肿瘤治疗电场阵列对胶质母细胞瘤放疗剂量的影响

目的 初步研究放疗同期联合肿瘤治疗电场（TTF）治疗胶质母细胞瘤（GBM）时，TTF阵列对放射剂量分布的影响。方法 使用胶片和MatriXX平板电离室，分别在表面贴和不贴TTF阵列与无乳胶海绵的情况下测量不同组织深度（<1、3、5 mm、1、1.5、3、5、10、15 cm）的吸收剂量，进行计算、对比和分析。对10例GBM患者的VMAT计划，利用Sun Nuclear公司ArcCheck三维剂量验证系统进行深部剂量验证，评估肿瘤和危及器官的D_99%、D_mean和D_1%。结果 贴TTF阵列与无乳胶海绵比不贴时表面剂量增加了173%，密度较低的无乳胶海绵使表面剂量增加61.7%，随着深度增加，剂量偏差逐渐减小，在1.5 cm以下时稳定在4%左右。VMAT计划验证结果显示，贴TTF阵列与无乳胶海绵比不贴时，PTV和CTV的D_99%、D_mean和D_1%下降1.1%~1.2%；危及器官如脑干、垂体、视交叉、视神经、眼球和眼晶状体的D_mean和D_1%下降0.7%~1.5%。结论 TTF和放疗同步进行时，会造成靶区和危及器官吸收剂量降低，且影响较小，但皮肤表面吸收剂量上升，建议在进行放疗计划设计时，尽可能降低头皮剂量，以减少患者头皮反应。

Effects of tumor treating fields (TTF) arrays on the radiation doses to glioblastoma

Objective To preliminarily explore the effects of tumor treating fields (TTF) arrays on the dose distribution in the treatment of Glioblastoma (GBM) using combined radiotherapy and concurrent TTF. Methods EDR2 and MatriXX plate ionization chamber were employed to measure the absorbed doses of tissues at different depths (< 1 mm, 3 mm, 5 mm, 1 cm, 1.5 cm, 3 cm, 5 cm, 10 cm, and 15 cm) in the case that TTF arrays and latex-free foam were attached and not attached on the surface. Then the absorbed doses were calculated, compared, and analyzed. For the volumetric arc therapy (VMAT) of 10 GBM patients, deep dose verification was performed using the Sun Nuclear ArcCheck 3D dose verification system and the D_99%, D_mean, and D_1% of tumors and OARs were assessed. Results The surface dose increased by 173% in the case that TTF arrays and latex-free foam were attached to the surface compared with the case of the surface with nothing attached. The surface dose increased by 61.7% due to the attachment of low-density latex-free foam. The dose deviation gradually decreased with an increase in the depth and stabilized (about 4%) at a depth of greater than 1.5 cm. As indicated by the VMAT verification result, the D_99%, D_mean, and D_1% of PTV and CTV decreased by 1.1%-1.2% and the D_mean and D_1% of OARs (i.e., brainstem, pituitary gland, optic chiasma, optic nerve, eyeball, and eye crystal) decreased by 0.7%-1.5% in the case that TTF array and latex-free foam were attached on the surface compared with the case the surface with nothing attached. Conclusions The combined radiotherapy and concurrent TTF in the GBM treatment will lead to a slight reduction of the absorbed doses of targets and OARs but a significant increase in the absorbed doses of the scalp. Therefore, it is recommended that the scalp doses should be reduced as far as possible in the design of the radiation treatment plan to reduce the adverse reactions on the scalp of GBM patients.