@article{oai:repo.qst.go.jp:00047558,
 author = {Hirano, Yoshiyuki and Nitta, Munetaka and Nishikido, Fumihiko and Yoshida, Eiji and Inadama, Naoko and Yamaya, Taiga and 平野 祥之 and 新田 宗孝 and 錦戸 文彦 and 吉田 英治 and 稲玉 直子 and 山谷 泰賀},
 issue = {13},
 journal = {Physics in medicine and biology},
 month = {Jul},
 note = {The accumulation of induced radioactivity within in-beam PET scanner
scintillators is of concern for its long-term clinical usage in particle therapy.
To estimate the effects on OpenPET which we are developing for in-beam PET
based on GSOZ (Zi doped Gd2SiO5), we measured the induced radioactivity
of GSO activated by secondary fragments in a water phantom irradiation by a
12C beam with an energy of 290 MeV u−1. Radioisotopes of Na, Ce, Eu, Gd,
Nd, Pm and Tb including positron emitters were observed in the gamma ray
spectra of the activated GSO with a high purity Ge detector and their absolute
radioactivities were calculated. We used the Monte Carlo simulation platform,
Geant4 in which the observed radioactivity was assigned to the scintillators
of a precisely reproduced OpenPET and the single and coincidence rates
immediately after one treatment and after one-year usage were estimated for
the most severe conditions. Comparing the highest coincidence rate originating
from the activated scintillators (background) and the expected coincidence
rate from an imaging object (signal), we determined the expected signal-tonoise
ratio to be more than 7 within 3 min and more than 10 within 1 min from
the scan start time. We concluded the effects of scintillator activation and their
accumulation on the OpenPET imaging were small and clinical long-term
usage of the OpenPET was feasible.
Keywords: in-beam PET, GSO scintillator, particle therapy, openPET,
induced radioactivity, secondary fragments
(Some figures may appear in colour only in the online journal)},
 pages = {4870--4889},
 title = {Induced radioactivity of a GSO scintillator by secondary fragments in carbon ion therapy and its effects on in-beam OpenPET imaging},
 volume = {61},
 year = {2016}
}