Avec une population mondiale vieillissante, de plus en plus de personnes sont à risque de présenter des pathologies pour lesquelles l’Imagerie par Résonance Magnétique (IRM) est une modalité de choix : ainsi, le nombre d’examens IRM est en constante augmentation. Les patients âgés étant par ailleurs une population davantage susceptible de recevoir une implantation de dispositifs médicaux (tels qu’un pacemaker ou une prothèse de hanche), la sécurité des patients implantés en IRM est primordiale. En effet, cet appareil d’imagerie médicale fait intervenir différents champs électromagnétiques pouvant interagir avec un implant métallique et donner lieu à des risques potentiels pour le patient. Si des normes de compatibilité existent aujourd’hui pour soumettre individuellement les dispositifs médicaux à des tests standardisés et assurer leur innocuité en environnement IRM, les interactions entre multiples dispositifs médicaux vis-à-vis des ondes électromagnétiques radiofréquence (et des dangers qui peuvent en résulter) sont un domaine complexe qu’il est nécessaire de comprendre. L’objet de cette thèse est d’étudier ces interactions sur plusieurs niveaux : interactions intra-dispositif, interactions inter-dispositifs et interactions entre dispositif et plusieurs antennes. Une méthode de prédiction d’échauffement a été proposée pour simplifier l’étude de larges gammes d’implants, suivant les variations de paramètres caractérisant les différentes parties au sein d’une prothèse. Des simulations électromagnétiques et thermiques, associées à des mesures expérimentales dans un environnement IRM clinique, ont permis de mettre en évidence des phénomènes de couplages entre deux implants simplifiés et d’introduire une nouvelle métrique pour les quantifier. Enfin, une étude multi-antennes a fourni des éléments de réponse à la question de la sécurité d’un patient implanté en présence de plusieurs antennes, dans une configuration semblable à celle des examens en routine clinique. Les travaux présentés dans cette thèse ont ainsi permis d’évaluer les interactions vis-à-vis de la radiofréquence de l’IRM en présence d’un ou plusieurs dispositifs médicaux et antennes, ouvrant plusieurs perspectives pour aller vers une IRM sûre pour tous / With an aging population worldwide, more and more persons are at risk of suffering from pathologies which are best diagnosed or monitored with Magnetic Resonance Imaging (MRI): thus, the number of MRI exams is constantly increasing. Moreover, elderly patients being likely to undergo a medical device implantation (such as a pacemaker or a hip prosthesis) the safety of implanted patient in MRI is crucial. The medical imaging technique involves indeed different electromagnetic fields which can interact with a metallic implant and lead to potential hazard for the patient. Even though compatibility guidelines exist today to subject individually medical devices to standardized tests and ensure their harmlessness in an MRI environment, the interactions between multiple medical devices with respect to radiofrequency electromagnetic waves (and to the hazards that may follow) are a complex research area that has to be understood. The aim of this thesis is to study these interactions on different levels: intra-device interactions, inter-devices interactions and interactions between a device and several antennas. A prediction method has been proposed to simplify the study of large range of implants, according to the variations of parameters characterizing the different parts of a prosthesis. Electromagnetic and thermal simulations, associated with experimental measurements in a clinical MRI environment, allowed to highlight a coupling phenomenon between two simplified implants and to introduce a new metric to quantify them. Finally, a multi-antenna study led to some insights to answer the question of the safety of an implanted patient with several antennas, in a configuration similar to a clinical routine exam. Thus, the research work presented in this thesis allowed to assess the interactions with respect to MRI radiofrequency in presence of one or several medical devices and antennas, opening new prospects towards a safe MRI for everyone

A incidência de casos de melanoma tem aumentado em todo o mundo sendo que, apesar do diagnóstico precoce e do advento das terapias moleculares, o número de pacientes que morrem com a doença em estágio avançado continua em elevação. Deste modo as pesquisas atuais têm focado no desenvolvimento de diferentes estratégias para a disponibilização de terapias eficazes e acessíveis. Nesse contexto, a via de administração transdérmica constitui uma alternativa promissora para aumentar a eficácia local e sistêmica de fármacos, incluindo agentes antitumorais. Diversos métodos têm sido desenvolvidos para maximizar a permeação cutânea de fármacos, destacando-se, entre esses, a ablação térmica por radiofrequência (RF). Esse processo resulta na criação de vários microcanais entre a epiderme e a derme, pelos quais diversas moléculas podem passar em direção às camadas mais profundas da pele. Nesse estudo, a eficácia da infusão transdérmica de etoposídeo por dispositivo de radiofrequência fracionada foi avaliada em modelo de melanoma murino. Camundongos da linhagem C56BL/6 foram divididos nos seguintes grupos experimentais: 1) controle; 2) tratados com radiofrequência; 3) tratados com a aplicação tópica de etoposídeo; e 4) tratados com radiofrequência e posterior aplicação tópica de etoposídeo. Os tratamentos foram realizados durante o período de 28 dias. O peso corpóreo, o volume tumoral e o perfil hematológico foram avaliados semanalmente. Ao término do tratamento os animais foram eutanasiados e procedeu-se a coleta da massa tumoral e dos órgãos (pulmão, baço, rins, linfonodos e fígado) para análise histopatológica. As células tumorais obtidas das massas tumorais foram analisadas quanto às alterações do ciclo celular e do potencial transmembrânico mitocondrial. Os resultados demonstraram que o tratamento com etoposídeo isolado reduziu a sobrevida dos animais e ocasionou alterações histológicas indicativas de toxicidade. Em contrapartida, a infusão transdérmica do etoposídeo por dispositivo de radiofrequência promoveu redução significativa do volume tumoral, em comparação com todos os grupos experimentais, sem ocasionar mortalidade. Esse tratamento também diminuiu a plaquetocitose e elevou o número de eritrócitos em comparação com os outros grupos. A análise histopatológica dos órgãos dos animais tratados com RF + etoposídeo evidenciou que não houveram alterações significativas na arquitetura tecidual. Ainda, o grupo tratado com RF + etoposídeo foi o que apresentou o maior percentual de células estacionadas na fase S/G2M e com mitocôndrias inativas, evidenciando o aumento da eficácia demonstrada no estudo in vivo. O conjunto de resultados sugere que o tratamento com a radiofrequência seguida do etoposídeo resulta em melhor resposta antitumoral do quimioterápico, com baixos índices de toxicidade sistêmica / The incidence of melanoma cases has increased worldwide and, despite early diagnosis and targeted molecular therapy, the number of patients dying from metastatic disease continues to rise. Thus, current research has focused on the development of different treatment strategies to provide efficient and accessible solutions. In this sense, transdermal delivery is a promising alternative enhancing the local and systemic efficacy of drugs, including antitumor agents. Several methods have been developed to improve the skin permeation of drugs, highlighting, among those, the radiofrequency thermal ablation (RFA). This process results in the creation of many microchannels between the epidermis and the dermis through which several molecules can pass towards the deeper layers of the skin. In this study, the efficacy of the transdermal delivery of etoposide by a fractional radiofrequency device was evaluated in a murine melanoma model. C56BL/6 lineage mice were divided into the following experimental groups: 1) control; 2) treated with radiofrequency; 3) treated with topical applications of etoposide; and 4) treated with radiofrequency followed by topical applications of etoposide. The animals were treated for 28 days and the body weight, tumor volume and hematological profile were analyzed weekly. At the end of the treatments, the animals were euthanized and the tumor mass and organs (lung, spleen, kidneys, lymph nodes and liver) were collected for histopathological analysis. Tumor cells obtained from the tumor masses were analyzed for changes in the cell cycle and mitochondrial transmembrane potential. The results showed that the treatment with etoposide alone reduced the survival of the animals and caused histological changes indicating toxicity. On the other hand, the transdermal delivery of etoposide by a radiofrequency device resulted in a significant reduction of the tumor volume, in comparison with all the experimental groups, not causing mortality. This treatment also decreased thrombocytosis and increased the number of red blood cells compared to the other groups. The histopathological analysis of the organs from animals treated with RFA + etoposide demonstrated that there was no significant change in tissue architecture. Furthermore, the group treated with RFA + etoposide presented the highest percentage of cells with inactive mitochondria and interruption at the S/G2M stage, corroborating the increased efficacy of the in vivo study. The set of results indicates that the treatment with radiofrequency followed by etoposide results in better antitumor responses of chemotherapy, with low toxicity rates

Magnetic Resonance Imaging (MRI) is a powerful non-invasive reconstruction tool used primarily in the medical community to produce high quality images of the human anatomy. Surface coils are Radio Frequency (RF) systems typically deployed for receiving the MR signals. Multiple surface coils, or an array of coils, are employed to obtain a localized improvement in the signal-to-noise ratio without limiting the field of view. In this research, a novel modeling and design method for decoupling RF surface coils in a phased array is investigated. This method employs an impedance transformation interface circuit along with a high input reflection coefficient preamplifier to decouple the coil. In this research report both the theory and design methodology are discussed in detail.

Magnetic Resonance Imaging (MRI) is a widely used soft tissue imaging technique that has gained considerable success because of its sensitivity to several tissue parameters. However, commercially available whole-body imaging systems with large encircling radio frequency (RF) and gradient coils are less efficient when the goal is to obtain detailed, high-resolution images with high specificity and sensitivity from localized regions of the body such as the female breast. This research addresses these problems by proposing a new design in RF coil development for breast cancer screening in a conventional 1.5T MRI system. The new design provides two resonant receiving modes that operate in a quadrature configuration, and a region of interest (ROI) that closely conforms to the shape of the female breast. We adopted an optimum design strategy that combined the analytic Biot-Savart intergral equation with the Method of Moment formulation in the development of electromagnetic models and simulation tools. These models were used to analyze the magnetic field distribution and the spatial field coverage, as well as the magnetic field uniformity in the ROI. Results from our analysis were employed in the construction of a highly scalable prototype. The validation of our design strategy is confirmed by comparisons with the commercial Ansoft HFSS v8.5 finite element package.

Made available in DSpace on 2016-04-27T17:05:59Z (GMT). No. of bitstreams: 1 Renato Pereira de Araujo.pdf: 1711666 bytes, checksum: b5ad19e844d9c137553ad64b03b603c7 (MD5) Previous issue date: 2015-03-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / For the visually impaired, identify which path to follow to reach the desired destination without assistance from healthy people is a challenge. To move in an unknown environment is required to interact with the mechanisms of information. However the visually impaired do not yet have a navigation system in indoor environments with real-time response that allows this this communication. This paper presents a device that allows interaction with the tactile floor to aid navigation and orientation. Through an audio interface, the device provides the visually impaired relevant information on the space around it and the navigation options available. The relevant information is disseminated using labels with radio frequency identification technology, integrated into a microcontroller and an audio playback card. Each label has an electronic product code that allows to identify it uniquely. The label installed in a standard place of tactile floor is linked to an audio file with information about the space and the available routes. The reader integrated development board reads the labels and sends the electronic code to the microcontroller, which in turn identifies the code and assigns this audio file to be played. The device was tested by a volunteer who found all labels positioned on the floor tactile alert, clearly identified its position and reached the desired destination without route errors. Used as a complement to tactile signage, this device provides an interaction between the visually impaired and the existing tactile signage. This project will directly contribute to society, providing a convenient navigation system for people with visual disabilities have greater autonomy / Para os deficientes visuais, identificar qual caminho deve ser seguido para chegar ao destino desejado, sem auxílio de pessoas hígidas, é um desafio. Para se deslocar em um ambiente desconhecido é necessária a interação com os mecanismos de informação. Entretanto os deficientes visuais ainda não contam com um sistema de navegação em ambientes internos com resposta em tempo real que possibilite essa comunicação. Este trabalho apresenta um dispositivo que possibilita a interação com o piso tátil para auxiliar a navegação e a orientação. Por meio de uma interface de áudio, o dispositivo proporciona ao deficiente visual as informações úteis sobre o espaço em seu entorno e as opções de navegação disponíveis. As informações pertinentes são difundidas utilizando etiquetas com tecnologia de identificação por rádio frequência, integradas a um micro controlador e uma placa de reprodução de áudio. Cada etiqueta possui um código de produto eletrônico que permite identificá-la de forma exclusiva. A etiqueta instalada em um local padronizado do piso tátil está atrelada a um arquivo de áudio com informações sobre o espaço e as rotas disponíveis. O leitor integrado a placa de desenvolvimento faz a leitura das etiquetas e envia o código eletrônico ao micro controlador, que por sua vez identifica o código e atribui a este o arquivo de áudio que será reproduzido. O dispositivo foi testado por um voluntário que encontrou todas as etiquetas posicionadas junto ao piso tátil de alerta, identificou claramente sua posição e chegou ao destino desejado sem erros de percurso. Usado como complemento da sinalização tátil, este dispositivo possibilita uma interação entre o deficiente visual e a sinalização tátil existente. Este projeto poderá contribuir diretamente para a sociedade, disponibilizando um sistema de navegação conveniente para que as pessoas com deficiência visual tenham maior autonomia

A ocorrência de contaminações de alimentos nas últimas décadas resultaram em maiores demandas por rastreabilidade por parte dos consumidores das cadeias de suprimentos de produtos agroindustriais. Algumas destas demandas se tornaram regulamentações para a comercialização de produtos no mercado internacional. A rastreabilidade diz respeito ao acompanhamento do produto ao longo da cadeia, permitindo a identificação de pontos críticos para o controle da qualidade do produto. Atualmente, as cadeias de granéis sólidos agrícolas voltados à exportação possuem sérios problemas de rastreabilidade: mistura de lotes; roubo; aumento das exigências por informações de qualidade, origem e processos; dificuldade na determinação de lotes no caso de recalls; e ausência de sistemas automáticos e em tempo real. Visando reduzir estes problemas, o objetivo do trabalho foi elaborar um modelo de rastreabilidade para estas cadeias, que permita a coleta e o acesso de informações em tempo real por seus elos. A metodologia utilizada compreendeu quatro etapas: revisão sistemática da literatura, levantamento de informações, elaboração de um modelo de rastreabilidade e elaboração do modelo conceitual de simulação. Analisaram-se aspectos relacionados a custo, impacto de fatores reguladores, gargalos na implementação e critérios de adaptação a outras cadeias. O açúcar foi utilizado como estudo de caso devido à sua importância para o país. Após um estudo das tecnologias disponíveis, optou-se pelo uso da tecnologia de identificação por radiofrequência, pois ela facilita o acompanhamento da movimentação do produto, em conjunto com a tecnologia de redes de sensores sem fio, que visa monitorar as variáveis ambientais às quais o produto é submetido. Caso anomalias com relação a limites pré-estabelecidos sejam detectadas, um sinal de alerta será enviado ao agente responsável, que pode então tomar a decisão necessária. As principais contribuições do trabalho são: o modelo de rastreabilidade proposto, em conjunto com os fatores que devem ser considerados em sua implementação, e o modelo conceitual de simulação desenvolvido para estimar seus impactos em termos de custos, tempos e frequência de erros em comparação à situação atual. / Food contamination events in the past decades have resulted in an increase of the agroindustrial supply chain consumers\' traceability demands. Some of these demands became product import regulations. Traceability is related to product monitoring throughout the supply chain, allowing for the identification of critical quality control points. Currently, the supply chains of bulk agricultural products exported by Brazil have serious traceability problems: lot mixing; product theft; increase in the demand for information related to quality, origin, and processes; difficulty in identifying specific lots in the case of recalls; and lack of automatic and real time systems. The main objective of this research was to develop a traceability model for these chains which allowed for real-time data gathering and information access by its links. The methodology used was divided into four stages: systematic literature review, information gathering, traceability model development, and theoretical simulation model development. The aspects analyzed were related to cost, impact of regulating bodies, implementation bottlenecks, and criteria to be used to adapt the model to other chains. Due to its importance, the sugar supply chain was used as a case study. An analysis of the technologies available led to the choice of radiofrequency identification, because it facilitates monitoring product movement, besides wireless sensor networks, which will monitor the environmental variables in the product surroundings. If anomalies in relation to pre-established limits are detected, an alert signal will be sent to the agents in charge, allowing them to make decisions. The main contributions of this research are: the traceability model developed and the factors that have to be considered during its implementation, and the conceptual simulation model developed to estimate its impacts in terms of cost, time, and error frequency, in comparison to the current situation.

Thesis (MSc.) -- University of Limpopo, 2018 / A Major concern in the past years was the traditional static spectrum allocation which gave rise to spectrum underutilization and scarcity in wireless networks. In an attempt to solve this problem, cognitive radios technology was proposed and this allows a spectrum to be accessed dynamically by Cognitive radio users or secondary users (SUs). Dynamic access can efficiently be achieved by making necessary adjustment to some MAC layer functionalities such as sensing and channel allocation. MAC protocols play a central role in scheduling sensing periods and channel allocation which ensure that the interference is reduced to a tolerable level. In order to improve the accuracy of sensing algorithm, necessary adjustments should be made at MAC layer. Sensing delays and errors are major challenges in the design of a more accurate spectrum sensing algorithm or MAC protocol. Proposed in this study, is a scheme (EXGPCSA) which incorporate sensing at the MAC layer and physical layer. Energy detector was used to detect the presence of primary users (SU). A choice of how long and how often to sense the spectrum was addressed at the MAC layer. The focal point of this study was on minimizing delays in finding available channels for transmission. EXGPCSA used channel grouping technique to reduce delays. Channels were divided into two groups and arranged in descending order of their idling probabilities. Channels with higher probabilities were selected for sensing. Three network scenarios were considered wherein a group of SUs participated in sensing and sharing their spectral observations. EXGPCSA was designed such that only SUs with higher SNR were allowed to share their observations with other neighbouring SUs. This rule greatly minimized errors in sensing. The efficiency of EXGPCSA was evaluated by comparing it to another scheme called generalized predictive CSA. A statistical t-test was used to test if there is significant difference between EXGPCSA and generalized predictive CSA in terms of average throughput. A test has shown that EXGPCSA significantly performed better than generalized predictive CSA. Both schemes were simulated using MATLAB R2015a in three different network scenarios.

Small intestinal neuroendocrine tumor (SI-NET) is the most common small bowel tumor in Europe and USA, with an annual incidence of around 0.3-1.3/100000 persons. SI-NETs are the most common type of gastroenteropancreatic NETs (GEP-NETs), and they are known for their ability to produce hormones such as tachykinins and serotonin, as well as for their favorable long-term prognosis in comparison to gastrointestinal adenocarcinoma. The overall aim of the thesis was to investigate unknown or unclear aspects of SI-NET disease, in connection with prognosis, treatment and follow-up. Paper I confirmed several known negative prognostic factors and also showed, for the first time, that para-aortal lymph node metastases and peritoneal carcinomatosis were associated with worse survival by multivariable analyses. Locoregional surgery was associated with a low post-operative mortality, and a prolonged long-term survival by multivariable analysis. In Paper II we continued to investigate peritoneal carcinomatosis and found it be a risk factor not only for death, but also for emergency re-surgery. Furthermore, genetic analyses of samples from primary tumors in patients with and without peritoneal carcinomatosis showed a difference in the DNA between these two groups. In Paper III the outcome after liver surgery and/or radiofrequency ablation of liver metastases was investigated. To summarize, no difference in survival was seen in patients treated with surgery/radiofrequency ablation in comparison with matched controls. However, a superior radiological response of liver metasases and lower U-5-HIAA values were seen in patients subjected to liver surgery and/or radiofrequency ablation compared to matched controls. Paper IV compared ultrasonography, computed tomography and 11C-5HTP-PET in the follow-up after radiofrequency ablation of NET liver metastases. The study concluded that 11C-5HTP-PET depicted all residual tumors after RFA and that it, if used, should be combined with computed tomography for easier interpretation, as RFA areas are not clearly distinguishable with 11C-5HTP-PET alone. Paper V studied gallstone complications after somatostatin analog treatment in SI-NET patients, and concluded that there was a rather high risk to be subjected to a cholecystectomy due to biliary colic, cholecystitis, cholangitis or pancreatitis after primary surgery in somatostatin analog treated patients.

Cognitive radio (CR) technology has recently been introduced to opportunistically exploit the spectrum. We present a robust and cost-effective design to ensure the improvement of spectrum efficiency with CR. We first propose probability-based spectrum sensing by utilizing the statistical characteristics of licensed channel occupancy, which achieves nearly optimal performance with relatively low complexity. Based on the statistical model, we then propose periodic spectrum sensing scheduling to determine the optimal inter-sensing duration and vary the transmit power at each data sample to enhance throughput and reduce interference. We further develop a probability-based scheme for combination of local sensing information collected from cooperative CR users, which enables combination of both synchronous and asynchronous sensing information. To satisfy the stringent bandwidth constraint for reporting, we also propose to simultaneously send local sensing data to a combining node through the same narrowband channel. With proper preprocessing at individual users, such a design maintains reasonable detection performance while the bandwidth required for reporting does not change with the number of cooperative users. To better utilize the spectrum and avoid possible interference, we propose spectrum shaping schemes based on spectral precoding, which enable efficient spectrum sharing between CR and licensed users and exhibit the advantages of both simplicity and flexibility. We also propose a novel resource allocation approach based on the probabilities of licensed channel availability obtained from spectrum sensing. Different from conventional approaches, the probabilistic approach exploits the flexibility of CR to ensure efficient spectrum usage and protect licensed users from unacceptable interference.

Nors vietinis naviko progresavimas yra esminė problema, atliekant piktybinių navikų kepenyse radijo dažnio abliaciją, dažniausiai tai yra vienintelis rodiklis, apibrėžiantis šio gydymo metodo veiksmingumą. Mūsų tyrimo tikslas buvo nustatyti kompiuterinės tomografijos ir ultragarso tyrimų bei histologinio stulpelinės biopsijos medžiagos, paimtos iš abliuoto naviko, histologinio tyrimo rezultato reikšmę anksti vertinant radijo dažnio abliacijos veiksmingumą. Tyrimo medžiaga ir metodai: Į tyrimą buvo įtraukti 68 pirminiai ir metastaziniai kepenyse esantys navikai. Radijo dažnio abliacija buvo atliekama naudojant perfuzijos elektrodus. Navikai prieš abliaciją ir po jos atliekant kontrolinius tyrimus buvo vertinami kompiuterinės tomografijos ir ultragarsinio tyrimo metodais. Po abliacijos praėjus vienam mėnesiui buvo atliekama abliacijos zonos punkcinė stulpelinė biopsija, audiniai tiriami histologiškai. Rezultatai ir išvados: Galutinei analizei buvo tinkami 58 sėkmingai gydyti navikai. Radiologinio stebėjimo metu buvo nustatyti devyni (15,5 %) vietinio naviko progresavimo atvejai. Vidutinis analizuotų navikų stebėjimo laikas buvo 16,3 mėnesiai (nuo 1,7 iki 38,7 mėnesių). Nustatyta, kad: 1. Biopsijos medžiagos, paimtos iš abliacijos zonos praėjus vienam mėnesiui po naviko, esančio kepenyse, radijo dažnio abliacijos, histologinio tyrimo rezultatas neleidžia prognozuoti vietinio naviko progresavimo 2. Naviko dydis 30 mm ir naviko lokalizacija arčiau kaip per 5 mm nuo didesnio nei 3... [toliau žr. visą tekstą] / Local tumour progression remains the main problem after radiofrequency ablation of liver tumours and it is usually the only measure of treatment efficacy. The aim of our study was to investigate and evaluate the prognostic value of computed tomography and ultrasonography as well as the histological result of core biopsy material from ablated tumour on assessment of radiofrequency ablation effectiveness. Materials and methods: We have studied 68 malignant primary and metastatic hepatic tumours treated by radiofrequency ablation. Ablation was performed using perfusion electrodes. Evaluation of tumours before ablation and follow up was performed by means of contrast enhanced computed tomography and ultrasonography. Ablation zone was biopsied for histological examination. Results and conclusions: 58 successfully treated hepatic tumours were suitable for the final analysis. The local progression of nine (15.5 %) tumours was detected on follow up. Mean follow up time for analysed tumours was 16.3 months with a range from 1.7 to 38.7 months. It was showed, that: 1. The result of histological examination of ablation zone biopsy material taken one month after radiofrequency ablation of malignant liver tumour does not predict local tumour progression. 2. Tumour size 30 mm and larger and tumour proximity closer than 5 mm to hepatic vessels larger than 3 mm are significant risk factors for local tumour progression after radiofrequency ablation of malignant liver tumours 3. Tumour type... [to full text]