Automatical segmentation : Application to 3D angiograms of the liver

As part of a hepatic surgery simulator, we have developed a new method for the extraction of the portal vein's vascular tree i n 3D liver angioscanners . In practice, this tree is used to localize the different anatomical segments that correspond to the unit o f surgical ablation of the liver . Our method thus facilitates the surgeon's task by automatically giving the 3D model of the portal vei n in a three-step segmentation . The first step reduces the image to the ROI defined by the liver contours and increases its qualit y by an anisotropic filtering . The second step performs the segmentation of vascular networks by a global thresholding followed b y a local analysis . The third step translates a priori knowledge in topological and geometrical constraints . This last step allows to remove mistakes due to the anisotropy of the images by disconnecting the different vascular trees in order to extract the porta l vein . Results on 12 patients, validated by a radiologist, showed that the algorithm automatically extracts the principal branche s of the portal vein, allowing to delimit the anatomical segments defined in the conventional liver anatomy .Dans le cadre de la réalisation d'un simulateur de chirurgie laparoscopique' du foie, nous avons développé une nouvelle méthode permettant d'extraire dans les angioscanners 3D du foie, le réseau vasculaire de la veine porte. Ce réseau est utilisé en pratique pour repérer les différents segments anatomiques, qui représentent l'unité d'intervention dans les exérèses2 du foie. Notre méthode facilite ainsi la tâche des chirurgiens, en leur fournissant automatiquement le modèle 3D de la veine porte par une segmentation décomposée en trois étapes. La première étape réduit l'image à la région d'intérêt correspondant au contour du foie et améliore sa qualité en réalisant un filtrage anisotrope. La seconde segmente les réseaux vasculaires et appliquant un seuillage global, suivi d'une analyse locale. La troisième étape traduit les connaissances a priori que nous avons des réseaux vasculaires, en contraintes topologiques et géométriques. Cette dernière étape permet de corriger les problèmes résultant de l'anisotropie des images, en déconnectant les différentes arborescences du foie pour en extraire la veine porte. Les résultats obtenus sur douze patients, et vérifiés par un radiologue, montrent que l'algorithme extrait automatiquement les principales branches de la veine porte, permettant de délimiter les segments anatomiques définis dans l'anatomie conventionnelle du foie

Physical Modelling of the Flow Field in an Undular Tidal Bore

A tidal bore may form in a converging channel with a funnel shape when the tidal range exceeds 6-9 m. The advancing surge has a major impact on the estuarine ecosystem. Physical modelling of an undular bore has been conducted based upon a quasi-steady flow analogy. The experimental data highlight rapid flow redistributions between successive wave troughs and crests as well as large bottom shear stress variations. The results suggest a sediment transport process combining scour beneath wave troughs associated with upward matter dispersion between a trough and the following wave crest. The process is repeated at each trough and significant sediment transport takes place with deposition in upstream intertidal zones. The conceptual model is supported by field observations showing murky waters after the bore passage and long-lasting chaotic waves

First Results for the Beam Commissioning of the CERN Multi-Turn Extraction

The Multi-Turn Extraction (MTE), a new type of extraction based on beam trapping inside stable islands in horizontal phase space, has been commissioned during the 2008 run of the CERN Proton Synchrotron. Both singleand multi-bunch beams with a total intensity up to 1.4 1013 protons have been extracted with efficiencies up to 98%. Furthermore, injection tests in the CERN Super Proton Synchrotron were performed, with the beam then accelerated and extracted to produce neutrinos for the CERN Neutrino-to-Gran Sasso experiments. The results of the extensive measurement campaign are presented and discussed in detail

Biosensors for the Environment

Numerous pollutants from industrial or agricultural origins are found in the environment, and especially in water. Compounds such as herbicides, pesticides, chlorinated solvents as well as compounds linked to petroleum utilization are frequently found as pollutants of aquifers. These chemicals are generally toxic for humans and animals and their presence in water must be monitored to avoid the contamination of drinking water sources. Classical analytical tools (GC, GC/MS, etc.) provide accurate, reproducible and sensitive determination of contaminant concentrations. Nevertheless, their use requires to take samples on the contaminated sites and to transport the samples to laboratory for analysis. Such handling of samples is time-consuming and expensive. Biosensors are new analytical tools, whose conception has benefited from advances in different scientific areas, and particularly in biology; they now allow the development of highly specific tools. They provide real-time determination and detection of very low concentrations of contaminant and they can be used directly on-site