Material Decomposition in Spectral CT using deep learning: A Sim2Real transfer approach

The state-of-the art for solving the nonlinear material decomposition problem in spectral computed tomography is based on variational methods, but these are computationally slow and critically depend on the particular choice of the regularization functional. Convolutional neural networks have been proposed for addressing these issues. However, learning algorithms require large amounts of experimental data sets. We propose a deep learning strategy for solving the material decomposition problem based on a U-Net architecture and a Sim2Real transfer learning approach where the knowledge that we learn from synthetic data is transferred to a real-world scenario. In order for this approach to work, synthetic data must be realistic and representative of the experimental data. For this purpose, numerical phantoms are generated from human CT volumes of the KiTS19 Challenge dataset, segmented into specific materials (soft tissue and bone). These volumes are projected into sinogram space in order to simulate photon counting data, taking into account the energy response of the scanner. We compared projection- and image-based decomposition approaches where the network is trained to decompose the materials either in the projection or in the image domain. The proposed Sim2Real transfer strategies are compared to a regularized Gauss-Newton (RGN) method on synthetic data, experimental phantom data and human thorax data

Les carreaux de faïence peints dans l'Africa du Nord

Precede al tít.: "Archéologie et histoire"Precede ó tít.: "Archéologie et histoire

L'emploi de l'artillerie dans le corps d'armée / par le Col. Broussaud,...

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ATOMIC STRUCTURE OF "VITREOUS" INTERFACIAL FILMS IN SIALON

Atomic resolution imaging of siliceous interfacial films in a sialon has been achieved using transmission electron microscopy at 1000 KV. Although such films have always been reputed as vitreous, we show that they are at least partially crystallized. An atomic model is proposed and simulated. The stability of these films is discussed when special crystallographic relationships exist between the two adjacent grains.Des images de résolution atomique de films siliceux interfaciaux ont été enregistrées en microscopie électronique à 1000 KV. Quoique de tels films aient toujours été considérés comme vitreux, on montre qu'ils sont en fait partiellement cristallisés. Un modèle atomique est proposé et simulé. La stabilité de tels films est discutée lorsque des relations cristallographiques particulières existent entre les deux grains adjacents

RELIABILITY OF METAL/GLASS-CERAMIC JUNCTIONS MADE BY SOLID STATE BONDING

L'assemblage par diffusion dit par thermo-compression permet de réaliser des liaisons céramique-métal étanches à l'hélium. Ce procédé engendre cependant des contraintes résiduelles d'origine thermique sous l'action desquelles les défauts de la céramique peuvent se propager et conduire à la rupture différée de l'assemblage. Ce phénomène est mis en évidence sur des assemblages vitrocéramique/Al/Invar où une meilleure fiabilité est assurée par une réduction des défauts de surface.The solid state diffusion bonding leads to helium-tight ceramic-metal junctions. However this technique induces residual stresses due to expansion mismatches which may cause ceramic flaws to propagate hence junction delayed failure. This phenomenon is evidenced on glass-ceramic/Al/Invar junctions from which a better reliability is ensured by a reduction of surface flaws

Rôle de l'IRM dans la détection de viabilité

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