Cross-calibration of ionization chambers in proton and carbon beams
Cross-calibration of ionization chambers in proton and carbon beams
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DOI：
10.1088/0031-9155/49/5/008
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发表时间：
2004-03-07
影响因子：
3.5
通讯作者：
Nishio, T
中科院分区：
文献类型：
--
作者：
Kanai, T;Fukumura, A;Nishio, T
通过比较三种方法得到的系数来检验平行平板电离室的校准系数：由Co-60校准系数N-D、N-W、N-60Co计算，在单能束的平台区用圆柱形电离室交叉校准平行板电离室，在治疗束的SOBP中间用圆柱形电离室交叉校准电离室。本文还研究了在治疗性碳束和质子束的情况下确定水的吸收剂量的参考条件。在国际原子能机构建议的剂量校准程序中，照射野的直径应大于10厘米，水模应在野的两边各延伸至少5厘米。这些建议在质子和碳束上得到了实验验证。对于质子束，这三种方法得到的定标系数基本一致。对于碳束，用第二种方法得到的校准系数比用第三种方法得到的校准系数大1.0%左右，用290 MeV/u束交叉校准得到的校准系数比用400 MeV/u束得到的校准系数低0.5%。用第一种方法得到的定标系数与用SOBP梁得到的结果基本一致。
The calibration coefficients of a parallel plate ionization chamber are examined by comparing the coefficients obtained through three methods: a calculation from a Co-60 calibration coefficient, N-D,N-W,N-60Co, a cross-calibration of a parallel plate ionization chamber using a cylindrical ionization chamber at the plateau region of a mono-energetic beam and a cross-calibration of the chamber using a cylindrical chamber at the middle of the SOBP of the therapeutic beams. This paper also examines reference conditions for determining absorbed dose to water in the cases of therapeutic carbon and proton beams. In the dose calibration procedure recommended by IAEA, irradiation fields should be larger than 10 cm in diameter and the water phantom should extend by at least 5 cm beyond each side of the field. These recommendations are experimentally verified for proton and carbon beams. For proton beams, the calibration coefficients obtained by these three methods approximately agreed. For carbon beams, the calibration coefficients obtained by the second method were about 1.0% larger than those obtained by the third method, and the calibration coefficients obtained by cross-calibration using 290 MeV/u beams were 0.5% lower than those obtained using 400 MeV/u beams. The calibration coefficient obtained by the first method agreed roughly with the results obtained by SOBP beams.