扩充型动态楔形板楔形因子的校正方法及跳数计算

发布时间：2018-03-08 09:41

本文选题：扩充型动态楔形板　切入点：楔形因子　出处：《南方医科大学学报》2015年02期 　论文类型：期刊论文

【摘要】：目的研究瓦里安扩充型动态楔形板楔形因子计算修正方法,比较楔形野中心点处手工和治疗计划系统计算结果相对测量结果的剂量/跳数差异。方法对于瓦里安直线加速器的6 MV、10 MV光子线,使用指形电离室测量水下10 cm处不同动态楔形野的楔形因子及射野中心点的剂量,采用治疗计划系统计算相应射野的剂量/跳数。使用加速器输出分割模型手工计算射野的楔形因子,并采用常数因子修正手工计算结果。对手工计算、治疗计划系统计算和测量结果进行比较,分析三种方法下常规二维治疗计划下动态楔形野的楔形因子和射野中心点跳数的误差。结果以测量结果为标准,校正后,手工计算的楔形因子误差明显减小。其中,6 MV光子线下,60°楔形角下对称野最大相对误差由4.2%减小到1.3%,非对称野最大相对误差由-4.7%减小到-1.8%。10 MV所有楔形野相对误差由最大-3.0%降低到1.1%。手工计算跳数与测量结果对比,对称野相应射野跳数计算相对误差在2%以内,但部分非对称野最大相对误差超过5%。比较治疗计划系统计算结果与测量结果,其最大相对误差小于1.5%。结论使用常数因子可以有效减小输出分割模型计算楔形因子的误差。对于常规二维治疗计划楔形野的跳数计算来说,校正后对称野射野中心点的计算结果符合临床治疗要求,但对于射野边缘与等中心最短距离小于4 cm的非对称野来说,需要使用相应的非对称射野处方剂量计算方法,或者采用测量方法或利用治疗计划系统计算相应的射野跳数。
[Abstract]:Aim to study a modified method for calculating the wedge factor of Varian expansion type dynamic wedge plate. The difference of dose / hops between manual and therapeutic planning system calculation results relative to the measured results at the center point of wedge field was compared. Methods for the 6 MV 10 MV photon line of Varian linear accelerator, The wedge factor of different dynamic wedge fields and the dose of the center point of the field were measured by using the finger ionization chamber at the depth of 10 cm below the water. The dose / hops of the corresponding field are calculated by the treatment planning system. The wedge factor of the field is calculated manually by using the accelerator output partition model, and the result is corrected by the constant factor. The calculated and measured results of the treatment planning system are compared, and the errors of the wedge factor of the dynamic wedge field and the number of hops at the center of the field under the conventional two dimensional treatment plan are analyzed under the three methods. The error of wedge factor calculated by hand is obviously reduced, in which the maximum relative error of symmetric field at 60 掳wedge angle is reduced from 4.2% to 1.3, and the maximum relative error of asymmetric field is reduced from -4.7% to -1.8 .10 MV relative error of all wedge fields. From the maximum of -3.0% to 1.1. The number of hops calculated by hand is compared with the measured results. The relative error of the calculation of the corresponding field hops of symmetric field is less than 2%, but the maximum relative error of partial asymmetric field is more than 5. The calculated results of the treatment plan system are compared with the measured results. The maximum relative error is less than 1.5. Conclusion using constant factor can effectively reduce the error of calculating wedge factor in output segmentation model. The calculated results of the center point of the symmetrical field after correction accord with the requirement of clinical treatment. However, for the asymmetric field with the shortest distance from the edge of the field to the isocenter less than 4 cm, it is necessary to use the corresponding method to calculate the dose of the asymmetric field prescription. Either the measurement method or the treatment plan system is used to calculate the corresponding field jump.
【作者单位】：中山大学肿瘤防治中心//华南肿瘤学国家重点实验室//肿瘤医学协同创新中心;
【基金】：国家自然科学基金(81272486) 广东省教育部产学研重点项目(2012B091000144)~~
【分类号】：TH774

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