中国测试技术研究院

ＡＤ２０２型辐射剂量仪（三维水箱自动测试装置）本装置经国家级计量部门检验认可,各项性能符合ＩＥＣ７３１号文的规定指标。它由双通道剂量仪、三维水模体、计算机、驱动器、打印机等部分构成,对医用放射治疗中心的各种加速器、钴机、Ｘ射线深部治疗机的剂量特性测试（离轴比、平坦度曲线、ＰＤＤ曲线、不同水深下的剂量分布等）和水中吸收剂量（率）的测量、空气中照射量（率）的测量等。对于Ｘ射线及γ射线,既可代替一般剂量仪作剂量检定测试（绝对量）,又可作相对比值测量。还可对各类加速器及Ｘ线刀设备剂量特性的测试和验收。Ｗ…     

基于能谱-剂量转换函数的NaI辐射探测器能量响应修正方法研究

针对NaI辐射探测器存在光子能量响应不一致现象从而导致周围剂量当量率测量精度较低的问题,该文利用自主研制的一套基于NaI探测器的环境水平剂量仪,完成在电离辐射计量标准实验室的能谱测量,并结合能谱-剂量转换函数G(E)进行能量响应修正方法测试验证.实验测试的结果表明,自主研制的环境水平剂量仪能量响应(平均能量范围48?k...     

DR在矩阵剂量仪精确对位中的应用

针对矩阵剂量仪采用γ指数分析法进行剂量验证(通过率达90%),仪器对位精度要求需达到0.2 mm的情况,为解决仪器外壳划线与探测器位置中心线对位误差带来了剂量验证误差,采用DR(直接数字化X射线摄影)系统摄像,仪器对位误差达到0.2 mm,保证剂量验证对阵列探测器中心位置与等中心的精确对准要求,剂量验证γ指数通过率达到95%以上。     

放射治疗用加速器吸收剂量的校准和检查

一、引言 x,r射线和电子束计量是电离辐射计量三大组成部分之一,而在放射治疗剂量学中它们的吸收剂量量值的准确可靠对于放射治疗至关重要。众所周知,用于放射治疗的加速器其剂量监督仪表是需要校准的,否则便不能给出准确可靠的吸收剂量量值。在校准加速器剂量监督仪表前,所使用的照射量计,需经计量标准实验室检定,并给出~(60) Co的γ射线照射量的校准因子N值。其次,校准工作只能在加速器的各项技术指标(如射线质、照射野、等中心,均匀度等) 调试到正常治疗的工作状态后进行。     

二维半导体面阵列实时剂量验证系统的研制及应用

调强放疗(IMRT)是放疗技术的发展方向。为实现精确放疗的目标和严格的射线质量控制,以及技术安全保证,自主研发的二维半导体面阵列剂量实时验证测量系统,(TQ-2000B剂量分布图检测仪)该系统由445个半导体探测器按面阵列栅格精确排列,主要用于放疗射线质量控制:加速器QAI、MRT的TPS实时验证。通过实测的等剂量图、剂量值与相同条件下TPS计算的结果以及剂量胶片测量的结果进行比较,从而实现对调强放疗TPS实时验证。同时还介绍了它在加速器QA方面部分项目的测试应用。二维半导体面阵列剂量实时验证测量系统的研制成功,填补了国内空白,其主要技术指标和性能达到了国外同类产品的先进水平。     

胶片剂量仪与半导体探测器在小野剂量数据测量中的比较分析

小照射野的建模数据对于调强放射治疗和立体放射治疗十分重要。在加速器使用6MV光子束条件下,采用胶片与0.01cm³的半导体探头,在IBA Blue Phantom 2水箱与固体水中,测量0.6cm×0.6cm至10.0cm×10.0cm照射野的百分深度剂量(PDD)曲线、profile、点剂量等数据,并计算射野总散射因子Scp。测试结果表明:对于PDD曲线,不同的照射野情况下,半导体探头与胶片在建成区测得数据基本吻合,在水深2～10cm测量结果存在微小偏差,当水深超过10cm以后差距明显(达7%);对于profile曲线,不同照射野下,胶片与半导体探头测量数据无明显差异,但胶片具有更好的空间分辨率,体现在半影区剂量跌落更明显;半导体探头、胶片剂量仪测得的点剂量与计划系统计算相同深度的点剂量比较,差异明显(最大误差分别为-2.7%、12%)。分析得出:不同的测量探头,对小野物理数据测量的准确性可能存在很大差异;胶片剂量仪具有优越的空间分辨率,但是胶片的吸收剂量范围有限,具有能量和方向依赖性。     

大面积塑料闪烁探测器剂量线性测量及修正

针对γ射线剂量增大时,大面积塑料闪烁探测器剂量线性会变差这一问题,采用能谱测量方式对塑料闪烁探测器的剂量线性进行修正。首先在单能辐射场中,探测器通过能谱测量电路在上位机形成辐射场能谱,然后按照能量线性规律算出每道址的权重因子,以标准剂量仪所测剂量率为参考值得到修正公式,接下来对待测辐射场进行能谱采样,根据每道计数和修正公式,得到修正后的总计数率和剂量率,从而对塑料闪烁探测器的剂量线性进行修正。结果表明:经过修正以后,在137Cs辐射场中剂量测量最大相对误差由-24.32%变为-6.90%,在60Co辐射场中最大相对误差由-72.22%变为-27.78%。可以看出,经过修正的探测器剂量线性得到很大改善,可为辐射场中γ射线剂量的准确测量提供技术参考。     

入侵探测器性能检测系统

入侵探测器试验装置主要用于模拟入侵探测器工作状态下各项性能参数的测试。该装置主要针对主动红外、被动红外、红外和微波复合等探测器的性能进行检测。该装置功能齐全、操作简单、性能稳定、控制精度高、采集准确、安全性好,另外采用了无线传输技术,可以进行远距离操作。     

不同方法对医用加速器对称性检定方法的比较

医用加速器是生物医学上一种用来对肿瘤进行放射治疗的仪器。目前,在放射治疗中使用最多的是电子直线加速器。医用电子加速器的质量控制在放射治疗中非常重要,其性能好坏直接影响到患者的治疗。但是传统的对医用加速器质量控制方法的成本非常高,即必须要使用三维水箱,然而现在很多边远城市,尤其是新疆的南北疆地区,城市人口密度,医用加速器使用频率低,而且路途遥远,使用三维水箱的成本高,所以对使用矩阵板探测器的可行性的研究就有重要的意义。     

配光性能探测器校准方法的探讨

文章研究的新校准方法用于配光测试光度探测器的校准,该校准装置采用积分球和标准光源相结合的方法完成校准,替代现有的光轨标定测量方法,其测量精度与标准要求符合,极大地提高检测效率。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。