Seminarieserien är ett informellt diskussionsforum för utbyte av tankar och idéer om forskning inom optimeringslära, algoritmer, problem och tillämpningar. Alla intresserade är välkomna.
Organisatör är Oleg Burdakov vid avdelning för Optimeringslära, Matematiska institutionen.
Tid och lokal
Seminarietiden är vanligtvis torsdagar kl 10:15 i Hopningspunkten som ligger i B-huset, ingång 23, plan 2, Campus Valla i Linköping.
Torsdag 21 mars 2019, Sebastiaan Breedveld, Erasmus University Medical Center, Rotterdam
Titel: Automated multi-criteria treatment planning in radiation therapy
Tid och plats: Torsdag 21 mars 2019, Hopningspunkten, kl 15:15
Sammanfattning: In radiotherapy, the treatment of cancer patients requires a personalised treatment plan. The plan describes how the dose (damage) resulting from irradiation is distributed inside the patient. The goal is to optimally irradiate the tumour, while keeping the doses to the healthy organs as low as possible. Distributing the dose over the different healthy organs is a multi-criteria problem with 10-30 correlated criteria. In current worldwide clinical practice, the multi-criteria optimisation and decision-making is performed by a human operator in an interactive trial-and-error procedure. Due to the complexity and dimensionality of the problem, this manual approach often results in suboptimal treatment, and a higher probability of developing complications. Besides the decision-making component, effectively solving the underlying numerical optimisation problem is another challenge.
By specifying a decision strategy upfront, clinically favourable treatment plans can be generated automatically. Such plans can be generated without manual interaction within minutes for external beam cases, and seconds for brachytherapy cases. In clinical comparison studies, we have demonstrated that automatically generated treatment plans are of at least equal, but generally more preferred for treatment.
Other advantages of automated treatment planning are performing objective studies in designing new treatment protocols, and objective patient selection for improved radiotherapy techniques with limited availability, such as proton therapy.
Torsdag 4 april 2019, Kaj Holmberg, Matematiska institutionen, Linköpings universitet
Titel: A new method for optimal proportional representation
Tid och plats: Torsdag 4 april 2019, Hopningspunkten, kl 10:15
Sammanfattning: In a democratic proportional election system, it is vital that the mandates in the parliament are allocated as proportionally as possible to the number of votes the parties got in the election. We formulate an optimization model for allocation of seats in a parliament so as to minimize the disproportionality. By applying separable programming techniques, we obtain an easily solvable problem, and present a method for solving it optimally. The obtained solution is the feasible solution that has the minimal
disproportionality (with the measure chosen), even in the presence of a parliament threshold, which is not always the case for the practical procedures used in many countries. We apply the approach to real life data from the last three elections in Sweden, and show that the result is better, i.e. more proportional, than what was obtained with the modified Sainte-Lague method, which is presently used. A natural suggestion would be to use our method instead.
We also consider the issue about constituencies, and suggest a procedure, based on the same kind of optimization problem, for allocating mandates in the constituencies, without changing the overall allocation with respect to parties. The numbers of mandates for the constituencies are based on the number of votes given, not on estimated numbers of inhabitants. This removes the need for compensatory mandates, and makes the question about sizes of the constituencies less important.