A Leaf Sequencing Software for Intensity-Modulated Radiation Therapy

This paper presents a leaf sequencing software called SLS (static leaf sequencing) for intensity-modulated radiation therapy (IMRT). SLS seeks to produce improved clinical IMRT treatment plans by (1) shortening their treatment times and (2) minimizing their machine delivery errors. Our SLS software is implemented using the C programming language on Linux workstations and is designed as a separate module to complement the current commercial treatment planning systems. The input to SLS is discrete radiation intensity maps computed by current planning systems, and its output is (modified) optimized control sequences for the radiotherapy machines. Our SLS approach is very different from the commonly used planning methods in medical literature in that it is based on graph algorithms and computational geometry techniques. Comparisons of SLS with the CORVUS commercial planning system indicated that for the same set of discrete radiation intensity maps, treatment times can be shortened by over 30% by our SLS plans while maintaining the same treatment quality. We have used SLS in clinical applications at two cancer treatment centers. This paper discusses the various aspects of the implementation, installation, commissioning, and testing of our SLS software system