Antenna Development for Radio Frequency Hyperthermia Applications

This thesis deals with the design steps, development and validation of an applicator for radio frequency hyperthermia cancer therapy. An applicator design to enhance targeted energy coupling is a key enabler for preferential temperature increments in tumour regions. A single-element, near-field approach requires a miniaturised solution, that addresses ergonomic needs and is tolerant to patient anatomy. The antenna war-field rriodality and the high-dielectric patient loading introduce significant analytical and computational resource challenges. The antenna input impedance has to be sufficiently insensitive to in-band resonant cletuning and the fields in the tissue can he targeted to selected areas in the patient. An introduction to the medical and biological background of hyperthermia is presented. The design requirements of antennas for medical and in particular for hyperthermia applications are highlighted. Starting from a conventional circular patch, the antenna evolved into a compact circular patch with a concentric annular ring and slotted groundplane, operating at the 434 MHz Industrial Scientific and Medical frequency band. Feed point location is optimized for an energy deposition pattern aligned with the antenna centre. The applicator is assessed with other published approaches and clinically used loop, dipole and square patch antennas. The antennas are evaluated for the unloaded condition and when loaded with a tri-layer body tissue numerical model. This model comprises skin, fat and transverse fiber of muscle of variable thicknesses to account for different body locations and patient. anatomy. A waterbolus containing de-ionized water is added at the skin interface for superficial tissue cooling aud antelina matching. The proposed applicator achieves a penetration depth that supersedes other approaches while remaining compact and an ergonomic fit to tumour areas on the body. To consider the inner and peripheral complex shapes of human bodies, the full human body numerical model developed by Remcom is used. This model was segmented from 1 mm step computed tomography (CT) and magnetic resonance imaging (MRI) cross-sections through and adult male and it comprises twenty-three tissue types with thermal and frequency-dependent dielectric properties. The applicator performance is evaluated at three anatomical body areas of the model to assess its suitability for treatment of tumours at different locations. These three anatomical regions present different aperture coupling and tissue composition. \u27Different conformal waterbolus and air gap thickness values are evaluated. The models used in this work are validated with measurements performed in a phantom containing a lossy liquid with dielectric properties representative of homogeneous human body tissue. The dosimetric assessment system (DASY) is used to evaluaxe the specific absorption rate (SAR) generated for the antenna into the liquid. The measurement setup with the antenna, phantom and liquid are simulated. Simulated and measured results in terrms of specific absorption rate and return loss are evaluated

Groundplane Dependent Performance of Printed Antenna for MB-OFDM-UWB

A printed ultra wideband (UWB) antenna suitable for multiband orthogonal frequency division multiplexing (MB-OFDM) UWB is presented in this paper. The proposed antenna covers a wide band from 3.1 GHz to 11.2 GHz. Good performance and low cost production was obtained using FR-4 substrate. An examination of the effects of ground plane dimensions on antenna properties such as gain, bandwidth and radiation pattern is made

Question Generation based on Lexico-Syntactic Patterns Learned from the Web

THE MENTOR automatically generates multiple-choice tests from a given text. This tool aims at supporting the dialogue system of the FalaComigo project, as one of FalaComigo's goals is the interaction with tourists through questions/answers and quizzes about their visit. In a minimally supervised learning process and by leveraging the redundancy and linguistic variability of the Web, THE MENTOR learns lexico-syntactic patterns using a set of question/answer seeds. Afterward, these patterns are used to match the sentences from which new questions (and answers) can be generated. Finally, several ï¬lters are applied in order to discard low quality items. In this paper we detail the question generation task as performed by T- Mand evaluate its performance

Las primeras civilizaciones. Mesopotamia y Egipto en la programación de Geografía e Historia (1º ESO).

La Unidad Didáctica que nos ocupa, “Las Primeras Civilizaciones: Mesopotamia y Egipto”, puede ser justificada, por lo menos, desde tres perspectivas diferentes. En primer lugar, tiene una justificación de carácter legal, ya que dicha Unidad se halla enmarcada en el currículo oficial. En segundo lugar, el estudio de este periodo histórico constituye una magnífica oportunidad para desarrollar habilidades relacionadas con el método del historiador cómo son aprender a datar y a secuenciar, pero al mismo tiempo entender que los acontecimientos y procesos históricos tienen lugar, en muchas ocasiones, a la vez. Y en tercer lugar, pero no por ello menos importante, debemos tener en cuenta la importancia que tiene de esta Unidad para la comprensión de aspectos trascendentales para el devenir humano como es la aparición de la escritura, la jerarquización social y el desarrollo de espacios urbanos de creciente complejidad.Departamento de Didáctica de las Ciencias Sociales y ExperimentalesMáster en Profesor de Educación Secundaria Obligatoria y Bachillerato, Formación Profesional y Enseñanzas de Idioma

In-Silico Hyperthermia Performance of a Near-Field Patch Antenna at Various Positions on a Human Body Model

A compact patch applicator designed to enhance targeted energy coupling at 434 MHz is a key enabler for sensitizing temperature increments in body regions containing superficial tumours. A detailed FDTD body model is used to explore simulated RF coupling and temperature increments for typical clinical conditions. The antenna impedance matching, specific absorption rate and thermal distribution parameters are evaluated to identify applied performance outcomes. The analysis reveals physiological-RF coupling patterns for an optimised closely-coupled single element applicator

Interaction of RF-hyperthermia Applicator with High Fidelity Human Body Model

A compact patch antenna working at the 434 MHz ISM frequency band is proposed as an RF-Hyperthermia applicator. The electromagnetic interaction in terms of S11, SAR and E-Field distribution of the antenna with a High Fidelity human body model is investigated. This analysis provides useful information for engineers and clinical staff to develop more efficient and smaller antennas for medical applications, in particular for RF-Hyperthermia cancer therapy, where the size of the antenna determines tumor accessibility

Groundplane Dependent Performance of Printed Antenna for MB-OFDM-UWB

A printed ultra wideband (UWB) antenna suitable for multiband orthogonal frequency division multiplexing (MB-OFDM) UWB is presented in this paper. The proposed antenna covers a wide band from 3.1 GHz to 11.2 GHz. Good performance and low cost production was obtained using FR-4 substrate. An examination of the effects of ground plane dimensions on antenna properties such as gain, bandwidth and radiation pattern is made

Investigación sobre factores de riesgo cardiovascular en Uruguay

Las enfermedades cardiovasculares son en Uruguay, como en la mayoría de los países, la primera causa de muerte y están entre las de mayor prevalencia. Por ello la investigación para la caracterización y cuantificación de los principales factores de riesgo y las conductas preventivas en la población, resulta fundamental para la prevención y el control de estas afecciones. Estudios previos determinaron una elevada prevalencia de obesidad o sobrepeso (51%) y de hipertensión arterial (entre 21% y 46%). En el presente trabajo, realizado por el Área de Epidemiología de la Comisión Honoraria para la Salud Cardiovascular con la colaboración de los clubes de Leones (Distrito Múltiple J - Uruguay), se encuestaron 1.959 personas en una muestra aleatoria representativa de la población del país. Se investigaron las características de los principales factores de riesgo relacionados con las enfermedades del aparato circulatorio y se encontraron las siguientes cifras globales: tabaquismo (45%), sedentarismo (28%), obesidad y sobrepeso (53%) e hipertensión arterial (22%). El estudio mostró una elevada proporción de fumadores y un importante número de personas que dejan de fumar. Datos de hipertensión compatibles con estudios anteriores, un alto porcentaje de obesidad y sobrepeso en ambos sexos, así como una proporción relevante de personas sedentarias. Se concluye en la necesidad de difusión de información adecuada para la prevención de los factores de riesgo y en particular para que el ejercicio físico se realice dentro de los parámetros mínimos y con los controles adecuados, ya que muchas personas realizan actividad física en forma insuficiente o incorrecta

Ethylcellulose-stabilized fat-tissue phantom for quality assurance in clinical hyperthermia

Background: Phantoms accurately mimicking the electromagnetic and thermal properties of human tissues are essential for the development, characterization, and quality assurance (QA) of clinically used equipment for Hyperthermia Treatment (HT). Currently, a viable recipe for a fat equivalent phantom is not available, mainly due to challenges in the fabrication process and fast deterioration. Materials and methods: We propose to employ a glycerol-in-oil emulsion stabilized with ethylcellulose to develop a fat-mimicking material. The dielectric, rheological, and thermal properties of the phantom have been assessed by state-of-the-art measurement techniques. The full-size phantom was then verified in compliance with QA guidelines for superficial HT, both numerically and experimentally, considering the properties variability. Results: Dielectric and thermal properties were proven equivalent to fat tissue, with an acceptable variability, in the 8 MHz to 1 GHz range. The rheology measurements highlighted enhanced mechanical stability over a large temperature range. Both numerical and experimental evaluations proved the suitability of the phantom for QA procedures. The impact of the dielectric property variations on the temperature distribution has been numerically proven to be limited (around 5%), even if higher for capacitive devices (up to 20%). Conclusions: The proposed fat-mimicking phantom is a good candidate for hyperthermia technology assessment processes, adequately representing both dielectric and thermal properties of the human fat tissue while maintaining structural stability even at elevated temperatures. However, further experimental investigations on capacitive heating devices are necessary to better assess the impact of the low electrical conductivity values on the thermal distribution