Dense deformation field estimation for atlas registration using the active contour framework

A key research area in computer vision is image segmentation. Image segmentation aims at extracting objects of interest in images or video sequences. These objects contain relevant information for a given application. For example, a video surveillance application generally requires to extract moving objects (vehicles, persons or animals) from a sequence of images in order to check that their path stays conformed to the regulation rules set for the observed scene. Image segmentation is not an easy task. In many applications, the contours of the objects of interest are difficult to delineate, even manually. The problems linked to segmentation are often due to low contrast, fuzzy contours or too similar intensities with adjacent objects. In some cases, the objects to be extracted have no real contours in the image. This kind of objects is called virtual objects. Virtual objects appear especially in medical applications. To draw them, medical experts usually estimate their position from surrounding objects. The problems related to image segmentation can be greatly simplified with information known in advance on the objects to be extracted (the prior knowledge). A widely used method consists to extract the needed prior knowledge from a reference image often called atlas. The goal of the atlas is to describe the image to be segmented like a map would describe the components of a geographical area. An atlas can contain three types of information on each object being part of the image: an estimation of its position in the image, a description of its shape and texture, and the features of its adjacent objects. The atlas-based segmentation method is rather used when the atlas can characterize a range of images. This method is thus especially adapted to medical images due to the existing consistency between anatomical structures of same type. There exist two types of atlas: the determinist atlas and the statistical atlas. The determinist atlas is an image which has been selected or computed, to be the most representative of an image category to be segmented. This image is called intensity atlas. The contours of the objects of interest (the objects to be extracted in images of the same type) have been traced manually on the intensity atlas, or by using a semi-automatic method. A label is often attributed to each one of these objects in order to differentiate them. In this way, we obtain a labeled version of the atlas called labeled atlas. The statistical atlas is an atlas created from a database of images in order to be the most representative of a certain type of images to be segmented. In this atlas, the position and the features of the objects of interest depend on statistical measures. In this thesis, we are focused on the use of determinist atlases for image segmentation. The segmentation process with a determinist atlas consists to deform the objects delineated in the atlas in order to better align them with their corresponding objects in the image to be segmented. To perform this task, we have distinguished two types of approaches in the literature. The first approach consists to reduce the segmentation problem in an image registration problem. First of all, a dense deformation field that registers (i.e. puts in point-to-point spatial correspondence) the atlas to the image to be segmented, is explicitly computed. Then, this transformation is used to project the assigned labels onto each atlas structure on the image to be segmented. The advantage of this approach is that the deformation field computed from the registration of visible contours allows to easily estimate the position of virtual objects or objects with fuzzy contours. However, the methods currently used for the atlas registration are often only based on the intensity atlas. That means that they do not exploit the object-based information that can be obtained by combining the intensity atlas with its labeled version. In the second approach, the atlas contours selected by the labeled atlas are directly deformed without using a geometrical deformation. For that, this approach is based on matching contour techniques, generally called deformable models. In this thesis, we are interested to a particular type of deformable models, which are the active contour segmentation models. The advantage of the active contour method is that this segmentation technique has been designed to exploit the image information directly linked to the object to be delineated. By using object-based information, active contour models are frequently able to extract regions where the atlas-based segmentation method by registration fails. On the other hand, the result of this local segmentation method is very sensitive to the initial atlas contour position regarding to the target contours. On the other hand, this local segmentation method is very sensitive to the initial position of the atlas contours: the closer they are to the contours to be detected, the more robust the active contour-based segmentation will be. Besides, this segmentation technique needs prior shape models to be able to estimate the position of virtual objects. The main objective of this thesis is to design an algorithm for atlas-based segmentation which combines the advantages of the dense deformation field computed by the registration algorithms, with local segmentation constraints coming from the active contour framework. This implies to design a model where the registration and segmentation by active contours are jointly performed. The atlas registration algorithm that we propose is based on a formulation allowing the integration of any segmentation or contour regularization forces derived from the theory of the active contours in a non parametric registration process. Our algorithm led us to introduce the concept of hierarchical atlas registration. Its principle is that the registration of the main image objects helps the registration of depending objects. This allows to bring progressively the atlas contours closer to their target and thus, to limit the risk to be stuck in a local minimum. Our model had been designed to be easily adaptable to various types of segmentation problems. At the end of the thesis, we present several examples of atlas registration applications in medical imaging. These applications highlight the integration of manual constraints in an atlas registration process, the modeling of a tumor growth in the atlas, the labelization of the thalamus for a statistical study on neuronal connections, the localization of the subthalamic nucleus (STN) for deep brain stimulation (DBS) and the compensation of intra-operative brain shift for neuronavigation systems

Third International Symposium on Artificial Intelligence, Robotics, and Automation for Space 1994

The Third International Symposium on Artificial Intelligence, Robotics, and Automation for Space (i-SAIRAS 94), held October 18-20, 1994, in Pasadena, California, was jointly sponsored by NASA, ESA, and Japan's National Space Development Agency, and was hosted by the Jet Propulsion Laboratory (JPL) of the California Institute of Technology. i-SAIRAS 94 featured presentations covering a variety of technical and programmatic topics, ranging from underlying basic technology to specific applications of artificial intelligence and robotics to space missions. i-SAIRAS 94 featured a special workshop on planning and scheduling and provided scientists, engineers, and managers with the opportunity to exchange theoretical ideas, practical results, and program plans in such areas as space mission control, space vehicle processing, data analysis, autonomous spacecraft, space robots and rovers, satellite servicing, and intelligent instruments

Performance Poetry A Tactile-Kinesthetic Poiesis

\u201cPerformance Poetry: A Tactile-Kinesthetic Poiesis\u201d rappresenta un tentativo di analisi intermediale e interdisciplinare della performance poetry. Osservando il rapporto tra performance e poesia, si considera la performance nella sua duplice veste di strumento divulgativo e caratteristica fondante del processo di scrittura, e della creazione poetica. L\u2019elemento performativo permette di superare l\u2019approccio testuale della tradizione occidentale allo studio del testo, intendendolo ora, non pi\uf9 come opera finita, ma come processo. Questa visione apre ad una concezione della performance poetry come testo etnografico postmoderno, in cui oralit\ue0, scrittura e performance sono elementi costitutivi del discorso poetico. L\u2019idea di testo come processo che si manifesta in moltiplici modi e forme permette di riconsiderare l\u2019apporto del \u201ccorpo\u201d all\u2019interno del processo poetico. Tale recupero della dimensione corporea nella produzione della poesia come testo etnografico e postmoderno ridefinisce la performance poetry come un sistema aperto, dinamico e polimorfo

Transnational Modern Languages

In a world increasingly defined by the transnational and translingual, and by the pressures of globalization, it has become difficult to study culture as primarily a national phenomenon. A Handbook offers students across Modern Languages an introduction to the kind of methodological questions they need to look at culture transnationally. Each of the short essays takes a key concept in cultural study and suggests how it might be used to explore and illuminate some aspect of identity, mobility, translation, and cultural exchange across borders. The authors range over different language areas and their wide chronological reach provides broad coverage, as well as a flexible and practical methodology for studying cultures in a transnational framework. The essays show that an inclusive, transnational vision and practice of Modern Languages is central to understanding human interaction in an inclusive, globalized society. A Handbook stands as an effective and necessary theoretical and thematically diverse glossary and companion to the ‘national’ volumes in the series

Evolving communities : adapting theories of Robert Kegan and Bernard Lonergan to intentional groups

It has been long known that groups of adults learn and enact their learning in certain ways; what is little known is how groups learn and how they develop in cognitive complexity. This dissertation proposes a theory of group cognitive development by arguing that intentional adult groups are complex and dynamic, and that they have the potential to evolve over time. Groups are complex in that they are made up of individuals within different orders of consciousness (Kegan), and they are dynamic in that different orders of consciousness interact and conflict (Lonergan) during the formation and enactment of group vision, values, and procedures. Dynamic complexity theory of group development as it is referred to in this study is grounded in Robert Kegan’s constructive developmental theory and in Bernard Lonergan’s transcendental method. While both Kegan and Lonergan attend to the growth of individuals, their theories are adapted to groups in order to understand the cognitive complexity of groups, intragroup and intergroup conflict, and the mental complexity of leader curriculum. This theory is applied to two case studies, one from antiquity in the case of the first century Corinthian community engaged in conflict with its founder, St. Paul, and in one contemporary study of American Catholic parishioners engaged in contentious dialogue with diocesan leaders from 1994 to 2004. The parish groups experienced a series of dialogues during a ten year period over the issues of parish restructuring and the priest sexual abuse crisis yielding cumulative and progressive changes in perspective-taking, responsibility-taking, and in group capacity to respond to and engage local and institutional authority figures. Group development is observed against a pedagogical backdrop that represents a mismatch between group complexity and leader expectations. In Corinth, Paul’s curriculum was significantly beyond the mental capacity of the community. In the case of Catholic parishioners the curriculum of diocesan leaders was beneath the mental capacities of most of the groups studied. It is proposed that individuals sharing the same order of consciousness, understood as cognitive constituencies, are in a dynamic relationship with other cognitive constituencies in the group that interact within an object-subject dialectic and an agency-communion dialectic. The first describes and explains the evolving cognitive complexity of group knowing, how the group does its knowing, and what it knows when it is doing it (the epistemologies of the group). This dialectic has implications for how intentional groups might be the critical factor for understanding individual growth. The second dialectic describes and explains the changing relationship between group agency, which is enacted either instrumentally or ideologically; and group communion, which is enacted ideationally. The agency-communion dialectic is held in an unstable balance in the knowing, identity, and mission of groups. With implications for the fields of adult education and learning organizations, dynamic complexity theory of group development notes predictable stages of group evolution as each cognitive constituency evolves, and notes the significance of internal and external conflict for exposing the presence of different ways of knowing and for challenging the group toward cognitive growth.Thesis (PhD) — Boston College, 2008.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Religious Education and Pastoral Ministry

Contributing to integrated sustainable development through a transnational law approach. Exploiting the linkages between economic, environmental and human rights legal regimes as applied to hydropower projects on the Mekong River

Unsustainability is often linked with to extreme trade-offs and imbalances between the different interests of a plurality of actors, scales and regimes. The objective of integration tackles the need to address this growing diversification and multiplication within decision-making/governance. The transboundary nature of these elements of governance often complicates and heightens the challenge of integration. The aim of this thesis is therefore to study the way international law can contribute to this objective. Its participation to implementing integrated sustainable development depends (itself) on its suitability and capacity to address legal pluralism. However, such integrated approach is not effectively provided by traditional international law. Its limited and strict legal classifications and scope related to the State create a key challenge to embracing legal pluralism and integration. This thesis suggests a new approach and insights to this inquiry through the concept of transnational law (TNL). Its unique pluralist, holistic and interconnected approach is explored and developed to measure up to the objective of integration. The design of an analytical framework built on the conceptual underpinnings of TNL helps developing this reflection and to go beyond its theoretical understanding. In addition, a case study of hydropower in the Lower Mekong River Basin and transboundary water management offers interesting conditions to apply and test TNL. TNL allows to envision a different/broader approach to legal pluralism and to the growing transboundary issues within sustainable development. The concept also suggests a way international law can make a stronger and more relevant contribution to the objective of integration

Automobility Beyond Car:Introducing a New Coordinate System for Transforming Urban Mobility

How is the future of automobility imagined today? What has structured such imaginary ? And what levers can steer its evolution towards a Post-Car World? These very three questions form the foundational motivations of this thesis. First, through a historical overview, I explore and analyze a selected corpus of verbal and visual discourses that have contributed to how we think of car, how we think of a transition from it, and interrelatedly how it is placed in our cities. An oppositional relation against walking seems to majorly explain the changing position of car. The comfort, speed, and privacy of car have been put against the effort, slowness and sociability of walking. By tracing the shifting values of these qualities, I detect and depict the evolution of car-pedestrian imaginaries. Second, two series of encounters with urban actors–urban experts and inhabitants– were conducted. (1) Interviewing eight urban experts (active practitioners in the field of urbanism), I quest for their assessment of the current “weak signs” of transition from car in urban space, their vision for its future in various urban forms, as well as the perks and perils of emerging technologies, as mobility’s “wild cards”. The transversal analysis of the interviews, using the theory-generating methodology (Bogner and Menz 2009), results in a set of extracted themes, common threads, visionary strategies, as well as contextualized tools. (2) In a Focus Group composed of eight inhabitants of the territory of Arc Lemanique Lausanne-Geneva area, the participants discussed various post-car scenarios that we had developed over the course of two Teaching Units held at EPFL’s school of Architecture. The analysis of the transcribed discussions revealed some of the salient motivations and impediments towards a post-car world. Cross-referencing the participants’ lifestyles with their expressed views indicates a dissociation of inhabitants’ daily practice of car mobility from their ideal of a mobile lifestyle. Considering the role of urban projects as a mediator, I confront the experts’ representations, ideas and references with the discourses of the inhabitants. As city is increasingly to be approached as a “work without author”, urban project (scenarios, visions, plans) becomes a dispositif of exchange and discussion, animating a process in which imaginations, assumptions, desires, and insights are exchanged, becoming the telltale of imaginaries rather than prescription for cities and territories. Third, I propose three conceptual axes along which the questions of post-car mobility are reformulated. Such reformulation, I discuss, not only can act upon the imaginaries, but also have implications for urban projects. The notions of Effort, Agility, and Vehicular Units are presented and shown that together can create a “coordinate system” in which mobility discourses go beyond the previously mentioned polarities of car pedestrian, towards values that set in-between, in order to reinvent the “auto” mobility for a more sustainable future. I present each axis in extent, situate them within the context of their emergence, and argue for their relevance and potentials. Finally, I argue for broadening the development of these three notions into cogent and cohesive analytical forces to constitute major axes of transformation capable of engendering new sets of understandings and discourses – new imaginaries

Crossing Boundaries: The Transnational Third Space of Contemporary Chinese-Francophone Writers

Over the past two decades, a group of Chinese writers who pen their works in French, their adopted language, have garnered prizes in France and received international acclaim. The transnational voices of these writers have drawn attention to Chinese history, literature, and human-rights issues, as well as to their own diverse intersections with French culture. The four Francophone-Chinese writers studied—François Cheng (b. 1929), Gao Xingjian (b. 1940), Dai Sijie (b. 1954), and Shan Sa (b. 1972)—constitute themselves as subjects at least partially through their Chinese birth and French citizenship or residency and through the production of literary works that range from realist and historiographic to experimental novels and avant-garde theater productions. This study examines the ways they inhabit a world that is “between,” a space resonating with Eastern and Western literary, historical, cultural, and political references, arriving at what Cheng calls a “third way,” or in Homi Bhabha’s words, a liminal “Third Space,” integral to transnational literatures, but especially to those by Francophone writers who are part of the Sinophone diaspora. This study examines the narratives that unfold and subjectivities that are constructed in this enunciative Third Space. It considers the transcultural nature of the literary border crossings of these four writers in their works and their lives, the ways in which these writers and their texts exist in a Third Space, a notion that is sometimes problematic as conceived by Bhabha but which has been productively expanded upon by others, including Benita Parry, Edward W. Soja, Julia Lossau, Karin Ikas, and Gerhard Wagner. Gayatri Chakravorty Spivak’s ideas on the tension between borders and borderlessness, viewed through the study of border poetics, encompass the boundary-crossing narratives of writers such as Cheng, Gao, Dai, and Sa. This study focuses on the counternarratives that are created through the intertextual use of Western literary works, ranging from Balzac and Romain Rolland to Freud and Lacan, in Dai Sijie’s Balzac et la petite tailleuse chinoise (2000) and Le Complexe de Di (2003); the avant-garde experimentation of Gao in his plays and novels; and the ex-centric subjectivities constructed in two works concerning the 1989 Tiananmen Square uprising, Gao’s La Fuite (1992) and Sa’s Porte de la Paix céleste (1997)