Fast joint detection-estimation of evoked brain activity in event-related fMRI using a variational approach

Résumé : In standard within-subject analyses of event-related fMRI data, two steps are usually performed separately: detection of brain activity and estimation of the hemodynamic response. Because these two steps are inherently linked, we adopt the socalled region-based Joint Detection-Estimation (JDE) framework that addresses this joint issue using a multivariate inference for detection and estimation. JDE is built by making use of a regional bilinear generative model of the BOLD response and constraining the parameter estimation by physiological priors using temporal and spatial information in a Markovian model. In contrast to previous works that use Markov Chain Monte Carlo (MCMC) techniques to sample the resulting intractable posterior distribution, we recast the JDE into a missing data framework and derive a Variational Expectation-Maximization (VEM) algorithm for its inference. A variational approximation is used to approximate the Markovian model in the unsupervised spatially adaptive JDE inference, which allows automatic fine-tuning of spatial regularization parameters. It provides a new algorithm that exhibits interesting properties in terms of estimation error and computational cost compared to the previously used MCMC-based approach. Experiments on artificial and real data show that VEM-JDE is robust to model misspecification and provides computational gain while maintaining good performance in terms of activation detection and hemodynamic shape recovery.
Contributeur : Dojat Michel <>
Soumis le : lundi 19 novembre 2012 - 17:00:16
Dernière modification le : lundi 19 novembre 2012 - 17:00:16


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Lotfi Chaari, Thomas Vincent, Florence Forbes, Michel Dojat, Philippe CIUCIU. Fast joint detection-estimation of evoked brain activity in event-related fMRI using a variational approach. IEEE Transactions on Medical Imaging, Institute of Electrical and Electronics Engineers (IEEE), 2013, 32 (5), pp.821-837. <10.1109/TMI.2012.2225636>. <inserm-00753873>