Dosimetric Effect on Selectable Optimization Parameters of Volumatric Modulated Arc Therapy

선택적 최적화 변수(Selectable Optimization Parameters)에 따른 부피적조절회전방사선치료(VMAT)의 선량학적 영향

  • Jung, Jae-Yong (Department of Biomedical Engineering, The Catholic University of Korea College of Medicine) ;
  • Shin, Yong-Joo (Department of Radiation Oncology, Sanggye Paik Hospital, Inje University) ;
  • Sohn, Seung-Chang (Department of Radiation Oncology, Sanggye Paik Hospital, Inje University) ;
  • Kim, Yeon-Rae (Department of Biomedical Engineering, The Catholic University of Korea College of Medicine) ;
  • Min, Jung-Wan (Department of Biomedical Engineering, The Catholic University of Korea College of Medicine) ;
  • Suh, Tae-Suk (Department of Biomedical Engineering, The Catholic University of Korea College of Medicine)
  • 정재용 (가톨릭대학교 의과대학 의공학교실) ;
  • 신영주 (인제대학교 상계백병원 방사선종양학과) ;
  • 손승창 (인제대학교 상계백병원 방사선종양학과) ;
  • 김연래 (가톨릭대학교 의과대학 의공학교실) ;
  • 민정환 (가톨릭대학교 의과대학 의공학교실) ;
  • 서태석 (가톨릭대학교 의과대학 의공학교실)
  • Received : 2012.01.13
  • Accepted : 2012.03.07
  • Published : 2012.03.31

Abstract

The aim of this study is to evaluate plan quality and dose accuracy for Volumetric Modulated Arc Therapy (VMAT) on the TG-119 and is to investigate the effects on variation of the selectable optimization parameters of VMAT. VMAT treatment planning was implemented on a Varian iX linear accelerator with ARIA record and verify system (Varian Mecical System Palo Alto, CA) and Oncentra MasterPlan treatment planning system (Nucletron BV, Veenendaal, Netherlands). Plan quality and dosimetric accuracy were evaluated by effect of varying a number of arc, gantry spacing and delivery time for the test geometries provided in TG-119. Plan quality for the target and OAR was evaluated by the mean value and the standard deviation of the Dose Volume Histograms (DVHs). The ionization chamber and $Delta^{4PT}$ bi-planar diode array were used for the dose evaluation. For treatment planning evaluation, all structure sets closed to the goals in the case of single arc, except for the C-shape (hard), and all structure sets achieved the goals in the case of dual arc, except for C-shape (hard). For the variation of a number of arc, the simple structure such as a prostate did not have the difference between single arc and dual arc, whereas the complex structure such as a head and neck showed a superior result in the case of dual arc. The dose distribution with gantry spacing of $4^{\circ}$ was shown better plan quality than the gantry spacing of $6^{\circ}$, but was similar results compared with gantry spacing of $2^{\circ}$. For the verification of dose accuracy with single arc and dual arc, the mean value of a relative error between measured and calculated value were within 3% and 4% for point dose and confidence limit values, respectively. For the verification on dose accuracy with the gantry intervals of $2^{\circ}$, $4^{\circ}$ and $6^{\circ}$, the mean values of relative error were within 3% and 5% for point dose and confidence limit values, respectively. In the verification of dose distribution with $Delta^{4PT}$ bi-planar diode array, gamma passing rate was $98.72{\pm}1.52%$ and $98.3{\pm}1.5%$ for single arc and dual arc, respectively. The confidence limit values were within 4%. The smaller the gantry spacing, the more accuracy results were shown. In this study, we performed the VMAT QA based on TG-119 procedure, and demonstrated that all structure sets were satisfied with acceptance criteria. And also, the results for the selective optimization variables informed the importance of selection for the suitable variables according to the clinical cases.

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