多目标优化在宫颈癌放疗中的临床应用分析

目的 研究多目标优化在宫颈癌放射治疗中的临床应用。方法 回顾性分析山东省肿瘤防治研究院已接受宫颈癌放射治疗的15例患者,于Halcyon平台9野均分重新优化固定野调强计划,以靶区覆盖率95%以上且危及器官受量最低为目标,反复优化直至达到目标（Plan I）,利用多目标优化对仅优化一次的计划进行多目标遴选直至达到目标（Plan MI）,并执行质量保证验证,采用Wilcoxon秩和检验比较计划的设计时间、靶区覆盖率、危及器官受照剂量和机器跳数。结果 2种计划均能达到临床要求。Plan I与Plan MI的靶区剂量指标差异无统计学意义（P> 0.05）,Plan MI降低了小肠的最大受照剂量0.51 Gy(P <0.05),对于膀胱和直肠的剂量覆盖,2种计划基本相同（P> 0.05）。Plan MI比Plan I的计划设计时间节省了34.04 min (P <0.05)。结论 多目标优化工具能够提高优化调整能力,明显缩短计划设计时间,提高工作效率。     

次级准直器对左乳腺癌放射治疗剂量的影响

目的 研究次级准直器对左乳腺癌放射治疗剂量的影响。方法 利用蒙特卡罗程序(BEAMnrc)模拟电子和光子在医用直线加速器治疗头中的输运行为,然后利用BEAMdp对相空间文件进行分析,获得次级准直器对光子能谱及剂量的影响。使用Oncentra计划系统,选取2020年1月至2023年6月医院左乳腺癌患者100例设计放射治疗计划,分析次级准直器的角度对放射治疗计划靶区及重要危及器官的影响。结果 通过分析标称能量为6 MV的医用直线加速器的光子能谱,发现次级准直器单一X、Y方向和整体次级准直器光子数占总光子数比例均不到0.2%,表明次级准直器对光子剂量影响较小;通过改变次级准直器的角度,发现左乳腺癌放射治疗计划左肺V₂₀、V₃₀和D_mean分别降低了1.49%、1.48%和6.35%,此外心脏V₁₀、V₃₀和D_mean分别降低了2.11%、1.59%和7.95%。结论 在设计左乳腺癌放射治疗计划时,可通过改变次级准直器的角度降低患者左肺及心脏受照剂量。     

调强适形放射治疗与三维适形放射治疗技术治疗原发性肝癌的临床剂量学研究

目的:探讨调强适形放射治疗(IMRT)与三维适形放射治疗(3D-CRT)技术治疗原发性肝癌的临床剂量学。方法:选取入住本院的45例原发性肝癌患者,针对每例患者制定2套放射治疗计划,比较计划靶区(PTV)的平均剂量、最小剂量、最大剂量及最大剂量与处方剂量的百分比、靶区适形指数以及靶区均匀指数,分析危及器官的照射剂量。结果:统计分析显示,最小受照剂量(PTVD min)中,两者差异无统计学意义(t=0.037,P>0.05);平均受照剂量(PTVD mean)、最大受照剂量(PTVDmax)、靶区最大剂量与处方剂量的百分比(PTVDmax/%)、靶区剂量均匀度指数(HI)和适形度指数(CI)IMRT与3D-CRT差异均具有统计学意义(t=35.631,t=4.136,t=3.428,t=2.123,t=15.996;P<0.05)。危及器官的照射剂量分析中,IMRT在肾脏、胃、十二指肠和脊髓的剂量明显低于3D-CRT的照射剂量。结论:IMRT能有效地提高靶区的照射剂量,降低危及器官的损伤。     

比较适形放射治疗中移动中心位置对多叶准直器宽度的影响

目的:拟用在三维适形放射治疗过程中移动等中心位置,提高靶区适形度,改善多叶准直器在等中心处的叶片宽度。方法:cT模拟,TPS计划系统,选取10个头颈部肿瘤患者,分别用三种方法: 固定等中心,多叶准直器适形(A);移动等中心5mm,多叶准直器适形,移动前后剂量比1:1(B); 固定中心,铅挡适形(C)。结果:从靶区适形度和危及器官的受照射量进行比较,移动治疗中心位置对多叶准直器的治疗宽度有一定的改善。结论:移动治疗中心位置可改善靶区的适形度及危及器官的受照射剂量。     

鼻咽癌螺旋断层放疗与常规调强放疗能剂量学分析

目的比较鼻咽癌在螺旋断层放疗（Helical Tomotherapy）和常规调强放疗（IMRT）两种不同治疗系统中治疗计划的剂量学分布,并对靶区和危及器官的剂量进行分析。材料与方法选择18例鼻咽癌病例,将其定位数据信息及靶区器官轮廓分别传输至TomotherapyTPS工作站及Varian EclipseTPS工作站并设计调强放疗计划,18例患者的处方剂量相同,其中鼻咽部原发灶GTVnx为73．92Gy／33F;可见的转移淋巴结GTVnd为69．96Gy／33F;高危临床靶区CTV1为60．06Gy／33F;预防照射区CTV2为50．96Gy／28F,通过对靶区的适形度指数（CN）、均匀性指数（H1）和危及器官（OARs）的最大剂量及平均剂量等各项指标比较2组治疗计划,对两组数据进行配对f检验。结果螺旋断层放疗组中PGTVnx、PTV1、PTV2的CN值分别为0．910±0．010、0．855±0．020、0．871±0．021,常规调强组中PGTVnx、PTV1、PTV2的CN值分别为0．867±0．025、0．822±0．020、0．811±0．012,螺旋断层放疗组中PGTVnx、PTV1、PTV2的HJ值分别为1．049±0．009、I_135±0．030、1．034±0．011,常规调强组中PGTVnx、PTV1、PTV2的HI值分别为1．060±0．011、1．222±0：023、1．094±0．015,各组P值均〈0．005。螺旋断层放疗组相比常规调强放疗组各靶区的的均匀性指数和适形度指数均有不同程度的改善;危及器官的最大剂量和平均剂量也有所下降,腮腺平均剂量较常规调强放疗组低4Gv左右,V30、V35也显著低于常规调强放疗,P值〈0．005。结论对于鼻咽癌,螺旋断层放疗技术相对于常规凋强技术改善了剂量学分布,使得靶区在获得更好的剂量分布同时显著降低了正常组织的受照剂量。     

胸段食管癌累及野放疗与扩大野放疗对危及器官的辐射剂量学分析

目的 研究胸段食管癌逆向调强放射治疗（IMRT）中累及野照射与扩大野照射对危及器官（OAR）受照剂量的影响。方法 40例胸段食管癌患者分别行累及野靶区勾画和扩大野靶区勾画并勾画危及器官,制定IMRT计划,评估2个计划的靶区适形指数（CI）和均匀性指数（HI）及危及器官的剂量学参数,剂量学参数比较采用配对t检验。结果 2种计划的PTV均能满足处方剂量要求,PTV在CI、HI上相近（P=0.317、0.130）。两组间平均肺剂量、两肺V5、两肺V20、两肺V30、脊髓Dmean、心脏Dmean、心脏Dmax、心脏V30、心脏V40、心脏V60差异均存在统计学意义（P <0.01）。结论 胸段食管癌患者行累及野照射与扩大野比较,可降低正常器官的受照剂量,从而降低放射性损伤风险。     

调强放疗中多叶准直器漏射线对晶体受照剂量的影响

目的研究多叶准直器（MLC）的漏射线及其对晶体的影响。方法使用PTW30013电离室测量MLC的透射因子,并针对5例头部肿瘤患者的调强计划,用PTW31010电离室在Topslane圆柱形模体中,对晶体受照剂量做验证测量。结果 MLC透射因子是1.42%,符合临床要求,5例患者晶体实测剂量均高于计划计算值（P〈0.05）。结论调强放疗中MLC的漏散射线,会使晶体实际受照剂量比计划值偏高,在特殊情况下,可以增加对危及器官的剂量验证测量。     

多叶准直器的设计与临床应用评价

多叶准直器是医用直线加速器中遮挡射线的装置，在放射治疗中调节射野形状和剂量分布，直接影响靶区与危及器官受量。目前，多叶准直器在结构上呈现出多样化，各类多叶准直器的剂量学对比也同步推进。本文按多叶准直器的基本构成将其分类，分别介绍各主流加速器厂商产品的硬件结构与设计特点（包括瓦里安Millennium MLC、HD120MLC、Halcyon；医科达MLCi/i2、Agility；安科瑞InCise 2 MLC、TomoTherapy二元气动光栅）；在临床应用评价方面，以鼻咽癌放疗计划为主，综述多叶准直器剂量学表现的对比研究，以及相关条件设置对剂量分布的影响。本文综述的多叶准直器的设计与临床应用评价，为更具创新性设计方案的提出、临床个体化治疗中加速器的选择与参数设定提供参考。     

三种放疗技术对早期鼻咽癌颈部皮肤设定限制剂量差异研究

目的:探究容积旋转调强放疗(VMAT)、固定野调强放疗(IMRT)、常规放疗对早期鼻咽癌颈部皮肤设定限制剂量差异。方法:对我院2017.7~2018.7收治的73例鼻咽癌患者展开对照研究,每例分别制作VMAT、IMRT、常规放疗共3套放疗计划,对比3种计划的危及器官受照剂量、靶区剂量分布。结果:与常规放疗及IMRT技术相比,VMAT显示了更高的适形指数,VMAT平均剂量显著更低(P<0.05),而在靶区均匀性上三种计划无显著差异(P>0.05),在最大剂量上,IMRT组显著较高(P<0.05),三种计划在脊髓剂量上无显著差异(P>0.05),VMAT在颞颌关节、腮腺剂量上显著比IMRT、常规放疗低(P<0.05)。结论:VMAT在靶区适形指数、平均剂量以及周围器官剂量上更低,对患者造成的影响更小,此方法值得应用与推广。     

固定准直器技术在食管癌根治性放射治疗中的应用

目的 在食管癌根治性放射治疗中应用固定准直器(FC)技术进行调强放射治疗(IMRT)计划设计,以期在达到计划靶区(PTV)目标剂量分布的同时降低危及器官(OAR)的受照射剂量,特别是降低肺部低剂量区的受照射体积.方法 应用瓦里安Ecplise 13.5放射治疗计划系统(TPS),选取2018年1月1日至2020年1月1...     

Incorporation of gantry angle correction for 3D dose prediction in intensity-modulated radiation therapy

Pretreatment dose verification with beam-by-beam analysis for intensity-modulated radiation therapy (IMRT) is commonly performed with a gantry angle of 0° using a 2D diode detector array. Any changes in multileaf collimator (MLC) position between the actual treatment gantry angle and 0° may result in deviations from the planned dose. We evaluated the effects of MLC positioning errors between the actual treatment gantry angles and nominal gantry angles. A gantry angle correction (GAC) factor was generated by performing a non-gap test at various gantry angles using an electronic portal imaging device (EPID). To convert pixel intensity to dose at the MLC abutment positions, a non-gap test was performed using an EPID and a film at 0° gantry angle. We then assessed the correlations between pixel intensities and doses. Beam-by-beam analyses for 15 prostate IMRT cases as patient-specific quality assurance were performed with a 2D diode detector array at 0° gantry angle to determine the relative dose error for each beam. The resulting relative dose error with or without GAC was added back to the original dose grid for each beam. We compared the predicted dose distributions with or without GAC for film measurements to validate GAC effects. A gamma pass rate with a tolerance of 2%/2 mm was used to evaluate these dose distributions. The gamma pass rate with GAC was higher than that without GAC (P = 0.01). The predicted dose distribution improved with GAC, although the dosimetric effect to a patient was minimal.     

Study of X-ray field junction dose using an a-Si electronic portal imaging device

Field junctions between megavoltage photon beams are important in modern radiotherapy for treatments such as head and neck and breast cancer. An electronic portal imaging device (EPID) may be used to study junction dose between two megavoltage X-ray fields. In this study, the junction dose was used to determine machine characteristics such as jaw positions and their reproducibility, collimator rotation and the effect of gantry rotation. All measurements were done on Varian linear accelerators with EPID (Varian, Palo Alto, CA). The results show reproducibility in jaw positions of approximately 0.3 mm for repeated jaw placement while EPID readings were reproducible within a standard deviation of 0.4% for fixed jaw positions. Junction dose also allowed collimator rotation error of 0.1° to be observed. Dependence of junction dose on gantry rotation due to gravity was observed; the gravity effect being maximum at 180° gantry angle (beam pointing up). EPIDs were found to be reliable tools for checking field junctions, which in turn may be used to check jaw reproducibility and collimator rotation of linacs.     

腰椎转移瘤不同射野角度调强放疗计划的剂量学研究

目的 比较腰椎转移瘤3种不同射野角度调强放疗（IMRT）计划中靶区及其周围正常组织受照剂量的差异。方法 选择10例腰椎转移瘤患者,以3000 cGy /10F处方剂量分别对同一患者设计七野均分（plan-A）、五后野（plan-B）、七后野（plan-C）3种调强放疗计划,所有计划均使用相同的目标函数和剂量限制条件。采用SPSS 21.0统计学软件进行数据分析,评价3种调强放疗计划的靶区、危及器官、正常组织的剂量学参数以及治疗参数差异。结果 3种调强放疗计划均能满足临床要求,对于计划靶区的D_mean、D_2%、D_98%、CI、HI,plan-A与plan-C的差异无统计学意义（P > 0.05）,且均优于plan-B（P < 0.05）。对于双侧肾脏的受照剂量,plan-B低于另外2种计划（P < 0.05）;对于脊髓的D_max,plan-B高于另外2种计划（P < 0.05）;对于正常组织的V₅、V₁₀,plan-B低于另外2种计划（P < 0.05）,对于正常组织的V₁₅、V₂₀、V₂₅,plan-B均高于另外2种计划（P < 0.05）。在治疗参数方面,plan-B的机器跳数和治疗时间最优 (P < 0.05)。结论 七野均分（plan-A）和七后野（plan-C）IMRT计划在靶区剂量分布及降低脊髓D_max方面较优;五后野（plan-B）IMRT计划在保护双侧肾脏及缩短治疗时间上更具优势。     

A dosimetric comparison of two-phase adaptive intensity-modulated radiotherapy for locally advanced nasopharyngeal cancer

The purpose of this investigation was to evaluate the potential dosimetric benefits of a two-phase adaptive intensity-modulated radiotherapy (IMRT) protocol for patients with locally advanced nasopharyngeal cancer (NPC). A total of 17 patients with locally advanced NPC treated with IMRT had a second computed tomography (CT) scan after 17 fractions in order to apply and continue the treatment with an adapted plan after 20 fractions. To simulate the situation without adaptation, a hybrid plan was generated by applying the optimization parameters of the original treatment plan to the anatomy of the second CT scan. The dose–volume histograms (DVHs) and dose statistics of the hybrid plan and the adapted plan were compared. The mean volume of the ipsilateral and contralateral parotid gland decreased by 6.1 cm³ (30.5%) and 5.4 cm³ (24.3%), respectively. Compared with the hybrid plan, the adapted plan provided a higher dose to the target volumes with better homogeneity, and a lower dose to the organs at risk (OARs). The Dmin of all planning target volumes (PTVs) increased. The Dmax of the spinal cord and brainstem were lower in 94% of the patients (1.6–5.9 Gy, P < 0.001 and 2.1–9.9 Gy, P < 0.001, respectively). The D_mean of the contralateral parotid decreased in 70% of the patients (range, 0.2–4.4 Gy). We could not find a relationship between dose variability and weight loss. Our two-phase adaptive IMRT protocol improves dosimetric results in terms of target volumes and OARs in patients with locally advanced NPC.     

Intensity modulated radiation therapy with field rotation—a time-varying fractionation study

This paper proposes a novel mathematical approach to the beam selection problem in intensity modulated radiation therapy (IMRT) planning. The approach allows more beams to be used over the course of therapy while limiting the number of beams required in any one session. In the proposed field rotation method, several sets of beams are interchanged throughout the treatment to allow a wider selection of beam angles than would be possible with fixed beam orientations. The choice of beamlet intensities and the number of identical fractions for each set are determined by a mixed integer linear program that controls jointly for the distribution per fraction and the cumulative dose distribution delivered to targets and critical structures. Trials showed the method allowed substantial increases in the dose objective and/or sparing of normal tissues while maintaining cumulative and fraction size limits. Trials for a head and neck site showed gains of 25%–35% in the objective (average tumor dose) and for a thoracic site gains were 7%–13%, depending on how strict the fraction size limits were set. The objective did not rise for a prostate site significantly, but the tolerance limits on normal tissues could be strengthened with the use of multiple beam sets.     

Dosimetric benefits of placing dose constraints on the brachial plexus in patients with nasopharyngeal carcinoma receiving intensity-modulated radiation therapy: a comparative study

This study aimed to evaluate whether placing dose constraints on the brachial plexus (BP) could provide dosimetric benefits in patients with nasopharyngeal carcinoma (NPC) undergoing intensity-modulated radiation therapy (IMRT). Planning CT images for 30 patients with NPC treated with definitive IMRT were retrospectively reviewed. Target volumes, the BP and other critical structures were delineated; two separate IMRT plans were designed for each patient: one set no restrictions for the BP; the other considered the BP as a critical structure for which a maximum dose limit of ≤66 Gy was set. No significant differences between the two plans were observed in the conformity index, homogeneity index, maximum dose to the planning target volumes (PTVs), minimum dose to the PTVs, percentages of the volume of the PTVnx and PTVnd receiving more than 110% of the prescribed dose, or percentages of the volume of the PTVs receiving 95% and > 93% of the prescribed dose. Dose constraints significantly reduced the maximum dose, mean dose, V45, V50, V54, V60, V66 and V70 to the BP. Dose constraints significantly reduced the maximum dose to the BP, V45, V60 and V66 in both N0–1 and N2–3 disease; however, the magnitude of the dosimetric gain for each parameter between N0–1 and N2–3 disease was not significantly different, except for the V60 and V66. In conclusion, placing dose constraints on the BP can significantly decrease the irradiated volume and dose, without compromising adequate dose delivery to the target volume.     

4D digitally reconstructed radiography for verifying a lung tumor position during volumetric modulated arc therapy

We have proposed four dimensional (4D) digitally reconstructed radiography (DRR) for verifying a lung tumor position during volumetric modulated arc therapy (VMAT). An internal target volume (ITV) was defined based on two clinical target volumes (CTVs) delineated on maximum exhalation and maximum inhalation images acquired by 4D planning computed tomography (CT). A planning target volume (PTV) was defined by adding a margin of 5 mm to the ITV on the maximum exhalation 3D CT images. A single-arc VMAT plan was created on the same CT data using Pinnacle SmartArc with a maximum multi-leaf collimator leaf speed of 1 mm/degree, thereby resulting in quasi-conformal field shapes while optimizing each beam intensity for each gantry angle. During VMAT delivery, cone-beam CT (CBCT) projection data were acquired by an on-board kilovoltage X-ray unit and a flat panel 2D detector. Four CBCT image sets with different respiratory phases were reconstructed using in-house software, where respiratory phases were extracted from the projection data. Subsequently a CTV was delineated on each of the 4D CBCT images by an oncologist. Using the resulting 4D CBCT data including the CTV contours, 4D DRRs during the VMAT delivery were calculated as a function of gantry angle. It was confirmed that the contoured CTV was within the radiation field during the four-fraction lung VMAT delivery. The proposed 4D DRR may facilitate the verification of the position of a respiratory moving lung tumor during VMAT delivery on each treatment day.     

多叶准直器在动态适形放射治疗中的应用初探－附27例分析

目的：研究多叶准直器在临床的应用价值。方法：利用带多叶准直器的直线加速器的三维治疗计划系统（TPS）结合CT定位制定并选取最佳放射治疗计划实施对恶性肿瘤的治疗。结果：27例患者的照射野较好的适形于靶区,治疗计划均符合临床要求,靶区位于90％的等剂量线内且剂量分布较均匀,并形成高剂量区,周围正常组织剂量降低,反应减轻。结论：利多叶准直器能实施三维适形放疗,提高靶区剂量,降低正常组织受量,减轻放疗反应,值得临床推广。