1,721,038 research outputs found
Volumetric Deformable Models with Parameter Functions: A New Approach to the 3D Moton Analysis of the LV from MRI-SPAMM
No full text
Deformable models with parameter functions for cardiac motion analysis from tagged MRI data
No full textWe present a new method for analyzing the motion of the heart's left ventricle (LV) from tagged magnetic resonance imaging (MRI) data, Our technique is based on the development of a new class of physics-based deformable models whose parameters are functions. They allow the definition of new parameterized primitives and parameterized deformations which can capture the local shape variation of a complex object, Furthermore, these parameters are intuitive and require no complex post-processing in order to be used by a physician, Using a physics-based approach, we convert the geometric models into dynamic models that deform due to forces exerted from the datapoints and conform to the given dataset. We present experiments involving the extraction of the shape and motion of the LV's mid-wall during systole from tagged MRI data based on a few parameter functions, Furthermore, by plotting the variations over time of the extracted LV model parameters from normal and abnormal heart data along the long axis, we are able to quantitatively characterize their differences
The Best Of Both Worlds: Combining 3d Deformable Models With Active Shape Models
No full textReliable 3D tracking is still a difficult task. Most parametrized 3D deformable models rely on the accurate extraction of image features for updating their parameters, and are prone to failures when the underlying feature distribution assumptions are invalid. Active Shape Models (ASMs), on the other hand, are based on learning, and thus require fewer reliable local image features than parametrized 3D models, but fail easily when they encounter a situation for which they were not trained. In this paper, we develop an integrated framework that combines the strengths of both 3D deformable models and ASMs. The 3D model governs the overall shape, orientation and location, and provides the basis for statistical inference on both the image features and the parameters. The ASMs, in contrast, provide the majority of reliable 2D image features over time, and aid in recovering from drift and total occlusions. The framework dynamically selects among different ASMs to compensate for large viewpoint changes due to head rotations. This integration allows the robust tracking of faces and the estimation of both their rigid and nonrigid motions. We demonstrate the strength of the framework in experiments that include automated 3D model fitting and facial expression tracking for a variety of applications, including sign language. ©2007 IEEE.Beymer, D., Poggio, T., Image representations for visual learning (1996) Science, 272 (5270), pp. 1905-1909Blake, A., Isard, M., (1998) Active Contours: The Application of Techniques from Graphics, Vision, Control Theory and Statistics to Visual Tracking of Shapes in Motion, , Springer-VerlagBlanz, V., Vetter, T., A morphable model for the synthesis of 3D faces (1999) SIGGRAPH, pp. 187-194Brand, M., Morphable 3D models from video (2001) CVPRCootes, T., Taylor, C., Active shape models - their training and application (1995) CVIU, 61 (1), pp. 38-59de Carlo, D., Metaxas, D., Optical flow constraints on deformable models with applications to face tracking (2000) IJCV, 38 (2), pp. 99-127. , JulyDimitrijevic, M., Ilic, S., Fua, P., Accurate face models from uncalibrated and ill-lit video sequences (2004) CVPR, pp. 1034-1041Goldenstein, S., Vogler, C., When occlusions are outliers (2006) Workshop on the 25 Years of RANSAC (in conjunction with CVPR)Goldenstein, S., Vogler, C., Metaxas, D., Statistical Cue Integration in DAG Deformable Models (2003) PAMI, 25 (7), pp. 801-813Goldenstein, S., Vogler, C., Metaxas, D., 3D facial tracking from corrupted movie sequences (2004) CVPRGoodall, C., Procrustes methods in the statistical analysis of shape (1991) Journal of the Royal Statistical Society B, 53, pp. 285-339Isard, M., Blake, A., (1998) Condensation: Conditional density propagation for visual tracking, 29 (1), pp. 5-28Jones, M., Poggio, T., Multidimensional morphable models (1998) ICCV, pp. 683-688Lanitis, A., Taylor, C.J., Cootes, T.F., Automatic interpretation and coding of face images using flexible models (1997) PAMI, 19 (7), pp. 743-756Pighin, F., Szeliski, R., Salesin, D., Modeling and animating realistic faces from images (2002) IJCV, 50 (2), pp. 143-169Tao, H., Huang, T., Visual Estimation and Compression of Facial Motion Parameters: Elements of a 3D Model-Based Video Coding System (2002) IJCV, 50 (2), pp. 111-125Cootes, T.F., Edwards, G., Taylor, C.J., Active appearance models (2001) PAMI, 23 (6), pp. 681-685Viola, P., Jones, M., Robust real-time face detection (2004) IJCV, 57 (2), pp. 137-154Vogler, C., Goldenstein, S., Stolfi, J., Pavlovic, V., Metaxas, D., Outlier rejection in high-dimensional deformable models (2007) IVC, 25 (3), pp. 274-284Wang, L., Hu, W., Tan, T., Face tracking using motion-guided dynamic template matching (2002) ACCVXiao, J., Baker, S., Matthews, I., Kanade, T., (2004) Real-time combined 2d+3d active appearance models, , CVP
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
