摘要
目的 探讨虚拟楔形板楔形角的验证 ;楔形因子与射线能量、照射野尺寸和楔形角大小之间的关系 ;虚拟楔形野、物理楔形野和平野百分深度剂量之间的关系。方法 对西门子公司Meva tronM加速器 6MV、Primus加速器 8、18MV 3种能量X射线 ,用RFA PLUS三维水箱、RK指形电离室分别测量其 15°、30°、45°和 6 0°虚拟楔形板的楔形角和不同大小照射野的楔形因子 ;用FDM 30 0黑度计、KodakXV 2检验胶片测量 6MVX射线 30°虚拟楔形野、物理楔形野和平野的百分深度剂量 ,归一到最大剂量点并进行比较。结果 4点法测得的虚拟楔形角与设定值有良好的一致性。不论射线能量、照射野大小和楔形角大小 ,虚拟楔形板楔形因子总是约等于 1,最大偏离为 0 .0 31;对于特定能量和照射野 ,大楔形角楔形因子较小楔形角略大 ;对于特定能量和楔形角 ,大野楔形因子较小野略大 ;虚拟楔形野深度剂量曲线非常接近平野 ,两者仅有很细微的差别。结论 4点法测量虚拟楔形板楔形角可作为日常质量保证手段。虚拟楔形野较物理楔形野治疗不仅简单易行 ,更可以节省加速器出束量。虚拟楔形野与平野的深度剂量曲线的一致性简化了治疗计划或者提高了楔形野实际治疗剂量精度。
Objective To verify the wedge angle of virtual wedge and the relation between wedge factor and beam energy, field size, wedge angle and to study the difference in percent depth dose (PDD) of virtual wedge field, hard wedge field and open field.Methods Using wedge angle and wedge factor of 15°,30°,45°and 60° virtual wedge of Siemens Mevatron 6?MV and Primus 8?MV, 18?MV X rays were measured by RFA-plus 3D water phantom and RK finger chamber the PDD of the virtual wedge field, hard wedge field and open field were measured by Kodak XV-2 verifying film and FDM-300 film dosimeter. These PDDs were normalized to Dmax then compared. Results There was good conformation between virtual wedge measured by four point method and set value. The virtual wedge was almost equal to 1,with a maximal variation of 0.031 no matter what the value of beam energy, field size or wedge angle was. Generally, for certain energy and field size, the wedge factor of larger wedge angle was slightly larger than smaller wedge angle. For certain energy and wedge angle, the wedge factor of larger field was also a little larger than smaller field. The PDD of virtual wedge field was similar to that of open field. Conclusions The four point method measurement for virtual wedge angle is good for daily QA. Radiotherapy of virtual wedge field is not only simpler than hard wedge field,but also spares the beam output. The PDD comfarmation between virtual field and open field simplifies radiation treatment planning and increases the accuracy of wedge field therapy.
出处
《中华放射肿瘤学杂志》
CSCD
北大核心
2002年第2期137-139,共3页
Chinese Journal of Radiation Oncology
