Beam complexity and monitor unit efficiency comparison in two different volumetric modulated arc therapy delivery systems using automated planning
Chengqiang Li,
Cheng Tao,
Tong Bai,
Zhenjiang Li,
Ying Tong,
Jian Zhu,
Yong Yin,
Jie Lu
Affiliations
Chengqiang Li
Department of Radiation Oncology Physics, Shandong Cancer Hospital and Institute, Cancer Hospital affiliated to Shandong First Medical University and Shandong Academy of Medical Sciences
Cheng Tao
Department of Radiation Oncology Physics, Shandong Cancer Hospital and Institute, Cancer Hospital affiliated to Shandong First Medical University and Shandong Academy of Medical Sciences
Tong Bai
Department of Radiation Oncology Physics, Shandong Cancer Hospital and Institute, Cancer Hospital affiliated to Shandong First Medical University and Shandong Academy of Medical Sciences
Zhenjiang Li
Department of Radiation Oncology Physics, Shandong Cancer Hospital and Institute, Cancer Hospital affiliated to Shandong First Medical University and Shandong Academy of Medical Sciences
Ying Tong
Department of Radiation Oncology Physics, Shandong Cancer Hospital and Institute, Cancer Hospital affiliated to Shandong First Medical University and Shandong Academy of Medical Sciences
Jian Zhu
Department of Radiation Oncology Physics, Shandong Cancer Hospital and Institute, Cancer Hospital affiliated to Shandong First Medical University and Shandong Academy of Medical Sciences
Yong Yin
Department of Radiation Oncology Physics, Shandong Cancer Hospital and Institute, Cancer Hospital affiliated to Shandong First Medical University and Shandong Academy of Medical Sciences
Jie Lu
Department of Radiation Oncology Physics, Shandong Cancer Hospital and Institute, Cancer Hospital affiliated to Shandong First Medical University and Shandong Academy of Medical Sciences
Abstract Background To investigate the beam complexity and monitor unit (MU) efficiency issues for two different volumetric modulated arc therapy (VMAT) delivery technologies for patients with left-sided breast cancer (BC) and nasopharyngeal carcinoma (NPC). Methods Twelve left-sided BC and seven NPC cases were enrolled in this study. Each delivered treatment plan was optimized in the Pinnacle3 treatment planning system with the Auto-Planning module for the Trilogy and Synergy systems. Similar planning dose objectives and beam configurations were used for each site in the two different delivery systems to produce clinically acceptable plans. The beam complexity was evaluated in terms of the segment area (SA), segment width (SW), leaf sequence variability (LSV), aperture area variability (AAV), and modulation complexity score (MCS) based on the multileaf collimator sequence and MU. Plan delivery and a gamma evaluation were performed using a helical diode array. Results With similar plan quality, the average SAs for the Trilogy plans were smaller than those for the Synergy plans: 55.5 ± 21.3 cm2 vs. 66.3 ± 17.9 cm2 (p 0.05) for the NPC cases and 444.8 ± 61.3 MU and 393.8 ± 75.3 MU (p > 0.05) for the BC cases. The gamma index agreement scores were never below 91% using 3 mm/3% (global) distance to agreement and dose difference criteria and a 10% lower dose exclusion threshold. Conclusions The Pinnacle3 Auto-Planning system can optimize BC and NPC plans to achieve the same plan quality using both the Trilogy and Synergy systems. We found that these two systems resulted in different SAs, SWs, LSVs, AAVs and MCSs. As a result, we suggested that the beam complexity should be considered in the development of further methodologies while optimizing VMAT autoplanning.
