title: Quantification of residual dose estimation error on log file-based patient dose calculation.
abstract: OBJECTIVE
  The log file-based patient dose estimation includes a residual dose estimation error caused by leaf miscalibration, which cannot be reflected on the estimated dose. The purpose of this study is to determine this residual dose estimation error.
  
  
  METHODS
  Modified log files for seven head-and-neck and prostate volumetric modulated arc therapy (VMAT) plans simulating leaf miscalibration were generated by shifting both leaf banks (systematic leaf gap errors: ±2.0, ±1.0, and ±0.5mm in opposite directions and systematic leaf shifts: ±1.0mm in the same direction) using MATLAB-based (MathWorks, Natick, MA) in-house software. The generated modified and non-modified log files were imported back into the treatment planning system and recalculated. Subsequently, the generalized equivalent uniform dose (gEUD) was quantified for the definition of the planning target volume (PTV) and organs at risks.
  
  
  RESULTS
  For MLC leaves calibrated within ±0.5mm, the quantified residual dose estimation errors that obtained from the slope of the linear regression of gEUD changes between non- and modified log file doses per leaf gap are in head-and-neck plans 1.32±0.27% and 0.82±0.17Gy for PTV and spinal cord, respectively, and in prostate plans 1.22±0.36%, 0.95±0.14Gy, and 0.45±0.08Gy for PTV, rectum, and bladder, respectively.
  
  
  CONCLUSIONS
  In this work, we determine the residual dose estimation errors for VMAT delivery using the log file-based patient dose calculation according to the MLC calibration accuracy.
authors.affiliation: Department of Radiology, Takeda General Hospital, Aizuwakamatsu, Japan; Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Katsuta
authors.affiliation: Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan. Electronic address: kadoya.n@rad.med.tohoku.ac.jp.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kadoya
authors.affiliation: Department of Radiation Oncology, Tokai University Graduate School of Medicine, Isehara, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Fujita
authors.affiliation: Department of Radiology, Takeda General Hospital, Aizuwakamatsu, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Shimizu
authors.affiliation: Department of Radiology, Takeda General Hospital, Aizuwakamatsu, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Matsunaga
authors.affiliation: Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Haruo
authors.initials: H
authors.lastname: Matsushita
authors.affiliation: Department of Radiology, Takeda General Hospital, Aizuwakamatsu, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Majima
authors.affiliation: Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Jingu
mesh_terms: D000465:Algorithms; D002138:Calibration; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D010315:Particle Accelerators; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011785:Quality Assurance, Health Care; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012306:Risk; D012984:Software
keywords: DVH; Log file; Patient QA; Radiotherapy; VMAT