The development of patient-specific quality assurance (PSQA) for a proton wobbling nozzle using PTSim Monte Carlo code

Luu Dang Hoang Oanh, Tsukasa Aso, Chun Chieh Wang, Tsi Chian Chao*, I. Chun Cho*

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

Abstract

The aim of this study is to develop a Monte Carlo-based platform for patient-specific quality assurance (PSQA) in the proton wobbling nozzle at Chang Gung Memorial Hospital. To efficiently reduce time usage and enhance simulated precision, this platform required an initial fine-tuning of the Guard volume (GV) and lateral displacement (LD) settings. Different GV sizes combined with LD modes were utilized to estimate depth dose profiles in a water phantom. The simulated central axis depth doses were then analyzed using PTSim and compared to measurement using a PTW MP3 water tank and a Markus ionization chamber type 34045. Treatment parameters for a liver case were extracted from the Eclipse DICOM RT Plan file. Simulated doses were compared to measurements using Zebra and MatriXX systems during PSQA process. Furthermore, a geometrical trigger technique was applied to assess the track positions in patient-specific components. The study found that the mean dose difference between measured and simulated values for the optimized LD/GV was below 1% at all depth positions. With passing rates of 97.4% at the middle SOBP and 90.3% at the proximal SOBP, the gamma analysis demonstrated satisfactory results. For the axial dose profile, SOBP flatness was within 2.5%. From the geometric trigger analysis, more than 95–98% of the dose was delivered through the range compensator, while approximately 2–5% originated from scattered protons from the Multi-Leaf Collimator (MLC) and block's edges. The PTSim simulation's performance in conducting PSQA demonstrated its capability and reliability.

Original languageEnglish
Article number111953
JournalRadiation Physics and Chemistry
Volume223
Early online date2024
DOIs
StatePublished - 10 2024

Bibliographical note

Publisher Copyright:
© 2024 Elsevier Ltd

Keywords

  • Guard volume
  • Lateral displacement
  • Patient-specific quality assurance
  • Wobbling nozzle
  • PTSim Monte Carlo

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