Measurement of gold nanofilm dose enhancement using unlaminated radiochromic film.
Measurement of gold nanofilm dose enhancement using unlaminated radiochromic film.
复制标题
使用未层压放射变色膜测量金纳米膜剂量增强。
DOI：
10.1118/1.4931054
复制
发表时间：
2015
期刊：
影响因子：
3.8
通讯作者：
G. Lawes
中科院分区：
文献类型：
--
作者：
J. Rakowski;S. Laha;M. Snyder;M. Buczek;M. Tucker;Fangchao Liu;G. Mao;Y. Hillman;G. Lawes
目的
用X射线辐射轰击高Z物质会释放俄歇电子和科斯特-克洛尼格电子，以及更深层次的穿透荧光X射线和光电子。在水或组织中，Auger和Coster-Kronig电子穿透距离在纳米到微米的数量级上，在细胞水平上产生了大的剂量增强，伴随着RBE大于1。作者的目的是通过原始的50kVp钨X射线谱相互作用，在细胞水平上测量金纳米膜剂量增强因子(DEF)，类似于电子近距离治疗谱。
方法
将非叠层Gafchroic(®)EBT2薄膜和蒙特卡罗模拟相结合，得到了DEF模型。将厚度为2 3.1± 4.3 nm、表面粗糙度为1.2±0.2 nm的金膜沿下游方向与未叠层的放射变色膜接触，并用50kVp的钨韧致辐射照射，平均能量为19.2keV。通过对薄膜有源层中电子能量沉积的蒙特卡罗模拟，并通过测量4.5keV到50kVp的薄膜能量依赖关系，得到了薄膜响应修正因子。
结果
在13.6μm厚的水层内测得的DEF为0.29，Au辐射的平均剂量为94±9.4cGy.50kVp的原始束的剂量为324±32.4cGy.蒙特卡罗校正因子允许以0.25μm间隔确定浅层Au的贡献剂量。前0.25μm水深最大，为18.31dEf。
结论
Au纳米薄膜的剂量增强可以在细胞水平上使用非叠层放射变色薄膜来测量。用蒙特卡罗计算补充测量的剂量值，可以估计细胞范围内深度增量的剂量增强。
PURPOSE
Bombarding high-Z material with x-ray radiation releases Auger electrons and Coster-Kronig electrons, along with deeper penetrating fluorescent x-rays and photoelectrons. The Auger and Coster-Kronig electron penetration distance is on the order of nanometers to micrometers in water or tissue, creating a large dose enhancement accompanied by a RBE greater than 1 at the cellular level. The authors' aim is to measure the gold nanofilm dose enhancement factor (DEF) at the cellular level with unlaminated radiochromic film via primary 50 kVp tungsten x-ray spectrum interaction, similar to an electronic brachytherapy spectrum.
METHODS
Unlaminated Gafchromic(®) EBT2 film and Monte Carlo modeling were combined to derive DEF models. Gold film of thickness 23.1 ± 4.3 nm and surface roughness of 1.2 ± 0.2 nm was placed in contact with unlaminated radiochromic film in a downstream orientation and exposed to a 50 kVp tungsten bremsstrahlung, mean energy 19.2 keV. Film response correction factors were derived by Monte Carlo modeling of electron energy deposition in the film's active layer, and by measuring film energy dependence from 4.5 keV to 50 kVp.
RESULTS
The measured DEF within a 13.6 μm thick water layer was 0.29 with a mean dose of 94 ± 9.4 cGy from Au emissions and 324 ± 32.4 cGy from the 50 kVp primary beam. Monte Carlo derived correction factors allowed determination of Au contributed dose in shallower depths at 0.25 μm intervals. Maximum DEF of 18.31 was found in the first 0.25 μm water depth.
CONCLUSIONS
Dose enhancement from Au nanofilm can be measured at the cellular level using unlaminated radiochromic film. Complementing the measured dose value with Monte Carlo calculations allows estimation of dose enhancement at depth increments within the cellular range.