A multiobjective approach to the leaf sequencing problem on intensity modulated radiation therapy
Radiation therapy, Multileaf collimator, Leaf sequencing
Algorithms are an essential part of the radiation therapy planning which consists of three major problems: beam angle and fluence map optimization, and realization. The issue of this study is the third problem, also called leaf sequencing. It consists in defining a sequence of configurations of a device (called multileaf collimator) that correctly delivers radiation to the patient. A usual model for this problem is the decomposition of a matrix into a weighted sum of (0,1)-matrices, called segments, in which the ones in each row appear consecutively. Other constraints can also be considered. Each (0,1)-matrix corresponds to a configuration of the device. The realization problem has three objectives. The first one is to minimize the sum of weights assigned to the (0,1)-matrices. The second is to minimize the number of segments. Finally, the third one is to find the best order to apply those configurations. This study presents a greedy and randomized algorithm to this problem and compares it to other multi-objective algorithm presented previously in the literature. Statistical tests show that our algorithm outperformed the previous one on all indicators.