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Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. Intensitymodulated radiotherapy  a large scale multicriteria programming problem
 OR spectrum 25 (2003), No.2, pp.223249 ISSN: 01716468 ISSN: 14366304 

 English 
 Journal Article 
 Fraunhofer ITWM () 
Abstract
Radiation therapy planning is often a tight rope walk between dangerous insufficient dose in the target volume and life threatening overdosing of organs at risk. Finding ideal balances between these inherently contradictory goals challenges dosimetrists and physicians in their daily practice. Todays inverse planning systems calculate treatment plans based on a single evaluation function that measures the quality of a radiation treatment plan. Unfortunately, such a one dimensional approach cannot satisfactorily map the different backgrounds of physicians and the patient dependent necessities. So, too often a time consuming iterative optimization process between evaluation of the dose distribution and redefinition of the evaluation function is needed. In this paper we propose a generic multicriteria approach based on Pareto's solution concept. For each entity of interest  target volume or organ at risk  a structure dependent evaluation function is defined measuring deviations from ideal doses that are calculated from statistical functions. A reasonable bunch of clinically meaningful Pareto optimal solutions are stored in a data base, which can be interactively searched by physicians. The system guarantees dynamic planning as well as the discussion of tradeoffs between different entities. Mathematically, we model the inverse problem as a multicriteria linear programming problem. Because of the large scale nature of the problem it is not possible to solve the problem in a 3Dsetting without adaptive reduction by appropriate approximation schemes. Our approach is twofold: First, the discretization of the continuous problem results from an adaptive hierarchical clustering process which is used for a local refinement of constraints during the optimization procedure. Second, the set of Pareto optimal solutions is approximated by an adaptive grid of representatives that are found by a hybrid process of calculating extreme compromises and interpolation methods.