Dosimetric evaluation of VMAT radiation therapy technique for breast cancer after conservative surgery based on three different types of multileaf collimators

Objective Radiotherapy combined with conservative surgery plays an important role in the treatment of early-stage breast cancer. Volumetric modulated arc therapy(VMAT) has been introduced into clinical practice. The purpose of this study was to investigate the dosimetric effects of different multileaf collimators(MLC) on VMAT radiotherapy plans for treating breast cancer.Methods Fifteen breast cancer patients who were treated using a conventional technique in our department were selected to participate in this retrospective analysis. VMAT plans based on three types of Elekta MLCs [Beam Modulator(BM) with 4-mm leaf width, Agility with 5-mm leaf width and MLCi2 with 10-mm leaf width] were independently generated for each patient. Plan comparisons were performed based on dose-volume histogram(DVH) analysis including dosimetric parameters such as the homogeneity index(HI), conformity index(CI), Dmax, Dmin, and Dmean for the planning treatment volume(PTV), in addition to dose-volume parameters for the organs at risk(OARs). The delivery efficiency of the three types of MLCs was compared in terms of the beam delivery time and the monitor units(MUs) per fraction for each plan. Results Both target uniformity and conformity were improved in plans for Agility and BM MLC compared with the plan using MLCi2. The mean HI decreased from 1.14 for MLCi2 to 1.13 for BM and 1.10 for Agility, while the mean CI increased from 0.68 for MLCi2 to 0.73 for BM and 0.75 for Agility. Furthermore, at both low and high dose levels, smaller volumes of ipsilateral lung, heart, contralateral lung, and breast were irradiated with Agility MLC than with the other two types of MLCs. The delivery time with Agility MLC was reduced by 10.8% and 32.1%, respectively, compared with that for MLCi2 and BM.Conclusion Our results indicate that the Agility MLC exhibits a dosimetric advantage and a significant improvement in delivery efficiency for the treatment of breast cancer using VMAT.

基于ArcCheck和电子射野影像装置脑瘤患者特异性容积调强放射治疗剂量验证过程容差限值与干预限值研究

目的:基于ArcCheck和电子射野影像装置(EPID)开展脑瘤患者特异性容积调强放射治疗(VMAT)剂量验证,明确两种不同类别验证工具对脑瘤VMAT剂量验证的适用性,探索剂量验证中γ通过率容差限值(TL)和干预限值(AL),为放射治疗质量控制提供参考。方法:采用随机数表法选取在医院实施VMAT计划的180例脑瘤患者。根据病种及部位的不同将其分为30例较大靶区胶质瘤计划(X方向≥14 cm)、30例中等靶区胶质瘤计划(X方向<14 cm)、30例较小靶区室管膜瘤计划、30例生殖细胞瘤全脑计划、30例生殖细胞瘤全脑室计划、60例生殖细胞瘤小野加量计划和30例脑膜瘤计划,分别基于ArcCheck和EPID开展剂量验证,并将其分为ArcCheck组和EPID组;γ分析均设置为3%/2 mm标准、10%剂量阈值下γ通过率≥95%;对比两组验证计划γ通过率,评价剂量验证的TL和AL。结果:(1)靶区较大胶质瘤和全脑计划中ArcCheck组γ通过率分别为98.40%和98.90%,均高于EPID组,其差异有统计学意义(Z=-4.423,Z=-4.685;P<0.05),ArcCheck组TL、AL明显高于通用限值,EPID组TL、AL较通用限值差近5%;(2)靶区中等胶质瘤和全脑室计划中ArcCheck组和EPID组γ通过率分别为96.98%、97.36%和97.11%、97.60%,两组γ通过率差异无统计学意义,两组TL和AL均≥94%和>90%;(3)小靶区的室管膜瘤计划和生殖细胞瘤小野加量计划,ArcCheck组γ通过率分别为93.45%和94.06%,均低于EPID组,其差异有统计学意义(t=-9.40%,t=-9.41;P<0.05),ArcCheck组TL较通用限值差分别为6.88%和8.47%,AL较通用限值差分别为10.40%和8.76%,EPID组TL>90%、AL接近90%;(4)靶区大小不一、形状复杂的脑膜瘤中ArcCheck组和EPID组γ通过率分别为96.75%和97.05%,差异均无统计学意义,ArcCheck组TL、AL分别为89.33%和86.86%;EPID组TL、AL分别为93.17%和89.69%,更接近通用限值。结论:在靶区较大胶质瘤和全脑VMAT计划中,推荐使用ArcCheck进行剂量验证。在靶区较小室管膜瘤、生殖细胞瘤小野和脑膜瘤VMAT计划中,推荐使用EPID进行剂量验证。

A dosimetric evaluation of flattening filter-free volumetric modulated arc therapy for postoperative treatment of cervical cancer

Objective The aim of the study was to compare flattening filter-free(FFF) beams and conventional flattening filter(FF) beams in volumetric modulated arc therapy(VMAT) for cervical cancer after surgery, through a retrospective planning study.Methods VMAT plans of FFF beams and normal FF beams were designed for a cohort of 15 patients. The prescribed dose was 45 Gy to 1.8 Gy per fraction, and at least 95% of the planning target volume received this dose. Doses were computed with a commercially available treatment planning system using a Monte Carlo(MC) algorithm. Plans were compared according to dose-volume histogram analysis in terms of planning target volume homogeneity and conformity indices(HI and CI), as well as organs at risk(OAR) dose and volume parameters. Results FFF-VMAT was similar to FF-VMAT in terms of CI, but inferior to FF-VMAT considering HI. No statistically differences were observed between FFF-VMAT and FF-VMAT in following organ at risks including pelvic bone marrow, small bowel, bladder, rectum, and normal tissue(NT)..Conclusion For patients with cervical cancer after hysterectomy, the FFF beam achieved target and OAR dose distribution similar to that of the FF beam. Reduction of beam-on time in cervical cancer is beneficial.

Dosimetric comparison of different multileaf collimators in volumetric modulated arc therapy for malignant pleural mesothelioma

Objective The aiom of the study was to compare the impacts of two types of multileaf collimators （MLC） [standard MLC with a width of 10 mm （sMLC） and micro-MLC with a width of 5 mm （mMLC）] on volumetric modulated arc therapy （VMAT） planning for malignant pleural mesothelioma. Methods VMAT for ten patients with inoperable malignant pleural mesotheliomas was retrospectively planned with the sMLC and mMLC. Histogram-based dose-volume parameters of the planning target vol- ume （PTV） [conformity index （CI） and homogeneous index （HI）] and organs-at-risk were compared for VMAT plans with sMLC （sMLC-VMAT） and mMLC （mMLC-VMAT）. Results The mMLC-VMAT plans were more efficient （average delivery time： 2.67±1.49 min） than the sMLC-VMAT plans （average delivery time： 4.21 ± 2.03 min; P 〈 0.05）. Moreover, compared to the sMLC plans, the mMLC plans demonstrated advantages in the dose coverage of the PTV （CI 0.75 ± 0.08 vs 0.73± 0.09; HI 1.09 ±0.02 vs 1.10± 0.02）, although the difference was not statistically significant （P 〉 0.05）. In addition, significant dose sparing in the fraction of the ipsilateral lung volume receiving 〉 20 Gy （V20; 54.72± 27.08 vs 58.52 ± 29.30） and 〉 30 Gy （V30; 42.74 ± 27.86 vs 46.86± 31.49） radiation, respectively, was observed for the mMLC plans （P 〈 0.05）. Conclusion Comparing sMLC-VMAT and mMLC-VMAT not only demonstrated the higher efficiency and better optimal target coverage of mMLC-VMAT, but also considerably improved the dose sparing of the ipsilateral lung in the VMAT plans for mali qnant pleural mesothelioma.

Benefits and Limitations of Volumetric Modulated Arc Therapy in Treating Bilateral Breast Cancer with Regional Lymph Nodes

Purpose: The study was performed comparing dosimetric characteristics of volumetric modulated arc therapy (VMAT) and field-in-field (FiF) techniques on a patient with synchronous bilateral breast carcinoma. Methods: The patients with bilateral breast cancer treatment were included in this study. A total dose of 40.05 Gy in 15 fractions was prescribed to the Planning Target Volume (PTV) of the whole bilateral breast cancer with the supraclavicular and infraclavicular nodes, with a complementary boost of 10 Gy in 4 fractions to the surgical bed (PTVboost). For both radiotherapy techniques, several VxGy parameters were analyzed for the PTVs, together with the Conformity index (CI), the Homogeneity index (HI) and the critical organs at risk (OARs), lungs and heart. Results: The patient was treated by the VMAT technique and the daily treatment time was less than 20 minutes with daily CBCT imaging. In the VMAT plan, the PTV 95% dose covered 38.89 ± 0.81 Gy, compared to 37.26 ± 1.02 Gy in the FiF technique. The VMAT plan improved the dose homogeneity index and lower dose in lung towards high dose region. Conclusion: The study demonstrates the viability of the VMAT technique in the treatment of bilateral breast cancer. The introduced single isocentric VMAT technique is fast to deliver and it increases the dose homogeneity of the target volume with some limitations. The treatment was well tolerated, without interruption of the treatment courses caused by treatment-related toxicities.

基于美国医学物理学家协会TG119报告的TaiChi加速器质量控制体系建立研究

目的:依据美国医学物理学家协会(AAPM)TG119号报告测试方法和项目对TaiChi加速器在RayStation治疗计划系统(简称RayStation系统)中的建模数据模型进行测试评估。方法:在治疗计划系统中按AAPM TG119号报告要求设计模拟多靶区、前列腺靶区、头颈靶区、容易型C形靶区计划和困难型C形靶区计划等不同临床情况测试病例的调强放射治疗(IMRT)和容积旋转调强放射治疗(VMAT)计划,测量两种计划中点剂量和面积量偏差,并将测试结果与AAPM TG119报告中推荐的标准进行对比分析。使用IBA CC13电离室和ArcCHECK矩阵电离室分别对点剂量和面剂量进行验证,评估标准为3%/3mm的γ通过率。采用置信度评判测量剂量与计算剂量的一致性。结果:测试病例计划剂量目标、点剂量偏差及面剂量分布准确性均满足报告要求:测试病例IMRT和VMAT计划的靶区高剂量点平均剂量偏差分别为(0.39±1.02)%和(1.27±0.64)%,置信度分别为2.39%和2.52%。IMRT和VMAT计划的危及器官(OAR)低剂量点平均剂量偏差分别为(0.53±1.73)%和(0.88±1.11)%,置信度分别为3.92%和3.06%。IMRT和VMAT计划3%/3mm标准下的平均γ通过率分别为(99.52±0.366)%和(99.86±0.136)%,置信度分别为1.196%和0.406%。结论:TaiChi加速器性能和Raystation系统6MV FFF模型拟合精度满足AAPM TG119号报告标准,依据此测试结果建立后续设备和患者质控的标准,并为后续加速器性能的改进提供了参考。

X射线体元蒙特卡罗算法计划统计不确定度对直肠癌容积旋转调强放射治疗计划的影响

目的:研究Monaco放射治疗计划系统X射线体元蒙特卡罗(XVMC)算法中计划统计不确定度(SUpC)对直肠癌容积旋转调强放射治疗(VMAT)计划优化与剂量计算的影响。方法:回顾性选取2018年1-12月广西医科大学第一附属医院收治的10例直肠癌患者放射治疗资料,在Monaco放射治疗计划系统中采用XVMC算法,分别设置SUpC为0.25、0.50、0.75、1.00、1.25和1.50,设计6种VMAT计划(SUpC_(0.25)、SUpC_(0.50)、SUpC_(0.75)、SUpC_(1.00)、SUpC_(1.25)和SUpC_(1.50))进行优化和计算,比较6种不同VMAT计划中靶区最大剂量(D_(max))、平均剂量(D_(mean))、均匀性(HI)和适形度(CI)的差异,以及危及器官(OAR)的膀胱、小肠、股骨头和正常组织剂量差异,分析SUpC值对VMAT计划的控制点SUpC(SUpCP)、损失值loss、历史密度(HD)、优化计算时间(Time)、子野数(Segment)、机器跳数(MU)、出束时间(DT)等参数的影响。结果:随着SUpC增大,与SUpCP_(0.25)相比,其余5种计划靶区D_(max)、D_(mean)及HI分别增大,CI分别降低,差异有统计学意义(F=45.62、13.83、24.94、15.79,P<0.05),OAR膀胱的D_(max)、D_(mean)和正常组织的D_(max)、50 Gy剂量体积百分比(V_(50))分别增大,差异具有统计学意义(F=26.54、0.87、45.52、7.05,P<0.05)。与SUpCP_(0.25)相比,其余5种计划优化计算时间Time随SUpC增大分别减少,差异具有统计学意义(F=329.69,P<0.05)。SUpC≤1时,靶区D_(max)相比于SUpC_(0.25)时剂量偏差≤3%;SUpC≥1时,优化计算时间<10 min。结论:随着SUpC值增大,高剂量区域的D_(max)增多,靶区剂量被高估,靶区HI和CI变差,加速优化计算效率。针对Monaco计划系统进行直肠癌VMAT计划设计时推荐使用SUpC值为1,可以在保证计划质量最好的情况下有效提高直肠癌VMAT计划的优化效率,为直肠癌VMAT临床计划设计提供理论依据。

运用ArcCHECK实施旋转调强全骨髓照射超长靶区的计划验证

探讨利用Arc CHECK对VMAT(Volumetric Modulated Arc Therapy)和HT(Helical Tomotherapy)全骨髓照射(TMI)超长靶区计划的验证方法。选取8例全身扫描患者,分别设计TMI计划。采用Arc CHECK对两组计划头颈、胸腹及盆腔三部位行验证分析。VMAT组采用模体Merge功能通过平移治疗床实现,HT组采用双计划(参考/执行)法得以完成,三部位验证通过率分别为98.9%±1.9%/94.3%±1.5%、98.4%±1.8%/96.5%±1.2%、97.4%±2.1%/94.1%±1.9%。表明利用Arc CHECK的Merge功能能较好地完成VMAT超长靶区的验证,采用双计划法实现了对HT超长靶区及远离中心部分靶区的验证。

准直器角度对宫颈癌VMAT的剂量学影响

目的:比较两种不同准直器角度对晚期宫颈癌VMAT计划的剂量学影响,为晚期宫颈癌VMAT计划的设计提供临床参考。方法:选择11例晚期宫颈癌患者,每例病人分别设计两种不同准直器角的双弧VMAT计划,计划A和计划B的准直器角度分别为15°/345°和0°/90°。PTV处方剂量为45Gy/(25f·1.8Gy)。所有计划都满足95%的靶区体积达到处方剂量要求。比较每个计划PTV的适形性指数(CI)与均匀性指数(HI)以及膀胱、直肠、股骨头和双肾的体积剂量(V30、V40、V50和V18)和平均剂量(D mean)等参数。结果:两组计划靶区覆盖均能满足临床要求,但B计划的CI明显优于A组计划(0.75±0.03 vs 0.66±0.06;P<0.05),并且有相似的均匀性指数。与A计划相比,B计划在危及器官的体积剂量和平均剂量均明显低于前者(P<0.05)或者两者没有差别(P>0.05)。计划A、B两组膀胱和直肠的平均剂量(D mean)和体积剂量V40分别为:(4 500.70±218.28)c Gy vs(4 168.56±212.62)c Gy(P=0.000)和(83.43%±11.73%)vs(61.46%±9.47%)(P=0.000);(4 836.12±313.33)cGy vs(4 719.27±182.24)c Gy(P=0.121)和(97.05%±3.29%)vs(93.78%±6.60%)(P=0.066)。结论:对于晚期宫颈癌VMAT计划的设计,准直器角度为0°/90°的计划结果优于15°/345°的计划。不仅PTV的剂量分布有更好的适形性,而且能更好地保护危及器官。因此推荐使用0°/90°的准直器角度设计晚期宫颈癌的VMAT计划。

混合放疗技术在全脑放疗中的应用

目的比较混合放射治疗技术与调强放射治疗(Intensity Modulated Radiation Therapy,IMRT)、容积调强放射治疗(Volumetric Modulated Arc Therapy,VMAT)、三维适形放射治疗(Three dimensional Conformal Radiation Therapy,3DCRT)在全脑放疗中的剂量学差异,研究混合放疗技术在全脑放疗的可行性。方法选取25例需要全脑放疗的患者为研究对象,分别设计3DCRT计划、基于3DCRT、IMRT技术的混合计划(Hybrid-IMRT)、基于3DCRT、VMAT技术的混合计划(Hybrid-VMAT)、IMRT计划、VMAT计划。Hybrid-IMRT计划与IMRT计划、Hybrid-VMAT计划与VMAT计划均采用相同的优化参数,2个混合计划3DCRT提供60%的处方剂量(2400 cGy/20 F),IMRT或VMAT部分提供剩余40%的处方剂量(1600 cGy/20 F)。比较5组计划的靶区均匀性指数、适形度指数、靶区最大剂量、机器跳数、危及器官(晶体、眼球、视神经、视交叉、脑干)的最大剂量。结果5种计划各项指标均满足临床需求。Hybrid-IMRT、Hybrid-VMAT计划靶区均匀度、靶区剂量最大点和晶体、视交叉、脑干的受量优于IMRT、VMAT计划,且差异有统计学意义(P<0.05);HybridIMRT、Hybrid-VMAT计划靶区适形度和眼球受量相对IMRT、VMAT计划差异有统计学意义(P<0.05)。Hybrid-IMRT、Hybrid-VMAT计划的机器跳数分别比IMRT、VMAT计划减少60%和10%(P<0.05)。结论Hybrid-IMRT、Hybrid-VMAT计划的各项参数均满足临床治疗要求,其靶区均匀度更好,治疗时间更短,对距离靶区较远和靶区内部的危及器官保护更好,因此混合放射治疗技术可以应用于全脑放疗中。

基于深度学习的子宫内膜癌术后容积旋转调强治疗计划剂量预测的研究

目的:探讨基于三维深度残差网络(3D Res-Unet)模型深度学习对子宫内膜癌术后容积旋转调强治疗(VMAT)计划剂量精度的预测价值。方法:回顾性收集2019-2021年内江市第一人民医院放疗中心治疗的154例子宫内膜癌患者VMAT放疗计划,将数据集按7∶1∶2采用随机抽样法分为训练集108例,验证集15例和测试集31例,以临床批准的剂量作为“金标准”,对3D Res-UNet预测的放疗剂量与临床的放疗剂量进行比较。结果:深度学习与临床“金标准”之间的靶区适型度指数(CI)和平均剂量(D_(mean))差异有统计学意义(t=-3.115、-0.124,P<0.05)。危及器官(OAR)膀胱40%处方剂量所覆盖的靶区体积(V_(40))差异有统计学差异(t=0.510,P<0.05),直肠V50差异有统计学差异(t=-2.121,P<0.05)。左股骨头V_(30)预测剂量小于临床剂量(t=0.415,P<0.05)。右股骨头V_(30)预测剂量小于临床剂量(t=-3.102,P<0.05)。骨盆D_(mean)预测剂量高于临床剂量(t=1.224,P<0.05)。小肠V_(40)预测剂量高于临床剂量(t=0.461,P<0.05)。其他指标差异均无统计学差异(P>0.05)。剂量差异图显示,预测结果与临床结果差异很小,预测与临床的剂量体积直方图基本重合。结论:3D Res-UNet模型可有效预测子宫内膜癌术后VMAT计划三维空间剂量,可指导临床放疗工作。

应用CBCT技术测量分析鼻咽癌VMAT治疗期间每周分次间及不同部位的摆位误差

目的通过CBCT测量鼻咽癌摆位误差,观察放射治疗期间、头部区域与颈部区域摆位误差,寻找适合VMAT技术的靶区边界,为提高放射治疗的精度提供临床依据。方法选择30例鼻咽癌患者,在放射治疗前进行CBCT扫描,将扫描图像与放疗定位影像匹配,记录放疗期间每周分次间的误差及头部、上颈部及下颈部的摆位误差。结果鼻咽癌放疗治疗期间平均摆位误差X(0.96±0.77)mm,Y(0.88±0.76)mm,Z(0.94±0.79)mm。治疗期间第4周起,各方的摆位误差较首次治疗有统计学差异。不同部位摆位误差,头部摆位误差与整体相当,无统计学差异;上颈部及下颈部摆位误差明显大于整体摆位误差。在整体结构中、MPTV在三维方向外扩范围分别为2.62 mm、2.50 mm、2.63 mm。结论在治疗的第4周开始摆位误差出现明显变化,需要通过在线校正或者计划修正减少治疗误差。同时头部区域摆位误差小于颈部区域摆位误差,因此在临床工作中必须核对配准图像。

乳腺癌根治术后VMAT技术对心脏受照剂量风险评估

目的分析乳腺癌根治术后VMAT技术对心脏的物理剂量学和生物学的指标，评估心脏的受照风险。方法随机选取10例左侧乳腺癌根治术后患者，设计4种常用计划：①改良野中野调强计划FIF（8-10个子野）；②四野调强计划4F—IMRT；③五野（增加正对心脏射野）计划5F—IMRT；④包含心脏正对弧双弧VMAT计划。统计每个患者靶区、心脏和冠状动脉左前降支区LAD剂量体积参数，用NTCP—RSM模型计算放射性心脏病死亡率。统计分析VMAT技术的结果与其余技术之间的差异。结果患者心脏Dmean和V25在4种计划下平均值分别是：7．7Gy，6．9Gy，9．7cGy，6．4Gy；9．1％，7．9％，9．7％，4．9％；LAD的平均剂量分别是29．0Gy，27．6Gy，32．8Gy，26．1Gy；NTCP的平均值分别为2．7％，1．1％，1．3％，0．86％。靶区CI四套计划平均值为：0．44、0．56、0．61、0．71，HI为0．82、0．78、0．70、0．53，VMAT技术的cI和HI结果与另外3种的结果有统计学差异（P〈0．05）。结论与常规调强技术相比，包含心脏正对弧的VMAT计划不会显著影响心脏的并发症概率（NTCP），同时VMAT计划靶区的CI、HI要优于静态IMRT计划，VMAT技术可以在提高靶区剂量的同时不明显增加心脏的受照风险。

准直器角度对肺癌SBRT-VMAT治疗计划的影响

目的:研究准直器角度对中央型非小细胞肺癌(NSCLC)患者体部立体定向放射治疗(SBRT)容积旋转调强(VMAT)计划剂量学影响。方法:选取10名中央型NSCLC患者进行VMAT计划设计。使用Varian Eclipse系统,6 MV FFF X射线,最大剂量率1400 MU/min。机架角度:CCW 179°~181°、CW 181°~179°,双弧准直器角度互组,0°~90°每间隔10°设置准直器角度,即为(0°,0°)、(10°,350°)、(20°,340°)、(30°,330°)、(40°,320°)、(50°,310°)、(60°,300°)、(70°,290°)、(80°,280°)和(90°,270°)制定十个计划。在处方剂量相同并且处方剂量线包绕相同靶区体积的前提下(归一至80%),比较计划靶区参数:D 95%、V 90%、适形度指数(CI)、梯度指数(GI)、D 2 cm以及机器跳数(MU),危及器官参数:双肺(D 1500 cm^(3)、D 1000 cm^(3))、心脏(D 15 cm^(3))、脊髓(D 1.2 cm^(3)、D 0.35 cm^(3))。用SPSS软件对每个分析指标做Wilcoxon符号秩检验,判断差异是否具有统计学意义。结果:在有统计学意义的基础上,10组计划中,准直器角度为60°时(P<0.05),靶区D 95%剂量最高,准直器角度为50°时(P<0.05),靶区V 90%最高。CI和GI在0°最佳。危及器官双肺(D 1500 cm^(3)、D 1000 cm^(3))、心脏(D 15 cm^(3))、脊髓(D 1.2 cm^(3))受照剂量均在0°最低,脊髓D 0.35 cm^(3)在整个角度范围内不具有统计学差异。此外,所有计划中危及器官受照剂量均远远低于计划规定值,其中双肺(D 1500 cm^(3))在50°的剂量与最低值仅相差4.1%(P<0.05),心脏(D 15 cm^(3))在60°的剂量与最低值仅相差3.4%(P<0.05)。结论:改变准直器角度对肺癌SBRT-VMAT计划剂量有明显的影响。选择合适的准直器角度,正常组织受照剂量远远低于计划限量时,靶区体积剂量明显提高,但计划复杂度也略有提升。在临床计划设计过程中,应充分考虑准直器角度的影响,制定更合适的治疗计划。

Comparison of the effects of two typesof multileaf collimators on tumor control probabilityin radiotherapy for breast cancer after conservativesurgery based on the EUD model

Objective To compute and compare the tumor control probability(TCP) of volumetric modulated arc therapy(VMAT) for breast cancer after conservative surgery based on two types of multileaf collimator(MLC) through a retrospective planning study.Methods For a group of 9 patients diagnosed with left breast cancer,VMAT plan based on Agility MLC and beam modulator(BM) MLC were designed.The prescription dose was 50 Gy covering at least 95% of the planning target volume,2 Gy per fraction.TCPs were calculated according to dose-volume histogram(DVH) analysis.Results The TCP of the BM VMAT plan was slightly higher than that of the Agility VMAT plan(94.61% vs 94.23%) but was inferior with respect to delivery efficiency;the delivery time was reduced for Agility VMAT plan by 35% compared to BM VMAT plan.Conclusion For breast cancer radiation therapy after conservative surgery,BM VMAT plans provide slightly higher TCP while the delivery of Agility VMAT plans is significantly faster than the BM VMAT plans.

Feasibility of the partial-single arc technique in RapidArc planning for prostate cancer treatment

The volumetric modulated arc therapy(VMAT)technique,in the form of RapidArc,is widely used to treat prostate cancer.The full-single arc(f-SA)technique in RapidArc planning for prostate cancer treatment provides efficient treatment,but it also delivers a higher radiation dose to the rectum.This study aimed to compare the dosimetric results from the new partial-single arc(p-SA)technique with those from the f-SA technique in RapidArc planning for prostate cancer treatment.In this study,10 patients with lowrisk prostate cancer were selected.For each patient,two sets of RapidArc plans(f-SA and p-SA)were created in the Eclipse treatment planning system.The f-SA plan was created using one full arc,and the p-SA plan was created using planning parameters identical to those of the f-SA plan but with anterior and posterior avoidance sectors.Various dosimetric parameters of the f-SA and p-SA plans were evaluated and compared for the same target coverage and identical plan optimization parameters.The f-SA and p-SA plans showed an average difference of±1%for the doses to the planning target volume(PTV),and there were no clear differences in dose homogeneity or plan conformity.In comparison to the f-SA technique,the p-SA technique reduced the doses to the rectum by approximately 6.1%to 21.2%,to the bladder by approximately 10.3%to 29.5%,and to the penile bulb by approximately 2.2%.In contrast,the dose to the femoral heads,the integral dose,and the number of monitor units were higher in the p-SA plans by approximately 34.4%,7.7%,and 9.2%,respectively.In conclusion,it is feasible to use the p-SA technique for RapidArc planning for prostate cancer treatment.For the same PTV coverage and identical plan optimization parameters,the p-SA technique is better in sparing the rectum and bladder without compromising plan conformity or target homogeneity when compared to the f-SA technique.

Complex Target Volume Delineation and Treatment Planning in Radiotherapy for Malignant Pleural Mesothelioma (MPM)

Introduction: Radiotherapy alone or combined with surgery and/or chemotherapy is being investigated in the treatment of malignant pleural mesothelioma (MPM). This study aimed to simulate a Volumetric Modulated Arc Therapy (VMAT) treatment of a patient with MPM. Materials and Methods: CT images from a patient with intact lungs were imported via DICOM into the Pinnacle3 treatment planning (TP) system (TPS) and used as a model for MPM to delineate organs at risk (OAR) and both clinical and planning target volumes (CTV and PTV) with a margin of 5 mm. Elekta Synergy with 6 MV photons and 80 leafs MLCi2 was employed. VMAT plans were generated using two coplanar arcs with gantry rotation angles of 178° - 182°, the collimator angles of each arc were set to 90°, Octavius® 4D 729 was employed for quality assurance while the calculated and measured doses were compared using VeriSoft. Results: A TP was achieved. The Gamma volume analysis with criteria of 3 mm distance to agreement and 3% dose difference yielded the gamma passing rate = 99.9%. The reference isodose was 42.75 Gy with the coverage constraints for the PTV D95 and V95 = 95.0% of 45 Gy. The remaining dosimetric parameters met the recommendations from the clinically acceptable guidelines for the radiotherapy of MPM. Conclusion: Using well-defined TV and VMAT, a consistent TP compared to similar ones from publications was achieved. We obtained a high agreement between the 3D dose reconstructed and the dose calculated.

Eclipse计划系统MU Objective工具在鼻咽癌容积调强放射治疗计划中的应用研究

目的:探讨Varian Eclipse计划系统MU Objective工具在鼻咽癌容积调强放射治疗(VMAT)计划中的应用,旨在保证治疗计划质量的同时降低治疗计划的机器跳数(MU)。方法:选取已接受容积调强放射治疗技术的21例鼻咽癌患者,在未使用MU Objective工具的情况下给每例患者设计治疗参考计划(MU_(ref));将使用MU Objective工具对MU_(ref)进行重新优化,分别设置MU_(ref)的MU的30%、50%、70%、90%和120%,分别命名为MU_(30%)、MU_(50%)、MU_(70%)、MU_(90%)和MU_(120%)。将治疗计划MU_(30%)、MU_(50%)、MU_(70%)、MU_(90%)和MU_(120%)分别与MU_(ref)进行配对t检验统计分析,比较两种治疗计划的靶区、危及器官(OAR)剂量分布和计划的MU。结果:使用MU Objective工具对参考计划优化MU后,与参考计划相比部分靶区和OAR剂量体积参数差异虽有统计学意义,但无临床意义。治疗计划参数为MU_(30%)、MU_(50%)、MU_(70%)和MU_(90%)时,与MU_(ref)比较计划MU平均分别减少21.5%、19.5%、16.6%和8%,差异有统计学意义(t=9.652,t=8.843,t=8.963,t=11.323;P<0.05)。在MU_(120%)时,治疗计划MU平均增加1.7%,但未显著提高靶区剂量覆盖。结论:对于鼻咽癌VMAT计划,使用Eclipse计划系统的MU Objective工具在减少计划MU的同时可获得与参考计划相似的剂量分布。MU Objective工具可作为鼻咽癌或其他部位VMAT计划的常规使用工具,以保证计划质量同时减少放射治疗计划的MU。

最小子野宽度对食管癌容积调强弧形治疗计划的影响

目的基于不同最小子野宽度(MSW)对于食管容积调强弧形放射治疗(VMAT)计划质量和执行效率的影响。方法随机选择15例食管癌患者,其中男性11例,女性4例;年龄45~68岁,中位年龄59岁。设计0.5 cm、1.0 cm、1.5 cm3种不同MSW的VMAT计划,保证其他计划参数不变。评价靶区均匀性指数(HI)、适形度指数(CI)和平均剂量及控制点数(CP)和机器跳数(MU)值,并进行三维剂量验证测量。结果不同MSW对危及器官的保护是相当的,在MSW 0.5 cm、1.5 cm时肿瘤靶区平均量GTV Dmean[(68.95±0.03)Gy vs(68.29±0.03)Gy]、在MSW 1.0 cm和1.5 cm时计划靶区(PTV)的HI差异有统计学意义(1.14±0.00 vs 1.13±0.00)(P<0.05);MSW 1.0 cm、1.5 cm时总MU和CP与0.5 cm比较,平均减少量分别为(12.5±4.1)%、(13.9±4.8)%和(28.5±5.4)%、(18.4±3.4)%。计划验证使用阈值为10%,3%/3 mm的Gamma分析方法,计划验证通过率分别为(96.73±0.27)%、(96.98±0.32)%、(97.25±0.42)%,差异无统计学意义,均能满足临床需求。结论增加MSW在保证计划食管癌的VMAT计划质量下,可以降低MU,提高计划执行效率,MSW为1.0 cm会是一个较优选择。

三维与四维锥形束CT在肺癌容积旋转调强计划精确放射治疗中的比较研究

目的:比较研究三维锥形束CT(3D-CBCT)与四维锥形束CT(4D-CBCT)在肺癌容积旋转调强治疗(VMAT)计划精确放射治疗中的应用。方法:选取在医院接受VAMT放射治疗的101例肺癌患者,根据治疗中扫描模式的不同,将使用3D-CBCT成像的患者纳入3D-CBCT组(45例),将使用4D-CBCT成像的患者纳入4D-CBCT组(56例),比较两组患者治疗中CT图像校正后分次间摆位误差、肿瘤靶区外放边界、肿瘤内靶区(ITV)体积、靶区计划靶体积(PTV)剂量和危及器官(OAR)心脏受照剂量。结果:两组患者治疗中CT图像校正后左右(X轴)方向、前后(Z轴)方向摆位误差均显著下降,差异有统计学意义(Z=-3.005,Z=-2.047;P<0.05),上下(Y轴)方向摆位误差无统计学差异;两组PTV外放范围均在Y轴方向最大;两组肺上叶肿瘤ITV体积差异无统计学意义,4D-CBCT组肺中下叶ITV体积明显低于3D-CBCT组,差异有统计学意义(Z=-2.245,P<0.05);4D-CBCT组靶区最大剂量(D_(max))、最小剂量(D_(min))、平均剂量(Dmeam)及靶区95%受照剂量(D_(95))Gy均大于3D-CBCT组,且D_(min)、D_(mean)及D_(95)差异有统计学意义(Z=-2.207,Z=-4.872,Z=-4.405;P<0.05);4D-CBCT组OAR心脏V_(20)、V_(30)、D_(mean)测量值均低于3D-CBCT组,其差异有统计学意义(Z=-2.077,Z=-2.208,Z=2.071;P<0.05)。结论:4D-CBCT与3D-CBCT相比,可减少摆位误差并提高摆位的精确性,缩小PTV的外放距离,提高靶区剂量,减少周围OAR的受量。