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Michaël Unser

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Publications associées (516)

Generalized Poisson Summation Formula for Tempered Distributions

Michaël Unser, Quy Ha Nguyen

The Poisson summation formula (PSF), which relates the sampling of an analog signal with the periodization of its Fourier transform, plays a key role in the classical sampling theory. In its current forms, the formula is only applicable to a limited class ...

IEEE2015

Fast Detection and Refined Scale Estimation Using Complex Isotropic Wavelets

Michaël Unser, Daniel Sage, Zsuzsanna Püspöki, John Paul Ward

The dyadic scaling in the discrete wavelet transform can lead to a loss of precision, in comparison to the computationally unrealistic continuous wavelet transform. To overcome this obstacle, we propose a novel method to locally scale wavelets between dyad ...

IEEE2015

Spline based iterative phase retrieval algorithm for X-ray differential phase contrast radiography

Michaël Unser, Masih Nilchian, Marco Stampanoni

Differential phase contrast imaging using grating interferometer is a promising alternative to conventional X-ray radiographic methods. It provides the absorption, differential phase and scattering information of the underlying sample simultaneously. Phase ...

Optical Soc Amer2015

Locally Refinable Parametric Snakes

Michaël Unser, Daniel Andreas Schmitter, Anaïs Laure Marie-Thérèse Badoual

Shape segmentation is an active field of research in biomedical imaging. In this context, we present a new parameterization of a snake that is locally refinable. We introduce the possibility of locally increasing the approximation power of the parametric m ...

IEEE2015

Learning Approach to Optical Tomography

Michaël Unser, Alexandre Goy, Cédric René Jean Vonesch, Ulugbek Kamilov, Demetri Psaltis

Optical tomography has been widely investigated for biomedical imaging applications. In recent years optical tomography has been combined with digital holography and has been employed to produce high-quality images of phase objects such as cells. In this p ...

Optical Soc Amer2015

Trigonometric Interpolation Kernel to Construct Deformable Shapes for User-Interactive Applications

Michaël Unser, Daniel Andreas Schmitter, Ricard Delgado Gonzalo

We present a new trigonometric basis function that is capable of perfectly reproducing circles, spheres and ellipsoids while at the same time being interpolatory. Such basis functions have the advantage that they allow to construct shapes through a sequenc ...

IEEE Institute of Electrical and Electronics Engineers2015

Divergence-Free Wavelet Frames

Michaël Unser, Emrah Bostan, John Paul Ward

We propose an efficient construction of wavelet frames in any number of dimensions that are divergence-free. Our approach is based on applying the Leray projector, which is scale-invariant, to a standard wavelet frame. We prove that the projected wavelets ...

IEEE Institute of Electrical and Electronics Engineers2015

Optimality of Operator-Like Wavelets for Representing Sparse AR(1) Processes

Michaël Unser, Pedram Pad

The discrete cosine transform (DCT) is known to be asymptotically equivalent to the Karhunen-Loève transform (KLT) of Gaussian first-order auto-regressive (AR(1)) processes. Since being uncorrelated under the Gaussian hypothesis is synonymous with independ ...

IEEE2015

Isotropic Inverse-Problem Approach for Two-Dimensional Phase Unwrapping

Michaël Unser, Ulugbek Kamilov, Demetri Psaltis

We propose a new technique for two-dimensional phase unwrapping. The unwrapped phase is found as the solution of an inverse problem that consists in the minimization of an energy functional. The latter includes a weighted data fidelity term that favors spa ...

JOSA2015

Interior Tomography Using 1D Generalized Total Variation. Part II: Multiscale Implementation

Michaël Unser, John Paul Ward

To address the classic interior tomography problem where projections at each view extend only to the shadow of a circular region completely interior to the subject being scanned, previously we showed that the exact recovery of two- and three-dimensional pi ...

Siam Publications2015

Optimized Kaiser-Bessel Window Functions for Computed Tomography

Michaël Unser, Cédric René Jean Vonesch, Masih Nilchian, John Paul Ward

Kaiser-Bessel window functions are frequently used to discretize tomographic problems because they have two desirable properties: 1) their short support leads to a low computational cost and 2) their rotational symmetry makes their imaging transform indepe ...

Ieee-Inst Electrical Electronics Engineers Inc2015

Interior Tomography Using 1D Generalized Total Variation. Part I: Mathematical Foundation

Michaël Unser, John Paul Ward

Motivated by the interior tomography problem, we propose a method for exact reconstruction of a region of interest of a function from its local Radon transform in any number of dimensions. Our aim is to verify the feasibility of a one-dimensional reconstru ...

Siam Publications2015

Optimized Steerable Wavelets for Texture Analysis of Lung Tissue In 3-D CT: Classification of Usual Interstitial Pneumonia

Michaël Unser, Adrien Raphaël Depeursinge, Pedram Pad

Our aim is to optimize wavelet-based feature extraction for differentiating between the classical versus atypical pattern of usual interstitial pneumonia (UIP) in volumetric CT. Our proposal is to act on the bandwidth of steerable wavelets while maintainin ...

IEEE2015

Compressibility of Symmetric-α-Stable Processes

Michaël Unser, John Paul Ward, Julien René Pierre Fageot

Within a deterministic framework, it is well known that n-term wavelet approximation rates of functions can be deduced from their Besov regularity. We use this principle to determine approximation rates for symmetric-α-stable (SαS) stochastic processes. Fi ...

IEEE2015

Analysis of S. pombe SIN protein association to the SPB reveals two genetically separable states of the SIN

Michaël Unser, Daniel Sage, Viesturs Simanis, Daniel Andreas Schmitter, Andrea Krapp, Jacques Rougemont, Anastasia Chasapi, Ioannis Xenarios

The Schizosaccharomyces pombe septation initiation network (SIN) regulates cytokinesis, and asymmetric association of SIN proteins with the mitotic spindle pole bodies (SPBs) is important for its regulation. Here, we have used semi-automated image analysis ...

Company Of Biologists Ltd2015

Template-Free Wavelet-Based Detection of Local Symmetries

Michaël Unser, Zsuzsanna Püspöki

Our goal is to detect and group different kinds of local symmetries in images in a scale- and rotation-invariant way. We propose an efficient wavelet-based method to determine the order of local symmetry at each location. Our algorithm relies on circular h ...

IEEE2015

Efficient Shape Priors for Spline-Based Snakes

Michaël Unser, Daniel Andreas Schmitter, Virginie Sophie Uhlmann, Ricard Delgado Gonzalo

Parametric active contours are an attractive approach for image segmentation, thanks to their computational efficiency. They are driven by application-dependent energies that reflect the prior knowledge on the object to be segmented. We propose an energy i ...

2015

Similarity-Based Shape Priors for 2D Spline Snakes

Michaël Unser, Daniel Andreas Schmitter

We present a new formulation of a shape space containing all continuously defined 2D spline curves up to a similarity transform of a reference shape. We are able to measure a distance between an arbitrary curve and the shape space itself. Our contribution ...

IEEE2015

Snakes on a Plane [A perfect snap for bioimage analysis]

Michaël Unser, Daniel Andreas Schmitter, Virginie Sophie Uhlmann, Ricard Delgado Gonzalo

2015

Stressed Mycobacteria Use the Chaperone ClpB to Sequester Irreversibly Oxidized Proteins Asymmetrically Within and Between Cells

Michaël Unser, Olivia Mariani, John McKinney, Neeraj Dhar

Mycobacterium tuberculosis (Mtb) defends itself against host immunity and chemotherapy at several levels, including the repair or degradation of irreversibly oxidized proteins (IOPs). To investigate how Mtb deals with IOPs that can neither be repaired nor ...

Cell Press2015

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