Maria Koutsoupidou

A Glucose Sensing System Based on Transmission Measurements at Millimetre Waves using Micro strip Patch Antennas

We present a sensing system operating at millimetre (mm) waves in transmission mode that can measure glucose level changes based on the complex permittivity changes across the signal path. The permittivity of a sample can change significantly as the concentration of one of its substances varies: for example, blood permittivity depends on the blood glucose levels. The proposed sensing system uses two facing microstrip patch antennas operating at 60 GHz, which are placed across interrogated samples. The measured transmission coefficient depends on the permittivity change along the signal path, which can be correlated to the change in concentration of a substance. Along with theoretical estimations, we experimentally demonstrate the sensing performance of the system using controlled laboratory samples, such as water-based glucose-loaded liquid samples. We also present results of successful glucose spike detection in humans during an in-vivo Intravenous Glucose Tolerance Test (IVGTT). The system could eventually be developed into a non-invasive glucose monitor for continuous monitoring of glucose levels for people living with diabetes, as it can detect as small as 1.33 mmol/l (0.025 wt%) glucose concentrations in the controlled water-based samples satisfactorily, which is well below the typical human glucose levels of 4 mmol/l.

A microwave breast imaging system using elliptical uniplanar antennas in a circular-array setup

Microwave tomography has attracted significant research interest as it offers a non-ionizing diagnostic technique for breast cancer. A microwave breast imaging (MBI) system comprises an array of antennas, which illuminates the tissue and measures the scattered energy in order to spatially allocate the dielectric permittivity and conductivity of the tissue. The radiating elements of a MBI system should be compact and wideband. This paper describes an elliptical uniplanar antenna 40 mm × 50 mm in size that operates in the 1.53-3.33 GHz range when placed against a breast phantom. The antenna is used as the radiating element in a circular-array setup around a hemispherical phantom. Simulated and measured data from the proposed array are presented, which show satisfying agreement and system performance.

Tract-based Spatial Statistics and fMRI Analysis in Patients with Small Cell Lung Cancer before Prophylactic Cranial Irradiation

Prophylactic cranial irradiation (PCI) is known to increase life expectancy to a significant degree in Small Cell Lung Cancer (SCLC) patients. The overall scope of this research is to investigate changes in structural and functional connectivity between SCLC patients and controls before and after PCI treatment. In the current study specifically we use diffusion tensor imaging (DTI) and functional Magnetic Resonance (fMRI) to identify potential alterations in white matter structure and brain function respectively, in SCLC patients before PCI compared to healthy participants. The results in DTI analysis have showed lower fractional anisotropy (FA) and higher eigenvalues in white matter regions in the patient group. Similarly, in fMRI analysis a lower level of activation in the primary somatosensory cortex was reported. The results presented herein are subject to further investigation with larger patient and control groups.

Antennas on metamaterial substrates as emitting components for THz biomedical imaging

Terahertz technology is considered a viable option for medical imaging, since many biological and chemical agents exhibit signatures in this spectral domain. Ultimately, large biomolecules and protein strands will be accessible, enabled by the coupling of THz science with near-field probes. In this paper, we present the recent advances of our research regarding a novel 2-D THz imaging system that it is intended to be used for imaging and characterization of tissue and biomolecule samples associated to brain functionality. Herein, we specifically focus on the emitting elements of the system, by studying two types of THz planar antennas for THz emission: a rectangular and a bow-tie patch antenna working at 1 THz. The aim and novelty of this work is to present an effective THz antenna with high gain and to this end we use left-handed materials for the substrate.

Design and Experimental Validation of a Multiple-Frequency Microwave Tomography System Employing the DBIM-TwIST Algorithm

We present a first prototype of a wideband microwave tomography system with potential application to medical imaging. The system relies on a compact and robust printed monopole antenna which can operate in the 1.0–3.0 GHz range when fully immersed in commonly used coupling liquids, such as glycerine–water solutions. By simulating the proposed imaging setup in CST Microwave Studio, we study the signal transmission levels and array sensitivity for different target and coupling liquid media. We then present the experimental prototype design and data acquisition process, and show good agreement between experimentally measured data and results from the CST simulations. We assess imaging performance by applying our previously proposed two-dimensional (2-D) DBIM TwIST-algorithm to both simulated and experimental datasets, and demonstrate that the system can reconstruct simple cylindrical targets at multiple frequencies.

Towards Multispectral Multimodal Non-ionising Diagnosis and Therapy

As the boundary between biology, medicine, and engineering remains indistinct, electromagnetics engineering applications are expanding to encapsulate a variety of public health issues. Medical applications of microwaves are a very rapidly developing research and application field, especially for intracranial applications. Currently, in order to acquire the most valuable complementary data in terms of quality and quantity, benefiting from the advantages of the various techniques, combination of two or more techniques is pursued both in diagnostics and therapy. The so-called multimodal approach may be achieved either by post-session analysis of data or via simultaneous use of techniques in order to reveal the multifactorial interplay of the underlying mechanisms during brain activation, disease and therapy. This chapter will review the progress in diagnostic, therapeutic and theranostic multi-modal multispectral methods, with specific attention to cerebrovascular diseases and monitoring of the brain activity.

Sensing local temperature and conductivity changes in a brain phantom using near-field microwave radiometry

Knowledge of thermal and/or conductivity local changes inside the brain may provide useful information about brain activity. Microwave radiometry may be able to monitor such changes. Based on previous research in brain mapping using microwave radiometry a new prototype near field radiometry system has been used to detect local changes of temperature and conductivity in brain phantom experiments which are herein presented.

Characterisation of ZnO NPs as contrast agents for MWI

This study presents the examination of zinc oxide (ZnO) nanoparticles (NPs) as potential contrast agents for microwave imaging (MWI). Polyethylene Glycol (PEG) with varying molecular weights (Mw) have been used to coat NPs. Characterisation of the colloidal dispersions have been recorded using Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), and Ultraviolet-Visible spectroscopy (UV-Vis). The dielectric characterisation of the aqueous colloidal suspensions was recorded over the microwave frequency range between 1–4 GHz, to assess effective contrast for microwave breast imaging applications. Our data shows zinc oxide NPs increase dielectric constant compared to the background medium. The PEGylation process further improved the suspension stability, which was confirmed by DLS and UV-Vis. ZnO-PEG achieved a significant increase in the dielectric constant and the increase was dependent on the different molecular weights of PEG.

Towards a microwave imaging prototype based on the DBIM-TwIST algorithm and a custom-made transceiver system

A microwave imaging prototype that uses a novel electromagnetic inverse scattering algorithm based on the distorted Born iterative method (DBIM) and the two-step iterative shrinkage thresholding (TwIST) algorithm to solve the linear problem at each DBIM iteration is presented. In previous work, the algorithm has been tested in simulations with realistic numerical breast phantoms, which demonstrated its resolution capabilities relative to traditional CGLS solvers, and its ability to take advantage of the whole frequency range of 1.0–3.0 GHz to produce high resolution images. This work is a preliminary investigation of the potential of this algorithm in reconstructing experimental data. The hardware setup for collecting the scattered signal from the investigation domain comprises a novel 16-port RF transceiver, an 8-element array of inverted triangular patch antennas to cover a two-dimensional view, and an imaging chamber with a high precision motor for rotation.

Two 27 MHz Simple Inductive Loops, as Hyperthermia Treatment Applicators: Theoretical Analysis and Development.

Background. Deep heating is still the main subject for research in hyperthermia treatment. Aim. The purpose of this study was to develop and analyze a simple loop as a heating applicator. Methods. The performance of two 27 MHz inductive loop antennas as potential applicators in hyperthermia treatment was studied theoretically as well as experimentally in phantoms. Two inductive loop antennas with radii 7 cm and 9 cm were designed, simulated, and constructed. The theoretical analysis was performed by using Greens function and Bessels function technique. Experiments were performed with phantoms radiated by the aforementioned loop antennas. Results. The specific absorption rate (SAR) distributions were estimated from the respective local phantom temperature measurements. Comparisons of the theoretical, simulation, and experimental studies showed satisfying agreement. The penetration depth was measured theoretically and experimentally in the range of 2–3.5 cm. Conclusion. The theoretical and experimental analysis showed that current loops are efficient in the case where the peripheral heating of spherical tumor formation located at 2–3.5 cm depth is required.