Monte-Carlo统计迭代图像重建算法

线性衰减系数图像重建是层析γ扫描(TGS)的一个核心问题。本文从粒子输运方程出发，应用Monte-Carlo方法，提出了一种基于Monte-Carlo方法的统计迭代图像重建算法。模拟结果表明，与一般TGS图像重建算法相比，该重建算法的重建图像误差大为减小，能够满足TGS装置的要求。     

先验图像约束的有限角度CT图像重建算法

对于有限角度CT图像重建,提出一种基于先验图像约束的迭代重建方法。将先验图像中各种均匀组织的平均值作为先验信息引入到重建图像目标函数中,约束待重建图像。对Shepp-Logan体模进行了仿真重建实验,并与ART、ART-TV算法进行了主观和客观的对比评价。实验结果表明,本文方法信噪比更高,平均误差更小,重建图像的伪影和变形程度大幅度减少。     

巨大长型物体的双直线扫描断层成像

本文从实际应用背景出发，对直线源轨迹的扇束重建公式进行了简单推导，给出了相应的计算机模拟结果，同时根据实际情况提出了双直线轨迹的图像重建公式，最后将此算法推广到三维锥束图像重建，克服了传统三维图像重建中在锥角处误差很大的缺点。     

层析γ扫描透射图像重建方法

研究了层析γ扫描(TGS)透射图像，并用两种TGS线性衰减系数重建方法进行TGS透射图像的计算机模拟仿真。结果表明：与国外文献报道的算法相比较，本文采用的两种重建方法的误差小、适应范围广，并能满足实际TGS装置的要求。     

X—射线分层成像中灰度重建的研究

利用边缘提取和立体匹配技术可以对X-射线立体透视图像进行分层成像，但分层后得到的物体图像仅仅是边缘图像，研究了一种利用原始的灰度图像对分层后的边缘图像进行灰度重建的方法，使得每一层的图像的接近实际的灰度图像。     

CT图像重建方法在半影成像中的应用

CT图像重建方法和半影成像是两种传统的辐射图像诊断方式。将CT图像重建方法应用到半影图像数据处理中,探索出一种新的半影图像处理方法。在新的半影编码孔图像数据处理中,首次应用了与图像诊断系统点扩散函数无关的编码孔图像处理方法,解决了传统编码孔图像处理中由于图像诊断系统点扩散函数不确定带来的技术难题。在理论研究的基础上进行了半影模拟成像及图像重建,获得了理想的研究结果。     

小波重建中的小波选取

近年来发展的小波重建方法可以直接重建得到图像的小被系数，而且可以只利用通过感兴趣区域的局部投影数据进行重建，从而在进行局部重建时节省了计算时间。在进行小被重建时，不同的小波对重建效果有着不同的影响。主要讨论了Daubechies正交小波和双正交小波的重建效果．并总结了实际应用中小波选取的一些原则。     

工业CT中探测器失效伪影的校正

在工业CT的扫描重建过程中，如果出现探测器失效的情况，重建图像中会出现严重的伪影，必须进行校正。如果用插值方法得到失效探测器数据，会引进不真实数据，而只用滤波方法处理图像，则不能完全消除伪影。本文提出了一种用结合中值滤波的Ordered Subsets Convex方法对探测器失效伪影进行校正，在校正速度和质量上都得到了较好的校正效果。     

高分辨针孔SPECT三维图像重建的实现

采用一种新颖的查找表法来实施有序子集期望值最大化（OSEM）的针孔SPECT图像重建算法，有效地将针孔响应修正包含在查找表中，进而实现高分辨针孔SPECT的三维图像重建。标准Jaszczak模具的成像实验结果表明：该方法不但能显著减少图像重建过程的计算时间和内存占用，且能显著改善重建图像的分辨率。因此，查找表法是能够快速实现针孔SPECTOSEM图像重建算法，并能将针孔响应修正包含在查找表中以获取高分辨断层图像的有效方法。     

X射线分层成像中灰度重建的研究

利用边缘提取和立体匹配技术可对Ｘ－射线立体透视图像进行分层成像， 但分层后得到的物体图像仅仅是边缘图像。研究了一种利用原始的灰度图像对分层后的边缘图像进行灰度重建的方法。使得每一层的图像有接近实际的灰度图像。     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

The preclinical pharmacological study of dopamine transporter imaging agent 18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β- carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444,0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum,striatum/frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

Web Services interface of SSRF archive data analysis system

Accelerator database stores various static parameters and real-time data of accelerator. SSRF (Shanghai Synchrotron Radiation Facility) adopts relational database to save the data. We developed a data retrieval system based on XML Web Services for accessing the archive data. It includes a bottom layer interface and an interface applicable for accelerator physics. Client samples exemplifying how to consume the interface are given. The users can browse, retrieve and plot data by the client samples. Also, we give a method to test its stability. The test result and performance are described.     

Investigations on landmine detection by BF3 detector

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 16(2014)

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Radioactivity levels in soil of salt field area,Kelambakkam,Tamilnadu,India

Soil samples in and around salt field area have been analyzed for natural radioactivity concentration using gamma ray spectrometer.The activity concentration for ~(232)Th,~(238)U and ~(40)K are ranged from 27.88 to 45.27 Bq/kg, from BDL to 13.30 Bq/kg,and from 135.54 to 381.28 Bq/kg,respectively.The measured activity concentrations for these radionuclides were compared with world average activity of soil.The average activity concentration of ~(232)Th in the present study is 1.19 times higher than world median value while the activity of ~(238)U and ~(40)K is found to be lower. The absorbed dose rates due to these radionuclides were calculated.The average absorbed gamma dose rate due to the presence of ~(232)Th,~(238)U and ~(40)K in soil samples is 36.99 nGy·h~(-1).These results indicate no radiological anomaly. The data presented in this study will serve as a base line survey for primordial radionuclides concentration in the study area.     

Preparation and properties of 117m Sn(IV)-TTHMP in in-vitro and in small animals

In this work,TTHMP was synthesized and labelled with 117m Sn.The preparation conditions,stability and lipophilicity of 117m Sn(IV)-TTHMP were investigated.Biodistribution of the complex in rabbits and mice was studied.It was found that the quantity of TTHMP and pH value of the prepararion solution had vital effects on the labeling yield of 117m Sn(IV)-TTHMP.It was also found that 117m Sn(IV)-TTHMP was hydrophilic and stable at room temperature and 37℃ in open air 117m Sn(IV)-TTHMP showed unexpectedly high bone uptake and bone-to-blood ratio in the animals.This made it potentially useful as an reagent for skeletal scintigraphy and radiotherapy of bone tumors.