Journal Article Measurement of the secondary neutron dose distribution from the LET spectrum of recoils using the CR-39 plastic nuclear track detector in 10 MV X-ray medical radiation fields

Fujibuchi, Toshioh  ,  Kodaira, Satoshi  ,  Sawaguchi, Fumiya  ,  Abe, Yasuyuki  ,  Obara, Satoshi  ,  Yamaguchi, Masae  ,  Kawashima, Hajime  ,  Kitamura, Hisashi  ,  Kurano, Mieko  ,  Uchihori, Yukio  ,  Yasuda, Nakahiro  ,  Koguchi, Yasuhiro  ,  Nakajima, Masaru  ,  Kitamura, Nozomi  ,  Sato, Tomoharu

We measured the recoil charged particles from secondary neutrons produced by the photonuclearreaction in a water phantom from a 10-MV photon beam from medical linacs. The absorbed dose andthe dose equivalent were evaluated from the linear energy transfer (LET) spectrum of recoils using theCR-39 plastic nuclear track detector (PNTD) based on well-established methods in the field of spaceradiation dosimetry. The contributions and spatial distributions of these in the phantom on nominal photonexposures were verified as the secondary neutron dose and neutron dose equivalent. The neutrondose equivalent normalized to the photon-absorbed dose was 0.261 mSv/100 MU at source to chamberdistance 90 cm. The dose equivalent at the surface gave the highest value, and was attenuated to less than10% at 5 cm from the surface. The dose contribution of the high LET component of P100 keV/lmincreased with the depth in water, resulting in an increase of the quality factor. The CR-39 PNTD is apowerful tool that can be used to systematically measure secondary neutron dose distributions in a waterphantom from an in-field to out-of-field high-intensity photon beam.

Number of accesses :  

Other information