旋转偏移角度和剂量梯度跌落指数对多发脑转移瘤VMAT计划靶区相对覆盖率的影响  

Effect of rotational set-up error and dose gradient index on target relative coverage ratio for multiple brain metastases in volumetric modulated arc therapy

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作  者:龚帮金 郭昌[2] 黄大福 刘建刚 GONG Bang-jin;GUO Chang;HUANG Da-fu;LIU Jian-gang(Department of Radiation Oncology,Nanjing Lishui People’s Hospital·Zhongda Hospital Lishui Branch,Southeast University,Nanjing 211200,Jiangsu,China;The Affiliated Cancer Hospital of Nanjing Medical University·Jiangsu Cancer Hospital,Jiangsu Institute of Cancer Research,Nanjing 210009,Jiangsu,China)

机构地区:[1]南京市溧水区人民医院(东南大学附属中大医院溧水分院)放疗科,江苏南京211200 [2]南京医科大学附属肿瘤医院(江苏省肿瘤医院,江苏省肿瘤防治研究所),江苏南京210009

出  处:《生物医学工程与临床》2025年第2期198-204,共7页Biomedical Engineering and Clinical Medicine

基  金:南京市溧水区人民医院人才科研基金项目(2021YJ05)。

摘  要:目的探讨旋转偏移角度θ和剂量梯度跌落指数(GI)对多发脑转移瘤非共面容积调强放射治疗(VMAT)计划靶区相对覆盖率(Re)的综合影响。方法选择2018年1月1日至2023年12月1日南京市溧水区人民医院收治的脑转移瘤患者10例,其中男性4例,女性6例;年龄29~67岁,中位年龄54岁;身体质量指数(BMI)19.03~25.95 kg/m^(2),平均BMI 22.06 kg/m^(2)(标准差2.23 kg/m^(2))。在头部CT图像集上勾画3个不同体积的球形模拟脑转移瘤,直径依次为1 cm(T1)、2 cm(T2)和3 cm(T3),设计5弧非共面单等中心VMAT计划,等中心点到靶区中心的距离(旋转半径R)依次设置为3 cm和5 cm。在计划优化阶段通过调整靶区内最大受照射剂量上限来模拟靶区的剂量梯度变化。通过改变治疗床的角度(θ=0.5°、1.0°、1.5°、2.0°、2.5°、3.0°)模拟旋转摆位误差,不进行子野优化,直接计算剂量分布。计划评价参数包括靶区的Re及GI。采用非参数Kruskal-Wallis和Spearman检验分析θ和GI对靶区Re的影响。结果随着θ的增加,靶区的Re逐渐下降,且对体积较小的靶区的Re影响尤为明显。当R=3 cm,θ由0°增加到3°时,T1、T2和T3的Re分别为89.12%±3.02%、92.42%±1.35%和95.88%±1.71%(Z=8.880,P=0.012)。当R=5 cm,θ由0°增加到3°时,T1、T2和T3的Re分别为79.70%±4.80%、85.93%±4.49%和89.90%±4.24%(Z=14.929,P=0.001)。较小的θ(0.5°)对靶区的Re影响不大(<2%),差异无统计学意义(R=3 cm,Z=4.197,P=0.123;R=5 cm,Z=2.113,P=0.348)。靶区的Re和GI呈线性关系(R=3 cm,θ=3.0°:PT1=0.036,PT2=0.043,PT3=0.012;R=5 cm,θ=2.0°:PT1=0.006,PT2=0.017,PT3=0.044;R=5 cm,θ=2.5°:PT1=0.024,PT2=0.044,PT3=0.031;R=5 cm,θ=3.0°:PT1=0.048,PT2=0.049,PT3=0.049)。结论考虑放射治疗过程中存在摆位误差的情况下,较大的GI可以在一定程度上增加小靶区的Re,建议θ校正阈值设置为0.5°。Objective To evaluate the effect of rotational set-up errorθand dose gradient index(GI)on target relative coverage ratio(Re)of multiple brain metastases in volumetric modulated arc therapy(VMAT).Methods From January 1,2018 to December 1,2023,10 patients with brain metastases were enrolled,which included 4 males and 6 females,aged 29-67 years old with median age of 54 years old;body mass index(BMI)was 19.03-25.95 kg/m^(2) with mean BMI of 22.06 kg/m^(2)(standard deviation 2.23 kg/m^(2)).Three spherical simulated brain metastases of different volumes were delineated on head CT image set,with diameters of 1 cm(T1),2 cm(T2),and 3 cm(T3),respectively.The 5-arc non-coplanar single isocentric VMAT plan was designed,and the distance from isocentric point to center of target area(rotation radius R)was set as 3 cm and 5 cm,respectively.In planning optimization stage,the dose gradient change of target area was simulated by adjusting the upper limit of maximum irradiation dose in target area.The rotational positioning error was simulated by changing angle of treatment couch(θ=0.5°,1.0°,1.5°,2.0°,2.5°,3.0°),and directly calculated dose distribution without changing optimization conditions.The plan evaluation parameters included Re and GI of target area.The effects ofθand GI on target Re were analyzed by nonparametric Kruskal-Wallis and Spearman tests.Results Withθincreased,the target Re gradually decreased,especially for the target with smaller volume and larger rotation radius.R=3 cm andθincreased from 0°to 3°,the Re of T1,T2 and T3 were 89.12%±3.02%,92.42%±1.35%and 95.88%±1.71%,respectively(Z=8.880,P=0.012).R=5 cm andθincreased from 0°to 3°,the Re of T1,T2 and T3 were 79.70%±4.80%,85.93%±4.49% and 89.90%±4.24%,respectively(Z=14.929,P=0.001).The smallerθ(0.5°)had little effect on Re of target area(<2%),and the difference was no statistically significant(R=3 cm,Z=4.197,P=0.123;R=5 cm,Z=2.113,P=0.348).There was the linear relationship between Re and GI(R=3 cm,θ=3.0°:PT1=0.036,PT2=0.043,PT3=0.012;R=5 c

关 键 词:旋转摆位误差 剂量梯度 多发脑转移 容积调强放射治疗(VMAT) 相对覆盖率 梯度跌落指数 

分 类 号:R739.41[医药卫生—肿瘤] R730.55[医药卫生—临床医学]

 

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