目的 对一种矩形孔准直器伽玛刀的射野形状、大小、半影等剂量学参数进行测量,并对射野聚焦形成的剂量分布、静态和动态拉弧的剂量分布进行分析,以归纳矩形孔准直器的伽玛刀剂量学特征.方法 在Luna-260型伽玛刀上,用EBT3剂量胶片测量不同射野的剂量分布,通过胶片分析软件得到矩形孔准直器的剂量学参数,选取3号和6号准直器在放射治疗计划系统中进行不同角度拉弧聚焦,分析不同截面上形成的剂量线.结果 矩形孔准直器形成的矩形野大小、半影测量结果均符合国标WS 582-2017《X、γ射线立体定向放射治疗系统质量控制检测规范》的要求.1～6号准直器尺寸偏差均在1 mm内,静态聚焦野半影最大为4.3 mm.3种截面(横断面、冠状面、矢状面)的剂量分布形状与拉弧角度大小相关.对于50％剂量线大小,在Z方向上,两种准直器50％剂量线大小均为14mm左右,在X、Y方向上,两种准直器50％剂量线大小变化幅度不同,其中3号准直器变化幅度较大,6号准直器变化幅度较小.结论 矩形准直器射野尺寸及半影大小均符合国标要求,矩形孔准直器拉弧角度影响剂量分布,其剂量学特性能够为临床应用提供参考.

Purpose: Very high-energy electron (VHEE) can make up the insufficient treatment depth of the low-energy electron while offering an intermediate dosimetric advantage between photon and proton. Combining FLASH with VHEE, a quantitative comparison between different energies was made, with regard to plan quality, dose rate distribution (both in PTV and OAR), and total duration of treatment (beam-on time).Methods: In two patient cases (head and lung), we created the treatment plans utilizing the scanning pencil beam via the Monte Carlo simulation and a PTV-based optimization algorithm. Geant4 was used to simulate VHEE pencil beams and sizes of 0.3-5 mm defined by the full width at half maximum (FWHM). Monoenergetic beams with Gaussian distribution in x and y directions (ISOURC = 19) were used as the source of electrons. A large-scale non-linear solver (IPOPT) was used to calculate the optimal spot weights. After optimization, a quantitative comparison between different energies was made regarding treatment plan quality, dose rate distribution (both in PTV and OAR), and total beam duration.Results: For head (80 MeV, 100 MeV, and 120 MeV) and lung cases (100 MeV, 120 MeV, and 140 MeV), the minimum beam intensity needs to be-2.5 x 1011 electrons/s and-9.375 x 1011 electrons/s to allow > 90 % volume of PTV reaching the average dose rate (DADR) higher than 40 Gy/s. At this beam intensity (fraction dose: 10 Gy), the overall irradiation time for the head case is 5258.75 ms (80 MeV), 5149.75 ms (100 MeV), and 4976.75 ms (120 MeV), including scanning time 872.75 ms. For lung cases, this number is 1034.25 ms (100 MeV), 981.55 ms (120 MeV), and 928.15 ms (140 MeV), including scanning time 298.75 ms. The plan of higher energy always performs with a higher dose rate (both in PTV and OAR) and thereby costs less delivery time (beam-on time).Conclusion: The study systematically investigated the currently known FLASH parameters for VHEE radiotherapy and successfully established a benchmark reference for its FLASH dose rate performance.

目的 探讨全脑放射治疗联合射波刀治疗多发脑转移瘤的临床疗效及对患者生活自理能力的影响.方法 选取2014年1月至2020年10月我院收治的64例多发脑转移瘤患者纳入研究,根据患者所采用的治疗方案差异分为射波刀组(50例)与伽马刀组(14例).射波刀组采用全脑放疗联合射波刀治疗,伽玛刀组采用全脑放疗联合Luna伽玛刀治疗.比较2组临床治疗效果、生活自理能力及放疗安全性的差异.结果 射波刀组疾病控制率为96.0％(48/50),高于伽玛刀组的92.9％(13/14),但2组比较差异无统计学意义(P>0.05).日常生活自理动力(ADL)评分治疗后1个月[(87.1±7.3)与(82.2±7.9),t=2.20,P=0.032]、治疗后3个月[(92.1±6.5)与(87.0±6.7),t=2.55,P=0.013],射波刀组ADL评分均高于伽玛刀组,差异有统计学意义(P<0.05).射波刀组放疗期间不良反应总发生率为30.0％(15/50),低于伽玛刀组的50.0％(7/14),但2组比较差异无统计学意义(P>0.05).结论 全脑放射治疗联合射波刀治疗多发脑转移瘤的临床效果显著,有助于改善患者生活自理能力,且安全性良好.

目的 利用4种测量手段确定Luna-260型全身伽马刀各个准直器的输出因子,为伽马刀质量控制提供合理的测量方式和参考依据.方法 采用PTW微型宝石探测器60019、PTW指形电离室31010、IBA指形电离室cc04和EBT3胶片分别进行测量.在相同温度、气压测量条件下,使用不同的测量方式在伽马刀等中心位置处进行相同时间照射,归一化后得出输出因子并与计划系统中的输出因子进行比较.结果 测量大于3号准直器射野(14 mm×14 mm)的准直器输出因子时,各种测量方法得到的结果差异较小,最大误差为-0.9％;但测量小于3号准直器射野(14 mm×14 mm)的准直器输出因子时,不同测量工具的测量结果有着明显的差别,尤其射野尺寸最小的1号准直器(6 mm×6 mm)最大偏差达到-72％.结论 Luna-260型全身型伽马刀因准直器的特殊性,射野输出因子的测量选择EBT3胶片或者灵敏体积较小的宝石探测器60019等方式能得到准确的结果.

目的:研究固定铅门8野调强技术(8F-SJT)应用于左侧乳腺癌保乳术后的剂量优势,并与常规6野调强技术(6F-IMRT)进行剂量参数比较.方法:对10例左侧乳腺癌保乳术后患者分别制定固定铅门8野调强放疗计划和常规6野调强放疗计划,在保证靶区(PTV)处方剂量前提下,尽量降低危及器官受量,比较两组治疗计划的剂量-体积直方图(DVH),评估靶区及危及器官剂量参数.结果:2种调强技术计划之间比较,8F-SJT改善了靶区适形指数(CI),差异具有统计学意义(P<0.05),8F-SJT靶区最小剂量(Dmin)、最大剂量(Dmax)、平均剂量(Dmean)以及剂量均匀指数(HI)与6F-IMRT相比,差异无统计学意义(P>0.05);8F-SJT左肺V20、V30及Dmean明显低于6F-IMRT(P<0.05),8F-SJT左肺V5、V10与6F-IMRT相比,差异无统计学意义(P>0.05);8F-SJT心脏V5、V10、V20、V30及Dmean均明显低于6F-IMRT(P<0.05);8F-SJT右侧乳腺和冠状动脉左前降支(LAD)的Dmax、Dmean均明显低于6F-IMRT(P<0.05).结论:左侧乳腺癌保乳术后固定铅门8野调强计划要优于常规6野调强计划,可以考虑临床实践.