Development of a Neutron Dosimetry System Based on Double Self-Activated CsI Detectors for Medical Linac Environments.

In the present study, by using double self-activated CsI detectors, the development of a neutron dosemeter system whose response indicates better agreement with the International Commission on Radiological Protection-74 rem-response was carried out to simply evaluate the neutron dose with high accuracy. The present double neutron dosemeter system, using a slow-neutron dosemeter (thermal to 10 keV) and a fast-neutron dosemeter (above 10 keV), consists of CsI scintillators wrapped with two types of neutron energy filtering materials: polyethylene and B4C silicon rubber. After optimization of each filter thickness, to confirm the validity of our method, the neutron ambient dose equivalents under several operating conditions of medical linear accelerators (Linacs) were evaluated using a Monte Carlo simulation and an experiment with the present dosemeter. From these results, the present dosimetry system has enabled a more accurate neutron dose evaluation than our conventional dosemeter, and the present dosemeter was suitable for the neutron dosimetry for 10 MV Linac environments.

[1]  A. Nohtomi,et al.  A design study of application of the CsI self-activation method to the neutron rem-counter technique , 2019, Radiation Measurements.

[2]  L. Montgomery,et al.  The effect of the flattening filter on photoneutron production at 10 MV in the Varian TrueBeam linear accelerator , 2018, Medical physics.

[3]  A. Nohtomi,et al.  Improvement of neutron spectrum unfolding based on three-group approximation using CsI self-activation method for evaluation of neutron dose around medical linacs , 2018, Radiation Measurements.

[4]  Yasuhiko Nakamura,et al.  High Sensitive Neutron-Detection by Using a Self-Activation of Iodine-Containing Scintillators for the Photo-Neutron Monitoring around X-ray Radiotherapy Machines , 2016 .

[5]  A. Nohtomi,et al.  Accuracy of neutron self-activation method with iodine-containing scintillators for quantifying 128I generation using decay-fitting technique , 2015 .

[6]  Yasuhiko Nakamura,et al.  Applicability of self-activation of an NaI scintillator for measurement of photo-neutrons around a high-energy X-ray radiotherapy machine , 2014, Radiological Physics and Technology.

[7]  Hiroshi Nakashima,et al.  Particle and Heavy Ion Transport code System, PHITS, version 2.52 , 2013 .

[8]  G. Hartmann,et al.  Neutron spectrometry and determination of neutron ambient dose equivalents in different LINAC radiotherapy rooms , 2010 .

[9]  T. Fujibuchi,et al.  Nationwide survey on the operational status of electron accelerators for radiation therapy in Japan , 2010, Radiological physics and technology.

[10]  F. Lohr,et al.  Volumetric modulated arc therapy (VMAT) vs. serial tomotherapy, step-and-shoot IMRT and 3D-conformal RT for treatment of prostate cancer. , 2009, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[11]  D. J. Brenner Conversion Coefficients for Use in Radiological Protection against External Radiation , 1999 .

[12]  E. Hall,et al.  Photoneutrons from medical linear accelerators--radiobiological measurements and risk estimates. , 1995, International journal of radiation oncology, biology, physics.

[13]  Toshikazu Suzuki,et al.  Realization of a high sensitivity neutron rem counter , 1985 .