Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised

An integral multi-domain DPN_N operator as acceleration tool for the method of characteristics in unstructured meshes

International audienceThe paper presents the recent developments of the acceleration techniques for the Method Of Characteristics (MOC) in the code APOLLO2. The main contribution concerns the introduction of a multidomain DP$_N$ technique where all regions belonging to the same macro-domain are coupled by an integral operator that is strictly equivalent to the MOC. Different macro-domains are coupled via currents that are defined with the DP$_N$ formalism. This new Integral DP$_N$(IDP$_N$) operator is build by using transmission and escape probabilities factors that respect symmetries/anti-symmetries and complementary properties that are enforced to preserve the physics of the problem and to save computational effort. These factors are computed using the numerical tracking of the MOC operator. The paper presents results on realistic assembly calculations that demonstrate the effectiveness of the IDP$_N$ operator as a synthetic acceleration tool

Qualification physique et améliorations du modele numérique d'une méthode des caractéristiques pour la résolution de l'équation du transport des neutrons dans des maillages non structurés

EVRY-BU (912282101) / SudocSudocFranceF

A Novel High-Order Surface Characteristics Scheme for the Neutron Transport Equation in 2D Unstructured Meshes

International audienceMonte Carlo simulation is the reference method for reactor physics applications. Yet, the use of Monte Carlo for time-dependent problems (operational or accidental reactor transients) is still in its infancy, mainly due to the inherent challenges posed by the simultaneous presence of delayed neutron precursors and neutrons: the vast separation of their typical time scales, coupled to fission-induced correlations, leads to huge fluctuations and variance jumps. We will review the variance-reduction techniques recently developed in order to cope with these issues and enable the simulation of kinetic Monte Carlo in reactor physics and present a novel systematic approach possibly leading to considerable gains in computing time for a given target accuracy

Convergence Analysis for the Method of Characteristics in Unstructured Meshes

International audienceA conservative linear surface approximation (CLS) has been recently introduced to speed up the method of characteristics in unstructured meshes. In this work, we present an analysis of the convergence of the CLS in unstructured geometries, which shows that, under optimal conditions, the method converges quadratically with the size of the regions, while the classical step characteristics approximation converges linearly. The predicted convergence rates apply only to a homogeneous convex domain with a regular boundary and regular sources and can be viewed as upper bounds for realistic heterogeneous cases. We also analyze the errors induced by the numerical implementation of the step and CLS approximations and show their impact in the final error. Numerical calculations illustrate the convergence rates

Polynomial axial expansion in the Method of Characteristics for neutron transport in 3D extruded geometries

Recently a solver based on the Method Of Characteristics (MOC) for 3D extruded geometries has been developed in the APOLLO3® project [1]. In this method the domain is divided in regions and the Step Characteristics (SC) approximation is used in each of them to represent the solution of the transport problem. Since the biggest degree of heterogeneities is found along the radial direction, the idea proposed in this paper is to keep the SC approximation to compute the solution over the radial plane and to implement a polynomial expansion of the flux along the vertical direction. In fact the results of the previous works [1] show that the flux gradient along the z axis are likely to be represented by a classical polynomial basis. In this paper we weigh up the benefits of using a less refined mesh

An accelerated characteristics method including a spatial polynomial expansion for cross sections

International audienceThis paper deals with the spatial polynomial treatment for cross sections recently introduced in the 3D method of characteristics solver of APOLLO3 . The adaptation of the DPN synthetic acceleration method to the new approach is presented, showing how the acceleration coefficients are reformulated to take into account the polynomial description of media properties. An adaptive quadrature technique for the evaluation of the resulting transmission integrals is also addressed. The results of the depletion sequence of a 7x7 PWR assembly are presented, proving the clear advantage of using the polynomial method over the traditional step-constant one

Polynomial axial expansion in the Method of Characteristics for neutron transport in 3D extruded geometries

International audienceRecently a solver based on the Method Of Characteristics (MOC) for 3D extruded geometries has been developed in the APOLLO3® project [1]. In this method the domain is divided in regions and the Step Characteristics (SC) approximation is used in each of them to represent the solution of the transport problem. Since the biggest degree of heterogeneities is found along the radial direction, the idea proposed in this paper is to keep the SC approximation to compute the solution over the radial plane and to implement a polynomial expansion of the flux along the vertical direction. In fact the results of the previous works [1] show that the flux gradient along the z axis are likely to be represented by a classical polynomial basis. In this paper we weigh up the benefits of using a less refined mesh

Optimized tracking strategies for step MOC calculations in extruded 3D axial geometries

International audienc

Accelerated polynomial axial expansions for full 3D neutron transport MOC in the APOLLO3® code system as applied to the ASTRID fast breeder reactor

International audienceIn recent years a solver based on the Method of Characteristics (MOC) allowing the treatment of 3D extruded geometries has been developed inside the TDT code of APOLLO3. The standard Step Characteristics (SC) approximation is used and results show an excellent agreement with Monte-Carlo simulations. However a fine mesh refinement is needed to converge axially the strong flux gradients customarily appearing in 3D reactor physics applications. In this paper an improvement of this method is proposed: the results of the previous work show that much of the flux variations are likely to be represented by a polynomial basis along the vertical direction. Since most of the geometrical and physical heterogeneities are radially located, the SC approach is preserved to represent the solution over the radial plane. As a matter of fact the strong irregularities in the geometrical meshes prevent from an efficient use of a polynomial expansion. On the contrary along the axial direction the computational meshes assume a Cartesian shape, well suited for a polynomial representation of sources and fluxes. A convenient polynomial development in this direction allows us to approximate the strong flux slopes without the help of a large number of axial meshes. Finally we will show how synthetic accelerated results for the fourth generation fast breeder reactor ASTRID perform with respect to computational time, memory efficiency and precision against Monte-Carlo calculations. We will consider assembly geometries that span the full-height of the reactor and that are characterized by the strong heterogeneity conceived to enhance the axial leakage which improves the safety features of this new concept, especially under void conditions