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Proceedings ArticleDOI

Enhancing the focusing properties of an ellipsoidal beamformer based imaging system: a simulation study.

TL;DR: Improvement of the focusing properties of a microwave radiometry tomography system used for the imaging of the product of temperature and conductivity in biological tissues via contactless measurements using an ellipsoidal conductive wall cavity.
Abstract: Aim of this study is the improvement of the focusing properties of a microwave radiometry tomography system, used for the imaging of the product of temperature and conductivity in biological tissues via contactless measurements. The operation principle of the device in question is based on an ellipsoidal conductive wall cavity, which provides the required beamforming and focusing. The biological tissue under measurement is placed on one of the two focal points whereas on the other one, a dipole antenna measures the black body type radiation emitted from the head's tissue. In the framework of the present research several approaches are followed in order to improve and optimize the system's focusing properties on the tissue area of interest. Extensive simulations using a commercial FEM tool are performed in a wide range of operation frequencies. Dielectric spheres of various electromagnetic characteristics are placed either around the source (human head model) or the receiver (dipole antenna) in order to improve the matching on the head-air interface. The ability of focusing the electromagnetic energy in specific areas inside the human head is herein investigated in detail and further discussed.
Citations
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Journal ArticleDOI
TL;DR: Both computation and phantom measurement results show that deep focused brain hyperthermia may be achievable with adequate spatial resolution and sensitivity using the proposed methodology, subject to the appropriate combination of operation frequency and low-loss dielectric material used as filling in the ellipsoidal.
Abstract: During the past two decades, a great deal of research has been carried out with the aim of developing effective techniques for hyperthermia treatment, primarily using RF, microwave, and ultrasound energy. A system for deep brain hyperthermia treatment, designed to also provide passive measurements of temperature and/or conductivity variations inside the human body, is presented in this paper. The proposed system comprises both therapeutic and diagnostic modules, operating in a totally contactless way, based on the use of an ellipsoidal beamformer to achieve focusing on the areas under treatment and monitoring. In previous publications, the performance of the system's diagnostic module in phantom, animal, and human studies has been reported. In the current research, new theoretical and experimental results using the therapeutic hyperthermia module of the system are presented. The main scope of the theoretical analysis is the improvement of the system's focusing attributes. Moreover, phantom experimental results verify the proof of concept. Both computation and phantom measurement results show that deep focused brain hyperthermia may be achievable with adequate spatial resolution and sensitivity using the proposed methodology, subject to the appropriate combination of operation frequency and low-loss dielectric material used as filling in the ellipsoidal.

40 citations


Cites background from "Enhancing the focusing properties o..."

  • ...It has been already demonstrated through theoretical analysis [33]–[41] that the system’s focusing properties are not affected by this alteration compared to those achieved using the whole cavity volume....

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Journal ArticleDOI
TL;DR: In this paper, a hybrid system able to provide focused microwave radiometry and deep brain hyperthermia is experimentally tested using water phantoms surrounded by dielectric layers used as matching material to enhance detection/penetration depth and spatial resolution.
Abstract: In this paper a hybrid system able to provide focused microwave radiometry and deep brain hyperthermia is experimentally tested. The system's main module is an ellipsoidal conductive wall cavity which acts as a beam former, focusing the electromagnetic energy on the medium of interest. The system's microwave radiometry component has extensively been studied theoretically and experimentally in the past few years with promising results. In this work, further investigation concerning the improvement of the hybrid system's focusing properties is conducted. Specifically, microwave radiometry and hyperthermia experiments are performed using water phantoms surrounded by dielectric layers used as matching material to enhance detection/penetration depth and spatial resolution. The results showed that the dielectric material reduces the reflected electromagnetic energy on the air–phantom interface, resulting in improved temperature resolution and higher detection or penetration of the energy when microwave radiometry and hyperthermia are applied respectively.

11 citations


Cites background from "Enhancing the focusing properties o..."

  • ...9 detection/penetration depth is also improved [30], [37]....

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Proceedings ArticleDOI
22 Oct 2007
TL;DR: The ability of the microwave radiometry tomography system to operate as a hyperthermia clinical tool is revealed, not as a stand alone device but in conjunction with other already validated devices/methods.
Abstract: Aim of this study is twofold; on one hand, the investigation of the focusing attributes of a microwave radiometry tomography system with the use of a realistic human head model and on the other hand, the system's ability to perform a hyperthermia treatment. The operation principle of the device is based on an ellipsoidal conductive wall cavity, which provides the required beamforming and focusing. The biological tissue under treatment and/or measurement is placed on one of the two focal points whereas on the other one, a radiating or receiving antenna, which measures the black body type radiation emitted from the head's tissue, is placed. In previous studies simple spherical head models were used, comprising one or two layers for simulating the head tissues, along with a commercial FEM tool. In this work, a realistic adult head model developed from MRI scans of a human head is used. The realistic model with detailed structural and electromagnetic tissue characteristics enables more in depth theoretical investigation of the system capabilities. Extensive simulations using a commercial FDTD tool are performed in a wide range of operating frequencies. In order to explore the feasibility of heating and monitoring specific brain areas, the capability of focusing the electric field in specific areas inside the human head is investigated and further discussed. The results show that simple spherical head models, used in previous studies, provide similar results with the realistic one used herein for the given geometry; that is, the electric field focuses on the head's center, assuming the head as a homogeneous sphere. However, the deposition of the electromagnetic energy on the head tissues depends on the operating frequency and position of the head in the given geometry, so is therefore calculated, revealing the ability of the system to operate as a hyperthermia clinical tool, not as a stand alone device but in conjunction with other already validated devices/methods.

9 citations

Journal Article
TL;DR: The micro-CT analysis generated structure-orientated slices that in conjunction with the histological sections provide a high quality quantitative analysis of all cranial sutures and of the cranial bones diploae.
Abstract: The aim of the study was to assess the normal cranial suture and bone diploae ultrastructural morphology. Two types of sutures from different specimens were collected. The micro-CT scanning provided a three-dimensional view of the sutures at a microscopic level thus allowing the evaluation of the development stage and a rapid analysis evaluation of bone and diploae morphology. In the meantime, the micro-CT is able to generate more slices than the normal histology preserving the analyzed specimens and became one of the most powerful tools in the craniofacial area. The micro-CT analysis generated structure-orientated slices that in conjunction with the histological sections provide a high quality quantitative analysis of all cranial sutures and of the cranial bones diploae.

1 citations

References
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Journal ArticleDOI
TL;DR: Three experimental techniques based on automatic swept-frequency network and impedance analysers were used to measure the dielectric properties of tissue in the frequency range 10 Hz to 20 GHz, demonstrating that good agreement was achieved between measurements using the three pieces of equipment.
Abstract: Three experimental techniques based on automatic swept-frequency network and impedance analysers were used to measure the dielectric properties of tissue in the frequency range 10 Hz to 20 GHz. The technique used in conjunction with the impedance analyser is described. Results are given for a number of human and animal tissues, at body temperature, across the frequency range, demonstrating that good agreement was achieved between measurements using the three pieces of equipment. Moreover, the measured values fall well within the body of corresponding literature data.

3,996 citations

Journal ArticleDOI
TL;DR: 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, and potential limitations to the generalization of the results are discussed.
Abstract: 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.

64 citations

Journal ArticleDOI
TL;DR: In this paper, a double layered spherical human head model is placed on one focal point of the ellipsoidal reflector, while the receiving antenna was placed on the other focus.
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.

34 citations


"Enhancing the focusing properties o..." refers background or methods or result in this paper

  • ...... in order to solve and analyze the second theoretical issue that is of concern as mentioned above, two theoretical electromagnetic analyses have been carried out; the electric field distribution inside the ellipsoidal conductive wall cavity in the presence of a spherical human head model has been calculated by developing a semi- analytical technique based on the Green’s Function Theory [1], [2], [5], [7] and using a simulation FEM tool [ 1 ], ......

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  • ...The system mainly comprises an ellipsoidal conductive wall cavity and a sensitive radiometric receiver, operating at low microwave frequencies [ 1 ]-[7]....

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  • ...However, both numerical as well as experimental results [ 1 ]-[7] have shown that with the MiRaIS setup electromagnetic energy focuses on an area around the opposite focal point....

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  • ...This is the solution of the simple case of the problem and the results are in agreement with previous studies [ 1 ]-[7]....

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  • ...A novel Microwave Radiometry Imaging System (MiRaIS) based on the above Quantum Physics theory, has been used the past six years in various validation experiments as a potential intracranial imaging device [ 1 ]-[7]....

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Proceedings ArticleDOI
01 Jan 2004
TL;DR: A novel microwave radiometric system operating at 3.5 GHz, including an ellipsoidal conductive wall cavity, which provides the required beamforming and focusing, is developed, capable of providing distribution measurements of the product of conductivity and temperature of any object being at a temperature above the absolute zero.
Abstract: The capability of detecting electrical conductivity variations using focused microwave radiometry, a method used in clinical applications for temperature distribution imaging of subcutaneous tissues, is discussed in the present study. A novel microwave radiometric system operating at 3.5 GHz, including an ellipsoidal conductive wall cavity, which provides the required beamforming and focusing, is developed. The system is capable of providing distribution measurements of the product of conductivity and temperature of any object being at a temperature above the absolute zero. The implemented experimental procedure is based on the results of an electromagnetic numerical analysis using a semianalytical method which was developed in order to compute the focusing properties of the ellipsoidal reflector. Each measurement is realized by placing the region of interest in the area of the first focus of the cavity and collecting the radiation converged at the second by an almost isotropic dipole antenna connected to a sensitive radiometer. Experimental data from cylindrical shaped saline or de-ionized water filled tank phantoms in which saline solutions of different concentrations were infused, provide promising results concerning the system's ability of detecting conductivity variations. Future research is needed in order to elucidate the potential of the proposed methodology to be used for brain conductivity measurements.

21 citations


"Enhancing the focusing properties o..." refers methods in this paper

  • ...Thus, in order to solve and analyze the second theoretical issue that is of concern as mentioned above, two theoretical electromagnetic analyses have been carried out; the electric field distribution inside the ellipsoidal conductive wall cavity in the presence of a spherical human head model has been calculated by developing a semi- analytical technique based on the Green’s Function Theory [1], [2], [ 5 ], [7] and using a simulation FEM ......

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Journal ArticleDOI
01 Oct 2004-Itbm-rbm
TL;DR: In this article, the authors discuss the feasibility of a microwave radiometric system to measure, non-invasively, temperature distribution in subcutaneous tissues, including possibly intracranial brain diagnostic applications.
Abstract: The present paper discusses the feasibility of a novel microwave radiometric system to measure, non-invasively, temperature distribution in subcutaneous tissues, including possibly intracranial brain diagnostic applications. The operation principle of the system is based on the use of an ellipsoidal conductive wall cavity, which provides the required focusing and the ability of imaging via contactless measurements. The basis of the theoretical analysis of this work is the fundamental law of the chaotic radiation emitted by material objects (microwave electromagnetic thermal noise) being at a temperature above the absolute zero. In the framework of the present research the theoretical principles along with phantom and animal experiments are presented.

20 citations