Análise estrutural e fadiga em prótese implanto-suportada unitária através do método dos elementos finitos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização espectral de espécies de Mata Atlântica de Interior em nível foliar e de copa

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Multimodal target correction by local bone registration: a PET/CT evaluation

PET/CT guidance for percutaneous interventions allows biopsy of suspicious metabolically active bone lesions even when no morphological correlation is delineable in the CT images. Clinical use of PET/CT guidance with conventional step-by-step technique is time consuming and complicated especially in cases in which the target lesion is not shown in the CT image. Our recently developed multimodal instrument guidance system (IGS) for PET/CT improved this situation. Nevertheless, bone biopsies even with IGS have a trade-off between precision and intervention duration which is proportional to patient and personnel exposure to radiation. As image acquisition and reconstruction of PET may take up to 10 minutes, preferably only one time consuming combined PET/CT acquisition should be needed during an intervention. In case of required additional control images in order to check for possible patient movements/deformations, or to verify the final needle position in the target, only fast CT acquisitions should be performed. However, for precise instrument guidance accounting for patient movement and/or deformation without having a control PET image, it is essential to be able to transfer the position of the target as identified in the original PET/CT to a changed situation as shown in the control CT.

A Conceptual Model to Combine Creativity Techniques with Fuzzy Cognitive Maps for Enhanced Knowledge Management

This chapter introduces a conceptual model to combine creativity techniques with fuzzy cognitive maps (FCMs) and aims to support knowledge management methods by improving expert knowledge acquisition and aggregation. The aim of the conceptual model is to represent acquired knowledge in a manner that is as computer-understandable as possible with the intention of developing automated reasoning in the future as part of intelligent information systems. The formal represented knowledge thus may provide businesses with intelligent information integration. To this end, we introduce and evaluate various creativity techniques with a list of attributes to define the most suitable to combine with FCMs. This proposed combination enables enhanced knowledge management through the acquisition and representation of expert knowledge with FCMs. Our evaluation indicates that the creativity technique known as mind mapping is the most suitable technique in our set. Finally, a scenario from stakeholder management demonstrates the combination of mind mapping with FCMs as an integrated system.

Methodology for reconstructing early zebrafish development from in vivo multiphoton microscopy

Investigating cell dynamics during early zebrafish embryogenesis requires specific image acquisition and analysis strategies. Multiharmonic microscopy, i.e., second- and third-harmonic generations, allows imaging cell divisions and cell membranes in unstained zebrafish embryos from 1- to 1000-cell stage. This paper presents the design and implementation of a dedicated image processing pipeline (tracking and segmentation) for the reconstruction of cell dynamics during these developmental stages. This methodology allows the reconstruction of the cell lineage tree including division timings, spatial coordinates, and cell shape until the 1000-cell stage with minute temporal accuracy and micrometer spatial resolution. Data analysis of the digital embryos provides an extensive quantitative description of early zebrafish embryogenesis.

Contribuciones en sistemas de adquisición de datos inteligentes para entornos de fusión por confinamiento magnético

Los sistemas de adquisición de datos utilizados en los diagnósticos de los dispositivos de fusión termonuclear se enfrentan a importantes retos planteados en los dispositivos de pulso largo. Incluso en los dispositivos de pulso corto, en los que se analizan los datos después de la descarga, existen aún una gran cantidad de datos sin analizar, lo cual supone que queda una gran cantidad de conocimiento por descubrir dentro de las bases de datos existentes. En la última década, la comunidad de fusión ha realizado un gran esfuerzo para mejorar los métodos de análisis off‐line para mejorar este problema, pero no se ha conseguido resolver completamente, debido a que algunos de estos métodos han de resolverse en tiempo real. Este paradigma lleva a establecer que los dispositivos de pulso largo deberán incluir dispositivos de adquisición de datos con capacidades de procesamiento local, capaces de ejecutar avanzados algoritmos de análisis. Los trabajos de investigación realizados en esta tesis tienen como objetivo determinar si es posible incrementar la capacidad local de procesamiento en tiempo real de dichos sistemas mediante el uso de GPUs. Para ello durante el trascurso del periodo de experimentación realizado se han evaluado distintas propuestas a través de casos de uso reales elaborados para algunos de los dispositivos de fusión más representativos como ITER, JET y TCV. Las conclusiones y experiencias obtenidas en dicha fase han permitido proponer un modelo y una metodología de desarrollo para incluir esta tecnología en los sistemas de adquisición para diagnósticos de distinta naturaleza. El modelo define no sólo la arquitectura hardware óptima para realizar dicha integración, sino también la incorporación de este nuevo recurso de procesamiento en los Sistemas de Control de Supervisión y Adquisición de Datos (SCADA) utilizados en la comunidad de fusión (EPICS), proporcionando una solución completa. La propuesta se complementa con la definición de una metodología que resuelve las debilidades detectadas, y permite trazar un camino de integración de la solución en los estándares hardware y software existentes. La evaluación final se ha realizado mediante el desarrollo de un caso de uso representativo de los diagnósticos que necesitan adquisición y procesado de imágenes en el contexto del dispositivo internacional ITER, y ha sido testeada con éxito en sus instalaciones. La solución propuesta en este trabajo ha sido incluida por la ITER IO en su catálogo de soluciones estándar para el desarrollo de sus futuros diagnósticos. Por otra parte, como resultado y fruto de la investigación de esta tesis, cabe destacar el acuerdo llevado a cabo con la empresa National Instruments en términos de transferencia tecnológica, lo que va a permitir la actualización de los sistemas de adquisición utilizados en los dispositivos de fusión. ABSTRACT Data acquisition systems used in the diagnostics of thermonuclear fusion devices face important challenges due to the change in the data acquisition paradigm needed for long pulse operation. Even in shot pulse devices, where data is mainly analyzed after the discharge has finished , there is still a large amount of data that has not been analyzed, therefore producing a lot of buried knowledge that still lies undiscovered in the data bases holding the vast amount of data that has been generated. There has been a strong effort in the fusion community in the last decade to improve the offline analysis methods to overcome this problem, but it has proved to be insufficient unless some of these mechanisms can be run in real time. In long pulse devices this new paradigm, where data acquisition devices include local processing capabilities to be able to run advanced data analysis algorithms, will be a must. The research works done in this thesis aim to determining whether it is possible to increase local capacity for real‐time processing of such systems by using GPUs. For that, during the experimentation period, various proposals have been evaluated through use cases developed for several of the most representative fusion devices, ITER, JET and TCV. Conclusions and experiences obtained have allowed to propose a model, and a development methodology, to include this technology in systems for diagnostics of different nature. The model defines not only the optimal hardware architecture for achieving this integration, but also the incorporation of this new processing resource in one of the Systems of Supervision Control and Data Acquisition (SCADA) systems more relevant at the moment in the fusion community (EPICS), providing a complete solution. The final evaluation has been performed through a use case developed for a generic diagnostic requiring image acquisition and processing for the international ITER device, and has been successfully tested in their premises. The solution proposed in this thesis has been included by the ITER IO in his catalog of standard solutions for the development of their future diagnostics. This has been possible thanks to the technologic transfer agreement signed with xi National Instruments which has permitted us to modify and update one of their core software products targeted for the acquisition systems used in these devices.

Vibration frequency measurement using a local multithreshold technique

In this paper, we demonstrate the use of a video camera for measuring the frequency of small-amplitude vibration movements. The method is based on image acquisition and multilevel thresholding and it only requires a video camera with high enough acquisition rate, not being necessary the use of targets or auxiliary laser beams. Our proposal is accurate and robust. We demonstrate the technique with a pocket camera recording low-resolution videos with AVI-JPEG compression and measuring different objects that vibrate in parallel or perpendicular direction to the optical sensor. Despite the low resolution and the noise, we are able to measure the main vibration modes of a tuning fork, a loudspeaker and a bridge. Results are successfully compared with design parameters and measurements with alternative devices.

FPGA-based architecture for hyperspectral endmember extraction

Hyperspectral instruments have been incorporated in satellite missions, providing data of high spectral resolution of the Earth. This data can be used in remote sensing applications, such as, target detection, hazard prevention, and monitoring oil spills, among others. In most of these applications, one of the requirements of paramount importance is the ability to give real-time or near real-time response. Recently, onboard processing systems have emerged, in order to overcome the huge amount of data to transfer from the satellite to the ground station, and thus, avoiding delays between hyperspectral image acquisition and its interpretation. For this purpose, compact reconfigurable hardware modules, such as field programmable gate arrays (FPGAs) are widely used. This paper proposes a parallel FPGA-based architecture for endmember’s signature extraction. This method based on the Vertex Component Analysis (VCA) has several advantages, namely it is unsupervised, fully automatic, and it works without dimensionality reduction (DR) pre-processing step. The architecture has been designed for a low cost Xilinx Zynq board with a Zynq-7020 SoC FPGA based on the Artix-7 FPGA programmable logic and tested using real hyperspectral data sets collected by the NASA’s Airborne Visible Infra-Red Imaging Spectrometer (AVIRIS) over the Cuprite mining district in Nevada. Experimental results indicate that the proposed implementation can achieve real-time processing, while maintaining the methods accuracy, which indicate the potential of the proposed platform to implement high-performance, low cost embedded systems, opening new perspectives for onboard hyperspectral image processing.

Qualidade de imagem em mamografia: apresentação do músculo grande peitoral na incidência oblíqua médio-lateral

A mamografia é, atualmente, o principal método de diagnóstico imagiológico da patologia mamária, sendo, por isso, essencial a produção consistente de imagens mamográficas de elevada qualidade. Assim, e uma vez que a mamografia visa a maximização da visualização do tecido mamário, o principal objetivo deste estudo consiste em investigar a apresentação mamográfica do músculo grande peitoral na incidência oblíqua médio-lateral (OML) da mama. Pretendeu-se relacionar os padrões técnicos de aquisição de imagem à forma de apresentação do referido músculo, avaliando-os de acordo com os atuais critérios de qualidade de imagem. As imagens mamográficas foram recolhidas a partir de duas instituições hospitalares de referência do Porto, sendo posteriormente efetuada uma análise e tratamento estatístico dos indicadores qualitativos e quantitativos de qualidade das mesmas. Numa análise global por instituição, e tendo por base estes indicadores, a instituição que utiliza uma angulação fixa do potter-bucky, independentemente do biótipo corporal da paciente, apresentou resultados melhores, indicando assim que a existência de falhas devido a erros de posicionamento é menor por comparação aos critérios de qualidade padrão. Constatou-se, portanto, que a angulação do potter-bucky tem um impacto relevante e estatisticamente significativo na qualidade das imagens mamográficas.

Characterization of micro-bubble size distribution and flow configuration in DAF contact zone by a non-intrusive image analysis system and tracer tests

This paper aims to investigate the influence of some dissolved air flotation (DAF) process variables (specifically: the hydraulic detention time in the contact zone and the supplied dissolved air concentration) and the pH values, as pretreatment chemical variables, on the micro-bubble size distribution (BSD) in a DAF contact zone. This work was carried out in a pilot plant where bubbles were measured by an appropriate non-intrusive image acquisition system. The results show that the obtained diameter ranges were in agreement with values reported in the literature (10-100mm), quite independently of the investigated conditions. The linear average diameter varied from 20 to 30mm, or equivalently, the Sauter (d(3,2)) diameter varied from 40 to 50mm. In all investigated conditions, D(50) was between 75% and 95%. The BSD might present different profile (with a bimodal curve trend), however, when analyzing the volumetric frequency distribution (in some cases with the appearance of peaks in diameters ranging from 90-100mm). Regarding volumetric frequency analysis, all the investigated parameters can modify the BSD in DAF contact zone after the release point, thus potentially causing changes in DAF kinetics. This finding prompts further research in order to verify the effect of these BSD changes on solid particle removal efficiency by DAF.

Wavelet-based image segment representation

An efficient representation method for arbitrarily shaped image segments is proposed. This method includes a smart way to select wavelet basis to approximate the given image segment, with improved image quality and reduced computational load.

Color Models and Illumination Changes

Color model representation allows characterizing in a quantitative manner, any defined color spectrum of visible light, i.e. with a wavelength between 400nm and 700nm. To accomplish that, each model, or color space, is associated with a function that allows mapping the spectral power distribution of the visible electromagnetic radiation, in a space defined by a set of discrete values that quantify the color components composing the model. Some color spaces are sensitive to changes in lighting conditions. Others assure the preservation of certain chromatic features, remaining immune to these changes. Therefore, it becomes necessary to identify the strengths and weaknesses of each model in order to justify the adoption of color spaces in image processing and analysis techniques. This chapter will address the topic of digital imaging, main standards and formats. Next we will set the mathematical model of the image acquisition sensor response, which enables assessment of the various color spaces, with the aim of determining their invariance to illumination changes.

Effect of technical parameters on dose and image quality in a computed radiography system

The discovery of X-rays was undoubtedly one of the greatest stimulus for improving the efficiency in the provision of healthcare services. The ability to view, non-invasively, inside the human body has greatly facilitated the work of professionals in diagnosis of diseases. The exclusive focus on image quality (IQ), without understanding how they are obtained, affect negatively the efficiency in diagnostic radiology. The equilibrium between the benefits and the risks are often forgotten. It is necessary to adopt optimization strategies to maximize the benefits (image quality) and minimize risk (dose to the patient) in radiological facilities. In radiology, the implementation of optimization strategies involves an understanding of images acquisition process. When a radiographer adopts a certain value of a parameter (tube potential [kVp], tube current-exposure time product [mAs] or additional filtration), it is essential to know its meaning and impact of their variation in dose and image quality. Without this, any optimization strategy will be a failure. Worldwide, data show that use of x-rays has been increasingly frequent. In Cabo Verde, we note an effort by healthcare institutions (e.g. Ministry of Health) in equipping radiological facilities and the recent installation of a telemedicine system requires purchase of new radiological equipment. In addition, the transition from screen-films to digital systems is characterized by a raise in patient exposure. Given that this transition is slower in less developed countries, as is the case of Cabo Verde, the need to adopt optimization strategies becomes increasingly necessary. This study was conducted as an attempt to answer that need. Although this work is about objective evaluation of image quality, and in medical practice the evaluation is usually subjective (visual evaluation of images by radiographer / radiologist), studies reported a correlation between these two types of evaluation (objective and subjective) [5-7] which accredits for conducting such studies. The purpose of this study is to evaluate the effect of exposure parameters (kVp and mAs) when using additional Cooper (Cu) filtration in dose and image quality in a Computed Radiography system.

Reducing effective dose to a paediatric phantom by using different combinations of kVp, mAs and additional filtration whilst maintaining image quality

Purpose: To determine whether using different combinations of kVp and mAs with additional filtration can reduce the effective dose to a paediatric phantom whilst maintaining diagnostic image quality. Methods: 27 images of a paediatric AP pelvis phantom were acquired with different kVp, mAs and additional copper filtration. Images were displayed on quality controlled monitors with dimmed lighting. Ten diagnostic radiographers (5 students and 5 experienced radiographers) had eye tests to assess visual acuity before rating the images. Each image was rated for visual image quality against a reference image using 2 alternative forced choice software using a 5-point Likert scale. Physical measures (SNR and CNR) were also taken to assess image quality. Results: Of the 27 images rated, 13 of them were of acceptable image quality and had a dose lower than the image with standard acquisition parameters. Two were produced without filtration, 6 with 0.1mm and 5 with 0.2mm copper filtration. Statistical analysis found that the inter-rater and intra-rater reliability was high. Discussion: It is possible to obtain an image of acceptable image quality with a dose that is lower than published guidelines. There are some areas of the study that could be improved. These include using a wider range of kVp and mAs to give an exact set of parameters to use. Conclusion: Additional filtration has been identified as amajor tool for reducing effective dose whilst maintaining acceptable image quality in a 5 year old phantom.

Development of procedures for the design, optimization and manufacturing of customized orthopaedic and trauma implants: Geometrical/anatomical modelling from 3D medical imaging

Tese de Doutoramento (Programa Doutoral em Engenharia Biomédica)