title: A study on investigating the delivery parameter error effect on the variation of patient quality assurance during RapidArc treatment.
abstract: OBJECTIVE
  The purpose of this study is to evaluate delivery parameter errors (DPEs) and their impact on clinical dose variation with the Varian RapidArc technique.
  
  
  METHODS
  The dynalog files of 16 head-and-neck patients were retrospectively analyzed to characterize three RapidArc DPEs: dose MU, gantry angle, and MLC gap errors. A total of 64 reconstructed plans were created by creating four variants of each of the original 16 plans (three with the DPEs applied individually and one with the three DPEs combined). These reconstructed plans were compared to the original plans to evaluate the impact of the DPEs on the clinical dose distribution.
  
  
  RESULTS
  The mean dose MU, gantry angle, and MLC gap error for all patients were 0.00 ± 0.00 MU, -0.36 ± 0.03°, and 0.00 ± 0.01 mm, respectively. The DPEs had no obvious dosimetric impact on any of the studied dosimetric endpoints except the parotid dose. The gantry angle error, MLC gap error, and combined DPEs changed the parotid Dmean (mean dose) and parotid V30 (volume receiving at least 30 Gy) by 1%-2%.
  
  
  CONCLUSIONS
  It is feasible to use dose distributions reconstructed from dynalog file data as a quality assurance tool. The dose MU, gantry angle, and MLC errors have only minor effects on the accuracy of the delivered dose.
authors: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.
authors: Jiayuan
authors: J
authors: Peng
authors: Zhen
authors: Z
authors: Zhang
authors: Lijun
authors: L
authors: Zhou
authors: Jinfang
authors: J
authors: Zhao
authors: Jiazhou
authors: J
authors: Wang
authors: Lin
authors: L
authors: Kong
authors: Weigang
authors: W
authors: Hu
mesh_terms: D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy; D011786:Quality Control; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061106:Radiotherapy Setup Errors; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies