Door gamma and neutron survey for TrueBEAM 10 MV with and without flattening filter free mode
Keywords:
Radiation survey, Flattening filter free, Neutron doseAbstract
Background: The photoneutron production from the interaction of the high energy photon exceeds 8 MV and high atomic number materials within gantry are undesired.
Objective: To perform the gamma and neutron survey behind the TrueBEAM door for both 10 MV and 10 FFF
Materials and Methods: The RadEYE GN+ from Thermo was used for neutron survey at the TrueBEAM treatment door for 10 MV and 10 FFF. The parameters that impact the peak neutron dose rate includes such as gantry angle, field size, and dose rate. The Intensity Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) treatment planning forboth conventional dose fractionation and the high dose per fraction like the Stereotactic Body Radiation Therapy (SBRT) were investigated in the gamma and neutron survey.
Results: The peak neutron dose rate was at 90° gantry angle that faced directly through the door. The 10 MV showed higher gamma and neutron peak dose rate. The smaller field size, higher dose rate, and higher MU technique like IMRT increased the gamma and neutron peak dose rate. SBRT technique gave higher dose fractionation and dose rate, thus, it had to higher neutron peak dose rate than the conventional fractionation.
Conclusion: The gamma and neutron peak dose rate through the TrueBEAM door depends on gantry angle, field size, flattening filter usage, dose rate, total number of MU, etc, however, the accumulated neutron dose for SBRT technique with 10 FFF was not detected.
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