基于日志文件与CBCT进行鼻咽癌VMAT的剂量重建  

Dose reconstruction of volumetric modulated arc therapy for nasopharyngeal carcinoma basedon log files and CBCT

作　　者：朱翔 刘洪源[2] 聂鑫[2] 杨志勇[2] 梁志文[2] 柳刚[2] 全红[1] Zhu Xiang;Liu Hongyuan;Nie Xin;Yang Zhiyong;Liang Zhiwen;Liu Gang;Quan Hong(School of Physics and Technology,Wuhan University,Wuhan 430072,China;Cancer Center,Union Hospital,Tongji Medical College,Huazhong University of Science and Technology,Wuhan 430024,China)

机构地区：[1]武汉大学物理科学与技术学院,武汉430072 [2]华中科技大学同济医学院附属协和医院肿瘤中心,武汉430024

出　　处：《中华放射肿瘤学杂志》2023年第8期704-710,共7页Chinese Journal of Radiation Oncology

基　　金：国家自然科学基金(12005072)。

摘　　要：目的基于日志文件与锥形线束CT(CBCT)进行鼻咽癌的剂量重建并验证患者全流程放疗计划执行的结果。方法回顾性选取15例于2022年2一9月在华中科技大学同济医学院附属协和医院肿瘤中心接受速锐(Halcyon)加速器容积弧形调强放射治疗(VMAT)的鼻咽癌患者,记录患者所有分次放疗的日志文件与CBCT。分析日志文件中机器跳数(MU)、机架角度与多叶准直器(MLC)叶片位置;通过商用软件Velocity^(TM)把CBCT和计划CT(pCT)转换为自适应CT(aCT),并分析aCT与pCT以及CBCT三者的相似性;根据日志文件修改原始计划并导入到计划系统中,在对应分次的aCT上计算剂量得到分次重建剂量,将所有分次重建剂量映射到pCT上得到累积剂量。比较累积剂量与原始计划剂量2mm/2%和2mm/3%的通过率以及二者在计划靶区(PTV)与危及器官(OAR)的剂量差异。结果患者分次放疗MU、机架角度、MLC叶片位置三者误差的均方根与第95百分位数均处于可接受的范围内。Velocity^(TM)生成的aCT拥有CBCT的解剖结构和pCT的分辨率、对比度和噪声特性,可直接用于剂量计算。累积剂量与原始计划剂量相比,鼻咽原发灶PTV_(nx)的V_(70Gy)、颈淋巴结PTV_(nd)的V_(68Gy)计划靶区PTV1的V_(60Gy)变化分别为-0.88%±1.91%-2.99%±2.99%-0.63%±0.93%,腮腺的V_(40Gy)变化为2.65%±2.63%;靶区累积剂量有下降趋势(P<0.05),腮腺累积剂量有上升趋势(P<0.05);累积剂量和原始计划剂量二者2mm/3%的通过率为97.3%±2.7%,86.7%患者的通过率>95.0%。结论基于日志文件与CBCT进行鼻咽癌患者全流程的剂量重建,根据剂量重建结果可以对靶区与危及器官的放疗效果进行定量评估。在原始计划高剂量覆盖率与适形度的情况下,重建结果显示靶区累积剂量覆盖率下降,腮腺累积剂量覆盖率上升。Objective To reconstruct the dose of nasopharyngeal carcinoma and verify the results of the whole-process radiotherapy plan based on log files and cone beam CT(CBCT).Methods A total of 15 patients with nasopharyngeal carcinoma who received volumetric modulated arc therapy(VMAT)with Halcyon accelerator in the Cancer Center of Union Hospital,Tongji Medical College,Huazhong University of Science and Technology from February to September 2022 were retrospectively selected.Log files and CBCT for all fractionated radiotherapy were recorded.The errors of monitor unit(MU),gantry angle,and multi-leaf collimator(MLC)leaf position per control point were analyzed.The adaptive CT(aCT)were generated according to CBCT and planned CT(pCT)using a commercial software Velocity^(TM),and the similarities among aCT,pCT and CBCT were analyzed.The original plan was modified from the log files and imported into the treatment planning system to calculate the delivered dose on the corresponding fractionated acT to reconstruct the fractionated dose.And all the reconstructed doses were mapped back to pCT to obtain the cumulative dose.Thepass ratios with criteria of 2 mm/2%and 2 mm/3%and the dose differences between the planned dose and the cumulative dose in the planning target volume(PTV)and organs at risk(OAR)were compared.Results The root mean square(RMS)and the 95th percentile of the errors of MU,gantry angle and MLC leaf position errors were within an acceptable range.The aCT generated by Velocity^(TM)had the anatomical structure of CBCT and the resolution,contrast,noise characteristics of pCT,which could be directly used for dose calculation.Compared with the planned dose,the changes of Vzocy of nasopharyngeal primary tumor(PTV_(nd)),V_(60Gy)of cervical glands(PTV_(nd))and V_(60Gy)of planning target volume(PTV1)were-0.88%±1.91%,-2.99%±2.99%and-0.63%±0.93%,respectively,and V4o y of parotid gland was increased to 2.65%±2.63%.Cumulative dose showed different degrees of PTV dose decrease(P<0.05)and parotid dose was increased(P<0.05).Th

关 键 词：鼻咽肿瘤 Halcyon加速器 日志文件 锥形线束CT 剂量重建 

分 类 号：R739.63[医药卫生—肿瘤]