Search Results for author: John Ashburner

Found 23 papers, 15 papers with code

Synthetic Data for Robust Stroke Segmentation

1 code implementation2 Apr 2024 Liam Chalcroft, Ioannis Pappas, Cathy J. Price, John Ashburner

Deep learning-based semantic segmentation in neuroimaging currently requires high-resolution scans and extensive annotated datasets, posing significant barriers to clinical applicability.

Lesion Segmentation Segmentation +1

Deep Variational Lesion-Deficit Mapping

1 code implementation27 May 2023 Guilherme Pombo, Robert Gray, Amy P. K. Nelson, Chris Foulon, John Ashburner, Parashkev Nachev

Here we initiate the application of deep generative neural network architectures to the task of lesion-deficit inference, formulating it as the estimation of an expressive hierarchical model of the joint lesion and deficit distributions conditioned on a latent neural substrate.

Equitable modelling of brain imaging by counterfactual augmentation with morphologically constrained 3D deep generative models

no code implementations29 Nov 2021 Guilherme Pombo, Robert Gray, Jorge Cardoso, Sebastien Ourselin, Geraint Rees, John Ashburner, Parashkev Nachev

The model is intended to synthesise counterfactual training data augmentations for downstream discriminative modelling tasks where fidelity is limited by data imbalance, distributional instability, confounding, or underspecification, and exhibits inequitable performance across distinct subpopulations.

counterfactual

Factorisation-based Image Labelling

1 code implementation19 Nov 2021 Yu Yan, Yael Balbastre, Mikael Brudfors, John Ashburner

Segmentation of brain magnetic resonance images (MRI) into anatomical regions is a useful task in neuroimaging.

Brain Segmentation Segmentation

Correcting inter-scan motion artefacts in quantitative R1 mapping at 7T

1 code implementation24 Aug 2021 Yaël Balbastre, Ali Aghaeifar, Nadège Corbin, Mikael Brudfors, John Ashburner, Martina F. Callaghan

Conclusion: The proposed methods simplify inter-scan motion correction of $R_1$ maps and are applicable at both 3T and 7T, where a body coil is typically not available.

An MRF-UNet Product of Experts for Image Segmentation

1 code implementation12 Apr 2021 Mikael Brudfors, Yaël Balbastre, John Ashburner, Geraint Rees, Parashkev Nachev, Sébastien Ourselin, M. Jorge Cardoso

While convolutional neural networks (CNNs) trained by back-propagation have seen unprecedented success at semantic segmentation tasks, they are known to struggle on out-of-distribution data.

Image Segmentation Semantic Segmentation

A hierarchical Bayesian model to find brain-behaviour associations in incomplete data sets

1 code implementation11 Mar 2021 Fabio S. Ferreira, Agoston Mihalik, Rick A. Adams, John Ashburner, Janaina Mourao-Miranda

In synthetic data, GFA uncovered the underlying shared and specific factors and predicted correctly the non-observed data modalities in complete and incomplete data sets.

Bayesian Inference

Model-based multi-parameter mapping

1 code implementation2 Feb 2021 Yael Balbastre, Mikael Brudfors, Michela Azzarito, Christian Lambert, Martina F. Callaghan, John Ashburner

Instead, we propose a probabilistic generative (forward) model of the entire dataset, which is formulated and inverted to jointly recover (log) parameter maps with a well-defined probabilistic interpretation (e. g., maximum likelihood or maximum a posteriori).

Denoising

Flexible Bayesian Modelling for Nonlinear Image Registration

no code implementations3 Jun 2020 Mikael Brudfors, Yaël Balbastre, Guillaume Flandin, Parashkev Nachev, John Ashburner

We describe a diffeomorphic registration algorithm that allows groups of images to be accurately aligned to a common space, which we intend to incorporate into the SPM software.

Anatomy Image Registration

Joint Total Variation ESTATICS for Robust Multi-Parameter Mapping

1 code implementation28 May 2020 Yaël Balbastre, Mikael Brudfors, Michela Azzarito, Christian Lambert, Martina F. Callaghan, John Ashburner

Quantitative magnetic resonance imaging (qMRI) derives tissue-specific parameters -- such as the apparent transverse relaxation rate R2*, the longitudinal relaxation rate R1 and the magnetisation transfer saturation -- that can be compared across sites and scanners and carry important information about the underlying microstructure.

Groupwise Multimodal Image Registration using Joint Total Variation

1 code implementation6 May 2020 Mikael Brudfors, Yaël Balbastre, John Ashburner

In medical imaging it is common practice to acquire a wide range of modalities (MRI, CT, PET, etc.

Image Registration

A Tool for Super-Resolving Multimodal Clinical MRI

2 code implementations3 Sep 2019 Mikael Brudfors, Yael Balbastre, Parashkev Nachev, John Ashburner

The model-driven nature of the approach means that no type of training is needed for applicability to the diversity of MR contrasts present in a clinical context.

Empirical Bayesian Mixture Models for Medical Image Translation

no code implementations16 Aug 2019 Mikael Brudfors, John Ashburner, Parashkev Nachev, Yael Balbastre

Automatically generating one medical imaging modality from another is known as medical image translation, and has numerous interesting applications.

Translation

Bayesian Volumetric Autoregressive generative models for better semisupervised learning

1 code implementation26 Jul 2019 Guilherme Pombo, Robert Gray, Tom Varsavsky, John Ashburner, Parashkev Nachev

Second, we show that reformulating this model to approximate a deep Gaussian process yields a measure of uncertainty that improves the performance of semi-supervised learning, in particular classification performance in settings where the proportion of labelled data is low.

General Classification Semantic Segmentation

Nonlinear Markov Random Fields Learned via Backpropagation

1 code implementation27 Feb 2019 Mikael Brudfors, Yaël Balbastre, John Ashburner

Although convolutional neural networks (CNNs) currently dominate competitions on image segmentation, for neuroimaging analysis tasks, more classical generative approaches based on mixture models are still used in practice to parcellate brains.

Image Segmentation Segmentation +1

MRI Super-Resolution using Multi-Channel Total Variation

4 code implementations8 Oct 2018 Mikael Brudfors, Yael Balbastre, Parashkev Nachev, John Ashburner

This paper presents a generative model for super-resolution in routine clinical magnetic resonance images (MRI), of arbitrary orientation and contrast.

Brain Segmentation Super-Resolution

An Algorithm for Learning Shape and Appearance Models without Annotations

no code implementations27 Jul 2018 John Ashburner, Mikael Brudfors, Kevin Bronik, Yael Balbastre

This paper presents a framework for automatically learning shape and appearance models for medical (and certain other) images.

Image Registration Privacy Preserving

Diffeomorphic brain shape modelling using Gauss-Newton optimisation

no code implementations19 Jun 2018 Yaël Balbastre, Mikael Brudfors, Kevin Bronik, John Ashburner

Shape modelling describes methods aimed at capturing the natural variability of shapes and commonly relies on probabilistic interpretations of dimensionality reduction techniques such as principal component analysis.

Dimensionality Reduction

Generative diffeomorphic modelling of large MRI data sets for probabilistic template construction

no code implementations NeuroImage 2018 Claudia Blaiotta, Patrick Freund, M. Jorge Cardoso, John Ashburner

In this paper we present a hierarchical generative model of medical image data, which can capture simultaneously the variability of both signal intensity and anatomical shapes across large populations.

Diffeomorphic Medical Image Registration Image Registration

Generative diffeomorphic atlas construction from brain and spinal cord MRI data

no code implementations5 Jul 2017 Claudia Blaiotta, Patrick Freund, M. Jorge Cardoso, John Ashburner

In this paper we will focus on the potential and on the challenges associated with the development of an integrated brain and spinal cord modelling framework for processing MR neuroimaging data.

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