1、第 41 卷 第 4 期2023 年 8 月辐射研究与辐射工艺学报 J.Radiat.Res.Radiat.PVol.41 No.4August 2023多叶准直 器 角 度 改 变 对 左 侧 全 乳大分割放疗瘤 床 推 量 的 剂 量 学 影响陈 车 陈 睿 陆治江 罗德红(遵义市肿瘤临床医学中心 遵义市第一人民医院(遵义医科大学第三附属医院)放疗中心 遵义 563099)摘要 研究动态调强放疗方式下多叶准直器角度改变对左侧全乳大分割放疗内侧、中间和外侧瘤床同期推量的剂量学影响。选取2018年01月至2023年01月间于遵义第一人民医院收治的左侧乳腺癌保乳术后行全乳大分割放疗瘤床同期推量患
2、者60例,按瘤床位置分为内侧、中间和外侧3组,分别对比各组患者多叶准直器角度改变的放疗计划(标记为Plan-A)与多叶准直器角度为0的原放疗计划(标记为Plan-O)的靶区、心肺剂量学参数差异。结果显示:3组患者的Plan-A较Plan-O,靶区处方覆盖(V处方(%)、适形度指数(Conformity Index,CI)和均匀性指数(Homogeneity Index,HI)均无显著差异;在内侧组采用Plan-A相较于Plan-O,左肺(V5、V10和Dmean)、心脏(V8和Dmean)和冠状动脉左前降支(LAD)(Dmax和Dmean)均降低,差异有统计学意义(p0.05);同时Plan-
3、A较Plan-O,在中间和外侧组中仅外侧组LAD(Dmax和Dmean)明显减小(p0.05),其余心肺受量参数均无显著差异。准直器角度改变对左侧全乳大分割放疗瘤床推量靶区剂量学参数无明显影响,但能使内侧组患者的心肺受量较原放疗计划明显减小,故对于左侧大分割单纯全乳放疗内侧瘤床制定放疗计划建议选择改变多叶准直器角度。关键词 乳腺癌,多叶准直器,大分割放疗,瘤床位置,剂量学中图分类号 R815,R737.9DOI:10.11889/j.1000-3436.2022-0141引用该文:陈车,陈睿,陆治江,等.多叶准直器角度改变对左侧全乳大分割放疗瘤床推量的剂量学影响J.辐射研究与辐射工艺学报,20
4、23,41(4):040302.DOI:10.11889/j.1000-3436.2022-0141.CHEN Che,CHEN Rui,LU Zhijiang,et al.Dosimetric effect of multi-leaf collimator angle change on the left-sided breast hypofractionated radiotherapy with simultaneous integrated boostJ.Journal of Radiation Research and Radiation Processing,2023,41(4):
5、040302.DOI:10.11889/j.1000-3436.2022-0141.Dosimetric effect of multi-leaf collimator angle change on the left-sided breast hypofractionated radiotherapy with simultaneous integrated boostCHEN Che CHEN Rui LU Zhijiang LUO Dehong(Cancer Clinical Medical Center,Radiation Oncology Center,the First Peopl
6、e Hospital of Zunyi/the Third Affiliated Hospital of Zunyi Medical University,Zunyi 563099,China)基金资助:遵义市科技计划项目(HZ(2020)103号)资助第一作者:陈车,男,1990年01月出生,2016年7月于重庆大学获得硕士学位通信作者:罗德红,副主任医师,E-mail:收稿日期:初稿 2022-12-28;修回 2023-04-18Supported by Zunyi Science and Technology Plan Project(HZ(2020)103)First author:
7、CHEN Che(male)was born in January 1990,and graduated from Chongqing University in July 2016Corresponding author:LUO Dehong,associate chief physician,E-mail:Received 28 December 2022;accepted 18 April 2023辐 射 研 究 与 辐 射 工 艺 学 报 2023 41:0403020403022ABSTRACT This study aimed to evaluate the effects of
8、multi-leaf collimator angle change on the dosimetric parameters of the medial,central,and lateral tumor bed boost in hypofractionated left whole-breast irradiation with dynamic multi-leaf collimator technology.Sixty patients with early breast cancer following conservative surgery who underwent hypof
9、ractionated radiotherapy with tumor bed boost were enrolled from The First People s Hospital of Zunyi between January 2018 and January 2023.All patients were classified into three groups according to the location of the tumor bed:medial,central,and lateral.The differences in target volume and cardio
10、pulmonary dosimetric parameters between the plan of multi-leaf collimator angle change(labeled as Plan-A)and the original plan of 0 multi-leaf collimator angle(labeled as Plan-O)were compared in each group.The results did not show any significant differences in the coverage of the target prescriptio
11、n,conformability index,and homogeneity index between Plan-A and Plan-O of the three groups.In the medial group,the left lung V5,V10,and Dmean;heart V8 and Dmean;and left anterior descending artery(LAD)Dmax and Dmean of Plan-A were significantly lower than those of Plan-O(p0.05).Meanwhile,in the cent
12、ral and lateral groups,only the LAD Dmax and Dmean of Plan-A decreased significantly in the lateral group,and no differences were observed in other cardiopulmonary parameters compared to those in Plan-O(p0.05).In conclusion,the change in collimator angle did not have a significant effect on the targ
13、et dosimetric parameters of hypofractionated radiotherapy with tumor bed boost for the left breast.On the contrary,it could significantly reduce the cardiopulmonary dose in the medial group compared to the original radiotherapy plan.Given this information,it is recommended to change the multi-leaf c
14、ollimator angle for the radiotherapy plan of the medial tumor bed group in left whole-breast hypofractionated radiotherapy.KEYWORDS Breast cancer,Multi-leaf collimator,Hypofractionated radiotherapy,Tumor bed location,DosimetryCLC R815,R737.9近年来,放射治疗技术已经在乳腺癌的各个阶段得到了较大的发展1,使得早期乳腺癌保乳术后辅助全乳放疗大分割方式在临床实践中
15、优势愈发明显2-3。但因瘤床形状、体积及位置的复杂多样性等因素给乳腺癌放疗计划带来极大的挑战;同时由于瘤床推量最佳年龄段、方式及分割次数等仍未确定,使得全乳大分割放疗瘤床同期推量方式尚存较大争议4。多叶准直器是现代调强放射治疗精确实施的关键部件5,动态调强放疗技术就是利用多叶准直器叶片的相对运动来实现射线强度的调节,其中包括调整准直器角度的方法。目前,针对不同瘤床位置来调整优化全乳放疗计划的研究还很少。本研究选取心肺限量控制难度相对较大的左侧乳腺癌全乳大分割瘤床同期推量放疗患者:通过对比多叶准直器角度改变的动态调强计划(Plan-A)和多叶准直器角度保持 0的原动态调强计划(Plan-O)的剂
16、量学参数,以明晰左侧全乳大分割放疗瘤床同期推量 Plan-A 较 Plan-O 剂量学的优劣,为不同瘤床位置乳腺癌通过调整多叶准直器角度改善放疗计划提供参考。1 资料与方法1.1 临床资料收集了遵义市第一人民医院 2018 年 01 月至2023年01月间收治的早期浸润性乳腺癌患者共60例。纳入标准:左侧乳腺癌单纯全乳大分割放疗瘤床同期推量患者,临床 TNM 分期为 pT1-2N0M0 IA、IIA期(AJCC第8版分期);KPS评分80分;双侧上臂满足治疗体位的需要患者。所有患者或家属均知情同意且签署了放疗知情同意书,经本院伦理委员会审核通过(伦审(2023)001 号)。排除标准:有放疗史
17、,双侧乳腺癌,乳房假体植入,以及肩膀活动受限患者。该60例患者中位年龄49岁(2674岁),根据其瘤床位置的CT横断面,以乳头乳晕为中心标志划分三组分别为:内侧、中间以及外侧瘤床组,各20例。1.2 CT定位和靶区、心肺勾画60例患者均采用乳腺托架固定的仰卧体位,适当调整托架板高度使胸壁走行与定位机床面平行,患侧上臂充分上举以及头略偏健侧,并记录乳腺托架数据。定位CT扫描范围从颏下到膈下陈 车等:多叶准直器角度改变对左侧全乳大分割放疗瘤床推量的剂量学影响04030235 cm,层厚5 mm。由同一副主任医师在Monaco工作站手动勾画肿瘤靶区(GTV)、临床靶区(CTV)和心肺器官:GTV参考
18、术前影像资料、术中放置的钛夹标记、术后血清肿、铅丝标记的瘢痕等决定;CTV上界不超过胸锁关节,下界至已无乳腺隆起处,内界不超过胸肋关节,外界不超过腋中线,前界为皮下0.4 cm,后界为胸大肌筋膜、肋骨及肋间肌前方;计划肿瘤靶区(PGTV)在GTV基础上各方向均扩 1 cm,收至 PTV 内;计划靶区(PTV)在CTV基础上各方向外扩0.5 cm,前界收至皮下0.3 cm。肺在肺窗下自肺尖勾画至肺底;心脏自肺动脉干分叉下一层开始勾画,止于横膈顶心尖部。LAD沿着左心室和右心室之间的室间沟走行。1.3 计划设计与评估采用瑞典医科达 Precise 型医用直线加速器6 MV能量光子线和MLCi2型多
19、叶准直器,通过Monaco5.11治疗计划系统进行设计。采用6个射野顺时针共面布置,角度分布与肺边缘大致相切,前3个射野位于靶区上方均错开15,后3个射野位于靶区下方均错开15,所有计划均给予相同的目标函数等优化条件设计。多叶准直器角度保持为0的原计划即临床计划,标记为Plan-O,如图1(a)所示;多叶准直器角度改变为平行于靶区PTV 长轴动态调强计划,标记为 Plan-A,如图 1(b)所示。通过治疗计划的剂量体积直方图(DVH)进行比较相应参数。(1)靶区参数:a)靶区处方剂量为PGTV 48 Gy/15f与PTV 40.5 Gy/15f,衡量靶区处方覆盖V处方(%);b)靶区与参考等剂
20、量曲面的适形程度参数 CI(IC),IC=VTref2/(VTVref),其中,VTref为处方剂量曲线包绕的靶区体积;VT为靶区体积;Vref为处方剂量曲线包绕的所有区域的体积。c)靶区内剂量的均匀性参数HI(IH),IH=D5%/D95%,其中,D5%为5%靶区体积受到的照射剂量;D95%为95%靶区受到的照射剂量。(2)心肺危及器官限量:a)左肺(V550%、V1040%、Dmean13 Gy);b)心脏不同剂量水平(V825%、Dmean6.5 Gy)、冠状动脉左前降支LAD Dmax40 Gy和Dmean20 Gy。1.4 统计学处理应用统计学软件 SPSS16.0 对数据进行分析,
21、结果以均数标准差(x s)表示。研究采用F检验对内侧、中间和外侧瘤床组三组间的PGTV与PTV体积差异进行比较,同时应用配对t检验分别对各组Plan-A和Plan-O的剂量差异进行比较,p0.05),具备临床可比性(表1)。所有患者的Plan-A和Plan-O设计均能实现95%处方剂量曲线对计划靶区的覆盖,满足临床要求(表2)。通过分析DVH统计数据发现:内侧组、中间组和外侧组Plan-A较Plan-O,放疗计划的PGTV与PTV的V处方(%)无明显差异(p0.05);同时这两组计划的靶区CI与HI结果相似(p0.05)。因此,多叶准直器角度改变的放疗计划与原计划的靶区覆盖、适形性和均匀性差异
22、较小即多叶准直器角度改变并未对各组靶区剂量学参数产生明显影响。图1多叶准直器角度为0:(a)和平行于PTV长轴;(b)PTV-蓝色,PGTV-红色(彩色见网络版)Fig.1Multi-leaf collimator with 0:(a)and parallel to the long axis of PTV;(b)PTV-blue,PGTV-red(color online)表表1PGTV和和PTV体积体积Table 1Volume of PGTV and PTV(cm)(x s)PGTVPTV内侧瘤床Medial tumor bed62.9537.17664.30219.41中间瘤床Cent
23、ral tumor bed56.1416.79679.56302.47外侧瘤床Lateral tumor bed63.2429.34657.42237.91F0.380.04p0.680.96辐 射 研 究 与 辐 射 工 艺 学 报 2023 41:04030204030242.2 心肺受量比较基于Plan-A与Plan-O放疗计划靶区剂量学差异较小,进一步对比60例患者两种计划的心肺受量发现:与Plan-O计划相比,在内侧组和外侧组采用Plan-A使得左侧肺V5、V10和Dmean均降低,但左侧肺受量差异仅在内侧组时有统计学意义(p0.05)。故内侧和外侧组采用Plan-A在降低左肺V5、
24、V10和Dmean方面要优于 Plan-O,其中在内侧组时优势更为明显(表3)。同时,还发现在内侧组时Plan-A的心脏V8和Dmean均低于Plan-O,差异有统计学意义(p0.05)。此外,在内侧与外侧瘤床组中,Plan-A的LAD Dmax和Dmean参数小于Plan-O,差异均有统计学意义(p0.05)。综合得出,同样只有在内侧组采用Plan-A较Plan-O对保护心脏及LAD优势最为明显,见表4。2.3 讨论左侧乳腺癌患者心脏在解剖学上接近靶区,相较于右侧乳腺癌患者更容易发生放射性心脏损伤,而乳腺癌瘤床形状与位置的复杂多样性增加了放疗计划制定难度6-9。以往研究大多数致力于通过变换射
25、线性质10-11和改善放疗技术12-13以优化乳腺癌放疗计划。常规动态调强技术方式下多叶准直器角度处于0,于是有一些研究者发现,适当调整多叶准直器角度对放疗计划质量有较大影响14-18。调整多叶准直器角度的设计已经在一表表2靶区剂量学参数比较靶区剂量学参数比较Table 2Comparison for target dosimetry parameters(x s)参数ParameterPGTVPTVV处方/%CIHIV处方/%CIHI内侧瘤床 Medial tumor bedPlan-A96.681.170.520.081.060.0196.971.200.750.061.210.01Pla
26、n-O96.701.130.520.071.060.0197.211.190.750.061.220.01p0.920.930.720.121.000.49中间瘤床 Central tumor bedPlan-A98.221.180.530.071.050.0196.950.840.770.061.210.01Plan-O98.191.030.530.061.050.0197.110.850.770.061.210.01p0.830.570.580.110.070.65外侧瘤床 Lateral tumor bedPlan-A98.371.050.560.091.050.0196.911.050
27、.770.051.210.02Plan-O98.411.160.560.091.050.0197.111.000.770.051.210.01p0.700.730.670.280.480.33表表3左肺受照剂量比较左肺受照剂量比较Table 3Dose comparison for the left lung(x s)参数ParameterV5/%V10/%Dmean/Gy内侧瘤床Medial tumor bedPlan-A51.146.1238.076.3111.101.53Plan-O52.435.6339.066.3311.351.57p0.0050.010.02中间瘤床Central
28、tumor bedPlan-A46.123.1231.333.039.980.61Plan-O45.933.4331.292.859.870.75p0.680.930.21外侧瘤床Lateral tumor bedPlan-A45.606.2233.236.199.851.36Plan-O46.156.2133.726.2710.071.31p0.310.320.07表表4心脏及心脏及LAD受照剂量比较受照剂量比较Table 4Dose comparison for the heart and LAD(x s)参数ParameterHeartLADV8/%Dmean/GyDmax/GyDmea
29、n/Gy内侧瘤床 Medial tumor bedPlan-A22.227.046.302.3230.1110.4320.257.16Plan-O22.787.656.522.4931.129.8720.937.01p0.010.020.020.005中间瘤床 Central tumor bedPlan-A19.777.235.361.5125.0011.8818.058.19Plan-O19.767.045.371.4625.5311.1717.767.05p0.950.810.070.62外侧瘤床 Lateral tumor bedPlan-A17.933.545.141.0629.077
30、.6218.386.78Plan-O17.913.485.221.0329.637.5718.866.80p0.950.230.0040.001陈 车等:多叶准直器角度改变对左侧全乳大分割放疗瘤床推量的剂量学影响0403025些病种里面得到很好实践,比如鼻咽癌、肺癌、宫颈癌和前列腺癌等,不仅提高了计划质量,而且降低相关特定危及器官的照射量19-22。陈恩乐等23在10例食管癌放疗计划通过相同方式改变多叶准直器角度使其平行于靶区长轴可提升计划效率,但在靶区剂量和危及器官受量上未做详细叙述。目前虽有不少关于乳腺癌放射治疗中通过调整准直器来优化放疗计划的尝试和结论,但是在具体乳腺癌保乳术后瘤床同期推
31、量大分割放射治疗设计中多叶准直器角度的设置仍然没有一定标准。研究中多叶准直器角度调整为平行于PTV长轴的设置,也使得多叶准直器运动方向与PTV长轴垂直,减少了心肺等危及器官优化区域体积和多叶准直器运动距离,但是针对不同瘤床位置同期推量全乳放疗中多叶准直器的角度改变产生的剂量学差异犹未可知。研究选取60例左侧全乳大分割放疗瘤床同期推量患者,以原发肿瘤所在位置分为内侧、中间和外侧三组,对比分析三组各自的Plan-A与其原计划Plan-O靶区剂量参数、左肺和心脏照射量的差异。研究结果表明:动态调强方式下,多叶准直器角度的改变放疗计划即Plan-A较原计划Plan-O靶区剂量参数差异较小,原因可能是选
32、取的60例患者计划都是采用两侧切线野布置,准直器角度改变基本上在5左右的范围,其改变幅度较小使得计划系统只需稍稍调整射线束即可达到优化目标,所以使得Plan-A与Plan-O的靶区剂量参数差异性并不大;这与顾恒乐等24在准直器角度对食管癌的剂量学影响研究中发现准直器角度0与5的靶区剂量学差异不明显的结果相一致。而准直器的角度改变使得多叶准直器的凹槽形状与靶区边缘更贴合,使得多叶准直器效率增加以及计划跳数的减少23,继而使得散射线及漏射线减小,最终降低了患侧肺低剂量范围V5、V10及Dmean;且内侧瘤床组准直器角度改变使得漏散射线减小更为明显,使得患侧肺的V5、V10及其Dmean较原计划有相
33、对明显的降低。同时,内侧瘤床的位置靠近心脏极易使得心脏受到照射损伤,所以其位置的特殊性一直是临床关注的重点;由本研究结果知道,同样的限制条件下通过准直器角度的改变来降低放疗对心脏的散射,因此降低了内侧瘤床组心脏V8及Dmean以及LAD的照射量;而在中间瘤床组准直器角度改变可能增加对心脏的散射量,反而略微增加心脏的受量,此时采用准直器角度改变计划不利于心脏的保护;由于瘤床位置远离心脏使得外侧瘤床准直器角度改变对心脏受量影响较小。由此可见,三组患者的调强放疗计划均未因多叶准直器角度改变造成靶区剂量覆盖率的明显降低或者增大,也并未造成靶区适形性和均匀度的明显下降;进一步分析得出多叶准直器角度改变的
34、动态调强计划较原计划在三组中心肺受量差异有所不同,特别是在内侧组时,选择多叶准直器角度改变能明显减少心肺的受量,这说明在内侧瘤床时多叶准直器角度改变才有较大剂量学优势。研究选取60的例患者均基于相同的6个照射野于两侧相切照射、特定的目标优化函数以及科室所配置的硬件设备来对比准直器角度改变对计划剂量学参数的影响,有一定的局限性。3 结论研究了多叶准直器角度改变对左侧全乳大分割放疗三组瘤床同期推量剂量学影响:(1)多叶准直器角度改变对靶区处方覆盖、CI和HI参数影响较小;(2)在内侧瘤床推量情况下,多叶准直器角度改变能明显减小心肺的照射,具有较大剂量学优势,值得临床推广。作者贡献声明作者贡献声明
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