Search Results for author: Xavier Pennec

Found 9 papers, 3 papers with code

Principal subbundles for dimension reduction

no code implementations6 Jul 2023 Morten Akhøj, James Benn, Erlend Grong, Stefan Sommer, Xavier Pennec

In this paper we demonstrate how sub-Riemannian geometry can be used for manifold learning and surface reconstruction by combining local linear approximations of a point cloud to obtain lower dimensional bundles.

Dimensionality Reduction Surface Reconstruction

Geodesic squared exponential kernel for non-rigid shape registration

no code implementations22 Dec 2021 Florent Jousse, Xavier Pennec, Hervé Delingette, Matilde Gonzalez

This work addresses the problem of non-rigid registration of 3D scans, which is at the core of shape modeling techniques.

Cardiac Motion Modeling with Parallel Transport and Shape Splines

no code implementations17 Feb 2021 Nicolas Guigui, Pamela Moceri, Maxime Sermesant, Xavier Pennec

In cases of pressure or volume overload, probing cardiac function may be difficult because of the interactions between shape and deformations. In this work, we use the LDDMM framework and parallel transport to estimate and reorient deformations of the right ventricle.

Geomstats: A Python Package for Riemannian Geometry in Machine Learning

1 code implementation ICLR 2019 Nina Miolane, Alice Le Brigant, Johan Mathe, Benjamin Hou, Nicolas Guigui, Yann Thanwerdas, Stefan Heyder, Olivier Peltre, Niklas Koep, Hadi Zaatiti, Hatem Hajri, Yann Cabanes, Thomas Gerald, Paul Chauchat, Christian Shewmake, Bernhard Kainz, Claire Donnat, Susan Holmes, Xavier Pennec

We introduce Geomstats, an open-source Python toolbox for computations and statistics on nonlinear manifolds, such as hyperbolic spaces, spaces of symmetric positive definite matrices, Lie groups of transformations, and many more.

BIG-bench Machine Learning Clustering +2

Curvature effects on the empirical mean in Riemannian and affine Manifolds: a non-asymptotic high concentration expansion in the small-sample regime

1 code implementation18 Jun 2019 Xavier Pennec

For distributions that are highly concentrated around their mean, and for any finite number of samples, we establish explicit Taylor expansions on the first and second moment of the empirical mean thanks to a new Taylor expansion of the Riemannian log-map in affine connection spaces.

Differential Geometry Statistics Theory Statistics Theory

A model of brain morphological changes related to aging and Alzheimer's disease from cross-sectional assessments

no code implementations23 May 2019 Raphaël Sivera, Hervé Delingette, Marco Lorenzi, Xavier Pennec, Nicholas Ayache

In this study we propose a deformation-based framework to jointly model the influence of aging and Alzheimer's disease (AD) on the brain morphological evolution.

Automatically Segmenting the Left Atrium from Cardiac Images Using Successive 3D U-Nets and a Contour Loss

no code implementations6 Dec 2018 Shuman Jia, Antoine Despinasse, ZiHao Wang, Hervé Delingette, Xavier Pennec, Pierre Jaïs, Hubert Cochet, Maxime Sermesant

In this preliminary study, we propose automated, two-stage, three-dimensional U-Nets with convolutional neural network, for the challenging task of left atrial segmentation.

Anatomy Image Segmentation +3

geomstats: a Python Package for Riemannian Geometry in Machine Learning

2 code implementations ICLR 2019 Nina Miolane, Johan Mathe, Claire Donnat, Mikael Jorda, Xavier Pennec

This paper also presents a review of manifolds in machine learning and an overview of the geomstats package with examples demonstrating its use for efficient and user-friendly Riemannian geometry.

BIG-bench Machine Learning Riemannian optimization

Template shape estimation: correcting an asymptotic bias

no code implementations6 Sep 2016 Nina Miolane, Susan Holmes, Xavier Pennec

We use tools from geometric statistics to analyze the usual estimation procedure of a template shape.

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