A robust approach for automated lung segmentation in thoracic CT

Lung segmentation in thoracic computed tomography (CT) scans is an important preprocessing step for computer-aided diagnosis (CAD) of lung diseases. This paper focuses on the segmentation of the lung field in thoracic CT images. Traditional lung segmentation is based on Gray level thresholding techniques, which often requires setting a threshold and is sensitive to image contrasts. In this paper, we present a fully automated method for robust and accurate lung segmentation, which includes a enhanced thresholding algorithm and a refinement scheme based on a texture-aware active contour model. In our thresholding algorithm, a histogram based image stretch technique is performed in advance to uniformly increase contrasts between areas with low Hounsfield unit (HU) values and areas with high HU in all CT images. This stretch step enables the following threshold-free segmentation, which is the Otsu algorithm with contour analysis. However, as a threshold based segmentation, it has common issues such as holes, noises and inaccurate segmentation boundaries that will cause problems in future CAD for lung disease detection. To solve these problems, a refinement technique is proposed that captures vessel structures and lung boundaries and then smooths variations via texture-aware active contour model. Experiments on 2,342 diagnosis CT images demonstrate the effectiveness of the proposed method. Performance comparison with existing methods shows the advantages of our method.

The effect of core electrons in e(+)-Na scattering

The scattering of positrons off sodium targets has been investigated using the coupled static model. The sodium atom is represented by the one-active-electron model in which all the electrons of the target have been considered explicitly and the loosely bound valence electron is only involved in transitions. The scattering parameters are presented at low and medium energies. Appreciable differences are noticed between the present results and those obtained by the one-electron model with and without the core potential.

Método de detecção e classificação de lesões de pele em imagens digitais a partir do modelo Chan-Vese e máquina de vetor de suporte

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Models and methods for power monolithic microwave integrated circuits

Computer aided design of Monolithic Microwave Integrated Circuits (MMICs) depends critically on active device models that are accurate, computationally efficient, and easily extracted from measurements or device simulators. Empirical models of active electron devices, which are based on actual device measurements, do not provide a detailed description of the electron device physics. However they are numerically efficient and quite accurate. These characteristics make them very suitable for MMIC design in the framework of commercially available CAD tools. In the empirical model formulation it is very important to separate linear memory effects (parasitic effects) from the nonlinear effects (intrinsic effects). Thus an empirical active device model is generally described by an extrinsic linear part which accounts for the parasitic passive structures connecting the nonlinear intrinsic electron device to the external world. An important task circuit designers deal with is evaluating the ultimate potential of a device for specific applications. In fact once the technology has been selected, the designer would choose the best device for the particular application and the best device for the different blocks composing the overall MMIC. Thus in order to accurately reproducing the behaviour of different-in-size devices, good scalability properties of the model are necessarily required. Another important aspect of empirical modelling of electron devices is the mathematical (or equivalent circuit) description of the nonlinearities inherently associated with the intrinsic device. Once the model has been defined, the proper measurements for the characterization of the device are performed in order to identify the model. Hence, the correct measurement of the device nonlinear characteristics (in the device characterization phase) and their reconstruction (in the identification or even simulation phase) are two of the more important aspects of empirical modelling. This thesis presents an original contribution to nonlinear electron device empirical modelling treating the issues of model scalability and reconstruction of the device nonlinear characteristics. The scalability of an empirical model strictly depends on the scalability of the linear extrinsic parasitic network, which should possibly maintain the link between technological process parameters and the corresponding device electrical response. Since lumped parasitic networks, together with simple linear scaling rules, cannot provide accurate scalable models, either complicate technology-dependent scaling rules or computationally inefficient distributed models are available in literature. This thesis shows how the above mentioned problems can be avoided through the use of commercially available electromagnetic (EM) simulators. They enable the actual device geometry and material stratification, as well as losses in the dielectrics and electrodes, to be taken into account for any given device structure and size, providing an accurate description of the parasitic effects which occur in the device passive structure. It is shown how the electron device behaviour can be described as an equivalent two-port intrinsic nonlinear block connected to a linear distributed four-port passive parasitic network, which is identified by means of the EM simulation of the device layout, allowing for better frequency extrapolation and scalability properties than conventional empirical models. Concerning the issue of the reconstruction of the nonlinear electron device characteristics, a data approximation algorithm has been developed for the exploitation in the framework of empirical table look-up nonlinear models. Such an approach is based on the strong analogy between timedomain signal reconstruction from a set of samples and the continuous approximation of device nonlinear characteristics on the basis of a finite grid of measurements. According to this criterion, nonlinear empirical device modelling can be carried out by using, in the sampled voltage domain, typical methods of the time-domain sampling theory.

Automatic Scan Planning for Magnetic Resonance Imaging of the Knee Joint

Automatic scan planning for magnetic resonance imaging of the knee aims at defining an oriented bounding box around the knee joint from sparse scout images in order to choose the optimal field of view for the diagnostic images and limit acquisition time. We propose a fast and fully automatic method to perform this task based on the standard clinical scout imaging protocol. The method is based on sequential Chamfer matching of 2D scout feature images with a three-dimensional mean model of femur and tibia. Subsequently, the joint plane separating femur and tibia, which contains both menisci, can be automatically detected using an information-augmented active shape model on the diagnostic images. This can assist the clinicians in quickly defining slices with standardized and reproducible orientation, thus increasing diagnostic accuracy and also comparability of serial examinations. The method has been evaluated on 42 knee MR images. It has the potential to be incorporated into existing systems because it does not change the current acquisition protocol.

Automatic multi-resolution shape modeling of multi-organ structures.

Point Distribution Models (PDM) are among the most popular shape description techniques and their usefulness has been demonstrated in a wide variety of medical imaging applications. However, to adequately characterize the underlying modeled population it is essential to have a representative number of training samples, which is not always possible. This problem is especially relevant as the complexity of the modeled structure increases, being the modeling of ensembles of multiple 3D organs one of the most challenging cases. In this paper, we introduce a new GEneralized Multi-resolution PDM (GEM-PDM) in the context of multi-organ analysis able to efficiently characterize the different inter-object relations, as well as the particular locality of each object separately. Importantly, unlike previous approaches, the configuration of the algorithm is automated thanks to a new agglomerative landmark clustering method proposed here, which equally allows us to identify smaller anatomically significant regions within organs. The significant advantage of the GEM-PDM method over two previous approaches (PDM and hierarchical PDM) in terms of shape modeling accuracy and robustness to noise, has been successfully verified for two different databases of sets of multiple organs: six subcortical brain structures, and seven abdominal organs. Finally, we propose the integration of the new shape modeling framework into an active shape-model-based segmentation algorithm. The resulting algorithm, named GEMA, provides a better overall performance than the two classical approaches tested, ASM, and hierarchical ASM, when applied to the segmentation of 3D brain MRI.

Project development for older adults : Orientation's contribution

This paper systematizes the work developed during the first year of the initiation scholarship for the research project entitled 'Orientation within the new Active Aging Model: educational, work-related, personal and social choices (1)'. This project articulates the Active Aging Model and the Theoretical Operative Model in Orientation, in order to learn how new projects are developed by older adults who used to be part of the formal system of labor and by those who were out of it, and to design programmatic proposals for educational, work-related, personal and social Orientation choices for such population. The sample is made up by seventy people between 64 and 74 years of age, residing in La Plata. The first conclusions evidence the importance that older adults place on project development at this stage of their life cycle, giving special importance to educational, personal and social projects; as well as on the identification of economic factors, health state, family needs for care and social support, among other things, as conditioning the fulfillment of such projects. The differences found in terms of the labor system they used to belong to can be especially observed in the type of project developed.

Elaboración de proyectos en adultos mayoresz : Aportes de la orientación

El presente trabajo sistematiza la labor desarrollada durante el primer año de la beca de iniciación del proyecto de investigación 'La Orientación en el nuevo modelo de envejecimiento activo: elecciones educativas, laborales, personales, sociales (1)'. Dicho proyecto articula el Modelo de Envejecimiento Activo y el Modelo Teórico Operativo en Orientación, con el propósito de conocer cómo elaboran los nuevos proyectos los adultos mayores que pertenecieron al sistema formal de trabajo y aquellos que permanecieron fuera de él, y diseñar propuestas programáticas de Orientación y elección educativa, laboral, personal y social destinadas a esta población. La muestra está conformada por sesenta personas de entre 64 y 74 años de edad, residentes en la Ciudad de La Plata. Las primeras conclusiones dan cuenta de la importancia que atribuyen los adultos mayores a la elaboración de proyectos en esta etapa del ciclo vital, prevaleciendo los proyectos educativos, personales y sociales; así como la identificación de factores económicos, condiciones de salud, demanda de cuidados de otros familiares y apoyo social, entre otros, como condicionantes para la concreción de dichos proyectos. Las diferencias encontradas con respecto al sistema de trabajo al que han pertenecido se observan principalmente en el tipo de proyecto elaborado

Project development for older adults : Orientation's contribution

This paper systematizes the work developed during the first year of the initiation scholarship for the research project entitled 'Orientation within the new Active Aging Model: educational, work-related, personal and social choices (1)'. This project articulates the Active Aging Model and the Theoretical Operative Model in Orientation, in order to learn how new projects are developed by older adults who used to be part of the formal system of labor and by those who were out of it, and to design programmatic proposals for educational, work-related, personal and social Orientation choices for such population. The sample is made up by seventy people between 64 and 74 years of age, residing in La Plata. The first conclusions evidence the importance that older adults place on project development at this stage of their life cycle, giving special importance to educational, personal and social projects; as well as on the identification of economic factors, health state, family needs for care and social support, among other things, as conditioning the fulfillment of such projects. The differences found in terms of the labor system they used to belong to can be especially observed in the type of project developed.

Elaboración de proyectos en adultos mayoresz : Aportes de la orientación

El presente trabajo sistematiza la labor desarrollada durante el primer año de la beca de iniciación del proyecto de investigación 'La Orientación en el nuevo modelo de envejecimiento activo: elecciones educativas, laborales, personales, sociales (1)'. Dicho proyecto articula el Modelo de Envejecimiento Activo y el Modelo Teórico Operativo en Orientación, con el propósito de conocer cómo elaboran los nuevos proyectos los adultos mayores que pertenecieron al sistema formal de trabajo y aquellos que permanecieron fuera de él, y diseñar propuestas programáticas de Orientación y elección educativa, laboral, personal y social destinadas a esta población. La muestra está conformada por sesenta personas de entre 64 y 74 años de edad, residentes en la Ciudad de La Plata. Las primeras conclusiones dan cuenta de la importancia que atribuyen los adultos mayores a la elaboración de proyectos en esta etapa del ciclo vital, prevaleciendo los proyectos educativos, personales y sociales; así como la identificación de factores económicos, condiciones de salud, demanda de cuidados de otros familiares y apoyo social, entre otros, como condicionantes para la concreción de dichos proyectos. Las diferencias encontradas con respecto al sistema de trabajo al que han pertenecido se observan principalmente en el tipo de proyecto elaborado

Project development for older adults : Orientation's contribution

This paper systematizes the work developed during the first year of the initiation scholarship for the research project entitled 'Orientation within the new Active Aging Model: educational, work-related, personal and social choices (1)'. This project articulates the Active Aging Model and the Theoretical Operative Model in Orientation, in order to learn how new projects are developed by older adults who used to be part of the formal system of labor and by those who were out of it, and to design programmatic proposals for educational, work-related, personal and social Orientation choices for such population. The sample is made up by seventy people between 64 and 74 years of age, residing in La Plata. The first conclusions evidence the importance that older adults place on project development at this stage of their life cycle, giving special importance to educational, personal and social projects; as well as on the identification of economic factors, health state, family needs for care and social support, among other things, as conditioning the fulfillment of such projects. The differences found in terms of the labor system they used to belong to can be especially observed in the type of project developed.

Elaboración de proyectos en adultos mayoresz : Aportes de la orientación

El presente trabajo sistematiza la labor desarrollada durante el primer año de la beca de iniciación del proyecto de investigación 'La Orientación en el nuevo modelo de envejecimiento activo: elecciones educativas, laborales, personales, sociales (1)'. Dicho proyecto articula el Modelo de Envejecimiento Activo y el Modelo Teórico Operativo en Orientación, con el propósito de conocer cómo elaboran los nuevos proyectos los adultos mayores que pertenecieron al sistema formal de trabajo y aquellos que permanecieron fuera de él, y diseñar propuestas programáticas de Orientación y elección educativa, laboral, personal y social destinadas a esta población. La muestra está conformada por sesenta personas de entre 64 y 74 años de edad, residentes en la Ciudad de La Plata. Las primeras conclusiones dan cuenta de la importancia que atribuyen los adultos mayores a la elaboración de proyectos en esta etapa del ciclo vital, prevaleciendo los proyectos educativos, personales y sociales; así como la identificación de factores económicos, condiciones de salud, demanda de cuidados de otros familiares y apoyo social, entre otros, como condicionantes para la concreción de dichos proyectos. Las diferencias encontradas con respecto al sistema de trabajo al que han pertenecido se observan principalmente en el tipo de proyecto elaborado

Soporte de redes activas para un servicio integrado de multipunto fiable con control de congestión

Las limitaciones de las tecnologías de red actuales, identificadas en la Agencia de Proyectos de Investigación Avanzados para la Defensa (DARPA) durante 1995, han originado recientemente una propuesta de modelo de red denominado Redes Activas. En este modelo, los nodos proporcionan un entorno de ejecución sobre el que se ejecuta el código asociado a cada paquete. El objetivo es disponer de una tecnología de red que permita que nuevos servicios de red sean desarrollados e instalados rápidamente sin modificar los nodos de la red. Un servicio de red que se puede beneficiar de esta tecnología es la transmisión de datos en multipunto con diferentes grados fiabilidad. Las propuestas actuales de servicios de multipunto fiable proporcionan una solución específica para cada clase de aplicaciones, y los protocolos existentes extremo a extremo sufren de limitaciones técnicas relacionadas con una fiabilidad limitada, y con la ausencia de mecanismos de control de congestión efectivos. Esta tesis realiza propuestas originales conducentes a solucionar parte de las limitaciones actuales en el ámbito de Redes Activas y multipunto fiable con control de congestión. En primer lugar, se especificará un servicio genérico de multipunto fiable que, basándose en los requisitos de una serie de aplicaciones consideradas relevantes, proporcione diferentes clases de sesiones y grados de fiabilidad. Partiendo de la definición del servicio genérico especificado, se diseñará un protocolo de comunicaciones sobre la tecnología de Redes Activas que proporcione dicho servicio. El protocolo diseñado estará dotado de un mecanismo de control de congestión para que la fuente ajuste dinámicamente el tráfico inyectado a las condiciones de carga de la red. En esta tesis se pretende también profundizar en el estudio y análisis de la tecnología de Redes Activas, experimentando con dicha tecnología para proporcionar una realimentación a sus diseñadores. Dicha experimentación se realizará en tres ámbitos: el de los servicios y protocolos que puede soportar, el del modelo y arquitectura de las Redes Activas y el de las plataformas de ejecución disponibles. Como aportación adicional de este trabajo, se validarán los objetivos anteriores mediante una implementación piloto de las entidades de protocolo y de su interfaz de servicio sobre uno de los entornos de ejecución disponibles. Abstract The limitations of current networking technologies identified in the Defense Advance Research Projects Agency (DARPA) along 1995 have led to a recent proposal of a new network model called Active Networks. In this model, the nodes provide an execution environment over which the code used to process each packet is executed. The objective is a network technology that allows the fast design and deployment of new network services without requiring the modification of the network nodes. One network service that could benefit from this technology is the transmission of multicast data with different types of loss tolerance. The current proposals for reliable multicast services provide specific solutions for each application class, and existing end-to-end protocols suffer from technical drawbacks related to limited reliability and lack of an effective congestion control mechanism. This thesis contains original proposals that aim to solve part of the current drawbacks in the scope of Active Networks and reliable multicast with congestion control. Firstly, a generic reliable multicast network service will be specified. This service will be designed from the requirements of a relevant set of applications, and will provide different session classes and different types of reliability. Then, a network protocol based on Active Network technology will be designed such that it provides the specified network service. This protocol will incorporate a congestion control mechanism capable of performing an automatic adjustment of the traffic injected by the source to the available network capacity. This thesis will also contribute to a deeper study and analysis of Active Network technology, by experimenting with the technology in order to provide feedback to its designers. This experimentation will be done attending to three different scopes: support of Active Network for services and protocols, Active Network model and architecture, and currently available Active Network execution environments. As an additional contribution of this work, the previous objectives will be validated through a prototype implementation of the protocol entities and the service interface based on one of the current execution environments.

Diseño e implementación de un módulo para la anotación de imágenes médicas

Se comenzó el trabajo recabando información sobre los distintos enfoques que se le había dado a la anotación a lo largo del tiempo, desde anotación de imágenes a mano, pasando por anotación de imágenes utilizando características de bajo nivel, como color y textura, hasta la anotación automática. Tras entrar en materia, se procedió a estudiar artículos relativos a los diferentes algoritmos utilizados para la anotación automática de imágenes. Dado que la anotación automática es un campo bastante abierto, hay un gran numero de enfoques. Teniendo las características de las imágenes en particular en las que se iba a centrar el proyecto, se fueron descartando los poco idoneos, bien por un coste computacional elevado, o porque estaba centrado en un tipo diferente de imágenes, entre otras cosas. Finalmente, se encontró un algoritmo basado en formas (Active Shape Model) que se consideró que podría funcionar adecuadamente. Básicamente, los diferentes objetos de la imagen son identicados a partir de un contorno base generado a partir de imágenes de muestra, siendo modicado automáticamente para cubrir la zona deseada. Dado que las imágenes usadas son todas muy similares en composición, se cree que puede funcionar bien. Se partió de una implementación del algoritmo programada en MATLAB. Para empezar, se obtuvieron una serie de radiografías del tórax ya anotadas. Las imágenes contenían datos de contorno para ambos pulmones, las dos clavículas y el corazón. El primer paso fue la creación de una serie de scripts en MATLAB que permitieran: - Leer y transformar las imágenes recibidas en RAW, para adaptarlas al tamaño y la posición de los contornos anotados - Leer los archivos de texto con los datos de los puntos del contorno y transformarlos en variables de MATLAB - Unir la imagen transformada con los puntos y guardarla en un formato que la implementación del algoritmo entendiera. Tras conseguir los ficheros necesarios, se procedió a crear un modelo para cada órgano utilizando para el entrenamiento una pequeña parte de las imágenes. El modelo obtenido se probó con varias imágenes de las restantes. Sin embargo, se encontro bastante variación dependiendo de la imagen utilizada y el órgano detectado. ---ABSTRACT---The project was started by procuring information about the diferent approaches to image annotation over time, from manual image anotation to automatic annotation. The next step was to study several articles about the diferent algorithms used for automatic image annotation. Given that automatic annotation is an open field, there is a great number of approaches. Taking into account the features of the images that would be used, the less suitable algorithms were rejected. Eventually, a shape-based algorithm (Active Shape Model) was found. Basically, the diferent objects in the image are identified from a base contour, which is generated from training images. Then this contour is automatically modified to cover the desired area. Given that all the images that would be used are similar in object placement, the algorithm would probably work nicely. The work started from a MATLAB implementation of the algorithm. To begin with, a set of chest radiographs already annotated were obtained. These images came with contour data for both lungs, both clavicles and the heart. The first step was the creation of a series of MATLAB scripts to join the RAW images with the annotation data and transform them into a format that the algorithm could read. After obtaining the necessary files, a model for each organ was created using part of the images for training. The trained model was tested on several of the reimaining images. However, there was much variation in the results from one image to another. Generally, lungs were detected pretty accurately, whereas clavicles and the heart gave more problems. To improve the method, a new model was trained using half of the available images. With this model, a significant inprovement of the results can be seen.

Age regression from soft aligned face images using low computational resources

The initial step in most facial age estimation systems consists of accurately aligning a model to the output of a face detector (e.g. an Active Appearance Model). This fitting process is very expensive in terms of computational resources and prone to get stuck in local minima. This makes it impractical for analysing faces in resource limited computing devices. In this paper we build a face age regressor that is able to work directly on faces cropped using a state-of-the-art face detector. Our procedure uses K nearest neighbours (K-NN) regression with a metric based on a properly tuned Fisher Linear Discriminant Analysis (LDA) projection matrix. On FG-NET we achieve a state-of-the-art Mean Absolute Error (MAE) of 5.72 years with manually aligned faces. Using face images cropped by a face detector we get a MAE of 6.87 years in the same database. Moreover, most of the algorithms presented in the literature have been evaluated on single database experiments and therefore, they report optimistically biased results. In our cross-database experiments we get a MAE of roughly 12 years, which would be the expected performance in a real world application.