In this study, new aspects of our research regarding a novel hybrid system able to provide focused microwave radiometric temperature and/or conductivity measurements and hyperthermia treatment via microwave irradiation are presented. On one hand, it is examined whether the system is capable of sensing real-time progressive local variations of temperature and/or conductivity in customized phantom setups; on the other hand, the focusing attributes of the system are explored for different positions and types of phantoms used for hyperthermia in conjunction with dielectric matching layers surrounding the areas of interest. The main module of the system is an ellipsoidal cavity, which provides the appropriate focusing of the electromagnetic energy on the area of interest. The system has been used for the past few years in experiments with different configuration setups including phantom, animal, and human volunteer measurements yielding promising outcome. The present results show that the system is able to detect local concentrated gradual temperature and conductivity variations expressed as an increase of the output radiometric voltage. Moreover, when contactless focused hyperthermia is performed, the results show significant temperature increase at specific phantom areas. In this case, the effect of the dielectric matching layers placed around the phantoms is critical, thus resulting in the enhancement of the energy penetration depth.

Abstract-Aiming at the enhancement of a non invasive Microwave Radiometry Imaging System's (MiRaIS) attributes, Left Handed Materials (LHM) with negative permittivity and negative permeability simultaneously, have been utilized. The optimization of the system focusing properties is being theoretically explored, implementing a semi-analytical Green's function technique and different matching structures. In the framework of this analysis the head is modeled by a double layered cylinder while a dielectric cylindrical layer consisting of LHM is placed on the surface of the human head model with a view to achieve focusing improvement inside the brain. Numerical code executions have been conducted for two different operating frequencies (0.5 GHz and 1.0 GHz) and for matching layers of various values of thicknesses and electromagnetic properties. The numerical results for the electric field distribution inside the head model, presented in this paper, verify that the LHM can provide an increased sensitivity of the system focusing properties and thus improve its overall performance.

Abstract-A Green's function based methodology has been developed and implemented with the view to optimize the focusing properties and thus the performance of a Microwave Radiometry Imaging System (MiRaIS). The system consists of an ellipsoidal conductive wall cavity and a sensitive radiometric receiver and its operation principal is based on the convergence of the radiation from one focal point, where the subject or phantom is placed, on the other, where the receiver antenna is positioned. A two-layered cylinder is used to model the human head with the semi-analytical Green's function technique. The imaging configuration is enhanced by different matching structures of various materials which are placed on the surface of both the human head model and the antenna inside the ellipsoidal. Numerical code executions have been realized and the results for the electric field distribution inside the head are presented for materials of various dielectric properties and for left handed materials at two different frequencies (0.5 GHz and 1.0 GHz). Increased sensitivity of the system focusing properties is observed using particular matching structures.

Chirped Bessel waves are introduced as stable (non-diffracting) solutions of the paraxial wave equation in optical antiguides with a power-law radial variation in their index of refraction.Through numerical simulations, we investigate the propagation of apodized (finite-energy) versions of such waves, with or without vorticity, in antiguides with practical parameters. The new waves exhibit a remarkable resistance against the defocusing effect of the unstable index potentials, outperforming standard Gaussians with the same full width at half maximum. The chirped profile persists even under conditions of eccentric launching or antiguide bending and is also capable of self-healing like standard diffraction-free beams in free space.

We present a formulation for deriving effective medium properties of infinitely periodic two-dimensional metamaterial lattice structures beyond the conventional static and quasi-static limits. We utilize the multipole expansions, where the polarization currents associated with the supported Bloch modes are expressed via the electric dipole, magnetic dipole, and electric quadrupole moments per unit length. We then propose a method to calculate the Bloch modes based on the lattice geometry and individual unit element structure. The results revert to well-known formulas in the traditional quasistatic limit and are useful for the homogenization of nanorod-type metamaterials which are frequently used in optical applications.

A non-invasive imaging system, consisting of an ellipsoidal conductive cavity and radiometric receivers, designed and constructed in our laboratory the past few years is restudied. A means for further improvement of the ellipsoidal reflector's focusing properties thus its performance is herein investigated. The main differentiating factor of our new approach is that the receiving antenna is more realistically modelled and also covered by two layers of different dielectric properties. The present paper provides details on the electromagnetic theoretical analysis of the problem and presents numerical results for the electric field distribution inside the head model, using two main operating frequencies, namely 0.5GHz and 1.5GHz for four distinct cases. The focusing optimization of the system in terms of spatial accuracy and penetration depth is assessed while the method and results are also separately validated.

A non-invasive imaging system, consisting of an ellipsoidal conductive cavity and radiometric receivers, designed and constructed in our laboratory the past few years is restudied. In order to enhance the system's focusing properties thus its performance, the head is covered by a dielectric matching layer while the receiving antenna is more realistically modelled and also covered by two layers of dielectric properties similar to those of the head. The electric field distribution inside the head is calculated for two frequencies and for matching layers of different dielectric properties and thicknesses, through a theoretical electromagnetic analysis using a Green's function technique. Sensitivity of the system focusing properties is observed when the head or the source center is moved away from the system's geometrical focal areas.

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