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Étude des effets de volume partiel en IRM cérébrale pour l'estimation d'épaisseur corticale

Abstract : The work developed in this thesis is within the scope of magnetic resonance imaging (MRI) acquisition and image processing for the automated analysis of brain structures. The measurement of structural modifications with time such as cortical atrophy requires the application of image processing algorithms. They must compensate for MRI artifacts such as intensity inhomogeneities or partial volume (PV) effects to allow for brain tissues segmentation then cortical thickness estimation. We suggest a new PV model relying on the physics of acquisition named bi-exponential model that differs from the commonly used linear model by modelling brain tissues and image acquisition. It requires the use of two differently contrasted and perfectly coregistered images. This model has been validated with simulations and physical and digital phantoms in a first place. In parallel, the recent MP2RAGE sequence provides two coregistered images and their combination results in a bias-field corrected image as well as a T1 map of the scanned tissues. We tested our model with in vivo MP2RAGE data and demonstrated that using the linear PV model leads to a systematic gray matter proportion underestimation in PV voxels. These errors result in cortical thickness underestimation. Our results favor the following assumption: PV modelling with MP2RAGE images must differ from the usual linear PV model applied for images obtained from more classic sequences. The bi-exponential model is an adapted solution to this particular sequence.
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Submitted on : Monday, November 16, 2015 - 5:34:42 PM
Last modification on : Wednesday, September 14, 2022 - 10:20:04 AM
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  • HAL Id : tel-01229530, version 1


Quentin Duché. Étude des effets de volume partiel en IRM cérébrale pour l'estimation d'épaisseur corticale. Traitement du signal et de l'image [eess.SP]. Université Rennes 1, 2015. Français. ⟨NNT : 2015REN1S035⟩. ⟨tel-01229530⟩



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