Search Results for author: Jens Sjölund

Found 31 papers, 16 papers with code

Online learning in motion modeling for intra-interventional image sequences

1 code implementation15 Oct 2024 Niklas Gunnarsson, Jens Sjölund, Peter Kimstrand, Thomas. B Schön

Image monitoring and guidance during medical examinations can aid both diagnosis and treatment.

Imputation

Taming Diffusion Models for Image Restoration: A Review

no code implementations16 Sep 2024 Ziwei Luo, Fredrik K. Gustafsson, Zheng Zhao, Jens Sjölund, Thomas B. Schön

Diffusion models have achieved remarkable progress in generative modelling, particularly in enhancing image quality to conform to human preferences.

Deblurring Image Denoising +1

Conditional sampling within generative diffusion models

1 code implementation15 Sep 2024 Zheng Zhao, Ziwei Luo, Jens Sjölund, Thomas B. Schön

Generative diffusions are a powerful class of Monte Carlo samplers that leverage bridging Markov processes to approximate complex, high-dimensional distributions, such as those found in image processing and language models.

Learning incomplete factorization preconditioners for GMRES

1 code implementation12 Sep 2024 Paul Häusner, Aleix Nieto Juscafresa, Jens Sjölund

Incomplete LU factorizations of sparse matrices are widely used as preconditioners in Krylov subspace methods to speed up solving linear systems.

Graph Neural Network

Conditioning diffusion models by explicit forward-backward bridging

1 code implementation22 May 2024 Adrien Corenflos, Zheng Zhao, Simo Särkkä, Jens Sjölund, Thomas B. Schön

Given an unconditional diffusion model $\pi(x, y)$, using it to perform conditional simulation $\pi(x \mid y)$ is still largely an open question and is typically achieved by learning conditional drifts to the denoising SDE after the fact.

Denoising

Efficient Radiation Treatment Planning based on Voxel Importance

no code implementations6 May 2024 Sebastian Mair, Anqi Fu, Jens Sjölund

We propose an approach to reduce the large optimization problem by only using a representative subset of informative voxels.

Photo-Realistic Image Restoration in the Wild with Controlled Vision-Language Models

2 code implementations15 Apr 2024 Ziwei Luo, Fredrik K. Gustafsson, Zheng Zhao, Jens Sjölund, Thomas B. Schön

Though diffusion models have been successfully applied to various image restoration (IR) tasks, their performance is sensitive to the choice of training datasets.

Image Generation Language Modeling +2

Entropy-regularized Diffusion Policy with Q-Ensembles for Offline Reinforcement Learning

1 code implementation6 Feb 2024 Ruoqi Zhang, Ziwei Luo, Jens Sjölund, Thomas B. Schön, Per Mattsson

We show that such an SDE has a solution that we can use to calculate the log probability of the policy, yielding an entropy regularizer that improves the exploration of offline datasets.

D4RL Offline RL +2

Variational Elliptical Processes

no code implementations21 Nov 2023 Maria Bånkestad, Jens Sjölund, Jalil Taghia, Thomas B. Schöon

We present elliptical processes, a family of non-parametric probabilistic models that subsume Gaussian processes and Student's t processes.

Gaussian Processes Variational Inference

On Feynman--Kac training of partial Bayesian neural networks

1 code implementation30 Oct 2023 Zheng Zhao, Sebastian Mair, Thomas B. Schön, Jens Sjölund

Recently, partial Bayesian neural networks (pBNNs), which only consider a subset of the parameters to be stochastic, were shown to perform competitively with full Bayesian neural networks.

Controlling Vision-Language Models for Multi-Task Image Restoration

1 code implementation2 Oct 2023 Ziwei Luo, Fredrik K. Gustafsson, Zheng Zhao, Jens Sjölund, Thomas B. Schön

In this paper, we present a degradation-aware vision-language model (DA-CLIP) to better transfer pretrained vision-language models to low-level vision tasks as a multi-task framework for image restoration.

Image Dehazing Image Denoising +8

Personalized Privacy Amplification via Importance Sampling

no code implementations5 Jul 2023 Dominik Fay, Sebastian Mair, Jens Sjölund

We first consider the general case where an arbitrary personalized differentially private mechanism is subsampled with an arbitrary importance sampling distribution and show that the resulting mechanism also satisfies personalized differential privacy.

Risk-sensitive Actor-free Policy via Convex Optimization

no code implementations30 Jun 2023 Ruoqi Zhang, Jens Sjölund

Traditional reinforcement learning methods optimize agents without considering safety, potentially resulting in unintended consequences.

reinforcement-learning Reinforcement Learning

Neural incomplete factorization: learning preconditioners for the conjugate gradient method

1 code implementation25 May 2023 Paul Häusner, Ozan Öktem, Jens Sjölund

The convergence of the conjugate gradient method for solving large-scale and sparse linear equation systems depends on the spectral properties of the system matrix, which can be improved by preconditioning.

Computational Efficiency

Archetypal Analysis++: Rethinking the Initialization Strategy

1 code implementation31 Jan 2023 Sebastian Mair, Jens Sjölund

Archetypal analysis is a matrix factorization method with convexity constraints.

A Tutorial on Parametric Variational Inference

no code implementations3 Jan 2023 Jens Sjölund

Variational inference uses optimization, rather than integration, to approximate the marginal likelihood, and thereby the posterior, in a Bayesian model.

Variational Inference

Probabilistic Estimation of Instantaneous Frequencies of Chirp Signals

1 code implementation12 May 2022 Zheng Zhao, Simo Särkkä, Jens Sjölund, Thomas B. Schön

We present a continuous-time probabilistic approach for estimating the chirp signal and its instantaneous frequency function when the true forms of these functions are not accessible.

Gaussian Processes

Graph-based Neural Acceleration for Nonnegative Matrix Factorization

no code implementations1 Feb 2022 Jens Sjölund, Maria Bånkestad

We describe a graph-based neural acceleration technique for nonnegative matrix factorization that builds upon a connection between matrices and bipartite graphs that is well-known in certain fields, e. g., sparse linear algebra, but has not yet been exploited to design graph neural networks for matrix computations.

Graph Neural Network

Unsupervised dynamic modeling of medical image transformation

2 code implementations1 Mar 2021 Niklas Gunnarsson, Peter Kimstrand, Jens Sjölund, Thomas B. Schön

For this, we use a conditional variational auto-encoder (CVAE) to nonlinearly map the higher-dimensional image to a lower-dimensional space, wherein we model the dynamics with a linear Gaussian state-space model (LG-SSM).

Denoising Dimensionality Reduction +3

Decentralized Differentially Private Segmentation with PATE

no code implementations10 Apr 2020 Dominik Fay, Jens Sjölund, Tobias J. Oechtering

For this reason, we turn our attention to Private Aggregation of Teacher Ensembles (PATE), where all local models can be trained independently without inter-institutional communication.

Brain Tumor Segmentation Federated Learning +2

Registration by tracking for sequential 2D MRI

no code implementations24 Mar 2020 Niklas Gunnarsson, Jens Sjölund, Thomas B. Schön

Together with a sparse-to-dense interpolation scheme we can then estimate of the displacement field.

Anatomy Image Registration

The Elliptical Processes: a Family of Fat-tailed Stochastic Processes

no code implementations13 Mar 2020 Maria Bånkestad, Jens Sjölund, Jalil Taghia, Thomas Schön

We present the elliptical processes -- a family of non-parametric probabilistic models that subsumes the Gaussian process and the Student-t process.

Gaussian Processes regression

A unified representation network for segmentation with missing modalities

no code implementations19 Aug 2019 Kenneth Lau, Jonas Adler, Jens Sjölund

The second is the unified representation network: a network architecture that maps a variable number of input modalities into a unified representation that can be used for downstream tasks such as segmentation.

Medical Image Analysis Segmentation

Gaussian process regression can turn non-uniform and undersampled diffusion MRI data into diffusion spectrum imaging

no code implementations9 Nov 2016 Jens Sjölund, Anders Eklund, Evren Özarslan, Hans Knutsson

We propose to use Gaussian process regression to accurately estimate the diffusion MRI signal at arbitrary locations in q-space.

regression Unity

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