Abstract
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.
Highlights
The reconstructed images and transmission and reflection parameter plots suggest that the MTS superstrate loading illustrated in Figure 2 has the potential to improve the performance of our custom-made tomographic system
The plots show that presence of the MTS superstrate loading improves the reflection coefficient of the printed square monopole antenna (PSMA) by 5 dB
As shown in the graphs, when the PSMA is loaded with our MTS superstrate, it leads to an overall improvement of the signal difference compared to
Summary
Stroke is a clinical syndrome causing acute dysfunction of a brain area and it is linked to a vascular mechanism resulting in a vessel occlusion or rupture. This definition of stroke refers to ischemic stroke (i-stroke), which involves a central nervous system infarction, and broadly includes intracerebral hemorrhage (h-stroke) and subarachnoid hemorrhage [1]. Stroke is a very frequent disorder and a major cause of adult disability and death. It is the fourth most common cause of death in the UK, with more than 100,000 cases each year and a cost to society around £26 billion a year [2]
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