Estimation of Background Radiation from e-LINAC for Direct Confirmation of Irradiated Area by Utilizing the Annihilation Photons.
In radiation therapy, there is no suitable method to confirm either the three-dimensional irradiated area or the absorbed dose during irradiation. If there were such a method it would allow verification of the absorbed dose as well as help to avoid extraneous irradiation. We previously proposed a method utilizing annihilation photons generated by therapeutic photon beams to measure the irradiated area directly during irradiation. In the present study, we designed and fabricated a fast YAP:Ce scintillation counter which uses a compact photosensor to measure annihilation photons. The energy resolution and detection efficiency were obtained experimentally using a (22)Na planar source. We measured count rates of background radiation by using the detector and estimated those of background radiation from an e-LINAC by correcting for detection efficiency. The obtained energy resolution of the YAP:Ce scintillation detector was 12.16+/-3.5% and its detection efficiency was 28.36+/-5.3%. The counting rates of background radiation from e-LINAC were approximately from 10(8) to 10(9) cps, and were proportional to the e-LINAC dose rate. Our developed detector had a high sensitivity, good time resolution and compact size which allows for easy radiation shielding. Therefore, we concluded that it was both practical and effective for the measurement of the position-distribution of annihilation photons.
Kojima
Hironori
H
Graduate School of Medical Science, Kitasato University, 1-15-1, Kitazato, Sagamihara-shi 228-8555 Japan. mm06023e@st.kitasato-u.ac.up.
Magara
Takatsugu
T
Fukushima
Yasuhiro
Y
Ishigami
Minoru
M
Matsubayashi
Fumiyasu
F
Hashimoto
Masatoshi
M
Saitoh
Hidetoshi
H
Saito
Kyoko
K
Maruyama
Koichi
K
D001417:Background Radiation; D007477:Ions; D009010:Monte Carlo Method; D010315:Particle Accelerators; D017785:Photons; D011874:Radiometry; D012588:Scintillation Counting
D007477:Ions