Outcomes of elective liver surgery worldwide: a global, prospective, multicenter, cross-sectional study

Background: The outcomes of liver surgery worldwide remain unknown. The true population-based outcomes are likely different to those vastly reported that reflect the activity of highly specialized academic centers. The aim of this study was to measure the true worldwide practice of liver surgery and associated outcomes by recruiting from centers across the globe. The geographic distribution of liver surgery activity and complexity was also evaluated to further understand variations in outcomes. Methods: LiverGroup.org was an international, prospective, multicenter, cross-sectional study following the Global Surgery Collaborative Snapshot Research approach with a 3-month prospective, consecutive patient enrollment within January–December 2019. Each patient was followed up for 90 days postoperatively. All patients undergoing liver surgery at their respective centers were eligible for study inclusion. Basic demographics, patient and operation characteristics were collected. Morbidity was recorded according to the Clavien–Dindo Classification of Surgical Complications. Country-based and hospital-based data were collected, including the Human Development Index (HDI). (NCT03768141). Results: A total of 2159 patients were included from six continents. Surgery was performed for cancer in 1785 (83%) patients. Of all patients, 912 (42%) experienced a postoperative complication of any severity, while the major complication rate was 16% (341/2159). The overall 90-day mortality rate after liver surgery was 3.8% (82/2,159). The overall failure to rescue rate was 11% (82/ 722) ranging from 5 to 35% among the higher and lower HDI groups, respectively. Conclusions: This is the first to our knowledge global surgery study specifically designed and conducted for specialized liver surgery. The authors identified failure to rescue as a significant potentially modifiable factor for mortality after liver surgery, mostly related to lower Human Development Index countries. Members of the LiverGroup.org network could now work together to develop quality improvement collaboratives

Caractérisation acoustique de nuages de microbulles: En vue d’une application aux réacteurs nucléaires de quatrième génération.

France has chosen to focus on liquid sodium cooled fast neutron reactors as part of its involvement in the GEN IV international forum. A prototype, ASTRID, is under development. This prototype must demonstrate the improvement of its safety and monitoring in operation. This passes, among other things, by the characterization of the sodium engulfment of the primary circuit.Indeed, due to the presence of Argon as a cover gas, a bubble cloud exists in a normal and continuous manner in the primary circuit. Due to the opacity of liquid sodium, ultrasonic testing methods are preferred for inspections in operation. However, the presence of bubbles greatly affects the acoustic properties of the medium. In addition, the presence of bubbles could also affects the heat and neutron exchanges within the core, as well as boiling and cavitation phenomena. The characterization of this cloud therefore responds to these controllability issues and allows the validation of evolution calculation codes of the engazement such as VIBUL.A bibliographic work has sought to determine the most appropriate methods of characterization to answer these problems. The strengths and weaknesses of each method were studied. The inversion methods of spectroscopic attenuation and velocity measurements seem particularly suitable. In order to minimize the prior knowledge of the bubble cloud, a method for determining the range of radii has been developed. This method has shown its ability to characterize clouds with void fractions between 10-6 and 10-4.Then, in order to allow the characterization of clouds with void levels less than 10-6, the possibility of inverting spectroscopic measurements of the nonlinearity coefficient has been studied and demonstrated.The results obtained offer numerous prospects for their industrial applications.Dans le cadre de son implication dans le forum international GEN IV, la France a fait le choix de se focaliser sur les réacteurs à neutrons rapides refroidis au sodium liquide. Un prototype, ASTRID, est en cours de développement. Ce dernier doit faire la démonstration de l’amélioration de sa sureté et de la surveillance en fonctionnement. Ceci passe, entre autre, par la caractérisation de l’engazement du sodium du circuit primaire.En effet, du fait de la présence d’Argon en tant que gaz de couverture, un nuage de bulle existe de façon normale et continue dans le circuit primaire. L’opacité du sodium liquide, et les aptitudes spécifiques des méthodes ultrasonores justifient leur utilisation, privilégiée lors des inspections en opération. En effet, la présence de bulles pourrait altérer non seulement les échanges thermiques et neutroniques au sein du coeur, mais aussi les phénomènes d’ébullition et de cavitation ainsi que les propriétés acoustiques du caloporteur. La caractérisation de ce nuage répond donc à ces problématiques de contrôlabilité, elle permet aussi la validation de codes de calculs d’évolution de l’engazement tel que VIBUL.Un travail bibliographique s’est attaché à déterminer les méthodes de caractérisation les plus adaptés pour répondre à ces problématiques en exploitant les forces et les faiblesses respectives. Ainsi, les méthodes d’inversion de mesures spectroscopiques d’atténuation et de célérité s’avèrent particulièrement robustes lorsqu’elles sont soutenues par des techniques de régularisation. Afin de limiter l’importance de l’arbitraire (a priori), l’intervalle des tailles des bulles du nuage est estimé préalablement à la distribution, durant la phase d’optimisation du paramètre de régularisation. Cette approche a montré sa capacité à caractériser des nuages dont les taux de vides sont compris entre 10−6 et 10−4.Pour des taux de vides inférieurs à 10−6, la faisabilité d’une inversion de mesures spectroscopiques du coefficient de non-linéarité a été étudiée et démontrée.Les résultats laissent entrevoir de nombreuses perspectives quant à leurs applications industrielles

Acoustical characterization of microbubbles clouds

Dans le cadre de son implication dans le forum international GEN IV, la France a fait le choix de se focaliser sur les réacteurs à neutrons rapides refroidis au sodium liquide. Un prototype, ASTRID, est en cours de développement. Ce dernier doit faire la démonstration de l’amélioration de sa sureté et de la surveillance en fonctionnement. Ceci passe, entre autre, par la caractérisation de l’engazement du sodium du circuit primaire.Du fait de la présence d’Argon en tant que gaz de couverture, un nuage de bulle existe dans le circuit primaire. L’opacité du sodium liquide, et les aptitudes spécifiques des méthodes ultrasonores justifient leur utilisation, privilégiée lors des inspections en opération. Un travail bibliographique s’est attaché à déterminer les méthodes de caractérisation les plus adaptés pour répondre à ces problématiques en exploitant les forces et les faiblesses respectives. Ainsi, les méthodes d’inversion de mesures spectroscopiques d’atténuation et de célérité s’avèrent particulièrement robustes lorsqu’elles sont soutenues par des techniques de régularisation. Afin de limiter l’importance de l’arbitraire (a priori), l’intervalle des tailles des bulles du nuage est estimé préalablement à la distribution, durant la phase d’optimisation du paramètre de régularisation. Cette approche a montré sa capacité à caractériser des nuages dont les taux de vides sont compris entre 10e-6 et 10e-4 .Pour des taux de vides inférieurs à 10e-6, la faisabilité d’une inversion de mesures spectroscopiques du coefficient de non-linéarité a été étudiée et démontrée.Les résultats laissent entrevoir de nombreuses perspectives quant à leurs applications industrielles.France has chosen to focus on liquid sodium cooled fast neutron reactors as part of its involvement in the GEN IV international forum. A prototype, ASTRID, is under development. This prototype must demonstrate the improvement of its safety and monitoring in operation. This passes, among other things, by the characterization of the sodium engulfment of the primary circuit.Indeed, due to the presence of Argon as a cover gas, a bubble cloud exists in a normal and continuous manner in the primary circuit. Due to the opacity of liquid sodium, ultrasonic testing methods are preferred for inspections in operation. A bibliographic work has sought to determine the most appropriate methods of characterization to answer these problems. The strengths and weaknesses of each method were studied. The inversion methods of spectroscopic attenuation and velocity measurements seem particularly suitable. In order to minimize the prior knowledge of the bubble cloud, a method for determining the range of radii has been developed. This method has shown its ability to characterize clouds with void fractions between 10e-6 and 10e-4.Then, in order to allow the characterization of clouds with void levels less than 10e-6, the possibility of inverting spectroscopic measurements of the nonlinearity coefficient has been studied and demonstrated.The results obtained offer numerous prospects for their industrial applications

Acoustical characterisation and monitoring of microbubble clouds

International audienceArgon microbubbles will exist in the primary sodium of the next generation of sodium-cooled fast reactors (SFR). Due to its opacity, acoustic methods will be used for the in-service inspection in these reactors, but the presence of such bubbles will greatly affect ultrasonic wave propagation. Moreover, these bubbles can lead to the formation of gas pockets in the reactor and impact cavitation and boiling phenomena. It is therefore necessary to characterise what is called the 'microbubble cloud' by providing the volume fraction and the bubble size distribution. Safety requirements in this field call for robust inspection methods based on very few assumptions about the bubble populations. The objective of this study is to assess the performance of spectroscopic methods in the presence of bubbles with high polydispersity and to monitor an evolving cloud of microbubbles. The histogram and void fractions were estimated according to the regularised inversion of the complex wave number's integral equation. To reduce the need for prior information on the bubble cloud, a specific procedure was used to estimate the maximum radius of the population. The results are presented on the basis of the experimental data obtained and then compared with optical measurements

Micro-bubbles cloud's spectroscopic nonlinear coefficient measurements towards its characterization

International audienceIn 4th generation nuclear reactors cooled with liquid sodium, argon microbubbles are present in the primary sodium. Due to the opacity of liquid sodium, acoustic control methods are chosen for operating inspections. However, this bubble presence greatly affects the acoustical properties of the medium. In bubbly liquids, nonlinear propagation can arise at very low amplitudes and therefore affect the viability of ultrasonic measurements. The spectroscopic measurement of the nonlinear parameter is therefore required to estimate the reliability of acoustics measurements. Moreover, adding nonlinear information to attenuations and celerity measurements could improve bubble distribution estimation and provide more reliability on very low void fractions measurements. A dynamic acoustic-elastic testing method is employed to measure the nonlinear parameter over a large bandwidth. Inversion of these measurements is performed with success

Mesure acoustique de très faibles taux de vide dans les liquides à bulles

La caractérisation des écoulements à bulles est une problématique fréquemment rencontrée dans les sciences, l’industrie et le médical. Le CEA y est confronté dans le cadre du développement des réacteurs nucléaires rapides refroidis au sodium liquide : il est en effet nécessaire d’être en mesure de caractériser la présence de microbulles d’argon dans ce fluide caloporteur. Il est difficile de caractériser un milieu à bulles présentant de très faibles taux de vide. Nous présentons ici une technique apte à mesurer des taux de vide aussi faibles que 10-6. Elle est basée sur la mesure de la vitesse acoustique à basse fréquence en association avec le modèle de Wood (1930). Ces mesures sont comparées à des mesures optiques, et leur faisabilité démontrée pour des taux de vide inférieurs à 10-5 constitue une réelle avancée. Les expériences sont menées sur le couple air-eau avec deux types de générateurs de microbulles: des générateurs microfluidiques et des générateurs cavitants. Les bulles générées sont des microbulles dont les rayons sont dans la plage [1 µm - 100 µm]. Les mesures en immersion de la célérité acoustique dans le milieu à basse fréquence sont effectuées à l'aide de transducteurs dans la gamme [18 kHz - 30 kHz]. Les résultats obtenus montrent une bonne concordance entre les mesures optiques et acoustiques malgré le fait que plusieurs hypothèses du modèle Wood - notamment le comportement isotherme et la contribution de la tension superficielle - sont à la limite de validité dans nos expériences

Acoustical Characterization of Micro-Bubbles Clouds by Attenuation and Velocity Spectroscopy

International audienceIn 4th generation nuclear reactors cooled with liquid sodium,argonmicrobubbles are present in the primary sodium. Due to the opacity of liquid sodium, acoustic control methods are chosen for operating inspections but this bubble presence greatly affects the acoustical properties of the medium. It is therefore required to characterize the microbubble cloud, i.e., to provide the bubble’s volume fraction and the size distribution. Safety demands the proposed method to be robust and applicable with few assumptions (about the bubble populations) as possible. The objective of this study is to evaluate the performance of spectroscopic methods (based on celerity and attenuation) in the presence of bubbles whose sizes and surface (or volume) contributions are very different. Two methods of evaluating the histogram and the void fraction are compared. The first is based on the inversion of the integral equation of the complex wave number derived by Commander and Prosperetti. The second, which assumes the populations to have log-normal or sums of Gaussians distributions, performs an adjustment of the distribution’s parameters to fit attenuation and celerity curves measurements. These methods are compared with experimental data obtained using ACWABUL facilities at CEA Cadarache

Non-linear bubbly Helmholtz resonator

International audienc

Recent modelling advances in NDT to improve safety and sustainability for the next generation of nuclear reactor

International audienceIn the frame of Generation 4 Nuclear Reactor developments, the French LMA Laboratory and the French CEA nuclear institute undertake a joint work for improving monitoring and inspection of future Sodium Fast Reactors.The goal is to properly test and monitor, with non-destructive acoustic methods, structures and materials at different scales (from micrometric to metric) and at different operating states (nominal, partial, shutdown, incidental or even accidental). Indeed, acoustic signatures can be recorded (reflected signals, vibrations, noise), and, after treatment, allow checking the good health or state of components and structures immersed in liquid sodium (detection of displacements, flaws, leaks, bubbles, buckling).This is a real challenge as the media are rather complex, due to their geometry (shapes and access), their physical properties (multiphase, heterogeneous, anisotropic, flowing fluid, thermal gradients), high temperature, irradiation and sodium. This leads to use active acoustic methods (volumetric and guided waves) or passive ones (acoustic emission), and linear and non-linear acoustic methods.A number of experiments are performed at full scale or less, mainly in simulating water fluid (in conventional water test vessels, on water loops, with Schlieren bench) but also in sodium facilities.Numerical simulations are performed with available or tuned codes (multi-physics, ray tracing and finite elements, spectral finite elements ) in order to predict wave propagation within materials and structures. In addition, among other inverse methods used, defect detection can be done with time reversal techniques coupling with adjoint method.The future MISTRAL common lab will allow to ease this joint work between CEA Cadarache and LMA