Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
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Impact of Smaller Gantry Arc Increments on Volumetric Modulated Arc Radiation Therapy in the Monaco Treatment Planning System

  • Seonghee Kang (Department of Radiation Oncology, Seoul National University Hospital) ;
  • Hyejo Ryu (Department of Radiation Oncology, Chung-Ang University Gwang Myeong Hospital) ;
  • Do Hoon Oh (Department of Radiation Oncology, Chung-Ang University Gwang Myeong Hospital) ;
  • Lee Yoo (Department of Radiation Oncology, Chung-Ang University Gwang Myeong Hospital) ;
  • Minsoo Chun (Institute of Radiation Medicine, Seoul National University Medical Research Center)
  • Received : 2024.08.26
  • Accepted : 2024.09.09
  • Published : 2024.09.30
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Abstract

Purpose: This study aims to evaluate the impact of smaller gantry arc increment (GAI) values on the plan quality and deliverability of volumetric modulated arc therapy (VMAT) for head and neck (HN) and prostate cancer cases using the Monaco treatment planning system. The study investigates whether a smaller GAI can enhance organ at risk (OAR) sparing without compromising target coverage or significantly increasing plan complexity. Methods: VMAT plans were created for 20 patients (10 HN and 10 prostate cancer) using GAI values of 15° and 30°. Dose-volumetric parameters, such as conformity number, homogeneity and gradient indices, were assessed alongside plan complexity metrics like the modulation complexity score for VMAT (MCSv) and monitor unit (MU). Statistical significance was determined using the Wilcoxon signed-rank test. Results: For HN cases, a 15° increment significantly reduced the D0.03cc for the spinal cord and the Dmean for both parotid glands compared to a 30° increment, improving OAR sparing. However, no significant differences were observed in the OAR doses for prostate cases. The 15° increment resulted in higher plan complexity, reflected by a lower MCSv, but the MU difference was not significant. Conclusions: Smaller GAI values, such as 15°, can significantly reduce OAR doses in HN VMAT plans, offering potential clinical benefits despite increased plan complexity. However, no substantial advantages were observed in prostate cases. These findings suggest that smaller GAI values may be particularly beneficial for cases requiring high modulation.

Keywords

Acknowledgement

This work was supported by Korea Institute of Energy Technology Evalutaion and Planning (KETEP) grant funded by the Korea government (MOTIE) (20227410100040, Development of patch-type flexible personal dosimeter and real-time remote monitoring system using high-performance inorganic perovskite).

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