Stereotactic radiosurgical treatment of brain metastases in older patients

BACKGROUND: This study was designed to evaluate the therapeutic effect of stereotactic radiosurgery (SRS) in patients aged > or =75 years who presented with brain metastasis. METHODS: The authors analyzed the data from 44 consecutive patients treated with SRS for > or =1 brain metastasis. The median age at the time of treatment for brain metastases was 79.3 years (range, 75 years-86 years), and the median Karnofsky performance status was 80 (range, 50-100). At the time of SRS, 31 patients were treated for a single metastasis, and the remaining 13 patients were treated for > or =2 lesions (n = 74 lesions). The median tumor volume was 1.2 cm(3) (range, 0.007 cm(3)-22.5 cm(3)). The median maximal and marginal doses were 36 grays (Gy) (range, 18.8 Gy-48.2 Gy) and 20 Gy (range, 10 Gy-24 Gy), respectively. RESULTS: Median survival was 7.3 +/- 1.65 months (range, 1.6 months-38.9 months) from the time of diagnosis of brain metastasis. Median survival of the patients with a single brain metastasis (10.1 +/- 1.92 months) was longer than that of the patients with > or =2 metastases (6.6 +/- 1.28 months) (P <.02). A single lesion was found to be an independent favorable prognostic factor (P +/- = +/- .017; odds ratio, 2.385 [95% confidence interval, 1.167-4.874]) in univariate and multivariate analysis. Patients with nonsmall cell lung cancer fared worse than patients with other tumor types (survival of 6.5 +/- 0.70 months vs 10.1 +/- 2.33 months [P<.05]). CONCLUSIONS: SRS for patients aged > or =75 years with brain metastases is an effective and safe treatment modality that appears to improve survival, with outcomes that compare favorably with those reported for younger patients in an appropriately selected population.     

Allergic contact dermatitis to thiourea in a neoprene knee brace

SUMMARY An elderly woman developed an itchy, weeping, erythematous, papular eruption, confined to the skin under her neoprene knee brace. Allergic contact dermatitis to diethylthiourea and to her neoprene knee brace were diagnosed by positive patch test reactions. Allergic contact dermatitis from thioureas may be underdiagnosed, as they are not tested as part of the standard patch test series. Clinicians are encouraged to consider this diagnosis in patients with reactions to synthetic rubber, especially neoprene.     

Monte-Carlo-Simulation von Multileafkollimatoren mit gekrümmten Lamellenenden

A model for the simulation of the accelerator heads of two identical linear accelerators was designed at the University Hospital of Tübingen, using the BEAM program developed at the National Research Council of Canada. Both linear accelerators are equipped with multileaf collimators (MLCs) and backup jaws (y-direction) with curved leaf-ends. The accelerator models were divided into two parts. The first part consisted of target, primary collimator, flattening filter, monitor chamber, and mirror. After the Monte Carlo simulation of these parts, the phase-space characteristics below the mirror were stored in a file and used as source for the second part of the accelerator head (jaw, MLC). The electron source was assumed to deliver a gaussian energy spectrum, with parallel direction to the beam axis. With this electron source, there was good agreement between the measured and simulated depth dose curves in water, with difference < 2%. A new module was created for the BEAM program to simulate backup jaws, while the standard MLCQ module from BEAM was used to simulate a MLC with curved leaf-ends. As a result, MLCs and backup jaws with curved leaf-ends make the shoulder of the y-profile higher than the straight-end MLCs.     

SD近交系大鼠经电子直线加速器照射后局部与全身自由基的变化

目的探讨直线加速器放射损伤后自由基的改变情况。方法采用直线加速器照射制作动物模型,同时观察其血清及局部组织中NOS、MDA、SOD、GSH-PX含量的改变。结果电子直线加速器照射后MDA、NOS在一定剂量范围内上升;SOD、GSH-PX则在一定剂量范围内下降。结论电子直线加速器照射后能产生自由基,并引起自由基清除酶系活性下降,但局部变化明显小于全身变化,这些改变是否可能为引起胶原损伤的原因,有待进一步研究。     

静态调强放疗中多叶光栅到位精度数字化分析

目的 研究医用直线加速器在静态调强放射治疗(IMRT)照射过程中,内置多叶光栅(MLC)叶片的到位精度及其受机架角度的影响.方法 回顾分析Varian 23EX医用直线加速器在重复10次执行1例鼻咽癌肿瘤静态IMRT过程中产生的动态日志文件,获取各照射野内每条叶片实际走位的相对坐标值,对比放疗计划系统给出的MLC位置坐标,计算Varian 23EX内置Millennium^TM 60对多叶光栅每一条叶片的到位误差和每一对叶片的叶间距误差,对比垂直野(0°)与水平野(103°和257°)不同机架角度对叶片到位精度的影响.结果 全部叶片到位误差分布在±1.00 mm范围内,叶间距误差分布在±0.15 mm范围内.同一射野角度下,每分次治疗间光栅到位误差的标准差值小于0.06 mm.当考虑全部叶片时,103°野的MLC到位误差小于0°野(t=58.74,P<0.01),而257°与0°野的MLC到位误差差异无统计学意义;当仅考虑参与移动的叶片时,103°野到位误差仍小于0°野,但257°野到位误差在有限范围(<0.1 mm)内大于0°野,两组对比,差异有统计学意义(t=41.95、-4.47,P<0.01).结论 Varian 23EX内置Millennium^TM 60对MLC在执行静态IMRT治疗过程中的到位精度满足IMRT质量控制要求.分次治疗间,光栅到位重复性好.不同射野角度下,重力因素对光栅到位精度有一定影响,但误差均在质量控制允许范围之内,满足IMRT机械精度要求.动态日志数字化分析的方法有望作为新的质量控制方式改善现有IMRT计划质量控制流程.     

广州市医用电子直线加速器质量控制的调研

目的本文对医疗机构中正在使用的医用电子直线加速器放射治疗质量控制进行调查,以期为发现并解决放射治疗中存在的问题、提高放射治疗质量提供理论依据。方法对广州市医疗机构中正在使用的医用电子直线加速器的质量控制,如靶区确定、治疗计划、模拟定位、剂量计算到摆位治疗等方面进行调查。结果放疗机构在放射治疗中的质量控制整体状况良好,但是有4个项目的质量控制状况不太理想,如大体靶区的确定占66.6%、考虑温湿度和气压的占33.3%、治疗计划的调整占26.7%、仪器的监测校准占60%。同时物理师在放射治疗中的作用并没有得到很好的重视,其所学专业相符性也较差。结论放疗单位在放射治疗过程仍存在不同程度的问题。因此,应加强放射治疗过程中质量控制工作。     

Development of high intensity ion sources for a Tandem-Electrostatic-Quadrupole facility for Accelerator-Based Boron Neutron Capture Therapy

Several ion sources have been developed and an ion source test stand has been mounted for the first stage of a Tandem-Electrostatic-Quadrupole facility For Accelerator-Based Boron Neutron Capture Therapy. A first source, designed, fabricated and tested is a dual chamber, filament driven and magnetically compressed volume plasma proton ion source. A 4 mA beam has been accelerated and transported into the suppressed Faraday cup. Extensive simulations of the sources have been performed using both 2D and 3D self-consistent codes.     

医用直线加速器使用中的潜在危害及防护

目的：对医用直线加速器使用中一些容易忽视的潜在危害进行系统总结,为医务人员在加速器操作中提供参考。方法：总结多年在加速器工作中的经验教训及参考技术资料。结果：介绍了有害气体液体、有害灰尘颗粒以及其他隐性的危害,并针对各种危害提出了相应的防护方法。结论：加速器工作人员面临很多潜在危害,工作人员需提高警惕,加强防护。     

医用直线加速器的感生放射性研究

医用直线加速器在治疗过程中会产生对人体有害的感生放射性,且这种危害正逐渐引起人们的重视。本文介绍了感生放射性的概念、产生机制,总结感生放射性对患者、工作人员及公众所造成的危害,探讨了感生放射性水平的影响因素,并总结减少其水平的措施。     

直线加速器日质控数据分析及过程评估

目的 应用统计过程控制方法对加速器日质控(QC)数据进行分析,并对使用晨检仪的QC过程进行评估。方法 加速器、晨检仪校准后分别收集由技师、物理师摆位的100组、30组QC数据,设备第2次校准后再次收集技师摆位的QC数据100组,分析两次校准后技师摆位数据(各100组)的归一化信噪比的变化规律。使用由技师和物理师摆位的QC数据(各30组)绘制控制图,比较中心线位置和上下控制线范围的不同。计算由技师、物理师摆位的3个组日QC的过程能力指数。结果 两次校准的技师摆位数据归一化信噪比均为前6周变化较大,6~8周后趋于稳定,8周后逐渐变小。物理师摆位的QC数据在输出量一致性方面,上下控制线范围更窄;在平坦度、对称性方面,中心线更接近目标值0。对输出量一致性、平坦度方面,3个组日QC的过程能力指数均满足≥1要求;对称性Transverse方向均不满足。结论 应采用30~40个数据点绘制加速器日QC过程的控制图。QC过程应由相对固定且较少的QC人员完成,检测项目也应设置更适合的容差。