Privacy-Preserving Screen Capture: Closing the Loop for Medical Informatics Usability

As information technology permeates healthcare (particularly provider-facing systems), maximizing system effectiveness requires the ability to document and analyze tricky or troublesome usage scenarios. However, real-world medical applications are typically replete with privacy-sensitive data regarding patients, diagnoses, clinicians, and EMR user interface details; any instrumentation for screen capture (capturing and recording the scenario depicted on the screen) needs to respect these privacy constraints. Furthermore, real-world medical informatics systems are typically composed of modules from many sources, mission-critical and often closed-source; any instrumentation for screen capture cannot rely on access to structured output or software internals. In this paper, we present a solution: a system that combines keyboard video mouse (KVM) capture with automatic text redaction (and interactively selectable unredaction) to produce precise technical content that can enrich stakeholder communications and improve end-user influence on system evolution. KVM-based capture makes our system both application and operating-system independent because it eliminates software-interface dependencies on capture targets. Using a corpus of EMR screenshots, we present empirical measurements of redaction effectiveness and processing latency to demonstrate system performances. We discuss how these techniques can translate into instrumentation systems that improve real-world medical informatics deployments

Seguimiento de objetos en video usando contornos activos y bounding boxes

El seguimiento de objetos en forma automática a lo largo de una secuencia de imágenes tiene aplicaciones en áreas tan diversas como robótica, animación, sistemas de seguridad o diagnóstico médico. El algoritmo de seguimiento utilizado en este trabajo comienza con la definición de una curva B-Spline que es el área inicial de búsqueda del contorno de un objeto. Luego se consideran una serie de segmentos de rectas normales a esta curva y se aplica algún método de detección de bordes para hallar puntos sobre el contorno a lo largo de las rectas. Para que el algoritmo de seguimiento del objeto sea exitoso es necesario que la estimación inicial sea muy precisa. En este trabajo se presenta un nuevo método estable y eficiente para evitar errores de parametrización al ajustar el contorno del objeto con una curva B-Spline al comienzo del método de seguimiento. Se utiliza una estructura de aceleración para evitar conflictos al estimar el contorno del objeto. El algoritmo modificado se prueba en videos reales y se observan excelentes resultados.The automatic tracking of objects along a sequence of images has applications in different areas as robotics, animation, security systems or medical diagnosis. The tracking algorithm used in this paper starts fitting the contour of an object, using a B-Spline curve as the initial search region. The next step is to sample normal vectors at regularly-spaced points along this curve and to detect points on the border of the object by applying some image-processing filter along the curve normals. A good initial estimate is required for the tracking algorithm to be successful. This paper presents a method to avoid parametrization errors when fitting the outline of the object at the beginning of the tracking. It has the advantage of being simple and efficient. Conflicts when fitting the contour of the object are avoided using an acceleration structure. The modified algorithm is tested against real videos with excellent results.V Workshop de Computación Gráfica, Imágenes Y VisualizaciónRed de Universidades con Carreras en Informática (RedUNCI

Seguimiento de objetos en video usando contornos activos y bounding boxes

El seguimiento de objetos en forma automática a lo largo de una secuencia de imágenes tiene aplicaciones en áreas tan diversas como robótica, animación, sistemas de seguridad o diagnóstico médico. El algoritmo de seguimiento utilizado en este trabajo comienza con la definición de una curva B-Spline que es el área inicial de búsqueda del contorno de un objeto. Luego se consideran una serie de segmentos de rectas normales a esta curva y se aplica algún método de detección de bordes para hallar puntos sobre el contorno a lo largo de las rectas. Para que el algoritmo de seguimiento del objeto sea exitoso es necesario que la estimación inicial sea muy precisa. En este trabajo se presenta un nuevo método estable y eficiente para evitar errores de parametrización al ajustar el contorno del objeto con una curva B-Spline al comienzo del método de seguimiento. Se utiliza una estructura de aceleración para evitar conflictos al estimar el contorno del objeto. El algoritmo modificado se prueba en videos reales y se observan excelentes resultados.The automatic tracking of objects along a sequence of images has applications in different areas as robotics, animation, security systems or medical diagnosis. The tracking algorithm used in this paper starts fitting the contour of an object, using a B-Spline curve as the initial search region. The next step is to sample normal vectors at regularly-spaced points along this curve and to detect points on the border of the object by applying some image-processing filter along the curve normals. A good initial estimate is required for the tracking algorithm to be successful. This paper presents a method to avoid parametrization errors when fitting the outline of the object at the beginning of the tracking. It has the advantage of being simple and efficient. Conflicts when fitting the contour of the object are avoided using an acceleration structure. The modified algorithm is tested against real videos with excellent results.V Workshop de Computación Gráfica, Imágenes Y VisualizaciónRed de Universidades con Carreras en Informática (RedUNCI

Parallel Geometric Algorithms for Multi-Core Computers

International audienceComputers with multiple processor cores using shared memory are now ubiquitous. In this paper, we present several parallel geometric algorithms that specifically target this environment, with the goal of exploiting the additional computing power. The d-dimensional algorithms we describe are (a) spatial sorting of points, as is typically used for preprocessing before using incremental algorithms, (b) kd-tree construction, (c) axis-aligned box intersection computation, and finally (d) bulk insertion of points in Delaunay triangulations for mesh generation algorithms or simply computing Delaunay triangulations. We show experimental results for these algorithms in 3D, using our implementations based on the Computational Geometry Algorithms Library (CGAL, http://www.cgal.org/). This work is a step towards what we hope will become a parallel mode for CGAL, where algorithms automatically use the available parallel resources without requiring significant user intervention

Parallel Geometric Algorithms for Multi-Core Computers

Computers with multiple processor cores using shared memory are now ubiquitous. In this paper, we present several parallel geometric algorithms that specifically target this environment, with the goal of exploiting the additional computing power. The d-dimensional algorithms we describe are (a) spatial sorting of points, as is typically used for preprocessing before using incremental algorithms, (b) kd-tree construction, (c) axis-aligned box intersection computation, and finally (d) bulk insertion of points in Delaunay triangulations for mesh generation algorithms or simply computing Delaunay triangulations. We show experimental results for these algorithms in 3D, using our implementations based on the Computational Geometry Algorithms Library (CGAL, http://www.cgal.org/). This work is a step towards what we hope will become a parallel mode for CGAL, where algorithms automatically use the available parallel resources without requiring significant user intervention

Hierarchical and Adaptive Filter and Refinement Algorithms for Geometric Intersection Computations on GPU

Geometric intersection algorithms are fundamental in spatial analysis in Geographic Information System (GIS). This dissertation explores high performance computing solution for geometric intersection on a huge amount of spatial data using Graphics Processing Unit (GPU). We have developed a hierarchical filter and refinement system for parallel geometric intersection operations involving large polygons and polylines by extending the classical filter and refine algorithm using efficient filters that leverage GPU computing. The inputs are two layers of large polygonal datasets and the computations are spatial intersection on pairs of cross-layer polygons. These intersections are the compute-intensive spatial data analytic kernels in spatial join and map overlay operations in spatial databases and GIS. Efficient filters, such as PolySketch, PolySketch++ and Point-in-polygon filters have been developed to reduce refinement workload on GPUs. We also showed the application of such filters in speeding-up line segment intersections and point-in-polygon tests. Programming models like CUDA and OpenACC have been used to implement the different versions of the Hierarchical Filter and Refine (HiFiRe) system. Experimental results show good performance of our filter and refinement algorithms. Compared to standard R-tree filter, on average, our filter technique can still discard 76% of polygon pairs which do not have segment intersection points. PolySketch filter reduces on average 99.77% of the workload of finding line segment intersections. Compared to existing Common Minimum Bounding Rectangle (CMBR) filter that is applied on each cross-layer candidate pair, the workload after using PolySketch-based CMBR filter is on average 98% smaller. The execution time of our HiFiRe system on two shapefiles, namely USA Water Bodies (contains 464K polygons) and USA Block Group Boundaries (contains 220K polygons), is about 3.38 seconds using NVidia Titan V GPU

Screen Capture for Sensitive Systems

Maintaining usable security in application domains such as healthcare or power systems requires an ongoing conversation among stakeholders such as end-users, administrators, developers, and policy makers. Each party has power to influence the design and implementation of the application and its security posture, and effective communication among stakeholders is one key to achieving influence and adapting an application to meet evolving needs. In this thesis, we develop a system that combines keyboard/video/mouse (KVM) capture with automatic text redaction to produce precise technical content that can enrich stakeholder communications, improve end-user influence on system evolution, and help reveal the definition of ``usable security.\u27\u27 Text-redacted screen captures reduce sensitivity of captured material and thus can facilitate timely data sharing among stakeholders. KVM-based capture makes our system both application and operating-system independent because it eliminates software-interface dependencies on capture targets. Thus, our work can be used to instrument closed or certified systems where capture software cannot be installed or documentation and support lack. It can instrument widely-varying platforms that lack standards-compliance and interoperability or redact special document formats while displayed onscreen. We present three techniques for redacting text from screenshots and two redaction applications. One application can capture, text redact, and edit screen video and the other can text redact and edit static screenshots. We also present empirical measurements of redaction effectiveness and processing latency to demonstrate system performance. When applied to our principal dataset, redaction removes text with over 93\% accuracy and simultaneously preserves more than 76\% of image pixels on average. Thus by default, it retains more visual context than a technique such as blindly redacting entire screenshots. Finally, our system redacts each screenshot in 0.1 to 21 seconds depending on which technique it applies

Theory and algorithms for swept manifold intersections

Recent developments in such fields as computer aided geometric design, geometric modeling, and computational topology have generated a spate of interest towards geometric objects called swept volumes. Besides their great applicability in various practical areas, the mere geometry and topology of these entities make them a perfect testbed for novel approaches aimed at analyzing and representing geometric objects. The structure of swept volumes reveals that it is also important to focus on a little simpler, although a very similar type of objects - swept manifolds. In particular, effective computability of swept manifold intersections is of major concern. The main goal of this dissertation is to conduct a study of swept manifolds and, based on the findings, develop methods for computing swept surface intersections. The twofold nature of this goal prompted a division of the work into two distinct parts. At first, a theoretical analysis of swept manifolds is performed, providing a better insight into the topological structure of swept manifolds and unveiling several important properties. In the course of the investigation, several subclasses of swept manifolds are introduced; in particular, attention is focused on regular and critical swept manifolds. Because of the high applicability, additional effort is put into analysis of two-dimensional swept manifolds - swept surfaces. Some of the valuable properties exhibited by such surfaces are generalized to higher dimensions by introducing yet another class of swept manifolds - recursive swept manifolds. In the second part of this work, algorithms for finding swept surface intersections are developed. The need for such algorithms is necessitated by a specific structure of swept surfaces that precludes direct employment of existing intersection methods. The new algorithms are designed by utilizing the underlying ideas of existing intersection techniques and making necessary technical modifications. Such modifications are achieved by employing properties of swept surfaces obtained in the course of the theoretical study. The intersection problems is also considered from a little different prospective. A novel, homology based approach to local characterization of intersections of submanifolds and s-subvarieties of a Euclidean space is presented. It provides a method for distinguishing between transverse and tangential intersection points and determining, in some cases, whether the intersection point belongs to a boundary. At the end, several possible applications of the obtained results are described, including virtual sculpting and modeling of heterogeneous materials