Optimal Multileaf Collimator Leaf Sequencing in IMRT Treatment Planning

  • Authors:
  • Z. Caner Taşkın;J. Cole Smith;H. Edwin Romeijn;James F. Dempsey

  • Affiliations:
  • Department of Industrial and Systems Engineering, University of Florida, Gainesville, Florida 32611;Department of Industrial and Systems Engineering, University of Florida, Gainesville, Florida 32611;Department of Industrial and Operations Engineering, University of Michigan, Ann Arbor, Michigan 48109;Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610, and ViewRay Inc., Village of Oakwood, Ohio 44146

  • Venue:
  • Operations Research
  • Year:
  • 2010

Quantified Score

Hi-index 0.00

Visualization

Abstract

We consider a problem dealing with the efficient delivery of intensity modulated radiation therapy (IMRT) to individual patients. IMRT treatment planning is usually performed in three phases. The first phase determines a set of beam angles through which radiation is delivered, followed by a second phase that determines an optimal radiation intensity profile (or fluence map). This intensity profile is selected to ensure that certain targets receive a required amount of dose while functional organs are spared. To deliver these intensity profiles to the patient, a third phase must decompose them into a collection of apertures and corresponding intensities. In this paper, we investigate this last problem. Formally, an intensity profile is represented as a nonnegative integer matrix; an aperture is represented as a binary matrix whose ones appear consecutively in each row. A feasible decomposition is one in which the original desired intensity profile is equal to the sum of a number of feasible binary matrices multiplied by corresponding intensity values. To most efficiently treat a patient, we wish to minimize a measure of total treatment time, which is given as a weighted sum of the number of apertures and the sum of the aperture intensities used in the decomposition. We develop the first exact algorithm capable of solving real-world problem instances to optimality within practicable computational limits, using a combination of integer programming decomposition and combinatorial search techniques. We demonstrate the efficacy of our approach on a set of 25 test instances derived from actual clinical data and on 100 randomly generated instances.