Antennas and Propagation (EuCAP)

Kosmas

2020

Self Cite

In this paper we investigate the capabilities of metamaterials technology to enhance the quality of reconstructed images for the problem of brain stroke detection. We integrate the metamaterial in our headband system for brain imaging in CST, and evaluate the reconstructed images of the head model that is placed inside the microwave tomographic head system for the cases with and without the incorporated metamaterial. For image reconstruction we apply the distorted Born iterative method (DBIM) combined with two-step iterative shrinkage/thresholding (TwIST) algorithm. Our results indicate that the use of our metamaterial can increase the signal difference due to the presence of a blood target, which translates into more accurate reconstructions of the target.