Paper
Towards Routine 2-Step Based IMRT/IMAT Treatment Planning in the Clinic
- Authors:
- Mark Gainey; Kostyantyn Holubyev; Klaus Bratengeier
- Abstract
- The purpose of this work is to describe the automation of 2-Step IMRT/IMAT segmentation. 2-Step IMRT/IMAT employs analysis of the PTV-OAR topology to determine the initial segment shapes for each gantry angle. Previous retrospective planning studies by the authors have shown that the quality of 2-Step IMRT/IMAT plans is at least as good as that of plans calculated based solely upon the optimization module in commercial treatment planning system (TPS) software. Hitherto the generation of the 2-Step segment shapes was performed manually employing the TPS, a time consuming process requiring approximately 5 minutes per PTV-OAR pair for each gantry angle. The software was written in C++ programing language and tested to process the structure set files to generate the 2-Step segments. Six clinical prostate cases incorporating a simultaneously integrated boost were employed to test segment generation for a typical seven field IMRT using the Synergy linac and BeamModulator MLC commissioned in the Pinnacle TPS available at the University Hospital Wuerzburg. Additionally, two clinical paraspinal tumour cases were also used to test segment generation for IMAT. The C++ classes were designed to be extensible for other MLCs and TPSs, which permit seeding of the optimiser with segment forms. For each PTV-OAR pair, a conformal (zeroth order), OAR blocked (first order) and “dose saturation” (second order) segment was automatically generated employing the BEV projection of the PTV and OAR. Subsequently these segment shapes were sequenced into deliverable MLC segments and exported to the TPS as IMRT or VMAT plans. For the prostate cases the mean time per generated segment was 36 ± 6 ms (total 70 segments). For the paraspinal tumour cases, three complete arcs were generated with 2˚ spacing per control point (179 segments for a complete rotation). The total time taken was 13.1 and 12.0 s (537 segments) or 24 ms and 22 ms per segment respectively. These exported plans may be further optimized by the TPS. Alternatively the software may be used as the basis for adaption of treatment plans on the basis of daily cone beam CT (CBCT) studies. This work demonstrates the automatic generation of 2-Step IMRT and IMAT cases for the Pinnacle TPS. It enables more comprehensive planning studies to be performed.
- Keywords
- Radiotherapy; Treatment Plannung; IMRT; VMAT; Adaption
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