Automatic Selection of Beam Orientations in Intensity-Modulated Radiation Therapy Ahmad-Saher Azizi-Sultan 1,2 International Center for Computational Logic Technische Universit¨ at Dresden Dresden, Germany Abstract Finding an optimal set of beam orientations in intensity-modulated radiation ther- apy (IMRT) planning is an important, but unfortunately, large-scale NP-hard op- timization problem with impractical and excessive time complexity. Selecting ap- propriate beam directions in IMRT is still a time-consuming manual trial-and-error search procedure that depends on intuition and empirical knowledge. This work utilizes the methods of beam’s eye view and observer’s view, which are recognized for beam orientations in conventional conformal radiation therapy, to present an automatic algorithm that works in clinically practical time and aims at determining a suitable set of beam orientations for IMRT. Keywords: Optimization, beam orientations, intensity-modulated radiation therapy, beam selection. 1 Supported by the department of optimization at Fraunhofer Institute for Industrial Math- ematics (ITWM), Kaiserslautern, Germany. 2 Email: sultansaher@hotmail.com Electronic Notes in Discrete Mathematics 36 (2010) 127–134 1571-0653/$ – see front matter © 2010 Elsevier B.V. All rights reserved. www.elsevier.com/locate/endm doi:10.1016/j.endm.2010.05.017