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Variational regularization of ill-posed inverse problems is based on minimizing the sum of a data fidelity term and a regularization term. The balance between them is tuned using a positive regularization parameter, whose automatic choice…

Numerical Analysis · Mathematics 2025-11-12 Markus Juvonen , Bjørn Jensen , Ilmari Pohjola , Yiqiu Dong , Samuli Siltanen

We describe and examine an algorithm for tomographic image reconstruction where prior knowledge about the solution is available in the form of training images. We first construct a nonnegative dictionary based on prototype elements from the…

Computer Vision and Pattern Recognition · Computer Science 2015-08-18 Sara Soltani , Martin S. Andersen , Per Christian Hansen

We propose two new variational models aimed to outperform the popular total variation (TV) model for image restoration with L$_2$ and L$_1$ fidelity terms. In particular, we introduce a space-variant generalization of the TV regularizer,…

Image and Video Processing · Electrical Eng. & Systems 2019-06-28 Alessandro Lanza , Serena Morigi , Monica Pragliola , Fiorella Sgallari

A new parameter choice rule for inverse problems is introduced. This parameter choice rule was developed for total variation regularization in electron tomography and might in general be useful for $L^1$ regularization of inverse problems…

Numerical Analysis · Mathematics 2008-04-28 Hans Rullgård

Magnetic resonance fingerprinting (MRF) provides a unique concept for simultaneous and fast acquisition of multiple quantitative MR parameters. Despite acquisition efficiency, adoption of MRF into the clinics is hindered by its dictionary…

Image and Video Processing · Electrical Eng. & Systems 2020-08-11 Fabian Balsiger , Alain Jungo , Olivier Scheidegger , Pierre G. Carlier , Mauricio Reyes , Benjamin Marty

X-ray tomographic image reconstruction consists of determining an object function from its projections. In many applications such as non-destructive testing, we look for a fault region (air) in a homogeneous, known background (metal). The…

Data Analysis, Statistics and Probability · Physics 2007-05-23 A. Mohammad-Djafari , Ken Sauer

In this paper we present a spatially-adaptive method for image reconstruction that is based on the concept of statistical multiresolution estimation as introduced in [Frick K, Marnitz P, and Munk A. "Statistical multiresolution Dantzig…

Applications · Statistics 2012-04-19 Klaus Frick , Philipp Marnitz , Axel Munk

In this work, we propose a new paradigm of iterative model-based reconstruction algorithms for providing real-time solution for zooming-in and refining a region of interest in medical and clinical tomographic images. This algorithmic…

Image and Video Processing · Electrical Eng. & Systems 2025-12-01 Junqi Tang , Guixian Xu , Jinglai Li

In this work we consider the image reconstruction problem of sparsely sampled dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI). DCE-MRI is a technique for acquiring a series of MR images before, during and after intravenous…

Image and Video Processing · Electrical Eng. & Systems 2020-02-24 Kati Niinimäki , Matti Hanhela , Ville Kolehmainen

In tomographic reconstruction, the goal is to reconstruct an unknown object from a collection of line integrals. Given a complete sampling of such line integrals for various angles and directions, explicit inverse formulas exist to…

Numerical Analysis · Mathematics 2018-01-18 Tristan van Leeuwen , Simon Maretzke , K. Joost Batenburg

Photoacoustic tomography is a hybrid biomedical technology, which combines the advantages of acoustic and optical imaging. However, for the conventional image reconstruction method, the image quality is affected obviously by artifacts under…

Image and Video Processing · Electrical Eng. & Systems 2024-06-26 Bowei Yao , Yi Zeng , Haizhao Dai , Qing Wu , Youshen Xiao , Fei Gao , Yuyao Zhang , Jingyi Yu , Xiran Cai

In the past, optimization-based registration models have used spatially-varying regularization to account for deformation variations in different image regions. However, deep learning-based registration models have mostly relied on…

Image and Video Processing · Electrical Eng. & Systems 2023-03-14 Junyu Chen , Yihao Liu , Yufan He , Yong Du

As a powerful statistical image modeling technique, sparse representation has been successfully used in various image restoration applications. The success of sparse representation owes to the development of l1-norm optimization techniques,…

Computer Vision and Pattern Recognition · Computer Science 2015-05-20 Weisheng Dong , Lei Zhang , Guangming Shi , Xiaolin Wu

We propose a new space-variant regularization term for variational image restoration based on the assumption that the gradient magnitudes of the target image distribute locally according to a half-Generalized Gaussian distribution. This…

Image and Video Processing · Electrical Eng. & Systems 2019-06-27 Alessandro Lanza , Serena Morigi , Monica Pragliola , Fiorella Sgallari

Optical molecular tomographic imaging is to reconstruct the concentration distribution of photon-molecular probes in a small animal from measured photon fluence rates. The localization and quantification of molecular probes is related to…

Biological Physics · Physics 2017-07-18 Wenxiang Cong , Xavier Intes , Ge Wang

We propose a framework to perform streaming covariance selection. Our approach employs regularization constraints where a time-varying sparsity parameter is iteratively estimated via stochastic gradient descent. This allows for the…

Machine Learning · Statistics 2016-11-03 Ricardo Pio Monti , Romy Lorenz , Robert Leech , Christoforos Anagnostopoulos , Giovanni Montana

This study presents the development of a spatially adaptive weighting strategy for Total Variation regularization, aimed at addressing under-determined linear inverse problems. The method leverages the rapid computation of an accurate…

Numerical Analysis · Mathematics 2025-01-20 Elena Morotti , Davide Evangelista , Andrea Sebastiani , Elena Loli Piccolomini

Image deconvolution is still to be a challenging ill-posed problem for recovering a clear image from a given blurry image, when the point spread function is known. Although competitive deconvolution methods are numerically impressive and…

Computer Vision and Pattern Recognition · Computer Science 2016-09-07 Hang Yang , Zhongbo Zhang , Yujing Guan

The paper surveys variational approaches for image reconstruction in dynamic inverse problems. Emphasis is on methods that rely on parametrised temporal models. These are here encoded as diffeomorphic deformations with time dependent…

Image and Video Processing · Electrical Eng. & Systems 2020-07-21 Andreas Hauptmann , Ozan Öktem , Carola Schönlieb

We develop a statistical-mechanical formulation for image restoration and error-correcting codes. These problems are shown to be equivalent to the Ising spin glass with ferromagnetic bias under random external fields. We prove that the…

Disordered Systems and Neural Networks · Physics 2009-10-31 H. Nishimori , K. Y. M. Wong