Article 陽子線治療場における標的核破砕反応による二次粒子の計測技術と線量評価

小平, 聡

43 ( 1 )  , pp.25 - 28 , 2017-04 , 応用物理学会放射線分科会
In aaddition to energy loss bay ionization process, protons, of energy >~50MeV,such as those used in proton radiotherapy, can undergo nuclear interactions wiyh nuclei of Z>1, resulting in the production of short range (<10μm),high-LET (linear energy transfer) target fragment particles. One of the few methods to detect these short-range particles is by means of CR-39 plastic nuclear track detector analyzed with an atomic force microscope. However due to the LET-dependent angular sensitivity of CR-39, multiple detectors exposed at a range of incident angles to the primary proton beam, must be analyzed in order to accurately determine the LET spectrum, absorbed dose and dose equivalent. The LET spectrum of 160 MeV oroton induced secondary particles was experimentally measured with CR-39, which were exposed at six different incident angles to take into account the intrinsic sensitivity of the critical angle for track registration. The irradiated detectors were chemically processed to remove a 1 μm thick volume of CR-39. The measured LET range of short range tracks was from 15 keV/μm. The dose equivalent contribution (Hs/Dp) was found to be 208.1±5.5mSv/Gy.

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