Monte-Carlo simulation of pinhole collimator of a small field of view gamma camera for small animal imaging

Needs in scintimammography applications,especially for small animal cardiac imaging,lead to develop a small field of view,high spatial resolution gamma camera with a pinhole collimator.However the ideal pinhole collimator must keep a compromise between spatial resolution and sensitivity.In order to design a pinhole collimator with an optimized sensitivity and spatial resolution,the spatial resolution and the geometric sensitivity response as a function of the source to collimator distance has been obtained by means of Monte-Carlo simulation for a small field of view gamma camera with a pinhole collimator of various-hole diameters.The results show that the camera with pinhole of 1 mm,1.5 mm and 2 mm diameter has respectively spatial resolution of 1.5 mm,2.25 mm and 3 mm and geometric sensitivity of 0.016%,0.022% and 0.036%,while the source to collimator distance is 3 cm.We chose the pinhole collimator with hole diameter size of 1.2 mm for our the gamma camera designed based on the wade-off between sensitivity and resolution.     

聚碳酸酯和聚酯核孔膜的性能研究

聚碳酸酯(Polycarbonate,PC)和聚对苯二甲酸乙二酯(Polyethylene Terephthalate,PET)薄膜因其可被碱性溶液有效刻蚀而被用于核孔膜材料。采用11.4 MeV·u-1的Au离子和20 MeV·u~(-1)的Kr离子分别辐照PC及PET薄膜,然后经NaOH溶液蚀刻,制得膜孔径分别为20-400 nm和100-700 nm的PC和PET核孔膜。扫描电子显微镜(Scan Electron Microscope,SEM)和气-液排除法等表征和测试结果显示孔密度与辐照剂量有关;蚀刻时间越长,膜孔径越大,实验制备的核孔膜孔分布越均匀。被辐照后的PET膜亲水性比PC膜高。在0.15 MPa和室温下,水溶液中的牛血清白蛋白(Bovine Serum Albumin,BSA)可被不同孔径的PET核孔膜有效截留;膜孔径越小,截留率越高,过滤所需压力越大,膜越易被污染。     

核医学显像在三维适形调强放疗中的应用

核医学显像不仅因其能确定肿瘤范围及对肿瘤进行分期，而且因对治疗计划和病人随访的作用，目前在放射肿瘤学方面正变得愈加重要。正电子发射断层(PET)和单光子发射计算机断层(SPECT)显像在对三维适形调强放射治疗的病人确定肿瘤范围和分期中起重要作用。由于肿瘤组织的代谢改变先于形态学改变，使用功能显像技术常常能在形态学显像检出之前鉴别肿瘤组织。检测肿瘤复发^18F-FDGPET有最好的灵敏度、特异性和正确率。另外，回顾了核医学显像在适形放疗的脑肿瘤、鼻咽癌、肺癌等患者中的应用。     

直接解调成像方法在核医学图像重建中的应用

将一种天文成像的直接解调法用于核医学中的图像重建，就最简单的一个切片时的蒙特卡罗样本进行计算分析，结果显示了该方法的小尺度放射源具有较高的灵敏度和空间分辨率，这一方法同其他传统方法相比有一定的优越性，可应用于核医学图像数据的分析以及对微小“点状”癌肿的早期诊断     

我国东部地区部分省市核医学放射卫生防护现状调查

国内现有的针对核医学防护的调查研究大多局限于某家医疗机构,或是较小范围内的现状调查,所得出的结论较为局限。本研究以我国东部地区7个省/直辖市共28家医疗机构核医学科为研究对象,通过实地调研的方式,对各医院核医学科的场所设置、设备配置、核素来源、场所监测和放射防护管理现状等情况进行了分析,发现部分医院核医学科存在场所选址布局不合理、设备较老旧以及性能检测不完善等问题。日后的放射防护及监督工作应注意此类问题并提出相应解决方法。     

PIXE and the nuclear microprobe: Tools for quantitative imaging of complex natural materials

The 40 year history of nuclear microscopy has seen sustained progress in the development of technology needed to improve PIXE analysis and trace element imaging performance. Focussing systems have been developed for improved spatial resolution, detector systems have evolved to collect more signal, full-spectral scanning data acquisition approaches have been devised. The complexity of PIXE spectra has driven the development of techniques for fitting numerous overlapping components in spectra for quantitative analysis, methods have been developed for specialized problems in geology, such as the analysis of fluid and melt inclusions in minerals, and techniques for the deconvolution of elemental components in full-spectral scanning data sets have been developed to produce accurate element images. The future of nuclear microscopy using PIXE is promising. Lens system approaches have evolved and point towards ‘full bore’ acceptance, optimal matching to accelerator emittance, high current density and sub-μm spatial resolution using many nA beam currents. Detector arrays and integrated data acquisition and scanning systems are emerging that can collect all events across a large solid-angle collection area and process these events for element image display in real-time. The combination of these advances provides a path to greatly enhanced sensitivity for PIXE analysis and imaging and a more productive user experience. The emergence of detector array approaches for scattered particles and reaction products, and the development of software tools for coupled PIXE-RBS data reduction, suggest a path towards complementary RBS and NRA tools. The stage is set for an exciting and productive future for PIXE imaging on the nuclear microprobe.     

核医学数据获取动态存储器的设计

介绍了核医学图像数据获取的基本方法和与计算机的接口,重点介绍接口中数据获取动态存储器的设计,给出了硬件电路和设计原理。     

我国临床核医学发展现状及相关人员放射防护措施探究

随着核医学诊疗技术的不断发展,其在我国应用逐渐增多,但尚存在对核医学诊疗认识程度不够、配套管理和防护措施跟进不及时等不足。为提高公众对我国临床核医学发展状况的认识,本文就我国核医学诊疗技术的应用现状和如何提高其辐射防护措施,特别是医院核医学科的布局、管理要求,核医学科相关技术人员及放射性核素诊疗患者的防护措施进行了综述和建议,旨在为未来核医学科发展相配套的管理及辐射防护提供参考。     

Effect of geometric construction on residual stress distribution in designing a nuclear rotor joined by multipass narrow gap welding

The purpose of this study is to investigate the effect of geometric construction on the distribution of residual stresses before and after heat treatment in designing a nuclear welded rotor. The local material removal method was used to measure internal residual stress of the experimental pipe after post weld heat treatment. Three finite element models were employed as follows: a model of experimental pipe, a model with a bottom protrusion existed at the weld region, and a model of two rotor discs butt-welded with a bottom protrusion at the weld region. Investigated results showed that the bottom protrusion existed at the weld region can decrease the residual stress and mitigate the stress evolution significantly on the inner surface. Under the binding effect of the rotor discs, the axial stress of inner surface region is compressive stress; the through-wall axial stress at the weld center line can be deemed to a bending type; both the hoop stress and axial stress at the weld center line on the inner surface are compressive. The impact of geometric construction on the stress evolution at the root bead begins after pass 15 deposited.     

湖南省2016年度临床核医学和放射治疗频度调查与分析

为了了解湖南省临床核医学和放射治疗的基本现状与其相应的频度水平,采用普查与抽样调查相结合的形式,对湖南地区所有开展临床核医学和放射治疗的医疗机构进行基本情况调查,对抽样医院进行分性别、年龄段及诊疗类型的频次调查。结果表明,湖南省临床核医学诊断与治疗年频率分别为1.37和0.139人次/千人口,放射治疗年频率为0.412人次/千人口。与1998年进行的全省医疗照射频度调查进行对比,湖南省临床核医学和放射治疗的频度水平有大幅度的增长,并且随着社会经济的发展必将继续增加。做好患者与工作人员的放射防护,做好诊断和治疗过程中的质量控制是需重点关注的问题。     

Collimated LaBr3 detector response function in radioactivity analysis of nuclear waste drums

The properties of a Lanthanum bromide （LaBr3） detector and its response functions were investigated via experiments and simulations in this paper. The LaBr3 detector had good relative energy resolution and higher efficiency than a high-purity germanium detector. Monte Carlo and other numerical methods were used to calculate the efficiencies of a LaBr3 detector with a square collimation window. A model of the numerical method was established based on a pure geometric model that was consistent with the experimental situation. The results showed that the detector response functions calculated by these methods were in great agreement with experimental results.     

Charge resolution of CR-39 plastic nuclear track detectors for intermediate energy heavy ions

The charge resolution (δZ) for heavy ions (nuclear charge: Z < 40) of 0.1-1 GeV/n energy in CR-39 plastic nuclear track detector (PNTD) and its dependence on etching time, and on projectile Z and energy were investigated and optimized as part of an effort to make precise measurements of projectile charge-changing cross sections. Two types of CR-39 PNTD, HARZLAS TD-1 and BARYOTRAK, were exposed to heavy ion beams with seven values of Z behind thick targets to produce projectile fragments. Following chemical etching (7 N NaOH at 70 °C) for varying etch times, δZ of the projectiles was determined for each detector type. A strong dependence of δZ on the amount of bulk etch (B) was seen. It was also observed that δZ can be remarkably improved with longer etching time as a function of B^−1/2, in accordance with the trend seen in other types of track detector such as glass nuclear track detector. However, for B ? 60 μm (30 h etching), saturation occurs and there is no further improvement in δZ. Analysis of the correlations between projectile Z, energy, detector response, and fluctuation of the response make it possible to develop a model to predict the δZ for projectiles of given Z and energy. The predicted and measured values of δZ show good agreement within 10%. We conclude that 4 ? Z ? 30 at intermediate energy can be identified with good δZ in these detectors. The predictive model will be used in designing future cross section measurement experiments.     

Challenge of nuclear data for innovative nuclear energy

The article devoted to assessment of present-day demand to nuclear data for transmutation problem, including the discussion of required accuracies, status and perspectives of nuclear data evaluation and development of nuclear models. The effect of nuclear data uncertainties on radiation damage of structural materials is discussed. An analysis of ISTC projects related to nuclear data measurement and evaluation is presented. The recommendations for differential, integral experiments and recommendations on the evaluated data preparation are presented.     

光子晶体制备方法对同步辐射闪烁体探测器成像分辨率的影响

探测效率和空间分辨率是成像探测器的重要性能。采用光子晶体,可提高闪烁体的光提取效率和增加光输出,进而提高基于闪烁体的同步辐射X射线成像探测器的探测效率并缩短成像时间。探究光子晶体对于成像探测器分辨率的影响具有重要应用意义。在闪烁体上添加三种典型的光子晶体,在上海光源BL13W1线站进行探测器有无光子晶体的成像实验,对比分辨率靶成像效果以及衬度比的量化结果,得到影响分辨率的因素。结果表明,均匀有序、三角构型的光子晶体具有最佳的成像效果,对于光子晶体在成像探测器领域的应用研究具有指导意义。     

Micro-structured nuclear fuel and novel nuclear reactor concepts for advanced power production

Many applications (e.g. terrestrial and space electric power production, naval, underwater and railroad propulsion and auxiliary power for isolated regions) require a compact-high-power electricity source. The development of such a reactor structure necessitates a deeper understanding of fission energy transport and materials behavior in radiation dominated structures. One solution to reduce the greenhouse-gas emissions and delay the catastrophic events' occurrences may be the development of massive nuclear power. The actual basic conceptions in nuclear reactors are at the base of the bottleneck in enhancements. The current nuclear reactors look like high security prisons applied to fission products. The micro-bead heterogeneous fuel mesh gives the fission products the possibility to acquire stable conditions outside the hot zones without spilling, in exchange for advantages – possibility of enhancing the nuclear technology for power production. There is a possibility to accommodate the materials and structures with the phenomenon of interest, the high temperature fission products free fuel with near perfect burning. This feature is important to the future of nuclear power development in order to avoid the nuclear fuel peak, and high price increase due to the immobilization of the fuel in the waste fuel nuclear reactor pools.     

Estimation method for parameters of overlapping nuclear pulse signal

Identification of nuclear pulse signal is of importance in radioactive measurements,especially in recognizing adjacent overlapping nuclear pulses.In this article,we propose an estimation method for parameters of typical overlapping nuclear pulse signals.First,the nuclear pulses are regarded as individual genes and the norm is set as the fitness function.Second,the global optimal solution is found by searching the population of genetic algorithm,so as to estimate the parameters of nuclear pulse.With high precision,this method can identify parameters of overlapping nuclear pulses in the Sallen-Key Gaussian signal decomposition experiments.This pulse recognition method is of great significance to improve the precision of radioactive measurement and is suitable for serious overlap of nuclear pluses.     

微机核子皮带秤硬软件设计

论述了核子皮带秤(简称核子秤)监测系统的软件设计原理和单片微型计算机8031与系统主要外围芯片(8253,8255,8279)的设计。     

Study on efficiency of DCP for nuclear hydrogen production

With many advantages, hydrogen is considered as the fuel of the future. But there is no natural resource of hydrogen and it must be produced by other kinds of energy. As for the primary energy, nuclear energy is a promising alternative. Using heat from nuclear reactor to produce hydrogen is receiving more and more concerns in recent years. This paper mainly emphasizes the study of the direct contact pyrolysis （DCP） of methane using heat from nuclear reactor. A facility was designed to investigate the efficiency of DCP process in certain conditions. The experimental results show that this process produces only hydrogen and carbon. The conversion efficiency increases with temperature and residence time, but decreases as flow rate increases. The highest efficiency of DCP obtained in this exoedment is about 22%.     

The F4E programme on nuclear data validation and nuclear instrumentation techniques for TBM in ITER

A dedicated effort on nuclear data validation and nuclear instrumentation techniques for Test Blanket Modules (TBM) in ITER is conducted as an integral part of Fusion for Energy's (F4E) programme to ensure validated nuclear analysis capabilities for fusion technology applications. It is closely linked to nuclear data development activities, which are jointly coordinated and conducted by F4E and nuclear data consortia formed by European research institutions. The current experimental activities, an integral copper validation experiment and gas production experiments in EUROFER elements, as well as activities on the development and testing of candidate nuclear detectors for TBM in ITER and the related design integration assessment are presented in this paper.