利用深度剂量数据重建放射治疗X射线能谱  

Reconstruction of X-ray Spectra for Radiation Therapy

作　　者：姚杏红[1] 黄斐增[1] 吴昊[1,2] 包尚联[1] 

机构地区：[1]北京大学医学物理和工程北京市重点实验室,北京100871 [2]北京大学临床肿瘤学院,北京100142

出　　处：《原子能科学技术》2010年第4期464-468,共5页Atomic Energy Science and Technology

基　　金：国家自然科学基金资助项目(10675013;60672104);北京市教委共建项目资助(JD100010607)

摘　　要：利用深度剂量测量数据重建放射治疗X射线能谱,并对重建方法进行评价。先用Monte-Carlo模拟计算60个单能光子束的深度剂量分布作为基函数,然后使用Cimmino迭代法对测量的深度剂量进行线性拟合,得到相应射野每个单能光子束对测量深度剂量的贡献权重,即放射治疗所用的轫致辐射X射线的相对能谱。考虑机头组件散射对能谱的影响,计算中采用双源模型,在等中心平面分3个区域(5cm×5cm、10cm×10cm～5cm×5cm、20cm×20cm～10cm×10cm)重建能谱。最后将分区重建能谱与10cm×10cm射野重建能谱进行比较,对重建方法进行评价。结果表明:利用双源模型重建能谱更符合临床实际情况,分区能谱较不分区能谱计算的深度剂量更符合实际测量深度剂量。This study describes a method to reconstruct energy spectra of clinical bremsstahlung X-rays from measured depth dose data. The measured depth dose can be expressed as a linear combination of basis functions, namely the depth doses of monoenergetic photon beams derived from Monte Carlo simulations. The weights of the basis functions, which were obtained with the Cimmino iteration, represent the relative energy spectra. The real energy spectra are changed gradually with the off-axis distance because of the photons scattered from components of treatment head. The energy spectra of X-rays in the isocenter plane were reconstructed using a dual-source model in three regions. 5 cm×5 cm, 10 cm×10 cm^-5 cm×5 cm, 20 cm×20 cm^-10 cm×10 cm. Depth doses produced from the uniform spectrum （10 cm×10 cm） and from regional spectrum were compared with measured depth doses respectively. The results show that using the dualsource model in reconstructing spectrum is more appropriate in clinical, and depthdoses produced from regional spectrum are more identical to measured depth doses.

关 键 词：深度剂量分布 Monte—Carlo模拟 双源模型 Cimmino迭代 X射线能谱 

分 类 号：O571.436[理学—粒子物理与原子核物理] TL53[理学—物理]