A Mathematical Programming Model for Radiotherapy Scheduling with TimeWindows

In external-beam radiotherapy (RT), high-energy radiation beams are delivered by a linear accelerator in a series of irradiation sessions undertaken over multiple days. In this work, we consider the problem of scheduling and sequencing RT sessions considering time window preferences given by patients for the starting time of their appointments. Most studies in the literature focus on assigning patients to linacs and days, neglecting the sequencing component, and existing sequencing algorithms are only able to solve the problem using approximation methods due to the intractability of the formulated models. We propose a mixed-integer linear programming model and test it using data from a large Dutch RT center. Results show that the problem can be solved in reasonable computation time for real-world size instances using our model.</p

Active Preference Elicitation by Bayesian Updating on Optimality Polyhedra

International audienceWe consider the problem of actively eliciting the preferences of a Decision Maker (DM) that may exhibit some versatility when answering preference queries. Given a set of multicriteria alternatives (choice set) and an aggregation function whose parameter values are unknown, we propose a new incremental elicitation method where the parameter space is partitioned into optimality polyhedra in the same way as in stochastic multicriteria acceptability analysis. Each polyhedron encompasses the subset of parameter values for which a given alternative is optimal (one optimality polyhedron, possibly empty, per alternative in the choice set). The uncertainty about the DM's judgment is modeled by a probability distribution over the polyhedra of the partition. At each step of the elicitation procedure, the distribution is revised in a Bayesian manner using preference queries whose choice is based on the current solution strategy, that we adapt to minimize the expected regret of the recommended alternative. We interleave the analysis of the set of alternatives with the elicitation of the parameters of the aggregation function (weighted sum or ordered weighted average). Numerical tests have been performed to evaluate the interest of the proposed approach

Opciones terapéuticas actuales en el manejo de la coledocolitiasis asociada a colecistolitiasis

The term Choledocholithiasis refers to the presence of biliary stones in the extrahepatic bile ducts, which are found in 5 to 10% of patients undergoing cholecystectomy for gallstones. Nowadays, with the adoption of the laparoscopic cholecystectomy(LC) as a standard, multiple minimally invasive treatment options for bile duct stones are feasible, with no consensus to date on the procedure of choice. The two stage endoscopic techniques involve the use of Endoscopic Retrograde Cholangiopancreatography(ERCP) before or after performing a LC, which has the main advantage of separating the bile duct procedure from the LC. However, the need for two separate anesthesia times, the possibility of blank or failed ERCP, and the chance for calculi migration between procedures increase the length of hospital stay and associated costs. The single stage procedures include the Laparoscopic Bile Duct Exploration (LBDE), and more recently, the performance of a laparoscopy guided intraoperative ERCP(Rendez Vous). The LBDE, when performed by an experienced surgical team, is an effective and safe technique. Nonetheless, it is considered a technically demanding procedure, whose results cannot be extrapolated to the general surgical community. Recently, the Rendez Vous has become a treatment alternative that simplifies both the surgical and the endoscopic procedures, decreases morbidity, and requires a single anesthesia time. On the downside, Rendez Vous technique involves complex operating room (OR) logistics, requiring both a trained surgical and endoscopic team at the same time