Abstract
Radiation therapy is a common treatment for some specific tumors in the treatment of cancer now. In recent years, there has been a new development in radiation therapy, which is called intensity modulated radiation therapy (IMRT). The outstanding advantage of IMRT is it can modulate the intensity of the radiation beam effectively, and focus a higher radiation dose on the tumor while minimizing radiation exposure to surrounding normal tissues. Multileaf Collimator (MLC) is one of the essential equipments when IMRT is executed. MLC is composed by several pairs of leaves, and it can achieve the objective of intensity modulated by series moving of leaves. Although the medical radiation therapy has been studied for a long time, the efficiency of MLC operations can be further improved. For a radiation therapy plan, a long total delivery time may not only diminish the quality of therapy but also cause uncomfortable perception to a patient. Three criteria which effect total delivery time are number of monitor units (MUs), number of segments, and distance of leaf traveled. This study aims to develop a three-stage-optimization algorithm to achieve a shortest total delivery time. We minimize the number of monitor units at first. Then we minimize the number of segments with minimum number of monitor units. Finally, we try to shorten the distance of leaf traveled when minimum number of monitor units and segments are used. According to the outcomes of series of experiments, we show that the performance of our algorithm is better than previous works significantly to solve a radiation therapy plan.