电子射野影像系统用于患者调强放射治疗计划剂量验证分析

Dose verification in radiotherapy patient treatment plan with electronic portal imaging device

目的分析电子射野影像系统(EPID)用于调强放射治疗计划剂量验证的准确性。方法选择2014年南通市第一人民医院住院行放射治疗宫颈癌术后患者10例,年龄45~71岁,中位年龄56岁。采用7野均分(0°、52°、104°、156°、208°、260°、310°7个角度)进行计划设计及剂量分布计算,获取归零野和实际野验证时叶片位移偏移、射野通过率,并将EPID归零野验证结果与PTW电离室矩阵归零野验证的射野通过率结果进行比较。结果EPID归零野和实际野验证获得的叶片偏移1 mm以内百分比数值的绝对值差异不大,但在208°、260°及310°3个角度差异有统计学意义。射野验证通过率在0°、52°时差异无统计学意义,而104°、156°、208°、260°、310°时差异有统计学意义。EPID归零野验证时获得的射野通过率与PTW电离室矩阵的验证结果差异无统计学意义。结论 EPID可以应用于调强计划的验证。

Objective To analyze the accuracy of electronic portal imaging device（EPID） for intensity modulated radiotherapy（IMRT） dose verification. Methods A total of 10 postoperative cervical cancer patients treated with radiotherapy in Nantong First People＇s Hospital in 2014 were enrolled, which aged 45-71 years old with median age of 56 years old. The treatment plan was designed with 7 fields（0°, 52°, 104°, 156°, 208°, 260°, 310°） and dose distribution were calculated, then obtained multi-leaf collimator（MLC） offset percentage less than 1 mm, field coincidence for 2 EPID verification methods（all field angles transformed into 0 and actual angle）, also field coincidence verification results were compared with that of PTW ionization chamber matrix. Results EPID verification between 2 verification methods showed that little difference of absolute value of MLC offset percentage less than 1 mm were found, but at 208°, 260° and 310°, the differences were statistically significant;About field coincidence at 0°, 52°, the difference was no statistical significance, while at 104°, 156°, 208°, 260°, 310°, the difference was statistically significant. There was no significant difference of field coincidence between PTW ionization chamber matrix and EPID. Conclusion It is demonstrated that EPID could be used for IMRT plan verification.