Improved Model on Minimizing Static Intensity Modulation Delivery Time

In Intensity Modulated Radiation Therapy static intensity modulation delivery, leaf sequencing is basically a process where the intensity map is broken down into subfields or segments that can be implemented by multileaf collimators. The purpose of this study was to investigate a new method to improve the Langer´s integer programming model. The method is to choose the horizontal or orthogonal leaf direction of intensity map according with Xia and Verhy´s alogrithm and invoke a new constraint to optimize multileaf collimator leaf travel distances. A comparative study of three different leaf sequencing methods, Xia and Verhey, Langer et al., and our improved model is presented. The numerical outputs reveal that model modifications can yield better results according with the three criteria: total number of monitor unit, number of segment and leaf travel distances.