Unity影像评估脑部肿瘤放疗应用开孔面罩体位固定的可行性观察

Observation on the feasibility of open-face mask immobilization for brain tumor radiotherapy via Unity MR image

目的 采用Unity MR影像评估脑部肿瘤应用开孔面罩体位固定的可行性。方法 选取2021-06-01-2021-10-30在中山大学肿瘤防治中心行调强放疗的35例脑部肿瘤患者,其中14例患者采用发泡胶、开孔面罩固定和Unity MR验证(A组),21例患者采用发泡胶、闭孔面罩固定和锥形束CT(CBCT)验证(B组)。分别收集A组患者分次间、分次内误差数据和B组患者分次间摆位误差数据。采用曼-惠特尼秩和检验,比较分析不同固定方式下的分次间摆位误差差异;采用计划靶区外扩边界(MPTV)公式:MPTV=2.5Σ+0.7σ计算不同固定方式下的靶区外扩边界。结果 A组在患者左右(x)、头脚(y)、前后(z)方向的分次间平移误差分别为[-0.10(1.70)] mm、[0(2.00)] mm和[-0.10(0.90)] mm;分次内平移误差分别为(-0.04±0.31) mm、(0.17±0.57) mm和(0.05±0.33) mm;分次内旋转误差分别为俯仰角(-0.01±0.23)°、翻滚角(-0.06±0.21)°和偏摆角(-0.08±0.31)°;对应外扩边界为2.55、2.96和2.72 mm。B组患者的分次间平移误差相应为[0(3.00)] mm、[1.00(2.50)] mm和[0(2.00)] mm;对应外扩边界为3.63、3.69和2.97 mm。2组患者在x轴(Z=-3.971)和y轴(Z=-3.476)方向上的分次间摆位误差数据差异有统计学意义,均P<0.05,在z轴方向上的分次间摆位误差数据差异无统计学意义,Z=-0.644,P=0.520。结论 在Unity特有的摆位条件及验证模式下,开孔面罩的应用减小了长时间治疗过程中对患者面部的束缚,同时其安全性、稳定性和有效性也得到了保障,满足临床对于脑部肿瘤体位固定的要求。

Objective Unity MR image was used to assess the feasibility of open-face mask immobilization for brain tumor.Methods Totally 35 patients with brain tumor who were treated with IMRT in Sun Yat-sen University Cancer Center from June 1,2021 to October 30,2021 were divided into two groups.In group A,14 patients, immobilized with open-face thermoplastic masks and polyurethane foam sealing agent, were treated with Unity MR-guided radiotherapy.In group B,21 patients, immobilized with full-head thermoplastic masks and polyurethane foam sealing agent, were treated with CBCT-guided radiotherapy.Data of inter-fractional setup errors were collected for two groups and only intra-fraction motions were collected for group A.Mann-Whitney U test was used to evaluate the differences of setup errors between group A and group B.Formula margin of planning target volume: MPTV= 2.5Σ + 0.7σ was also applied to calculate the margin of the target in different groups.Results In group A,the setup errors in X(LR),Y(SI),and Z(AP)direction were [-0.10(1.70)] mm, [0(2.00)] mm, and [-0.10(0.90)] mm, respectively;translational intra-fraction errors were(-0.04±0.31) mm,(0.17±0.57) mm, and(0.05±0.33) mm, respectively;rotational intra-fraction errors were, pitch(-0.01±0.23)°,roll(-0.06±0.21)°,yaw(-0.08±0.31)°and the margin were 2.55 mm, 2.96 mm, 2.72 mm.In group B,the setup errors were [0(3.00)] mm,[1.00(2.50)] mm,[0(2.00)] mm,the margin were 3.63 mm, 3.69 mm, 2.97 mm, respectively.The difference of inter-fraction setup errors in X(Z=-3.971),Y(Z=-3.476)direction between two groups was statistically significant,both P<0.05and there was no statistical significance in Z direction,Z=-0.644,P=0.520.Conclusion With the unique immobilization ways and verification mode of Unity,the use of open-face thermoplastic mask is less stressful in patient immobilization during the long time of treatment,and the safety,stability and effectiveness are also guaranteed,meeting the clinical requirements of brain tumor immobilization for radiotherapy.