Estudo e implementação de dosimetria com Mosfet em braquiterapia de alta taxa de dose

Tese de mestrado, Engenharia Física, Universidade de Lisboa, Faculdade de Ciências, 2010A dosimetria in vivo em braquiterapia, quando devidamente implementada, produz importantes beneficios, tais como a possibilidade de correccoes de fraccoes de dose, alertar para doses eventualmente excessivas em orgaos de risco, a avaliacao dose-efeito mais precisa, a deteccao de falhas e a comparacao de doses reais com doses planeadas. Estudos recentes mostram o uso de pequenos MOSFET em dosimetria in vivo de braquiterapia com incertezas totais de 8%. As dependencias com dose acumulada, energia e temperatura sao, contudo, ainda caracteristicas controversas destes dosimetros. O objectivo global deste estudo e caracterizar e calibrar um sistema de dosimetria com MOSFET para dosimetria in vivo em braquiterapia de alta taxa de dose no Servico de Radioterapia do Hospital de Santa Maria. O metodo envolve simulacao Monte Carlo e testes experimentais de reprodutibilidade, linearidade, dose acumulada, temperatura, anisotropia e optimizacao da calibracao dos MOSFET. As experiencias foram realizadas num fantoma de agua validado por dosimetria ionometrica. Os testes in vivo foram tambem importantes para a validacao final do sistema. A simulacao Monte Carlo da fonte clinica de 192Ir no fantoma, permitiu a determinacao de doses de referencia com incertezas inferiores a 2%. Os resultados dos MOSFET mostram um erro de reprodutibilidade de 3% e um erro de linearidade de 2% no intervalo de distancias fonte-dosimetro clinicamente relevantes. As dependencias com dose acumulada e temperatura foram inferiores ao erro de reprodutibilidade. A anisotropia foi estimada em 1%. O metodo de optimizacao da calibracao com regressao linear indica que a distancia mais adequada para calibracao, no fantoma utilizado e no intervalo de distancias clinicas, e cerca de 4 cm. Para a medicao de dose in vivo no recto em braquiterapia da prostata, o metodo desenvolvido permite obter incertezas totais de 11%. Num teste realizado num caso real obteve-se uma diferenca de 2% entre a medicao no MOSFET e a estimativa de dose do sistema de planeamento.In vivo dosimetry in brachytherapy, when adequately implemented, brings important benefits such as corrective planning of dose fractions, closer followup of possible affected organs at risk, more rigorous dose-effect information of organs at risk, failure detection and the evaluation of the treatment planning system doses. Recent studies show the use of small MOSFET dosimeters for in vivo dose measurements in brachytherapy with global uncertainty of 8%. Cumulative dose, energy and temperature dependence are controversial characteristics of the MOSFET. The global purpose of this study is to characterize and calibrate a MOSFET dosimetry system for in vivo dosimetry in high dose rate 192Ir brachytherapy at the Radiotherapy Department of Santa Maria Hospital. The method involves Monte Carlo simulation and experimental tests of reproducibility, linearity, cumulative dose, temperature, angular dependence and dose calibration optimization of the MOSFET. The experiments were made in a water phantom validated by ionometric dosimetry. In vivo tests were also important for final validation. Monte Carlo simulation of the 192Ir clinical source in the phantom allowed for determination of reference doses with uncertainties of less than 2%. MOSFET results show a reproducibility error of 3% at 100 mV and a linearity error of 2% in the clinical relevant source-dosimeter distances. Cumulative dose and temperature dependence were inferior to the reproducibility error. The MOSFET angular dependence was within 1%. The dose calibration optimization procedure with linear regression suggests that the best calibration source distance, in the phantom and for clinical distances, is about 4 cm. For rectum in vivo dose measurements in prostate brachytherapy the developed method allows for overall uncertainties of 11%. A real test showed a small difference of about 2% from the treatment planning system dose estimates

International Year of Soils 2015: oportunity to promote an integrated administration of soils in Portugal?

Resumo: Neste trabalho assinala-se o retrocesso da administração do recurso solo em Portugal ao longo dos últimos 40 anos, em contraponto com a evolução recente a nível europeu (Estratégia Temática para a Protecção do Solo) e a nível global (Parceria Global para o Solo, Dia Mundial do Solo e Ano Internacional dos Solos 2015, AIS-2015). Aproveitando o impulso internacional neste domínio apresenta-se a Parceria Portuguesa para o Solo (PPS), como mais uma iniciativa que procura inverter o processo de regressão e de dispersão de esforços na administração dos solos do país. Correspondendo aos objectivos estratégicos da PPS, também apresentados, propõem-se e justificam-se sumariamente duas acções a mais curto prazo: a harmonização da cartografia de solos do país à escala 1:250.000 ou 1:500.000 e a constituição de um Sistema Nacional de Informação de Solos (SNIS). A Carta Mundial dos Solos, revista em 2015, insta os governos nacionais a desenvolverem uma política nacional do solo, um sistema nacional de informação de solos e uma estrutura institucional para monitorizar os recursos do solo. O AIS-2015 representa uma oportunidade excepcional para despoletar a implementação de uma política (integrada) do solo em Portugal e de um SNIS como ferramenta pivô para essa política. ---------- Abstract: In this work it is pointed out the recession of the administration of soil resources in Portugal in the last 40 years, as opposed to the recent development actions at European level (Thematic Strategy for Soil Protection) and at global level (Global Soil Partnership, World Soil Day and International Year of Soils 2015, IYS-2015). Taking advantage of the international momentum in this field it is presented the Portuguese Soil Partnership (PtSP) as an initiative that aims to reverse the process of regression and the dispersion of efforts in the national administration of the soils. Accordingly with the PtSP's strategic objectives, also presented, two short-term actions are proposed: the harmonization of the country's soil maps at 1: 250,000 or 1: 500,000 scale, and the establishment of a National Soil Information System (NSIS). The World Soil Charter, revised in 2015, strongly recommends that national governments develop a national land policy, a national land information system and an institutional framework to monitor soil resources. The IYS-2015 would be an exceptional opportunity to trigger the implementation of an (integrated) soil policy in Portugal and a NSIS as a pivot tool for this policy

High-Current Double Pulse ECT Technique for Inspection of Ferromagnetic Materials

The detection of surface cracks of conductive materials that have a magnetic permeability higher than μ0, are usually made using the Magnetic Flux Leakage (MFL) technique. It requires the saturation of the specimen so that some magnetic flux lines escape the material when a defect is present. However, saturating the material can be very power consuming and if there is motion involved, eddy currents induced due to motion decrease or even null this method sensitivity as speed increases, which can be a disadvantage in cases such as railroad inspection. This work proposes a new technique to inspect the surface of ferromagnetic materials based on eddy currents. It is denominated high-current double pulse (Hi-CDP) ECT. The technique creates two consecutive pulses of currents (up to 1500 A) in a coil in the vicinity of the sample. Fig. 1 shows the simulation model used and the corresponding magnetic flux obtained in a point in the axis of a pancake coil (25 turns, id=15 mm, od=25 mm, heigh=10 mm), and in the vicinity of the sample material. The first pulse (starts at 0.1 ms) saturates the material, making it behave almost like a non-ferromagnetic material. The second pulse starts at 0.25 ms when the maximum current of the first pulse occurs (when the material is most saturated). When the second pulse occurs, eddy currents are induced. As the material is saturated, the ferromagnetic properties almost do not interfere with penetration depth and distribution of eddy currents, making it suitable for eddy current testing. Fig. 2 shows the derivative of the magnetic field obtained in a point located between the windings of the coil and the sample material, for a case without defect and in the presence of two similar defects with different depths (0.5 mm and 1.5 mm deep) in the vicinity of the point. It is possible to observe that the second current peak contains a perturbation that is different according to the defect. The signal derivative was chosen in order to distinguish the MFL from eddy currents perturbations

Iron Ore Pelletizing Process: An Overview

The iron ore production has significantly expanded in recent years, owing to increasing steel demands in developing countries. However, the content of iron in ore deposits has deteriorated and low-grade iron ore has been processed. The fines resulting from the concentration process must be agglomerated for use in iron and steelmaking. This chapter shows the status of the pelletizing process with a special focus on binders. Bentonite is the most used binder due to favorable mechanical and metallurgical pellet properties, but it contains impurities especially silica and alumina. The importance of many researches concerning alternative binders is also discussed in this chapter. Better quality wet, dry, preheated, and fired pellets can be produced with combined binders, such as organic and inorganic salts, when compared with bentonite-bonded pellets. While organic binders provide sufficient wet and dry pellet strengths, inorganic salts provide the required preheated and fired pellet strengths

ECT characterization of a linear defect from multiple angle measurements

Peer Reviewe

Mixed rain forest in southeastern Brazil: tree species regeneration and floristic relationships in a remaining stretch of forest near the city of Itaberá, Brazil

The aim of this work was to evaluate the floristic composition, richness, and diversity of the upper and lower strata of a stretch of mixed rain forest near the city of Itaberá, in southeastern Brazil. We also investigated the differences between this conservation area and other stretches of mixed rain forest in southern and southeastern Brazil, as well as other nearby forest formations, in terms of their floristic relationships. For our survey of the upper stratum (diameter at breast height [DBH] &gt; 15 cm), we established 50 permanent plots of 10 × 20 m. Within each of those plots, we designated five, randomly located, 1 × 1 m subplots, in order to survey the lower stratum (total height &gt; 30 cm and DBH < 15 cm). In the upper stratum, we sampled 1429 trees and shrubs, belonging to 134 species, 93 genera, and 47 families. In the lower stratum, we sampled 758 trees and shrubs, belonging to 93 species, 66 genera, and 39 families. In our floristic and phytosociological surveys, we recorded 177 species, belonging to 106 genera and 52 families. The Shannon Diversity Index was 4.12 and 3.5 for the upper and lower strata, respectively. Cluster analysis indicated that nearby forest formations had the strongest floristic influence on the study area, which was therefore distinct from other mixed rain forests in southern Brazil and in the Serra da Mantiqueira mountain range.7186Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Araucaria angustifolia (Bertol.) O. Kuntze secondary forest phytosociology on the Bananal Ecological Station, Brazil

In the present work, we aimed to evaluate successional forest stage and horizontal, vertical and diametric structures of upper and under strata on a secondary forest stretch under Araucaria angustifolia on the Bananal Ecological Station, São Paulo state, Brazil. During upper stratum survey (circumference at breast height (CBH) &gt; 15 cm), 43 permanent plots of 10 × 20 m were established. In each plot, five sub-plots of 1 × 1 m were randomly allocated for under stratum (total height &gt; 30 cm and CBH <15 cm) survey. Regarding upper stratum, density and dominance were estimated on 2142 ind./ha and 32.49 m²/ha, respectively, in absolute total values. Concerning under stratum, total absolute density was estimated on 48,302 ind./ha. The diametric structure of the community follows the J-invert pattern, which was not observed for Brazilian Pine population, compromising its maintenance in the community. The auto-ecology of the species supports the catalyzation of secondary succession under its crown, which was classified at middle successional stage.O presente estudo teve por objetivo caracterizar o estágio sucessional e as estruturas horizontal e vertical dos estratos adulto e regenerante de um trecho de floresta secundária com Araucaria angustifolia, na Estação Ecológica de Bananal-SP, Brasil. Para amostragem do estrato adulto (CAP &gt; 15 cm), foram alocadas 43 parcelas permanentes de 10 × 20 m. Em cada uma destas, foram aleatoriamente distribuídas cinco subparcelas de 1 × 1 m, para amostragem do componente regenerante (altura &gt; 30 cm e CAP < 15 cm). Considerando-se o componente adulto, a densidade e a dominância foram estimadas em 2.142 ind./ha e 32,49 m²/ha, respectivamente, em valores totais absolutos. Para o componente regenerante, o valor estimado para a Densidade Total absoluta foi de 48.302 ind./ha. A estrutura diamétrica da comunidade segue o padrão J-invertido, o qual não ocorre na população de A. angustifolia; tal condição pode vir a comprometer a manutenção dessa espécie na comunidade.15917

A new reproductive mode in anurans: Natural history of Bokermannohyla astartea (Anura: Hylidae) with the description of its tadpole and vocal repertoire

Anurans have the greatest diversity of reproductive modes among tetrapod vertebrates, with at least 41 being currently recognized. We describe a new reproductive mode for anurans, as exhibited by the Paranapiacaba Treefrog, Bokermannohyla astartea, an endemic and poorly known species of the Brazilian Atlantic Forest belonging to the B. circumdata group. We also describe other aspects of its reproductive biology, that are relevant to understanding the new reproductive mode, such as courtship behavior, spawning, and tadpoles. Additionally, we redescribe its advertisement call and extend its vocal repertoire by describing three additional call types: courtship, amplectant, and presumed territorial. The new reproductive mode exhibited by B. astartea consists of: (1) deposition of aquatic eggs in leaf-tanks of terrestrial or epiphytic bromeliads located on or over the banks of temporary or permanent streams; (2) exotrophic tadpoles remain in the leaf-tanks during initial stages of development (until Gosner stage 26), after which they presumably jump or are transported to streams after heavy rains that flood their bromeliad tanks; and (3) tadpole development completes in streams. The tadpoles of B. astartea are similar to those of other species of the B. circumdata group, although with differences in the spiracle, eyes, and oral disc. The vocal repertoire of B. astartea exhibits previously unreported acoustic complexity for the genus. Bokermannohyla astartea is the only bromeligenous species known to date among the 187 known species within the tribe Cophomantini. We further discuss evolutionary hypotheses for the origin of this novel reproductive mode.Fil: Malagoli, Leo Ramos. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Leite Pezzuti, Tiago. Universidade Federal de Minas Gerais; BrasilFil: Lee Bang, Davi. Universidade de Sao Paulo; BrasilFil: Faivovich, Julián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Lyra, Mariana Lúcio. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Ribeiro Giovanelli, João Gabriel. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: de Anchietta Garcia, Paulo Christiano. Universidade Federal de Minas Gerais; BrasilFil: Sawaya, Ricardo Jannini. Universidad Federal do Abc; BrasilFil: Baptista Haddad, Célio Fernando. Universidade Estadual Paulista Julio de Mesquita Filho; Brasi

RAIO DE VOO DE ABELHAS NATIVAS NO IFC CAMPUS SANTA ROSA DO SUL E POTENCIAIS RISCOS

No arquivo em PDF