头颈恶性肿瘤调强放射治疗的现状

头颈恶性肿瘤调强放射治疗能较大限度降低相邻重要器官的剂量，其对腮腺功能的保护能改善患者生活质量。目前困扰颈部淋巴结描绘的关键因素是如何将颈淋巴结的解剖分区转换成CT层面可描绘的影像边界。怎样实现更高提升肿瘤靶区剂量而进一步提高局部和区域控制率是今后一段时问内头颈恶性肿瘤放射治疗发展方向。     

调强放射治疗计划

调强放射治疗（IMRT）作为一种新近发展起来的先进放射治疗技术。在一些发达国家已经应用于临床,其优势在于肿瘤靶区三维剂量分布的适形程度及其均匀性较标准的适形放疗更好,从而在减少或不增加正常组受高剂量照射的前提下增加肿瘤组织的受照剂量,这样就可以提高肿瘤的局部控制率,降低正常组织并发症的发生率,本文对调强放疗的计划过程、剂量计算及优化方式等进行了综述。     

鼻咽癌调强放射治疗进展

调强放射治疗技术日趋成熟,鼻咽癌是最适于调强放射治疗的肿瘤之一.Ⅱ期临床研究结果显示,IMRT技术优于传统放射技术,IMRT技术提高了鼻咽癌的局部区域性控制率和总生存率,并改善了生存质量.准确勾画靶区和正常组织是保证鼻咽癌IMRT疗效的前提.本文将讨论鼻咽癌的靶区勾画、给量方式、临床治疗结果及治疗相关毒副反应.     

适形调强放射治疗技术

适形调强放射治疗(intensity modulated radiation therapy，IMRT)是近年来发展起来的一项新技术，是按设计好的强度分布在治疗机上采用某种调强方式而实施的治疗。IMRT精确定位、精确计划、精确照射使靶区接受的剂量最大，靶区周围正常组织受量最小，增加肿瘤控制率；减少正常组织的损伤，改善病人的生存质量。全文介绍。IMRT的特点，调强方式的实现，调强治疗实施过程以及调强靶区位置和治疗剂量学的验证、适应证。     

脑胶质瘤调强放疗机架角度优化的剂量学研究

目的 探讨调强放疗计划中机架角度优化的剂量学特点。方法 随机选取 15例脑胶质瘤术后患者,每例患者分别设计两种治疗计划,其中射野数目(5~9个野)、剂量体积约束条件相同,但第1种计划(计划1)的机架按等角度共面布置,第2种计划(计划2)的机架角由计划系统内含的机架角度几何优化算法自动选择。在处方剂量要求相同情况下,比较两种计划的靶区和危及器官剂量学参数、机器跳数差异。结果 靶区剂量学参数中,计划1的计划瘤床体积适形指数好于计划2(0.84∶0.85,t=2.77,P=0.015);对于危及器官,计划2的左右晶体和左视神经受量明显低于计划1(528.91 cGy∶662.40%,t=3.15,P=0.007;535.87 cGy∶631.99 cGy,t=2.72,P=0.017;2189.85 cGy∶2676.41 cGy,t=3.06,P=0.008);对于正常组织\[全脑正常组织减去PTV 即B-P\],计划2中受照 5~20 Gy体积占总B-P体积百分比 V₅、V₁₀、V₁₅、V₂₀小于计划1的(52.17%∶55.43%,t=3.76,P=0.002;42.91%∶46.66%,t=4.44,P=0.001;36.05%∶40.01 cGy,t=5.91,P=0.000;29.45%∶32.35%,t=4.89,P=0.000);计划2的机器跳数比计划1的平均减少10.7%(851∶760,t=3.60,P=0.003)。结论 脑胶质瘤调强放疗机架角度优化能一定程度减少危及器官受量,更好保护靶区周围的正常组织,同时还减少了机器跳数,具有一定的剂量学优势。     

不同体位容积调强放射治疗和调强适形放射治疗宫颈癌患者膀胱的剂量学差异

目的 探讨仰卧位与俯卧位容积调强放射治疗(VMAT)与调强适形放射治疗(IMRT)术后补充放疗时宫颈癌患者膀胱的剂量学差异。方法 采用随机抽样法选取20例宫颈癌术后患者,在CT模拟定位时分别采用仰卧位与俯卧位两种体位进行定位,在Eclipse计划系统中分别对每例患者进行VMAT和7野IMRT设计,分别比较两种体位、两种放疗技术宫颈癌患者膀胱的剂量学差异。结果 仰卧位时,宫颈癌患者VMAT时膀胱受照射剂量超过30 Gy的体积(V₃₀)、V₄₀及平均剂量(D_mean)均明显低于IMRT,差异均有统计学意义(P<0.01)。俯卧位时,宫颈癌患者VMAT时膀胱V₃₀、V₄₀、V₅₀及D_mean,均低于IMRT,差异均有统计学意义(P<0.05)。无论是IMRT还是VMAT,俯卧位宫颈癌患者的膀胱V₃₀、V₄₀及D_mean均低于仰卧位,差异均有统计学意义(P<0...     

基于改良遗传算法的调强射野角度优化

免了手工多次调整射野方向,提高了效率和效果.     

鼻咽癌调强放射治疗进展

文章从调强放射治疗的优势，以及鼻咽癌靶区的确定及勾画入手，分析总结调强放射治疗在鼻咽癌中的应用进展及其存在的问题与对策，并对其发展趋势影像介导的调强放射治疗作了展望。     

调强适形放射治疗肺癌临床研究

目的总结调强适形放射治疗肺癌的临床体会及其近期疗效.方法应用美国NORMOS公司的调强多叶准直器(MIMiC)及CORVU3.0逆向调强适形放疗计划系统,治疗肺癌46例,其中单纯调强适形放疗12例,常规照射与单纯调强适形放疗结合治疗34例.结果一年生存率Ⅰ、Ⅱ期为75%(6/8),Ⅲa期50.0%(8/16),Ⅲb期为33.3%(5/15),Ⅳ期14.3%(1/7).全组生存时间≥24个月者8例,占同期病人的57.1%(8/14).结论调强适形放射治疗肺癌为一有效的治疗方法,有关其时间-剂量分割及与常规照射的衔接有待于进一步细致地研究.     

准直器角度优化对胃癌调强放疗计划影响

目的 探讨4种准直器角度优化技术对胃癌调强放疗计划靶区(PTV)及危及器官(OAR)剂量学的影响。方法 选取2015-2016年间武汉大学中南医院接受调强放疗的10例胃癌患者,调强放疗计划均采用常规5个野(330°、10°、45°、90°、180°),其他优化参数一致。在Eclipse计划系统中分别用4种不同的准直器角度优化技术设计调强放疗计划。准直器角度优化技术包括准直器角度设为默认0°(CL0)、与0°垂直的90°(CL90)、采用Eclipse自动角度优化(CLA)以及将准直器角度设为X-Jaws围绕靶区PTV距离最短时的角度(CLX)。主要剂量学参数包括PTV适形指数(CI)、均匀指数(HI)、平均剂量(Dmean)及OAR受量,并且考虑治疗时间(Time)、治疗跳数(MU)、控制点(CP)、分野数(SF)及适形距离(Fx)等参数。结果 以CL0优化为对照,4种准直器角度优化技术PTV的CI、HI及Dmean比较差异无统计学意义(P>0.05),然而CLX能显著增加靶区PTV的Dmean(P<0.05);CLX优化能够减少肝(V30减少1.54%)、左肾(V12减少1.46%)等受量,但会轻微增加小肠和脊髓的最大剂量(<1%),而CL90与CLA优化会导致增加胃受量。4种不同的准直器角度优化中,CLX优化能够减少MU (减少25.02%)、CP (减少26.03%)、Fx (减少20.27%)及SF (平均减少1.3个分野)。对于Time,CLX相对减少10.03%;CL90与CLA能够减少MU、CP、Fx和SF,且CL90在减少Time方面有一定的优势,而CLA会相对增加Time (增加5.04%)。结论 在胃癌的调强放疗计划中,采用CL90、CLA和CLX 3种准直器角度优化技术能够获得与常规CL0的准直器角度优化相当的剂量分布,且能减少MU,从而减少漏射和照射时间,提高治疗效率。     

调强放疗计划多目标优化算法比较研究

目的 探讨多目标优化(MCO)算法在调强放疗计划优化中的应用。方法 随机抽取已接受治疗的10例前列腺癌和10例肺癌患者的调强治疗计划,这些计划都是基于直接子野优化算法进行优化的。在射野方向等设置条件不变前提下,改用MCO算法重新优化治疗计划。比较两种优化算法得到的剂量体积直方图参数、计划优化时间和机器跳数,并行配对t检验。结果 两种优化算法得到的调强计划均满足临床要求。与DMPO算法相比,在靶区剂量分布无差别下MCO算法使得前列腺癌计划中的直肠、膀胱及小肠受量均有不同程度降低,计划优化时间减少58%,机器跳数平均增加32%;在肺癌计划中肺、心脏和脊髓受量均有不同程度降低,计划优化时间减少59%,机器跳数平均增加11%。结论 与DMPO算法相比,MCO算法可显著降低危及器官受照剂量、缩短计划优化时间。     

基于危及器官剂量预测和射野角度优化的食管癌调强放疗自动计划研究

目的 在Raystation计划系统上实现基于危及器官剂量预测和射野角度优化的食管癌调强放疗(IMRT)计划自动设计。方法 选取50例食管癌IMRT计划数据作为训练集,训练危及器官剂量预测模型。另外选取20例病例应用RuiPlan自动计划脚本和人工方法分别进行计划设计,其中在自动计划中使用射野角度优化和危及器官剂量预测模型。配对t检验比较两组计划的剂量差异和工作效率。结果 人工计划和自动计划计划靶体积的适形指数、均匀性指数,全肺V5Gy与脊髓Dmax均相近(均P>0.05)。自动计划的左肺和右肺V20Gy、Dmean较人工计划下降1.1%、0.37Gy和1.2%、0.38Gy (均P<0.05),心脏V30Gy、V40Gy、Dmean较人工计划下降5.1%、3.0%、1.41Gy (均P<0.05)。自动计划的人工操作时间、计算机处理时间、机器跳数较人工计划分别减少了65.8%、14.1%、17.2%(均P<0.05)。结论 RuiPlan自动计划脚本能够通过危及器官剂量预测和射野角度优化的方法提高食管癌计划设计效率,为食管癌放疗计划设计提供了另一种可选途径。     

Simultaneous beam geometry and intensity map optimization in intensity-modulated radiation therapy

PURPOSE: In current intensity-modulated radiation therapy (IMRT) plan optimization, the focus is on either finding optimal beam angles (or other beam delivery parameters such as field segments, couch angles, gantry angles) or optimal beam intensities. In this article we offer a mixed integer programming (MIP) approach for simultaneously determining an optimal intensity map and optimal beam angles for IMRT delivery. Using this approach, we pursue an experimental study designed to (a) gauge differences in plan quality metrics with respect to different tumor sites and different MIP treatment planning models, and (b) test the concept of critical-normal-tissue-ring--a tissue ring of 5 mm thickness drawn around the planning target volume (PTV)--and its use for designing conformal plans. METHODS AND MATERIALS: Our treatment planning models use two classes of decision variables to capture the beam configuration and intensities simultaneously. Binary (0/1) variables are used to capture "on" or "off" or "yes" or "no" decisions for each field, and nonnegative continuous variables are used to represent intensities of beamlets. Binary and continuous variables are also used for each voxel to capture dose level and dose deviation from target bounds. Treatment planning models were designed to explicitly incorporate the following planning constraints: (a) upper/lower/mean dose-based constraints, (b) dose-volume and equivalent-uniform-dose (EUD) constraints for critical structures, (c) homogeneity constraints (underdose/overdose) for PTV, (d) coverage constraints for PTV, and (e) maximum number of beams allowed. Within this constrained solution space, five optimization strategies involving clinical objectives were analyzed: optimize total intensity to PTV, optimize total intensity and then optimize conformity, optimize total intensity and then optimize homogeneity, minimize total dose to critical structures, minimize total dose to critical structures and optimize conformity simultaneously. We emphasize that the objectives that include optimizing conformity make use of the critical-normal-tissue-ring. Three tumor sites: head-and-neck, pediatric brain, and prostate are used for comparison. RESULTS: The critical-normal-tissue-ring acts as a good device for enforcing conformity. Trends in the characteristics and quality of plans resulting from each model were observed. Attempts to reduce dose to critical structures tend to worsen PTV conformity (1.542 to 3.092) and homogeneity (1.223 to 1.984), depending on the relative size and spatial distance of the critical structures to the PTV. When the critical structures are relatively small compared with the PTV (as in the case for the pediatric brain tumor, where each is less than 15% in volume), dose reduction to critical structures is accompanied by much worse scores in conformity (2.482) and homogeneity (1.984). When the critical structures are larger, as in the case of head-and-neck (approximately 50%), the conformity and homogeneity deterioration is less significant (1.542 and 1.239, respectively). There is a clear tradeoff between homogeneity, conformity, and minimum dose to organs at risk (OARs). For head-and-neck and pediatric brain tumor, the model that minimizes total dose to critical structures and optimizes conformity simultaneously offers a compromise among these factors, resulting in reduced critical structure dose with conformal and homogeneous plans. In the prostate case, the tumor is smaller than the two large nearby critical structures, and all models provide very homogeneous PTV dose distribution. However, minimizing dose to critical structures worsens conformity, as it spreads the radiation to the area surrounding the PTV. The maximum dose to the critical structures also increases slightly. Compared with plans used in the clinic which generally have uniformly spaced beam angles, the optimal clinically acceptable plans obtained via the methods herein do not have equispaced beams. The optimal beam angles returned appear to be nonintuitive, and depend on PTV size and geometry and the spatial relationship between the tumor and critical structures. CONCLUSIONS: The MIP model described allows simultaneous optimization over the space of beamlet fluence weights and beam and couch angles. Based on experiments with tumor data, this approach can return good plans that are clinically acceptable and practical. This work distinguishes itself from recent IMRT research in several ways. First, in previous methods beam angles are selected before intensity map optimization. Herein, we employ 0/1 variables to model the set of candidate beams, and thereby allow the optimization process itself to select optimal beams. Second, instead of incorporating dose-volume criteria within the objective function as in previous work, herein, a combination of discrete and continuous variables associated with each voxel provides a mechanism to strictly enforce dose-volume criteria within the constraints. Third, using the construct of critical-normal-tissue-ring within the objective function can enhance the achievement of conformal plans. Based on the three tumor sites considered, it appears that volume and spatial geometry with respect to the PTV are important factors to consider when selecting objectives to optimize, and in estimating how well suited a particular model is for achieving a specified goal.     

应用射野角度和多目标优化提高肺癌放疗计划的执行效率

背景与目的：呼吸运动会给肺癌的放疗带来不利影响，而提高放疗计划的执行效率会在一定程度上减轻这一影响。该研究旨在探究运用射野角度和多目标优化（beam angle and multicriteria optimization，BAMCO）技术进行肺癌放疗计划设计的可行性和执行效率。方法：将10个肺癌临床计划数据由Pinnacle计划系统导出到RayStation计划系统。在RayStation系统中新建计划，以对应的临床计划射野角度为初始条件，在三维适形模块下优化射野角度。以优化结果为基础，执行多目标优化（multicriteria optimization，MCO），导航并确定临床需要的最佳妥协方案，然后生成可执行计划。最后，对比分析BAMCO计划和临床计划。结果：BAMCO计划设计不需要反复试错，一次MCO优化可确定最优计划；BAMCO计划和临床计划的靶区剂量分布和危及器官受量差异无统计学意义。BAMCO计划的跳数相比临床计划明显减少（31.1%±16.9%）。结论：BAMCO技术在保证计划质量的前提下，可有效提升计划的执行效率。     

基于遗传算法的三维适形放疗射野入射角度最优化研究

目的 建立一种基于遗传算法的三维适形放疗治疗机架入射角度最优化算法.方法 从Pinnacle v7.2计划系统上读取患者几何轮廓信息和三维剂量分布文件,把几何轮廓信息和三维剂量分布在同一坐标系下融合后作为最优化算法输入数据.对每组角度组合都计算其最优射野权重,用基于遗传算法角度最优化方法挑选出最优角度组合,最后把得到的角度组合和各角度射野权重重新输入到Pinnacle v7.2计划系统,和常规三维适形计划相比较.对2例肺癌病例和1例脑瘤病例比较了优化入射角度和常规三维适形计划下剂量分布、DVH图差异和适形度指标.结果 和常规三维适形计划相比,优化计划适形指数分别为0.59和0.70,高于常规三维适形计划的0.36和0.58.DVH图上看肺癌病例,使用优化算法后脊髓受到的最高量分别下降了17.8%和22.4%,肺V:.分别降低了3.1%和4.4%,肺V30分别降低了4.5%和1.5%;对脑瘤病例,晶体和眼球受照剂量也有显著下降.结论 所建立的角度最优化方法可作为计划设计的辅助工具.     

Beam angle optimization and reduction for intensity-modulated radiation therapy of non-small-cell lung cancers

PURPOSE: To optimize beam angles and reduce the number of beams used for intensity-modulated radiation therapy (IMRT) of non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: An exhaustive search scheme was used to perform beam angle optimization (BAO) for IMRT of NSCLC. This approach involved intercomparison of all possible beam angle combinations and selection of the best angles based on the scores or costs of the objective functions used in the treatment plan optimization. Ten Stage III NSCLC cases were selected to evaluate the BAO algorithm and dosimetry benefits of IMRT-BAO. IMRT plans using five or seven coplanar beams were optimized and compared with those using nine equal-spaced beams. Results of BAO were also compared between plans using different numbers of beams with or without fluence modulation. RESULTS: Each anatomic structure, e.g., tumor or lung, had its own preferred beam angles. Thus, BAO required appropriate balance of competing objective functions. Plans using fewer angles (five or seven beams) could achieve plan quality similar to those using nine equal-spaced beams, however with reduced monitor units and field segments. The number of beams used for the treatment (five vs. seven) and the fluence modulation (open or IMRT beams) did not have a significant impact on the results of the BAO. CONCLUSIONS: Use of fewer beams (e.g., five) for lung IMRT could result in acceptable plan quality but improved treatment efficiency. A multiresolution search scheme could be developed for BAO using fewer and nonmodulated beams to reduce the computation cost of BAO.