Focused microwave radiometry, aiming mainly in clinical applications at measuring temperature distributions inside the human body, may provide the capability of detecting electrical conductivity variations at microwave frequencies of excitable cell clusters, such as in the case of brain tissues. A novel microwave radiometric system, including an ellipsoidal conductive wall cavity, which provides the required beamforming and focusing, is developed for the imaging of biological tissues via contactless measurements. The measurement is realized by placing the human head in the region of the first focus and collecting the radiation converged at the second by an almost isotropic dipole antenna connected to a sensitive radiometer operating at 3.5 GHz. In order to compute the focusing properties of the ellipsoidal reflector, an accurate electromagnetic numerical analysis is developed using a semianalytical method. The experimental part of this study focuses on measurements of activation of the primary somatosensory (SI) brain area, elicited during the application of the cold pressor test, a standard experimental condition inducing pain. Analysis of the measured data from 16 healthy subjects suggests that this methodology may be able to pick up activation of the SI during the pain conditions as compared with the nonpainful control conditions. Future research is needed in order to elucidate all the interacting factors involved in the interpretation of the presented results. Finally, potential limitations to the generalization of our results and strategies to improve the system's response are discussed.Index Terms-Activation of primary somatosensory (SI) cortex, ellipsoidal conductive wall cavity, focused microwave radiometry, imaging of conductivity variations in biological tissues.

Abstract-A technique based on the Green's function theory is used in the present research in order to study theoretically the focusing properties of a constructed 3D non-invasive microwave imaging system, consisting of an ellipsoidal conductive cavity and a radiometric receiver. A double layered spherical human head model is placed on one focal point of the elliptical reflector, while the receiving antenna is placed on the other focus. Making use of the reciprocity theorem, the equivalent problem of the coupling between an elementary dipole and the double layered lossy dielectric human spherical model is solved. Numerical results concerning the electric field distribution inside the head model and in the rest of the cavity, at two operating frequencies (1.5 GHz and 3.5 GHz), are presented and compared to the results of an electromagnetic simulator. Finally, phantom experimental results validate the proof of concept and determine the temperature and spatial attributes of the system.

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Vehicle collision mitigation, cooperative driving, and vehicle-to-vehicle (V2V) and/or vehicle-to-infrastructure (V2I) communication constitute a broad multidisciplinary research field that focuses on improving road safety. Statistics indicate that the primary cause of most road accidents is vehicles' excessive speed and delayed drivers reaction. Thus, road safety can be improved by early warning based on V2V communication. An innovative system called wireless local danger warning (WILLWARN), which is based on recent and future trends of cooperative driving, enables an electronic safety horizon for foresighted driving by implementing onboard vehicle-hazard detection and V2V communication. One of the key innovative features of the proposed system is the focus on low penetration levels in rural traffic by a new messagemanagement strategy that is based on storing warning information in the vehicle and distributing warnings through communication, particularly with oncoming traffic. The system timely warns the driver about a dangerous situation ahead by decentralized distribution of warnings and incident messages via ad hoc intervehicle communication. The WILLWARN system is based on a modular object-oriented architecture consisting of the V2V communication module (VVC), the warning message-management module (WMM), the hazard-detection-management module (HDM), the hazard-warning-management module (HWM), a Global Positioning System (GPS) receiver, and various onboard sensors. In this paper, all system modules, as well as their interoperability, are presented in detail.

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Abstract-Temperature variations in tissues inside the body have been measured using microwave radiometry for more than three decades in a variety of passive body monitoring applications. In this paper, we study a prototype system for passive intracranial monitoring using microwave radiometry.It comprises L-notch microstrip patch antennas in conjunction with a sensitive multiband microwave receiver for detection. The particular design characteristics of the antenna are its conformality and a special L cut on its upper left edge, features that make it suitable for human biomedical applications and lead to its multiband operation in the frequency range of 2-3 GHz. The theoretical electromagnetic study indicates that the radiometric contact system in question operates well at two frequencies, with satisfying detection depths and adequate portability (small dimensions). In order to verify the findings of these simulations, experimental measurements with phantoms and various setups were carried out, resulting in the definition of the actual temperature detection level and the spatial resolution of the system. Theoretical and experimental results conclude that with the appropriate combination of conformal patch antennas and microwave receiver it is possible to monitor areas of interest inside human head models with a variety of temperature resolutions and detection depths.

Objective: Near-field microwave radiometry has emerged as a tool for real time passive monitoring of local brain activation possibly attributed to local changes in blood flow that correspond to temperature and/or conductivity changes. The aim of this study is to design and evaluate a prototype system based on microwave radiometry intended to detect local changes of temperature and conductivity in depth in brain tissues. A novel radiometric system that comprises a four port total power Dicke-switch sensitive receiver that operates at 1.5 GHz has been developed. Methods and Results: The efficacy of the system was assessed through simulation and experiment on brain tissue mimicking phantoms under different setup conditions, where temperature and conductivity changes were accurately detected. In order to validate the radiometer's capability to sense low power signals occurring spontaneously from regions in the human brain, the somatosensory cortices of one volunteer were measured under pain inducing psychophysiological conditions. The promising results from the initial in-vivo measurements prove the system's potential for more extensive investigative trials. Conclusion and significance: The significance of this study lies on the development of a compact and sensitive radiometer for totally passive monitoring of local brain activation as a potential complementary tool for contributing to the research effort for investigating brain functionality.Index Terms-Microwave radiometry, real time monitoring, non-invasive passive measurement, measurement of local brain temperature and / or conductivity variations maria.koutsoupidou@kcl.ac.uk).Irene S. Karanasiou is with the