Publications by Philippe Thévenaz

On the Linearity of Bayesian Interpolators for Non-Gaussian Continuous-Time AR(1) Processes

Philippe Thévenaz, Michaël Unser, Arash Amini, John Paul Ward

Bayesian estimation problems involving Gaussian distributions often result in linear estimation techniques. Nevertheless, there are no general statements as to whether the linearity of the Bayesian estimator is restricted to the Gaussian case. The two comm ...

Ieee-Inst Electrical Electronics Engineers Inc2013

Exponential splines and minimal-support bases for curve representation

Philippe Thévenaz, Michaël Unser, Ricard Delgado Gonzalo

Our interest is to characterize the spline-like integer-shift-invariant bases capable of reproducing exponential polynomial curves. We prove that any compact-support function that reproduces a subspace of the exponential polynomials can be expressed as the ...

Elsevier2012

GPU Prefilter for Accurate Cubic B-spline Interpolation

Philippe Thévenaz

Achieving accurate interpolation is an important requirement for many signal-processing applications. While nearest-neighbor and linear interpolation methods are popular due to their native GPU support, they unfortunately result in severe undesirable artif ...

Oxford University Press2012

Bi-Exponential Edge-Preserving Smoother

Philippe Thévenaz, Michaël Unser, Daniel Sage

Edge-preserving smoothers need not be taxed by a severe computational cost. We present, in this paper, a lean algorithm that is inspired by the bi-exponential filter and preserves its structure-a pair of one-tap recursions. By a careful but simple local ad ...

Institute of Electrical and Electronics Engineers2012

Snakes With an Ellipse-Reproducing Property

Philippe Thévenaz, Michaël Unser, Chandra Sekhar Seelamantula, Ricard Delgado Gonzalo

We present a new class of continuously defined parametric snakes using a special kind of exponential splines as basis functions. We have enforced our bases to have the shortest possible support subject to some design constraints to maximize efficiency. Whi ...

IEEE2012

The Ovuscule

Philippe Thévenaz, Michaël Unser, Ricard Delgado Gonzalo

We propose an active contour (a.k.a. snake) that takes the shape of an ellipse. Its evolution is driven by surface terms made of two contributions: the integral of the data over an inner ellipse, counterbalanced by the integral of the data over an outer el ...

IEEE2011

Non-Rigid Consistent Registration of 2D Image Sequences

Philippe Thévenaz

We present a novel algorithm for the registration of 2D image sequences that combines the principles of multiresolution B-spline-based elastic registration and those of bidirectional consistent registration. In our method, consecutive triples of images are ...

IOP Science2010

Regularized Interpolation for Noisy Images

Philippe Thévenaz, Michaël Unser, Sathish Ramani

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 im ...

Institute of Electrical and Electronics Engineers2010

Model-Based Estimation of Three-Dimensional Stiffness Parameters in Photonic-Force Microscopy

Andrzej Kulik, Philippe Thévenaz, Michaël Unser, Elena Bertseva, Amardeep Singh

We propose a system to characterize the 3-D diffusion properties of the probing bead trapped by a photonic-force microscope. We follow a model-based approach, where the model of the dynamics of the bead is given by the Langevin equation. Our procedure comb ...

Institute of Electrical and Electronics Engineers2010

Intracellular nanomanipulation by a photonic-force microscope with real-time acquisition of a 3D stiffness matrix

László Forró, Gérard Gremaud, Andrzej Kulik, Philippe Thévenaz, Michaël Unser, Giovanni Dietler, Stefania Puttini, Sylvia Jeney, Elena Bertseva, Amardeep Singh

A traditional photonic-force microscope (PFM) results in huge sets of data, which requires tedious numerical analysis. In this paper, we propose instead an analog signal processor to attain real-time capabilities while retaining the richness of the traditi ...

Institute of Physics2009

Variational B-Spline Level-Set: A Linear Filtering Approach for Fast Deformable Model Evolution

Philippe Thévenaz, Michaël Unser, Olivier Bernard

In the field of image segmentation, most level-set-based active-contour approaches take advantage of a discrete representation of the associated implicit function. We present in this paper a different formulation where the implicit function is modeled as a ...

IEEE2009

MOMS-based Programmable Sampling Rate Converters

Philippe Thévenaz

In this paper design options when implementing programmable sampling rate converters are discussed. The theory and performance of the classical and new converters based on maximum order and minimum support (MOMS) splines is presented. FPGA designs are show ...

2009

Short basis functions for constant-variance interpolation

Philippe Thévenaz, Michaël Unser, Thierry Blu

An interpolation model is a necessary ingredient of intensity-based registration methods. The properties of such a model depend entirely on its basis function, which has been traditionally characterized by features such as its order of approximation and it ...

Spie-Int Soc Optical Engineering, Po Box 10, Bellingham, Wa 98227-0010 Usa2008

Halton Sampling for Image Registration Based on Mutual Information

Philippe Thévenaz, Michaël Unser, Michel Bierlaire

Mutual information is a widely used similarity measure for aligning multimodal medical images. At its core it relies on the computation of a discrete joint histogram, which itself requires image samples for its estimation. In this paper we study the influe ...

Sampling Publishing2008

Elastic Image Registration of 2-D Gels for Differential and Repeatability Studies

Philippe Thévenaz, Michaël Unser

One of the main applications of electrophoretic 2-D gels is the analysis of differential responses between different conditions. For this reason, specific spots are present in one of the images, but not in the other. In some other occasions, the same exper ...

Wiley InterScience2008

Quantitative Morphometrical Characterization of Human Pronuclear Zygotes

Philippe Thévenaz, Michaël Unser

BACKGROUND: Identification of embryos with high implantation potential remains a challenge in in vitro fertilization (IVF). Subjective pronuclear (PN) zygote scoring systems have been developed for that purpose. The aim of this work was to provide a softwa ...

Oxford University Press2008

Parametric B-Spline Snakes on Distance Maps—Application to Segmentation of Histology Images

Philippe Thévenaz, Michaël Unser, François Aguet, Chandra Sekhar Seelamantula

We construct parametric active contours (snakes) for outlining cells in histology images. These snakes are defined in terms of cubic B-spline basis functions. We use a steerable ridge detector for obtaining a reliable map of the cell boundaries. Using the ...

EURASIP2008

Variational B-Spline Level-Set Method for Fast Image Segmentation

Philippe Thévenaz, Michaël Unser

In the field of image segmentation, most of level-set-based active contour approaches are based on a discrete representation of the associated implicit function. We present in this paper a different formulation where the level-set is modelled as a continuo ...

IEEE2008

Snakuscules

Philippe Thévenaz, Michaël Unser

A snakuscule (a minuscule snake) is the simplest active contour that we were able to design while keeping the quintessence of traditional snakes: an energy term governed by the data, and a regularization term. Our construction is an area-based snake, as op ...

IEEE2008

Myocardial perfusion assessment by use of system identification method in a one-compartment model

Philippe Thévenaz, Michel Kocher

Cardiovascular magnetic resonance has been shown to provide high data quality for myocardial perfusion assessment However, to analyze the perfusion data, some signal processing and modeling is needed to correct for motion related artifacts and limited spat ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2007