临床质子束水吸收剂量测量方法  

Measurement Method of Absorbed Dose in Water for Clinical Proton Beam

作　　者：刘毅[1,2] 王培臣[1,2] 张新[1,2] 

机构地区：[1]国家食品药品监督管理局北京医疗器械质量监督检验中心,北京101111 [2]北京市医疗器械检验所,北京101111

出　　处：《中国医学物理学杂志》2014年第6期5227-5229,5257,共4页Chinese Journal of Medical Physics

基　　金：国家科技支撑计划课题(2012BAI22B04);国家科技支撑计划课题(2013BAI17B07)

摘　　要：目的:探讨结合我国放射剂量量值传递体系,给出临床质子束水吸收剂量测量方法。方法:依据IAEA 398和IAEA 277技术报告,并结合我国吸收剂量标准计量体系,研究较为实用的测量方法。IAEA 398技术报告推荐了两种电离室用于质子束水吸收剂量的测量,即平行板电离室和石墨指型电离室;推荐使用水模体,模体的横向尺寸(长和宽)至少比测量点处辐射野四边向外扩展5 cm,模体深度与测量参考点的最大深度相比,不小于5 g/cm2,并给出了测定质子束辐射质的参考条件。但是由于我国没有质子束水吸收剂量标准,即无法给出校准因子ND,W,以及60Co水吸收剂量标准,无法进行质子束水吸收剂量的测量计算。通过上述情况的的讨论,若要测量质子束水吸收剂量,首先必须解决校准因子ND,w,Q0的问题。结果:首先解决校准因子ND,w,Q0的问题。目前我国现行使用的是60Co空气比释动能标准Nk或者60Co空气照射量标准NX。根据我国现行的60Co空气比释动能标准Nk,按照IAEA 277报告描述的方法 ,可以通过文中公式(4)计算得到ND,w,Q0。关于辐射质Q相对于参考辐射质为Q0的电离室响应校正因子kQ,Q0,IAEA 398报告给出了几种常用电离室的计算值,图3为根据校正因子kQ,Q0的计算值绘制的校正曲线,图中kQ表示当参考辐射质Q0为60Co时的校正因子kQ,Q0。结论 :本文研究了临床质子束水吸收剂量可行的测量方法 ,应用公式(2)、(4)、(5)可以测量计算得到质子束水吸收剂量,有关文献的研究结果证明使用NX方法与使用ND,W方法是基本上等同的。Abjective： In conjunction with the calibration system of radiation dose in China, to provide the measurement method of absorbed dose in water for clinical proton beam is given in this articlel Methods： BaSed on the IAEA Technical Report Series 398 and 277, in line with the absorbed dose calibration system in China, practical measuring method is studied. The IAEA TRS No.398 recommended two ion chambers for measurement of proton beam absorbed dose in water, i.e. plane-parallel ionization chambers and graphite cylindrical ionization chambers; water phantom is recommended, which should extend to at least 5 cm beyond all four sides of the field size of the field size employed at the depth of measurement and also extend to at least 5 g/cm2 beyond the maximum depth of measurement; reference condihons for the determination of proton beam quality is also recommended. But because calibration system of absorbed dose to water for proton beam is not estibilished in China, i.e. calibration factor of NE,W, and ^60Co cannot be determined, absorbed dose, to water for proton beam is unable to be calculated. Through the discussion of two situations listed above, it is essential to get Calibration factor of ND、w、Q, before absorbed dose to water for proton beam can be measured. Results： Firstly, ND、w、Qs should be determined. Currently air kerma of Cobalt-60 beam standard using Nk and air exposure of Cobalt-60 beam standard using Nx are established in China. According to IAEA TRS No.277, ND、w、Qs can be calculated through equation （4） using air kerma of Cobalt-60 .beam Calibration factor Nk. For chamber-specific factor which corrects for differences between the reference beam quality Q0 and the actual quality being used Q kQ.Qs, calculated valued of kQ.Qs for various commonly used chambers are provided in IAEA TRS No. 398. Figure 3 is correction cure of calculated value of correction factor kQ.Qs, in which ko stands for correction factor kQ.Qs when the reference beam quality Qo is for Cobalt-60 beam. Conclusions�

关 键 词：参考辐射质 实际射程 剩余射程 电离室 空气比释动能 水吸收剂量 

分 类 号：R730.55[医药卫生—肿瘤]