Output factor determination based on Monte Carlo simulation for small cone field in 10-MV photon beam

Kyohei Fukata, Satoru Sugimoto, Chie Kurokawa, Akito Saito, Tatsuya Inoue, Keisuke Sasai

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The difficulty of measuring output factor (OPF) in a small field has been frequently discussed in recent publications. This study is aimed to determine the OPF in a small field using 10-MV photon beam and stereotactic conical collimator (cone). The OPF was measured by two diode detectors (SFD, EDGE detector) and one micro-ion chamber (PinPoint 3D chamber) in a water phantom. A Monte Carlo simulation using simplified detector model was performed to obtain the correction factor for the detector measurements. About 12% OPF difference was observed in the measurement at the smallest field (7.5 mm diameter) for EDGE detector and PinPoint 3D chamber. By applying the Monte Carlo-based correction factor to the measurement, the maximum discrepancy among the three detectors was reduced to within 3%. The results indicate that determination of OPF in a small field should be carefully performed. Especially, detector choice and appropriate correction factor application are very important in this regard.

Original languageEnglish
Pages (from-to)192-201
Number of pages10
JournalRadiological Physics and Technology
Issue number2
Publication statusPublished - 2018 Jun 1



  • Dosimetry
  • Monte Carlo
  • Small field
  • SRS

ASJC Scopus subject areas

  • Radiation
  • Physical Therapy, Sports Therapy and Rehabilitation
  • Radiology Nuclear Medicine and imaging

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