Induced radioactivity dose of extended beam and pencil beam delivered by medical proton accelerator(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2018年第2期
- Page:
- 161-165
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Induced radioactivity dose of extended beam and pencil beam delivered by medical proton accelerator
- Author(s):
- SONG Tingting1; WANG Yang1; SHENG Xiaofang1; CHEN Qing2; LI Jiamin2
- 1. Department of Radiotherapy, Shanghai Gamma Hospital, Shanghai 200235, China; 2. Proton Therapy Center, Zibo Wanjie Cancer Hospital, Zibo 255000, China
- Keywords:
- ; Keywords: medical proton accelerator; radiation protection; induced radioactivity dose; extended beam; pencil beam
- PACS:
- R144.1；R815
- DOI:
- DOI:10.3969/j.issn.1005-202X.2018.02.008
- Abstract:
- Objective To compare the difference of X/γ ray induced radioactivity doses between extended beam and pencil beam delivered by medical proton accelerator, and explore some countermeasures for decreasing the irradiation level in the therapy room and reducing the annual accumulated irradiation doses of related staff. Methods After the tumor radiation field was simulated, 15 CGE dose was separately delivered by medical proton accelerator in extended beam therapy room and pencil beam therapy room. Sixty seconds after beam-off, two neutron radiation detectors (Neutron RAE II detectors) wereused to simultaneously measure the induced radioactivity dose at the output window center and therapy couch isocenter. We recorded the measurements and repeated the measurement three times at a 30-minute interval. Results The three measurements of induced radioactivity dose rates of extended beam at the beam output window were 32.3, 63.2, 70.1 μSv/h; the measurements at the center of the treatment couch were 4.5, 5.6 and 7.7 μSv/h, which indicated that the induced radioactivity dose rates at both measurement points increased with the measuring sequence. The three measurements of pencil beam at the beam output window were 3.2, 2.3, 2.1 μSv/h, and those at the center of the treatment couch were 0.21, 0.18, 0.18 μSv/h, which revealed that the induced radioactivity dose rates at the two measuring points did not increase with the measuring sequence. In the output window, the mean value of measurements of extended beam was 21.8 times larger than that of the pencil beam; at the center of the couch, the average value of measurements of extended beam was 31.2 times larger than that of pencil beam. Conclusion With the same deliver dose and beam-on time, the induced radioactivity dose of pencil beam was less than that of extended beam, and the environmental radiation level was far lower in pencil beam therapy room than extended beam therapy room, which provides a better protection to the related staff.
Last Update: 2018-01-29