Estudo da distribuição de dose em torno de fontes usadas em braquiterapia

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia Biomédica

Smart object for 3D interaction

This paper reports on the creation of an interface for 3D virtual environments, computer-aided design applications or computer games. Standard computer interfaces are bound to 2D surfaces, e.g., computer mouses, keyboards, touch pads or touch screens. The Smart Object is intended to provide the user with a 3D interface by using sensors that register movement (inertial measurement unit), touch (touch screen) and voice (microphone). The design and development process as well as the tests and results are presented in this paper. The Smart Object was developed by a team of four third-year engineering students from diverse scientific backgrounds and nationalities during one semester.

Trypanosoma cruzi: cell charge distribution

Differences in cell charge between epimastigote and trypomastigote populations were compared in Y, Cl and Colombiana strains of T. cruzi. Trypomastigote populations were more homogenous in relation to cell charge than epimastigotes. This homogeneity of cell charge was not the result of the selection of trypomastigote sub-populations by the host immunosystem, but may be the result of a surface coat formed by host blood components.

Numerical 3D modeling of heat transfer in human tissues for microwave radiometry monitoring of Brown fat metabolismo

Background: Brown adipose tissue (BAT) plays an important role in whole body metabolism and could potentially mediate weight gain and insulin sensitivity. Although some imaging techniques allow BAT detection, there are currently no viable methods for continuous acquisition of BAT energy expenditure. We present a non-invasive technique for long term monitoring of BAT metabolism using microwave radiometry. Methods: A multilayer 3D computational model was created in HFSS™ with 1.5 mm skin, 3-10 mm subcutaneous fat, 200 mm muscle and a BAT region (2-6 cm3) located between fat and muscle. Based on this model, a log-spiral antenna was designed and optimized to maximize reception of thermal emissions from the target (BAT). The power absorption patterns calculated in HFSS™ were combined with simulated thermal distributions computed in COMSOL® to predict radiometric signal measured from an ultra-low-noise microwave radiometer. The power received by the antenna was characterized as a function of different levels of BAT metabolism under cold and noradrenergic stimulation. Results: The optimized frequency band was 1.5-2.2 GHz, with averaged antenna efficiency of 19%. The simulated power received by the radiometric antenna increased 2-9 mdBm (noradrenergic stimulus) and 4-15 mdBm (cold stimulus) corresponding to increased 15-fold BAT metabolism. Conclusions: Results demonstrated the ability to detect thermal radiation from small volumes (2-6 cm3) of BAT located up to 12 mm deep and to monitor small changes (0.5°C) in BAT metabolism. As such, the developed miniature radiometric antenna sensor appears suitable for non-invasive long term monitoring of BAT metabolism.

Bitocast: a hybrid BitTorrent and IP Multicast content distribution solution

Dissertação apresentada para obtenção do Grau de Mestre em Informática, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia

Potencial de redução de dose em tomografia computorizada com técnicas de reconstrução iterativa

A TC é um valioso método diagnóstico radiológico. O exame TC pode expor o paciente a uma dose elevada de exposição à radiação, causando risco acrescido. Uma das possíveis soluções para a redução da dose é o uso de técnicas de reconstrução iterativa (IR) em vez das reconstruções tradicionais (FBP). Com base nas suas capacidades de redução de ruído na imagem, a IR pode ter o potencial de reduzir significativamente a dose em pacientes submetidos a TC sem prejudicar a qualidade de imagem. Manter a qualidade de imagem clínica com um nível de qualidade aceitável e expondo o paciente à menor dose possível.

Modelação 3D de um subsector das mineralizações auríferas de casas novas, Montemor-o-Novo

Dissertação apresentada à Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia Geológica (Georrecursos)

Therapeutical evaluation of different dose regimens of praziquantel in schistosomiasis mansoni, based on the quantitative oogram technique

A clinical trial involving 80 patients of both sexes, from ages 15 to 55, with chronic intestinal or hepatointestinal schistosomiasis mansoni, was carried out to evaluate the therapeutical efficacy of different dose regimens of praziquantel. The patients were randomly allocated into four groups with an equal number of cases and were then treated with one of the following dosages: 60 mg/kg for 1 day; 60 mg/kg daily for 2 days; 60 mg/kg daily for 3 days; and 30 mg/kg daily for 6 days. The assessment of parasitological cure was based on the quantitative oogram technique through rectal mucosa biopsies which were undertaken prior to, as well as, 1,2,4 and 6 months post-treatment. Concurrently, stool examinations according to the qualitative Hoffman, Pons & Janer (HPJ) and the quantitative Kato-Katz (K-K) methods were also performed. The best tolerability was observed with 30 mg/kg daily for 6 days whereas the highest incidence of side-effects (mainly dizziness and nausea) was found with 60 mg/kg daily for 3 days. No serious adverse drug reaction has occurred. The achieved cure rates were: 25% with 60 mg/kg for 1 day; 60% with 60 mg/kg daily for 2 days; 89.5% with 60 mg/kg daily for 3 days; and 90% with 30 mg/kg daily for 6 days. At the same time there has been a downfall of 64%, 73%, 87% and 84% respectively, in the median number of viable S. mansoni ova per gram of tissue. Thus, a very clear direct correlation between dose and effect could be seen. The corresponding cure rates according to stool examinations by HPJ were 39%, 80%, 100% and 95%; by K-K 89%, 100%, 100% and 100%. This discrepancy in results amongst the three parasitological methods is certainly due to their unequal accuracy. In fact, when the number of viable eggs per gram of tissue fell below 5,000 the difference in the percentage of false negative findings between HPJ (28%) and K-K (80%) became significative. When this number dropped to less than 2,000 the percentage of false negative results obtained with HPJ (49%) turned significant in relation to the oogram as well. In conclusion, it has been proven that praziquantel is a highly efficacious agent against S. mansoni infections. If administered at a total dose of 180 mg/kg divided into either 3 or 6 days, it yields a 90% cure rate. Possibly, one could reach 100% by increasing the total dose to 240 mg/kg. Furthermore, it was confirmed that the quantitative oogram technique is the most reliable parasitological method when evaluating the efficacy of new drugs in schistosomiasis mansoni.

Preventable exposure in routine chest CT examinations: evaluation of effective dose beyond prescribed anatomical landmarks

Objective - Evaluate preventable exposure dose in routine chest CT examinations beyond prescribed anatomical landmarks and estimate extra dose delivered to the patient. Background/rationale - Recent technical advances have greatly increased the clinical applications of CT; developments in multidetector-row CT (MDCT) technology have occurred; the major disadvantage with the increased use of MDCT is associated radiation exposure.

Avaliação da dose de exposição em tomografia computorizada: estudo comparativo antes e após otimização dos protocolos em neurorradiologia pediátrica

O número de exposições à radiação com fins médicos têm vindo a aumentar drasticamente devido ao crescimento do número de exames de Tomografia Computorizada (TC) realizados anualmente em crianças, o que faz com que aumentem também os potenciais efeitos indesejados associados à radiação ionizante. Este assunto torna-se ainda mais crítico na população pediátrica pelo que é imprescindível a otimização dos protocolos de aquisição e adoção de boas práticas no que respeita à redução da dose de exposição. A aplicação dos protocolos em neurorradiologia pediátrica carece de estratégias eficazes, as quais visam uma eficaz redução de dose mantendo a qualidade de imagem. Comparativamente aos descritores de dose (CTIvol e DLP) e parâmetros técnicos (Kvp, mAs, tempo de exposição e espessura de corte), foi objetivo deste estudo avaliar a redução da dose nos exames de neurorradiologia pediátrica através da comparação entre 2012 e 2013, ou seja, antes e depois da intervenção de otimização efetuada aos protocolos de aquisição.

Comparação da dose calculada entre a tomoterapia helicoidal e a arcoterapia de intensidade modulada em glioblastomas multiformes

Objetivo do estudo - Comparar a dose calculada nos órgãos de risco (OR’s) e no volume alvo de planeamento (PTV), entre a tomoterapia helicoidal (TH) e a arcoterapia de intensidade modulada (RapidArc®), em glioblastomas multiformes (GBM).

Um equilíbrio entre qualidade de imagem e dose efetiva na radiografia às órbitas para procura de objetos estranhos ferromagnéticos intraoculares: um estudo piloto

Objectivo do estudo - Investigar se os fatores standard de aquisição de radiografias às órbitas estão otimizados para a deteção de corpos estranhos ferromagnéticos intraoculares em pacientes que irão ser submetidos a ressonâncias magnéticas.

Species and biotype distribution of thermotolerant Campylobacters in animal reservoirs in Southern Chile

The prevalence of thermotolerant Campylobacters in mammals and birds from Southern Chile was determined. Campylobacters were isolated from 46.3% of the animals studied being C. jejuni biotipe 1 the most frequent (25.7%) followed by C. coli (17.4%) and C. jejuni biotipe 2 (3.2%).