Optimisation of exposure parameters for spinal curvature measurements in paediatric radiography

This review aims to identify strategies to optimise radiography practice using digital technologies, for full spine studies on paediatrics focusing particularly on methods used to diagnose and measure severity of spinal curvatures. The literature search was performed on different databases (PubMed, Google Scholar and ScienceDirect) and relevant websites (e.g., American College of Radiology and International Commission on Radiological Protection) to identify guidelines and recent studies focused on dose optimisation in paediatrics using digital technologies. Plain radiography was identified as the most accurate method. The American College of Radiology (ACR) and European Commission (EC) provided two guidelines that were identified as the most relevant to the subject. The ACR guidelines were updated in 2014; however these guidelines do not provide detailed guidance on technical exposure parameters. The EC guidelines are more complete but are dedicated to screen film systems. Other studies provided reviews on the several exposure parameters that should be included for optimisation, such as tube current, tube voltage and source-to-image distance; however, only explored few of these parameters and not all of them together. One publication explored all parameters together but this was for adults only. Due to lack of literature on exposure parameters for paediatrics, more research is required to guide and harmonise practice.

Optimisation of paediatrics computed radiography for full spine curvature measurements using a phantom: a pilot study

Aim: Optimise a set of exposure factors, with the lowest effective dose, to delineate spinal curvature with the modified Cobb method in a full spine using computed radiography (CR) for a 5-year-old paediatric anthropomorphic phantom. Methods: Images were acquired by varying a set of parameters: positions (antero-posterior (AP), posteroanterior (PA) and lateral), kilo-voltage peak (kVp) (66-90), source-to-image distance (SID) (150 to 200cm), broad focus and the use of a grid (grid in/out) to analyse the impact on E and image quality (IQ). IQ was analysed applying two approaches: objective [contrast-to-noise-ratio/(CNR] and perceptual, using 5 observers. Monte-Carlo modelling was used for dose estimation. Cohen’s Kappa coefficient was used to calculate inter-observer-variability. The angle was measured using Cobb’s method on lateral projections under different imaging conditions. Results: PA promoted the lowest effective dose (0.013 mSv) compared to AP (0.048 mSv) and lateral (0.025 mSv). The exposure parameters that allowed lower dose were 200cm SID, 90 kVp, broad focus and grid out for paediatrics using an Agfa CR system. Thirty-seven images were assessed for IQ and thirty-two were classified adequate. Cobb angle measurements varied between 16°±2.9 and 19.9°±0.9. Conclusion: Cobb angle measurements can be performed using the lowest dose with a low contrast-tonoise ratio. The variation on measurements for this was ±2.9° and this is within the range of acceptable clinical error without impact on clinical diagnosis. Further work is recommended on improvement to the sample size and a more robust perceptual IQ assessment protocol for observers.

Dimensionless analysis of constrained damping treatments

One of the most effective ways of controlling vibrations in plate or beam structures is by means of constrained viscoelastic damping treatments. Contrary to the unconstrained configuration, the design of constrained and integrated layer damping treatments is multifaceted because the thickness of the viscoelastic layer acts distinctly on the two main counterparts of the strain energy the volume of viscoelastic material and the shear strain field. In this work, a parametric study is performed exploring the effect that the design parameters, namely the thickness/length ratio, constraining layer thickness, material modulus, natural mode and boundary conditions have on these two counterparts and subsequently, on the treatment efficiency. This paper presents five parametric studies, namely, the thickness/length ratio, the constraining layer thickness, material properties, natural mode and boundary conditions. The results obtained evidence an interesting effect when dealing with very thin viscoelastic layers that contradicts the standard treatment efficiency vs. layer thickness relation; hence, the potential optimisation of constrained and integrated viscoelastic treatments through the use of properly designed thin multilayer configurations is justified. This work presents a dimensionless analysis and provides useful general guidelines for the efficient design of constrained and integrated damping treatments based on single or multi-layer configurations. (C) 2012 Elsevier Ltd. All rights reserved.

Aplicação dos princípios da manutenção Lean na indústria farmacêutica

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica

Optimização de recursos na construção de linhas de caminhos de ferro

Os Caminhos-de-ferro representam um conjunto de abordagens quase ilimitadas, nestes termos, o tema proposto – “A optimização de recursos na construção de linhas de Caminhos de Ferro”, incidirá particularmente sobre a optimização dos recursos: i) materiais; ii) mão-de-obra; iii) equipamentos, afectos a construção da via e da catenária. O presente estudo pretende traçar um encadeamento lógico e intuitivo que permita manter um fio condutor ao longo do todo o seu desenvolvimento, razão pela qual, a sequência dos objectivos apresentados constitui um caminho que permitira abrir sucessivas janelas de conhecimento. O conhecimento da via e da catenária, a compreensão da forma como os trabalhos interagem com os factores externos e a experiência na utilização das ferramentas de planeamento e gestão, são qualidades que conduzem certamente a bons resultados quando nos referimos a necessidade de optimizar os recursos na construção da via e da catenária. A transmissão e reciprocidade da informação, entre as fases de elaboração de propostas e de execução da obra, representam um recurso que pode conduzir a ganhos de produtividade. A coordenação e outro factor determinante na concretização dos objectivos de optimização dos recursos, que se efectua, quer internamente, quer exteriormente. A optimização de recursos na construção da via e da catenária representa o desafio permanente das empresas de construção do sector ferroviário. E neste pressuposto que investem na formação e especialização da sua mão-de-obra e na renovação tecnológica dos seus equipamentos. A optimização dos materiais requer aproximações distintas para o caso da via e para o caso da catenária, assim como, os equipamentos e a mão-de-obra não podem ser desligados, pois não funcionam autonomamente, no entanto a respectiva optimização obedece a pressupostos diferentes.

Image quality in diagnostic radiology

This chapter provides a theoretical background about image quality in diagnostic radiology. Digital image representation and also image quality evaluation methods are here discussed. An overview of methods for quality evaluation of diagnostic imaging procedures is provided. Digital image representation and primary physical image quality parameters are also discussed, including objective image quality measurements and observer performance methods.

Optimização do posicionamento de câmaras de vídeo-vigilância

Dissertação de Mestrado em Engenharia de Redes de Comunicação e Multimédia

Biblioteca de navegação autónoma baseada em campos de potencial

Trabalho de Final de Mestrado para obtenção do grau de Mestre em Engenharia Informática e de Computadores

A composição coreográfica na Academia de Dança Contemporânea de Setúbal dirigida ao ensino secundário

Relatório Final de Estágio apresentado à Escola Superior de Dança, com vista à obtenção do grau de Mestre em Ensino de Dança.

A importância do espaço exterior para as brincadeiras e aprendizagens das crianças

Relatório da Prática Profissional Supervisionada Mestrado em Educação Pré-Escolar

Utilização de plataformas de fonte aberta no controlo de condição

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica

GLODS: Global and Local Optimization using Direct Search

Locating and identifying points as global minimizers is, in general, a hard and time-consuming task. Difficulties increase in the impossibility of using the derivatives of the functions defining the problem. In this work, we propose a new class of methods suited for global derivative-free constrained optimization. Using direct search of directional type, the algorithm alternates between a search step, where potentially good regions are located, and a poll step where the previously located promising regions are explored. This exploitation is made through the launching of several instances of directional direct searches, one in each of the regions of interest. Differently from a simple multistart strategy, direct searches will merge when sufficiently close. The goal is to end with as many direct searches as the number of local minimizers, which would easily allow locating the global extreme value. We describe the algorithmic structure considered, present the corresponding convergence analysis and report numerical results, showing that the proposed method is competitive with currently commonly used global derivative-free optimization solvers.

Desenvolvimento de métodos de análise físico-química em águas usando um analisador multiparamétrico AQUAKEM

Trabalho Final de mestrado para obtenção do grau de Mestre em Engenharia Química e Biológica