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.

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.

Microwave imaging (MWI) is a promising noninvasive technique for breast cancer screening, utilizing differences in dielectric properties between tissues to generate images. This study focuses on developing a robust imaging pipeline to optimize the design of specialized antenna arrays, enhancing measurement efficiency and reducing image reconstruction time. Simulations were conducted in the 1-5 GHz frequency range using a simplified breast model consisting of a single layer of skin surrounding a homogeneous healthy tissue, with a tumor target embedded within the background material. To test our pipeline, we used different antenna distributions for data acquisition. Additionally, we varied the dielectric properties of the background, the number of tumors, and their size and location. To streamline the simulation workflow, the models were built in HFSS, and simulations were processed on Compute Canada's supercomputer, allowing for efficient computation in a short time frame. Images were reconstructed using a delay-andsum (DAS) radar-based imaging algorithm called MERIT. Metrics such as signal-to-noise ratio (SNR) and location error were then used to assess image quality. Our preliminary findings indicate that while non-equally spaced antennas show potential for detecting targets near the sensors, equally spaced configurations consistently yield superior image quality. This work lays the groundwork for strategic diagnostic hardware design, aiming to improve MWI accuracy through refined antenna array configurations.

Objective. Peripheral edema is a common issue among elderly individuals with chronic conditions such as heart failure (HF). Continuous, non-invasive monitoring may enable earlier intervention, reduced hospital readmissions, and improved quality of life. This systematic review aims to evaluate the use of bioimpedance (BI) as a method for monitoring peripheral edema, with a particular focus on portable and wearable applications for remote health management. Approach. A systematic search was conducted across PubMed, IEEE Xplore, and Web of Science to identify studies utilizing BI for the detection or monitoring of lower limb edema with potential for portability or wearability. Main results. Fourteen studies met the inclusion criteria. Five studies focused on HF patients, while nine involved other populations, such as healthy individuals, patients with limb injuries, or those on hemodialysis. Ten studies featured or proposed portable BI devices, whereas four remained at the proof-of-concept stage without portable implementations. There was significant variability in device design, measurement protocols, and target populations. While existing results show promise, few studies evaluated systems in real-world or long-term monitoring scenarios. Significance. BI is a promising, non-invasive approach for the continuous monitoring of peripheral edema, particularly in remote and home-based settings. However, current research is limited by small sample sizes, lack of standardization, and minimal validation in diverse, real-world environments. Further development of wearable systems and robust clinical validation is essential to support broader clinical adoption.

Non-invasive biosensing faces major challenges due to impedance mismatch at the skin interface, which causes significant signal reflection and limits power transmission through biological tissues. In this paper, we propose and evaluate a novel, subwavelength-thick impedance-matching metasurface (MTS) designed for direct skin contact to enhance electromagnetic (EM) wave transmission in the Ka-band. Our evaluation includes controlled laboratory experiments and a first-in-human study. Using an in-house developed benchtop system, we performed transmission measurements through aqueous glucose solutions and, most importantly, through the hands of six human volunteers. Our results show that the MTS significantly enhances signal transmission into human skin tissue, yielding an average improvement of up to 5 dB in the 36–37 GHz frequency range compared to the bare-skin condition, thereby improving sensitivity for analyte detection without increasing system size or power consumption. These findings demonstrate the potential of MTS-based impedance-matching layers as practical, integrable solutions to overcome key hardware limitations in wearable biomedical sensing devices. The study represents the first human investigation of an impedance-matching MTS designed to improve microwave signal penetration for non-invasive sensing applications.