| 引用本文： |
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张颖,陶建民,胡杰,等.直线加速器低MU照射对高能X线剂量学的影响[J].同济大学学报（医学版）,2010,31(4):35-38. [点击复制]
- ZHANG Ying,TAO Jian-min,HU Jie,et al.The dosimetry influence of high energy X-rays generated from linear accelerator with low monitor units[J].同济大学学报（医学版）,2010,31(4):35-38. [点击复制]
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| 摘要: |
| 目的直线加速器机器跳教MU设置的减少可能导致射线束特性发生变化，探讨直线加速器低MU照射对高能X线剂量学的影响。方法对Siemens Mevatron MD7745直线加速器6MV-X线辐射源，机器跳数设置1～1（30MU范围，先测量辐射质指数TPR10^20；然后在最大剂量深度1．5cm处测量相应MU数时的吸收剂量DMU，并计算每MU对应的cGy；最后测量10cm×10cm射野百分深度剂量（percent depth dose，PDD）以及边长3～20cm范围方野的总散射因子Sc，p，然后分析数据。结果不同大小MU设置，MU与cGy的对应关系有很大的差别，偏差最大达10．6％，低MU设置对辐射质指数TPR10^20、百分深度剂量PDD和总散射因子Sc，p影响很小，〈1％。结论为保证体模中剂量计算精度达到WHO规定的精度要求，当MU〈8时，必须修正MU与cGy的对应关系，而低MU照射对辐射质指数、百分深度剂量和总散射因子的影响可忽略不计。 |
| 关键词: 直线加速器 低剂量监测计数 放射治疗 剂量 |
| DOI： |
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| 基金项目:上海市铁路局科技研究开发项目(2002Y04) |
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| The dosimetry influence of high energy X-rays generated from linear accelerator with low monitor units |
| ZHANG Ying,TAO Jian-min,HU Jie,ZHANG Ying |
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| Abstract: |
| Objective Low MU may change the beam characteristics. To study the influence on dosimetry of high energy X rays with low monitor units from linear accelerator. Methods The monitor units were set between 1 and 100 MU, TPR10^20 were first measured; then the dose at depth of 1.5 cm with 10 cm × 10 cm field and 100 cm source skin distance （SSD） were measured and cGy per monitor and the deviation with monitors were calculated; finally the percent depth dose（PDD） with 10 cm× 10 cm field and Collimator and Phantom Scattor Factor（Sc,p） for the field between 3 cm ×3 cm and 20 cm ×20 cm were measured. Results The influence on PDD and Sc, p were less than 1% at low monitor traits but the deviation to cGy per unit was increased, and the most deviation was as high as 10.6%. Conclusion In order to attain the rules of WHO for Quality Assurance in radiotherapy that the accuracy for dose in phantom must be better than 3%, cGy per MU must be corrected when the MU settings are less than 8, but the influence on TPR10^20 PDD and Sc, p from low monitor unit setting can be neglected. |
| Key words: linear accelerator low monitor units radiotherapy dosimetry |
