Background: We measured and assessed ways to reduce the secondary neutron dose from a system for proton
Methods: Proton beams of 60.30 MeV were delivered through an eye-treatment snout in passive scattering mode.
Allyl diglycol carbonate (CR-39) etch detectors were used to measure the neutron dose in the external field at 0.00,
1.64, and 6.00 cm depths in a water phantom. Secondary neutron doses were measured and compared between
those with and without a high-hydrogen?boron-containing block. In addition, the neutron energy and vertices
distribution were obtained by using a Geant4 Monte Carlo simulation.
Results: The ratio of the maximum neutron dose equivalent to the proton absorbed dose (H(10)/D) at 2.00 cm
from the beam field edge was 8.79 ± 1.28 mSv/Gy. The ratio of the neutron dose equivalent to the proton
absorbed dose with and without a high hydrogen-boron containing block was 0.63 ± 0.06 to 1.15 ± 0.13 mSv/Gy at
2.00 cm from the edge of the field at depths of 0.00, 1.64, and 6.00 cm.
Conclusions: We found that the out-of-field secondary neutron dose in proton eye treatment with an eye snout is
relatively small, and it can be further reduced by installing a borated neutron absorbing material.
Dong Wook Kim1, Weon Kuu Chung1, Jungwook Shin2, Young Kyung Lim3, Dongho Shin3*, Se Byeong Lee3,
Myongguen Yoon4, Sung-Yong Park5, Dong Oh Shin6 and Jung Keun Cho7
1Department of Radiation Oncology, Kyung Hee University Hospital at
Gandong, Seoul, Korea. 2Radiation Oncology, University of California, San
Francisco, USA. 3Proton Therapy Center, National Cancer Center, Ilsan, Korea.
4Department of Radiological Science, Korea University, Seoul, Korea. 5Proton
Therapy Center, McLaren Cancer Institute, Flint, MI, USA. 6Department of
Radiation Oncology, Kyung Hee University Medical Center, Seoul, Korea.
7Department of Radiological Science, Jeonju University, Jeonju, Korea.
Kim et al. Radiation Oncology 2013, 8:182