MOUNTAIN REDUCTION, BLOCK MATCHING, AND APPLICATIONS IN INTENSITY-MODULATED RADIATION THERAPY

In this paper, we present a new geometric algorithm for the 3-D static leaf sequencing (SLS) problem arising in intensity-modulated radiation therapy (IMRT), a modern cancer treatment technique. The treatment time and machine delivery error are two crucial factors for measuring the quality of a solution (i.e., a treatment plan) for the SLS problem. In the current clinical practice, physicians prefer to use treatment plans with the lowest possible amount of delivery error, and are also very concerned about the treatment time. Previous SLS methods in both the literature and commercial treatment planning systems either cannot minimize the error or achieve that only by using treatment plans which require a prolonged treatment time. In comparison, our new geometric algorithm is computationally efficient; more importantly, it guarantees that the output treatment plans have the lowest possible amount of delivery error, and the treatment time for the plans is significantly shorter. Our solution is based on a number of novel schemes and ideas (e.g., mountain reduction, block matching, profile-preserving cutting, etc) which may be of interest in their own right. Experimental results based on real medical data showed that our new algorithm runs fast and produces much better quality treatment plans than current commercial planning systems and well-known algorithms in medical literature.