Learning to Predict Ischemic Stroke Growth on Acute CT Perfusion Data by Interpolating Low-Dimensional Shape Representations

Cerebrovascular diseases, in particular ischemic stroke, are one of the leading global causes of death in developed countries. Perfusion CT and/or MRI are ideal imaging modalities for characterizing affected ischemic tissue in the hyper-acute phase. If infarct growth over time could be predicted accurately from functional acute imaging protocols together with advanced machine-learning based image analysis, the expected benefits of treatment options could be better weighted against potential risks. The quality of the outcome prediction by convolutional neural networks (CNNs) is so far limited, which indicates that even highly complex deep learning algorithms are not fully capable of directly learning physiological principles of tissue salvation through weak supervision due to a lack of data (e.g., follow-up segmentation). In this work, we address these current shortcomings by explicitly taking into account clinical expert knowledge in the form of segmentations of the core and its surrounding penumbra in acute CT perfusion images (CTP), that are trained to be represented in a low-dimensional non-linear shape space. Employing a multi-scale CNN (U-Net) together with a convolutional auto-encoder, we predict lesion tissue probabilities for new patients. The predictions are physiologically constrained to a shape embedding that encodes a continuous progression between the core and penumbra extents. The comparison to a simple interpolation in the original voxel space and an unconstrained CNN shows that the use of such a shape space can be advantageous to predict time-dependent growth of stroke lesions on acute perfusion data, yielding a Dice score overlap of 0.46 for predictions from expert segmentations of core and penumbra. Our interpolation method models monotone infarct growth robustly on a linear time scale to automatically predict clinically plausible tissue outcomes that may serve as a basis for more clinical measures such as the expected lesion volume increase and can support the decision making on treatment options and triage

Sensitivity and reliability analysis of articulated heavy vehicle

SIA, MULHOUSE, FRANCE, 04-/10/2011 - 06/10/2011The aim of this paper is to develop a stochastic based approach to prevent rollover and jackkning risk of articulated heavy vehicle. A specific 6-DOF heavy vehicle model is developed and safety criteria are used. Parameters involved in the model are modeled by random variables or stochastic processes in order to take into account incertainties. These parameters are deduced from two different sensitivity analysis methods. Then, structural reliability methods are employed to assess the probability of failure and compared to Monte-Carlo based method

Influences des caractéristiques mécaniques et physiques des sables sur le comportement hydraulique et biologique des filtres à sable

International audienceSand filters systems are widely used around the world for on-site and small communities wastewater treatment. Their treatment efficiency depends on several parameters like the media used, temperature, wastewater characteristics, hydraulic and organic loads. One of the most important design parameter in relation to treatment efficiency and sustainability (clogging phenomena) is the sand characteristics and its implementation. To precise the impact of sand implementation on hydraulic and biological behaviors, a study has been done in laboratory columns (surface 0.1m2) in relation to physical and mechanical characteristics of the sand. Two sands (d10 0.42 and 0.8 mm) as well as two implementations (natural compaction and 100% proctor compaction) have been studied during 8 months fed with synthetic wastewater. The weight of the columns was followed continuously and it allowed the following of different parameters (media humidity, infiltration rate, drainage flow). Other parameters linked to biological activity (treatment efficiency (BOD5, COD, SS, nitrogen forms, etc.), oxygen content of the porous gas phase) were followed on a daily basis. The results give information on the importance of media implementation on treatment efficiency and gas and water transfers within the sand filter. Physical parameters, like particle size distribution, are not the only ones to be determinant on biological and hydraulic behaviors of sand filters. If sand compaction can be detrimental in terms of clogging for fine sands, it can be beneficial for coarser sands. This has to be known to avoid bad design and clogging risks

Diagnostic de filtres à sable d'assainissement non collectif

International audienceOn-site domestic wastewater treatment (ODWT) systems are receiving renewed interest due to their simplicity of implementation, affordability and efficiency. The most widespread ODWT system is the sand filter with vertical drained flow (SFVDF). To optimise the design and maintenance of SFVDFs, it is important to be able to check the conformity of the installations, judge their treatment performance in service and estimate possible evolution and life expectancy. As yet, however, no methodology has been developed to perform these tasks. This paper proposes a new methodology for diagnosing SFVDF systems in service. The development of this methodology relies on the development of on-site characterisation of the filtering material based on the use of a light dynamic penetration test and image processing. From this, the paper proposes an automatic tool for detecting the presence of clogging in a filter and a methodology to estimate the hydraulic conductivity of the filtering material without destroying the filter. The global methodology for diagnosing SFVDF systems is presented and illustrated for a real case in order to demonstrate its advantages and efficiency

Méthode de diagnostic du fonctionnement d'un système d'épuration d'eau de type dispositif à milieu filtrant et outil de diagnostic adapté à cette méthode

L'invention concerne une méthode de diagnostic du fonctionnement d'un système d'épuration d'eau de type dispositif à milieu filtrant, comportant les étapes suivantes : - une étape de caractérisation d'au moins un paramètre physique et/ou mécanique du dispositif à milieu filtrant permettant d'établir une valeur de perméabilité Ks (m/s), - une étape de comparaison entre ladite valeur de perméabilité établie Ks et une plage de valeurs de perméabilité prédéterminée [k k ] représentative d'un état de fonctionnement satisfaisant du système d'épuration, et - une étape de diagnostic au cours de laquelle on attribue un indicateur du fonctionnement du dispositif à milieu filtrant en fonction du résultat de l'étape de comparaison. Application aux systèmes d'assainissement non collectifs (ANC) ou autonomes

Autopsies de petites installations d'assainissement. Démantèlement de 5 des 8 filières testées sur la plateforme du CSTB dans le cadre de l'étude comparative Veolia Eau (1ère partie)

National audienceÀ l'issue de 3 ans d'alimentation en conditions connues, 5 filières d'assainissement autonome sont mises à l'arrêt. Avant de les démanteler et de libérer le site d'étude, il a semblé opportun de réaliser un état des lieux de ces dispositifs. L'idée a été d'identifier ce qui pouvait être mis en évidence au cours d'une telle intervention, dans l'optique de réalisation de diagnostics de fin de vie, ou de diagnostics de dysfonctionnement. Un protocole de démantèlement a été adapté à chaque type de système autopsié. Cette première vague d'autopsie a apporté des enseignements particulièrement intéressants sur le fonctionnement des systèmes extensifs, ainsi que plus globalement d'ordre méthodologique. Ils pourront être utilement complétés lors de la mise hors service des 3 dispositifs encore en place sur la plateforme du CSTB à Nantes, prévue en septembre 2010