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13
Fast parametric elastic image registration
 IEEE Transactions on Image Processing
, 2003
"... Abstract—We present an algorithm for fast elastic multidimensional intensitybased image registration with a parametric model of the deformation. It is fully automatic in its default mode of operation. In the case of hard realworld problems, it is capable of accepting expert hints in the form of so ..."
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Cited by 102 (8 self)
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Abstract—We present an algorithm for fast elastic multidimensional intensitybased image registration with a parametric model of the deformation. It is fully automatic in its default mode of operation. In the case of hard realworld problems, it is capable of accepting expert hints in the form of soft landmark constraints. Much fewer landmarks are needed and the results are far superior compared to pure landmark registration. Particular attention has been paid to the factors influencing the speed of this algorithm. The Bspline deformation model is shown to be computationally more efficient than other alternatives. The algorithm has been successfully used for several twodimensional (2D) and threedimensional (3D) registration tasks in the medical domain, involving MRI, SPECT, CT, and ultrasound image modalities. We also present experiments in a controlled environment, permitting an exact evaluation of the registration accuracy. Test deformations are generated automatically using a random hierarchical fractional waveletbased generator. Index Terms—Elastic registration, image registration, landmarks, splines. I.
Unwarping of Unidirectionally Distorted EPI Images
, 2000
"... Echoplanar imaging (EPI) is a fast nuclear magnetic resonance imaging method. Unfortunately, local magnetic field inhomogeneities induced mainly by the subject 's presence cause significant geometrical distortion, predominantly along the phaseencoding direction, which must be undone to allow ..."
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Cited by 40 (7 self)
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Echoplanar imaging (EPI) is a fast nuclear magnetic resonance imaging method. Unfortunately, local magnetic field inhomogeneities induced mainly by the subject 's presence cause significant geometrical distortion, predominantly along the phaseencoding direction, which must be undone to allow for meaningful further processing. So far, this aspect has been too often neglected.
Robust realtime segmentation of images and videos uisng a smoothingspline snakebased algorithm
 IEEE Transactions on Image Processing
, 2005
"... Abstract—This paper deals with fast image and video segmentation using active contours. Regionbased active contours using level sets are powerful techniques for video segmentation, but they suffer from large computational cost. A parametric active contour method based on BSpline interpolation has ..."
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Cited by 25 (6 self)
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Abstract—This paper deals with fast image and video segmentation using active contours. Regionbased active contours using level sets are powerful techniques for video segmentation, but they suffer from large computational cost. A parametric active contour method based on BSpline interpolation has been proposed in [26] to highly reduce the computational cost, but this method is sensitive to noise. Here, we choose to relax the rigid interpolation constraint in order to robustify our method in the presence of noise: by using smoothing splines, we trade a tunable amount of interpolation error for a smoother spline curve. We show by experiments on natural sequences that this new flexibility yields segmentation results of higher quality at no additional computational cost. Hence, realtime processing for moving objects segmentation is preserved. I.
Smoothing BSpline Active Contour or Fast and Robust Image and Video Segmentation
 In International Conference on Image Processing
, 2003
"... This paper deals with fast image and video segmentation using active contours. Region based active contours using levelsets are powerful techniques for video segmentation but they suffer from large computational cost. A parametric active contour method based on BSpline interpolation has been propo ..."
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Cited by 18 (10 self)
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This paper deals with fast image and video segmentation using active contours. Region based active contours using levelsets are powerful techniques for video segmentation but they suffer from large computational cost. A parametric active contour method based on BSpline interpolation has been proposed in [1] to highly reduce the computational cost but this method is sensitive to noise. Here, we choose to relax the rigid interpolation constraint in order to robustify our method in the presence of noise: by using smoothing splines, we trade a tunable amount of interpolation error for a smoother spline curve. We show by experiments on natural sequences that this new flexibility yields segmentation results of higher quality at no additional computational cost. Hence real time processing for moving objects segmentation is preserved.
Flexible motionadaptive video coding with redundant expansions
 IEEE TRANSACTIONS ON CIRCUIT AND SYSTEMS FOR VIDEO TECHNOLOGY
, 2006
"... This paper presents a highly flexible video coding scheme, based on the use of a redundant dictionary of spatiotemporal threedimensional (3D) functions. Directionality and anisotropic scaling are key ingredients to the spatial components, which form a rich collection of twodimensional (2D) visu ..."
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Cited by 10 (5 self)
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This paper presents a highly flexible video coding scheme, based on the use of a redundant dictionary of spatiotemporal threedimensional (3D) functions. Directionality and anisotropic scaling are key ingredients to the spatial components, which form a rich collection of twodimensional (2D) visual primitives. The temporal component is tuned to capture most of the energy in the temporal signal evolution, along motion trajectories in the video sequence. The video coding scheme (MP3D) first computes motion trajectories that are eventually entropy coded and sent as side information to the decoder. It then applies a spatiotemporal decomposition along motion trajectories, using an adaptive approximation algorithm based on matching pursuit (MP). Quantized coefficients and basis function parameters are entropycoded in a embedded stream that is constructed to respect multiple rate constraints. The geometric properties of the 2D primitive dictionary allow for flexible spatial resolution adaptation, so that the flexible MP3D stream enables decoding at different spatiotemporal resolutions, and multiple rates. The MP3D scheme is shown to provide ratedistortion performance that are comparable with stateoftheart schemes, such as H.264, MPEG4, at low and medium bit rate. However, the use of a redundant dictionary is penalizing at high coding rate, which makes the MP3D algorithm mostly interesting for low rate applications, or as a flexible base layer in hierarchical coding schemes.
Regularized Interpolation for Noisy Images
"... Abstract—Interpolation is the means by which a continuously defined model is fit to discrete data samples. When the data samples are exempt of noise, it seems desirable to build the model by fitting them exactly. In medical imaging, where quality is of paramount importance, this ideal situation unfo ..."
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Cited by 3 (2 self)
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Abstract—Interpolation is the means by which a continuously defined model is fit to discrete data samples. When the data samples are exempt of noise, it seems desirable to build the model by fitting them exactly. In medical imaging, where quality is of paramount importance, this ideal situation unfortunately does not occur. In this paper, we propose a scheme that improves on the quality by specifying a tradeoff between fidelity to the data and robustness to the noise. We resort to variational principles, which allow us to impose smoothness constraints on the model for tackling noisy data. Based on shift, rotation, and scaleinvariant requirements on the model, we show that thenorm of an appropriate vector derivative is the most suitable choice of regularization for this purpose. In addition to Tikhonovlike quadratic regularization, this includes edgepreserving totalvariationlike (TV) regularization. We give algorithms to recover the continuously defined model from noisy samples and also provide a datadriven scheme to determine the optimal amount of regularization. We validate our method with numerical examples where we demonstrate its superiority over an exact fit as well as the benefit of TVlike nonquadratic regularization over Tikhonovlike quadratic regularization. Index Terms—Interpolation, regularization, regularization parameter, splines, Tikhonov functional, totalvariation functional.
Sparse Approximation Using MTerm Pursuits with Applications to Image and Video Compression
"... This paper introduces an algorithm for sparse approximation in redundant dictionaries, called the MTerm Pursuit (MTP), based on the matching pursuit approach (MP). This algorithm decomposes the signal into a linear combination of selected atoms, chosen to represent the signal components. The MTP al ..."
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Cited by 1 (1 self)
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This paper introduces an algorithm for sparse approximation in redundant dictionaries, called the MTerm Pursuit (MTP), based on the matching pursuit approach (MP). This algorithm decomposes the signal into a linear combination of selected atoms, chosen to represent the signal components. The MTP algorithm provides adaptive representation for signals in any dictionary. The basic idea behind the MTP, is to partition the dictionary into disjoint subdictionaries, each carrying some meaningful information. Then it iteratively finds aterm approximation. During each iteration, atoms, where, are selected based on some thresholding parameter. A comparison against the matching pursuit algorithm is provided both from the theoretical and the practical point of views. The approximation performances of the MTP algorithm have shown to yield comparable results with those of the matching pursuit. Furthermore, it has a reduced computational complexity compared to MP. Two applications have been developed using the MTP: (i) an image compression scheme and (ii) a video compression technique. Both schemes have demonstrated the abilities of the MTP algorithm to be used for compact representation and coding in either image or video compression fields. The MTPbased image coder yields comparable results with those of JPEG2000 in terms of ratedistortion and scalability. Whereas for the MTPbased video coder, it is shown to provide interesting performances when compared to the stateoftheart coding schemes, such as H.264, MPEG4 or the scalable MP3D, in terms of ratedistortion.
Numerical Differentiation As An Example For Inverse Problems
, 1998
"... . We present an error analysis for the numerical differentiation of noisy data via smoothing cubic splines. Our treatment is elementary enough to be included in a course on numerical analysis. Still, it accounts for all numerical problems that arise in the solution of much more complex illposed inv ..."
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Cited by 1 (0 self)
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. We present an error analysis for the numerical differentiation of noisy data via smoothing cubic splines. Our treatment is elementary enough to be included in a course on numerical analysis. Still, it accounts for all numerical problems that arise in the solution of much more complex illposed inverse problems. Key words. Numerical differentiation, cubic splines, Tikhonov regularization, discrepancy principle AMS subject classifications. 6501, 65D07, 65D25, 41A15, 65J20 1. Introduction. Reliable numerical simulations of technical processes require detailed knowledge of the underlying physical models. Consider the simulation of heat transport in a homogeneous medium (in 1D), where the heat conductivity must be described by different models depending on the magnitude of the temperature. In this case the temperature distribution u is the solution of the onedimensional parabolic differential equation u t = \Gamma a(u)u x \Delta x ; 0 ! x ! 1 ; 0 ! t ! T ; (1.1) involving some n...
Manipulators under ElectroMechanical Constraints
"... Abstract – A simple direct method is applied to solve the problem of optimal trajectory generation for serial manipulators under electromechanical constraints. The goal is to increase the robot productivity by using its electric motors outside of their continuous operating range. This is possible o ..."
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Abstract – A simple direct method is applied to solve the problem of optimal trajectory generation for serial manipulators under electromechanical constraints. The goal is to increase the robot productivity by using its electric motors outside of their continuous operating range. This is possible only if dynamics of actuators is considered and inherent constraints are included. For this purpose, a general electromechanical model for serial robots is first presented. Then, the problem of trajectory generation is cast as a nonlinear optimization program using an approximation of joint position variables by means of algebraic polynomial splines which interpolate a set of control points. Finally, the optimization problem is solved using a sequential quadratic programming method for the unknown transfer time and the unknown position of control points, while minimizing a cost function and respecting elecromechanical constraints. Numerical and experimental results are presented to illustrate the efficiency of the proposed
SCATTERED DATA AND IT’S APPLICATION
, 2002
"... A numerical differentiation method for scattered data and it’s application by ..."
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A numerical differentiation method for scattered data and it’s application by