An improved MLC segmentation algorithm and software for step‐and‐shoot IMRT delivery without tongue‐and‐groove error

Publisher Website
Google Scholar
Abstract
We present an improved multileaf collimator (MLC) segmentation algorithm, denoted by (static leaf sequencing with no tongue‐and‐groove error), for step‐and‐shoot intensity‐modulated radiation therapy (IMRT) delivery. is an improvement over the MLC segmentation algorithm called SLS that was developed by Luan et al. [Med. Phys. 31(4), 695–707 (2004)], which did not consider tongue‐and‐groove error corrections. The aims of are (1) shortening the treatment times of IMRT plans by minimizing their numbers of segments and (2) minimizing the tongue‐and‐groove errors of the computed IMRT plans. The input to is intensity maps (IMs) produced by current planning systems, and its output is (modified) optimized leaf sequences without tongue‐and‐groove error. Like the previous SLS algorithm [Luan et al., Med. Phys. 31(4), 695–707 (2004)], is also based on graph algorithmic techniques in computer science. It models the MLC segmentation problem as a weighted minimum‐cost path problem, where the weight of the path is the number of segments and the cost of the path is the amount of tongue‐and‐groove error. Our comparisons of with CORVUS indicated that for the same intensity maps, the numbers of segments computed by are up to 50% less than those by CORVUS 5.0 on the Elekta LINAC system. Our clinical verifications have shown that the dose distributions of the plans do not have tongue‐and‐groove error and match those of the corresponding CORVUS plans, thus confirming the correctness of . Comparing with existing segmentation methods, also has two additional advantages: (1) can compute leaf sequences whose tongue‐and‐groove error is minimized subject to a constraint on the maximum allowed number of segments, which may be desirable in clinical situations where a treatment with the complete correction of tongue‐and‐groove error takes too much time, and (2) can be used to minimize a more general type of error called the tongue‐or‐groove error.
Funding Information
  • National Science Foundation (CCR‐9988468)
  • National Science Foundation (CCF‐0515203)