肿瘤治疗电场对胶质母细胞瘤放疗位置精度的影响

目的初步研究放疗同期联合肿瘤治疗电场(TTF)治疗恶性胶质瘤时,TTF阵列对放疗摆位精度的影响。方法使用kV级锥形束CT(CBCT)以及X射线容积成像系统(XVI),分别对29例常规放疗患者和12例TTF同步放疗患者进行放疗摆位验证分析,在左右(Lat)、头脚(Lng)和胸背(Vrt)、侧旋(Roll)、侧倾(Pitch)和旋转(Rtn)6个方向上评估放疗摆位中心和治疗计划中心的误差。根据摆位误差数据重新确定计划中心点,并在不改变射野参数的条件下,重新计算剂量分布,评估计划靶区(PTV)和临床靶区(CTV)的V_(40)、D_(mean)、D98%、D2%,以及头皮组织的D_(mean)、D20 cm^(3)、D30 cm^(3)。结果行TTF同步放疗的患者在佩戴TTF阵列时,摆位误差朝脚方向平均增加了2 mm,最大增加了3.5 mm;朝背方向平均增加了1.3 mm,最大增加了2.7 mm;Roll和Rtn方向的摆位误差均向一侧增加了1.1°。PTV的V40最大下降了4.78%,D98%最大下降了6%,头皮的Dmean最大增加2.6%,D20 cm3最大增加3.2%,D30 cm3最大增加3.5%。CTV及PTV其余剂量参数偏差均在2%以内。结论TTF阵列对患者的Lng和Vrt方向的摆位误差有较明显的影响,并且增加了Roll和Rtn方向的摆位难度,Lat方向和Pitch方向无明显误差;摆位误差过大会明显降低PTV的剂量。

Effects of tumor-treating field arrays on the radiation position and dose of glioblastoma

Objective To preliminarily investigate the effects of tumor treating field (TTF) arrays on the positioning accuracy of radiotherapy setup in the treatment of glioblastoma.Methods The kilovolt cone-beam CT (CBCT) and an X-ray volumetric imaging (XVI) system were used to verify the radiotherapy setup of 29 patients treated with conventional radiotherapy and 12 patients treated with TTF concurrent radiotherapy, respectively. The errors of radiotherapy position isocenter and treatment plan isocenter were evaluated in six directions, namely lateral (Lat), head pin (Lng), dorsoventral (Vrt), roll, pitch, and rotation (Rtn). Then, the plan isocenter was redetermined according to the setup error data. Moreover, the dose distribution was recalculated without changing the radiation field parameters. Finally, the V₄₀, D_mean, D_98% and D_2% of both PTV and CTV and the D_mean, D_<sub>20cm³, and D_<sub>30cm³ of scalp tissue were evaluated.Results When patients were treated with TTF concurrent radiotherapy wearing TTF arrays, the setup errors increased by 2 mm and 1.3 mm on average (maximum: 3.5 mm and 2.7 mm) toward the foot and dorsal directions, respectively. In addition, the setup errors in both Roll and Rtn directions increased by about 1.1° toward one side. The V₄₀ and D_98% of PTV decreased by up to 4.78% and 6%, respectively. The D_mean, D_20cm³, and D_30cm³ to scalp tissue increased by up to 2.6%, 3.2%, and 3.5%, respectively. The errors of other dose parameters for both CTV and PTV were within 2%.Conclusions TTF arrays have significant effects on the setup errors of patients in the Lng and Vrt directions and increase the setup difficulty in the Roll and Rtn directions, while there is no significant error in the Lat and Pitch directions. Moreover, too large setup errors can significantly reduce the dose to PTV.