| 王丹,何京学,高鸿,修霞,李雪南,李高峰.手工计算非对称动态楔形野处方剂量的校正[J].中华放射医学与防护杂志,2010,30(1):47-49 |
| 手工计算非对称动态楔形野处方剂量的校正 |
| Correction of manual monitor unit calculation for asymmetric fields using Varian enhanced dynamic wedge |
| 投稿时间：2008-12-28 |
| DOI： |
| 中文关键词: 动态楔形板 非对称射野 处方剂量 校正因子 |
| 英文关键词:Enhanced dynamic wedge Asymmetric fields Monitor unit Correction factor |
| 基金项目: |
|
| 摘要点击次数: 2927 |
| 全文下载次数: 2203 |
| 中文摘要: |
| 目的 研究非对称射野情况下使用动态楔形板时手工计算处方剂量的校正。方法 利用VarianEclipse治疗计划系统和23EX加速器的数据计算射野分别为6cm×6cm、8cm×8cm、10cm×10cm、12cm×12cm、14cm×14cm、16cm×16cm、18cm×18cm、20cm×20cm的处方剂量。计算时保持射野不变,非楔方向为对称,改变楔形方向的准直器大小,使射野的几何中心与等中心的距离以1cm为步长递增。动态楔形板度数取10°、15°、20°、25°、30°、45°和60°,能量取6和10MV。根据计算结果模拟出射野几何中心与等中心的距离与校正因子之间的关系曲线图。选择有代表性的角度和射野,利用该校正因子对手工计算所得到的结果进行校正,并进行实际测量,验证结果是否在误差允许范围内。结果 射野大小对校正因子的影响很小,所以取不同射野时的平均值作为实际计算时使用的校正因子。不做校正时,能量为6MVX线的情况下,30°楔形板最大误差可达18%,45°楔形板最大误差可达30%,与实际所需要的处方剂量相差很多,校正以后测量结果的误差范围分别为-1.8%～0.09%和-1.8%～-0.25%,该误差大小可以接受。结论 在非对称动态楔形野的情况下,手工计算时采用对称野的楔形因子得到的处方剂量与实际治疗时应该使用的处方剂量有很大差别,采用校正因子校正后,误差缩小到临床能够接受的范围。 |
| 英文摘要: |
| Objective To investigate the correction of manual monitor unit calculation for asymmetric fields using the Varian enhanced dynamic wedge. Methods Monitor unit(MU) was calculated when the field sizes ranged from 6 cm×6 cm to 20 cm×20 cm at a depth of 5 cm using Varian Eclipse and both 6 MV and 10 MV X-rays data from Varian Clinac 23EX for all seven available EDW angles, including 10°,15°,20°,25°,30°,45° and 60°. The field size was kept fixed, and the distance between geometry center of field and isocenter was increased in increments of 1 cm, ranging from-9 cm to 4 cm. When the field size was the same, the correction factor was defined as the ratio of MU calculated for asymmetric field to monitor unit calculated for symmetric field. To ensure the correction factors obtained above could be used in routine manual calculation for EDW fields, measurements were made at a depth of 5 cm for 30° and 45° EDW with field size of 10 cm×10 cm using 6 MV X-rays. Results The correction factor was independent of field dimensions, so the average value was adopted to make practical calculation. Without correction, the maximum error was 18% for 30°, and 30% for 45. After the results of monitor unit calculation were corrected, the largest error was-1.8% and-1.7% for 30° and 45° EDW, respectively. The magnitude of errors was within the clinical tolerance limits. Conclusions For asymmetric EDW fields, there is very large difference between the prescribed dose by manual calculation using EDW factors measured for symmetric fields and that delivered during treatment in order to obtain correct dose to reference point. The errors are decreased to be acceptable after correction. The method of correction is simple and independent of machine specific beam parameters. |
| HTML 查看全文 查看/发表评论 下载PDF阅读器 |
| 关闭 |
|
|
|