MO‐D‐351‐06: A Generalized Inverse Planning Tool for Arc‐Based IMRT Delivery

• Published in: Medical Physics 2008-06, Vol.35 (6), p.2868-2868
• Main Authors: Cao, D, Afghan, M, Ye, J, Wong, TP, Shepard, DM
• Format: Article
• Language: English
• Subjects: Control systems; Drug delivery; Intensity modulated radiation therapy; Linear accelerators; Multileaf collimators; Optimization; Sequence analysis
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.2962357

Purpose: The recent development of new linac control systems that are capable of delivering Volumetric Modulated Arc Therapy (VMAT) has attracted significant attention. There remains, however, a lack of robust inverse planning tools for VMAT. In this study, we will present a generalized inverse planning tool that can provide highly conformal VMAT solutions using either single‐arc or multiple‐arc deliveries for both Varian and Elekta MLCs. Method and Materials: To generate VMAT plans, we first created optimized multi‐field IMRT plans with equal‐spaced beam angles in Pinnacle3 using direct machine parameter optimization (DMPO). A “deliverable” fluence map was reconstructed using the resulting apertures for each beam. Next, we applied our home‐grown arc sequencer to translate these fluence maps into VMAT plans. Based on the user‐defined requirements, the sequencer can provide either single‐arc or multiple‐arc plans that meet the predefined VMAT leaf‐motion constraints. The obtained VMAT plans were then loaded into Pinnacle3 for a final dose calculation. In this study, 10 cases were tested in this study covering a variety of treatment sites including head‐&‐neck(5), prostate(3), lung(1) and brain(1). Results: A total of 24 VMAT plans were created using these 10 cases. Results demonstrated that highly conformal VMAT dose distributions can be achieved with an average sequencing time of under 8 minutes. On average, the VMAT plans required 513 MUs to deliver between 1 to 3 arcs. The average standard deviation in the target dose was 5.79 cGy/fraction; while the average target volume covered by 95% prescribed dose was 98.1%. Our results show that comparable VMAT plans can be achieved using either the Elekta 80‐leaf MLC or the Varian 120‐leaf Millennium MLC. Conclusion: Our generalized arc‐sequencing algorithm serves as a robust inverse planning solution for VMAT. Highly conformal single‐arc or multiple‐arc VMAT plans can be created for Elekta and Varian MLCs.