调强放疗计划床板修正的剂量学分析

【摘 要】 目的:分析调强放疗计划加速器床板和定位床板修正的剂量学影响。 方法:分别选取碳素板胸部定位食管癌患者14例和盆腔有机板定位宫颈癌术后患者14例，在修正床板和不修正床板条件下设计调强计划，得到4组计划数据；再将调强计划导入验证模体，做验证计划，各选取等中心层面5个剂量验证参考点，用电离室剂量仪测量参考点的吸收剂量，对测得的10组剂量数据进行统计分析。 结果:实测床板的衰减平均为3.4%～6.6%。胸部食管癌组床板修正前后剂量误差3.0%～4.5%，平均3.8%，P=0.000；盆腔宫颈癌术后组床板修正前后剂量误差3.5%～4.6%，平均4.1%，P=0.000。 结论:调强放疗计划设计过程中，有后野或后斜野射线穿过床板时，应充分考虑床板对剂量的衰减，必须对加速器床板和定位床板进行剂量修正。

Bedplate correction in intensity-modulated radiotherapy plan: a dosimetric analysis

Abstract: Objective To analyze the dosimetric effects of the correlation of accelerator bedplate and positioning bedplate in intensity-modulated radiotherapy (IMRT) plan. Methods Fourteen patients with esophageal cancer receiving chest positioning of carbon board and 14 postoperative patients with cervical cancer receiving abdominal positioning of organic board were selected. IMRT plans were designed with corrected bedplate or uncorrected bedplate. A total of 4 groups of plan data were obtained. Then IMRT plans were imported into the verification phantom for plan verification. Five dose verification reference points were selected at the isocenter layer, and the absorbed dose at reference points were measured with ionization chamber dosimeter. The statistical analysis was performed on the measured 10 groups of data. Results The average attenuation of bedplate was 3.4%-6.6%. The dose error of bedplate before and after correction was 3.0%-4.5% in patients with esophageal cancer, with an average of 3.8%, P=0.000; while the dose error of bedplate before and after correction was 3.5%-4.6% in postoperative patients with cervical cancer, with an average of 4.1%, P=0.000. Conclusion In the process of IMRT planning, if the back beam or back-flank beam passes through the bedplate, the dose attenuation of the bedplate should be considered and the dose correction must be performed on accelerator bedplate and positioning bedplate.