热释光剂量响应的统计学描述

采用统计学描述方法，从泊松分布导出的响应函数作为热释光剂量响应的基本方程，将线性、亚线性和超线性响应进行统一的描述。响应函数的特征参量，一次作用因子Ｒ和特征剂量Ｄ０，既有清楚的统计学含意又有明确的剂量学意义。结合热释光过程的微观机制很好地解释热释光剂量响应非线性相关的一系列实验结果。     

Simulation study of the dose and energy responses of FNTD personal neutron dosimetry

The objective of this work was to use the Geant4 toolkit to perform simulation studies on the personal dose response of fluorescent nuclear track detectors(FNTDs).The entire structure of the FNTD response can be designed,and the detector's energy and dose responses can be optimized in a broad energy range(0.01 eV-20 MeV). In general, the detectors used ~6LiF and CH_2 converters that have high energy and high dose response at neutron energies lower than 10 eV and greater than 1 MeV, respectively. The method of least squares was used to optimize the dose response of H*(10) and the energy response corresponding to Rtotal. The values of the optimized response of H*(10) lie between 0.8 and 1.4, corresponding to the energy ranges 0.01 eV-70 keV and 4-14 MeV, respectively. This occupies nearly eight out of the nine orders of the total energy range. Even though the optimized response of Rtotal is constrained between 0.89 and 1.1 in the energy range of 0.01 eV-20 MeV, it is suitable for obtaining the broad neutron spectrum of fluence with good accuracy.     

A method to determine the planar dose distributions in patient undergone radiotherapy

A 2D-array equipped with 729 vented plane parallel ion-chambers has been calibrated as a portal dose detector for radiotherapy in vivo measurements. The array has been positioned by a radiographic film stand at 120 cm from the source orthogonal to the radiotherapy beam delivered with the gantry angle at 180°. The collision between the 2D-array and the patient’s couch have been avoided. In this work, using the measurements of the portal detector, we present a method to reconstruct the dose variations in the patient treated with step and shoot intensity-modulated beams (IMRT) for head-neck tumours. For this treatment morphological changes often occur during the fractionated therapy.In a first step an in-house software supplied the comparison between the measured portal dose and the one computed by a commercial treatment planning system within the field of view of the computed tomography (CT) scanner. For each patient, the percentage P_γ of chambers, where the comparison is in agreement within a selected acceptance criteria, was determined 8 times. At the first radiotherapy fraction the γ-index analysis supplied P_γ values of about 95%, within acceptance criteria in terms of dose-difference, ΔD, and distance-agreement, Δd, that was equal to 5% and 4 mm, respectively. These acceptance criteria were taken into account for small errors in the patient’s set-up reproducibility and for the accuracy of the portal dose calculated by the treatment planning system (TPS) in particular when the beam was attenuated by inhomogeneous tissues and the shape of the head-neck body contours were irregular. During the treatment, some patients showed a reduction of the P_γ below 90% because due to radiotherapy treatment there was a change of the patient’s morphology.In a second step a method, based on dosimetric measurements that used standard phantoms, supplied the percentage dose variations in a coronal plane of the patient using the percentage dose variations measured by the 2D-array portal detector. The results showed that the dose variations due to the change of the patient’s morphology reached 15% and such discrepancies were displayed on the digitally reconstructed radiography of the patient. The dose discrepancies were confirmed by the hybrid plan obtained by the treatment planning system. The good results here reported show that once it is possible to have the portal dose distributions even for other gantry angles, these tests could be introduced in the clinical protocol to have major support to decide when to repeat the patient’s CT scan and to re-plan the new IMRT dose calculation.     

Investigation of dose characteristics in three-dimensional MAGAT-type polymer gel dosimetry with MSE MR imaging

A new type of normoxic polymer gel dosimeter, named MAGAT responses well to absorbed dose even when manufacturing in the presence of normal levels of oxygen. The aim of this study was to evaluate dose response, diffusion effect and cumulated dose response under multiple fractional irradiations of the MAGAT gel dosimeter using Multiple Spin-Echo (MSE) Magnetic Resonance (MR) sequence. Dose response was performed by irradiating MAGAT-gel-filled testing vials with a 6 MV linear accelerator and a linear relationship was present with doses from 0 to 6 Gy, but gradually, a bi-exponential function result was obtained with given doses up to 20 Gy. No significant difference in dose response was present between single and cumulated doses (p > 0.05). For study of diffusion effect, edge sharpness of the R2 map imaging between two split doses was smaller than 1 cm of dose profile penumbra between 20% and 80%. In conclusion, the MAGAT polymer gel dosimeter with MSE MR imaging is a promising method for dose verification in clinical radiation therapy practice.     

Annual dose rate for Qena governorate population due to consume the animal products

In this work, the natural radionuclide concentrations of the 226Ra, 228Ra, 232Th and 40K were estimated from samples of cattle and poultry fodder, South Valley University farms and Qena Governorate farm, Qena, Upper Egypt. The radionuclide concentrations and annual consumption rate of twenty-nine animal fodders were analyzed using low-level γ-spectrometer, including a mixture fodder, silage, hay, rice straw, and poultry fodder. The irradiation risk of human health was assessed due to indirect ingestion of the beef, milk, poultry and egg, the annual effective dose of the radionuclides for the local consumer was 2.7, 14, 0.1, and 0.14 μSv·y–1, respectively.     

CT检查个体化辐射剂量估算研究现状

2011年和2014年美国医学物理学会分别发布204号和220号报告,描述基于个体体征估算CT受检者的辐射剂量。204号报告介绍应用受检者前后径和左右径等描述个体体征,220号报告介绍用水当量直径描述受检者的体型特异性,利用体型特异性的转换因子估算CT扫描受检者体型相关的辐射剂量(SSDE)。近年来,国外一系列的文章在SSDE方面进行了深入的研究,本文首先介绍两则报告的主要内容,并对SSDE在儿童和成年人群CT检查诊断参考水平的制定、CT断层图像的质量、受检者器官剂量和有效剂量的估算方面的研究现状进行综述,为开展国内SSDE相关研究和应用提供参考。     

TLD calibration and absorbed dose measurement in a radiation-induced liver injury model under a linear accelerator

The application of a thermoluminescent detector(TLD) for dose detection at the liver irradiation site in mice under linear accelerator precision radiotherapy and the use of a single high dose to irradiate the mouse liver to construct a biological model of a radiation-induced liver injury(RILD) in mice were to determine the feasibility of constructing a precision radiotherapy model in small animals under a linear accelerator. A 360° arc volumetric rotational intensity-modulated radiotherapy(VMAT)...     

A rotational calibration method using thermoluminescent dosemeters for dose determination in computed tomography beams

A procedure for calibration of thermoluminescent dosimeters, called rotational calibration, was developed to create a procedure more adequate for dose procedures used in computed tomography. Thermoluminescent dosimeters were rotated during irradiation to simulate the set-up used in dosimetric procedures in computed tomography equipment. Three commercial types of thermoluminescent dosimeters were calibrated using this methodology. The results showed that the measured values were lower when the dosimeters were irradiated with rotation than in a static geometry. Although the reading differences were not very large, they are not negligible, and they contribute to underestimating the dose.     

Thermal conductivity degradation of ceramic materials due to low temperature, low dose neutron irradiation

The thermal conductivity degradation due to low-temperature neutron irradiation is studied and quantified in terms of thermal resistance terms. Neutron irradiation is assumed to have no effect on umklapp scattering. A theoretical model is presented to quantify the relative phonon-scattering effectiveness of the three dominant defect types produced by neutron irradiation: point defects, dislocation loops and voids. Several commercial ceramics have been irradiated with fission reactor fast neutrons at low temperatures to produce defects. Materials include silicon carbide, sapphire, polycrystalline alumina, aluminum nitride, silicon nitride, beryllium oxide, and a carbon fiber composite. The neutron dose corresponded to 0.001 and 0.01 displacements per atom (dpa) for a 60 °C irradiation and 0.01 and 0.1 dpa for a 300 °C irradiation. Substantial thermal conductivity degradation occurred in all of the materials except BeO following irradiation at 60 °C to a dose of only 0.001 dpa. The data are discussed in terms of the effective increase in thermal resistance caused by the different irradiation conditions. Evidence for significant point defect mobility during irradiation at 60 and 300 °C was obtained for all of the ceramics. The thermal stability of the radiation defects was investigated by isochronal annealing up to 1050 °C.     

主泵参数变化对压力容器液位测量影响分析

为了量化分析CPR1000核电厂主泵特性及相关参数（如电网频率、空泡份额等）变化对堆芯冷却监测系统（CCMS）压力容器液位(L VSL)测量引入的误差,评价该误差对事故处理进程的影响,基于CCMS L VSL测量原理,推导出主泵各参数变化对L VSL测量引入误差的计算公式,并进行量化计算。计算结果表明,除主泵本身的性能降级会导致L VSL较大的低估误差外,其余参数变化对L VSL测量引入的误差可忽略。结合状态导向法事故运行程序（SOP）,分析了主泵本身性能降级导致的低估误差对操纵员关键安全操作的影响。结果表明,该误差可能干扰SOP中主泵的相关操作,但不会阻碍SOP事故处理中关键安全操作的执行。     

Simulations of thermally transferred OSL signals in quartz: Accuracy and precision of the protocols for equivalent dose evaluation

Thermally-transferred optically stimulated luminescence (TT-OSL) signals in sedimentary quartz have been the subject of several recent studies, due to the potential shown by these signals to increase the range of luminescence dating by an order of magnitude. Based on these signals, a single aliquot protocol termed the ReSAR protocol has been developed and tested experimentally. This paper presents extensive numerical simulations of this ReSAR protocol. The purpose of the simulations is to investigate several aspects of the ReSAR protocol which are believed to cause difficulties during application of the protocol. Furthermore, several modified versions of the ReSAR protocol are simulated, and their relative accuracy and precision are compared. The simulations are carried out using a recently published kinetic model for quartz, consisting of 11 energy levels. One hundred random variants of the natural samples were generated by keeping the transition probabilities between energy levels fixed, while allowing simultaneous random variations of the concentrations of the 11 energy levels. The relative intrinsic accuracy and precision of the protocols are simulated by calculating the equivalent dose (ED) within the model, for a given natural burial dose of the sample. The complete sequence of steps undertaken in several versions of the dating protocols is simulated. The relative intrinsic precision of these techniques is estimated by fitting Gaussian probability functions to the resulting simulated distribution of ED values. New simulations are presented for commonly used OSL sensitivity tests, consisting of successive cycles of sample irradiation with the same dose, followed by measurements of the sensitivity corrected L/T signals. We investigate several experimental factors which may be affecting both the intrinsic precision and intrinsic accuracy of the ReSAR protocol. The results of the simulation show that the four different published versions of the ReSAR protocol can reproduce accurately the natural doses in the range 0-400 Gy with approximately the same intrinsic precision and accuracy of ∼1-5%. However, these protocols underestimate doses above 400 Gy; possible sources of this underestimation are investigated. Two possible explanations are suggested for the modeled underestimations, possible thermal instability of the TT-OSL traps, and the presence of thermally unstable medium OSL components in the model.     

湖南省数字X射线摄影设备(DR)主要检查类型所致受检者剂量水平调查

为了解湖南省X射线摄影设备(DR)6种主要检查部位不同的投照方位所致受检者的剂量水平,采用典型抽样法,在省内选取967例受检者作为调查样本,对常用的几种投照类型所致受检者的剂量进行调查。结果表明,湖南省内X射线摄影设备(DR),在腰椎前后位投照(AP)、腰椎侧位投照(LAT)、骨盆前后位投照(AP)、髋关节前后位投照(AP)、胸部后前位投照(PA)、胸部侧位投照(LAT)、胸椎前后位投照(AP)、胸椎侧位投照(LAT)、头颅后前位投照(PA)、头颅侧位投照(LAT)等部位投照时,所致受检者剂量的典型值分别为3.9、5.7、2.5、3.8、0.3、0.7、1.3、3.0、 0.7和0.7 mGy。无自动曝光控制(AEC)时,DR在胸部PA、胸部LAT摄影时所致受检者的剂量的平均值分别为0.77 mGy和1.44 mGy,有AEC时,DR在胸部PA、胸部LAT摄影时所致受检者的剂量的平均值分别为0.27 mGy和0.56 mGy。湖南省X射线摄影设备(DR)6种主要检查部位不同的投照方位所致受检者的剂量低于GB 18871—2002《电离辐射防护与辐射源安全基本标准》给出的典型成年受检者X射线摄影的剂量指导水平。在一定程度上, AEC能优化受检者在X射线摄影检查中受到的辐射剂量。     

Variation of pressure load on flexible plate due to interaction between an expansion wave and the flexible plate

The interaction between an expansion wave and a flexible plate was investigated as a model of the fluid-structure interaction which occurs during the loss-of-coolant accident in pressurized water reactors. The test section, which was connected to an expansion tube, was divided into two regions by the flexible dividing plate, and pressure variations in both regions were measured. Two-dimensional flow equations were numerically solved coupled with an equation of the deflection of the plate. The reduction of pressure loads on the plate due to the interaction between the plate and the expansion wave only occurred within the early stage when the pressure on the back side of the plate was constant. The pressure in the back-side region of the plate was based on the volume change in that region, and the net effect of the pressure change in that region was the reduction of the load on the plate. The pressure in the outlet-side region of the plate was not affected by the pressure in the back-side region. Pressure disturbances generated by the deflection of the dividing plate were found to propagate around the plate when the test section was not perfectly divided into two regions. It was concluded that the conditions around the structure (back-side volume of the structure, for example) should be considered in the evaluation of the pressure load on the structure when the fluid-structure interaction phenomena may be important.     

Monte Carlo applications to photon radiation protection and dosimetry at ENEA

A new version of the MCNP Monte Carlo Code has been written that transports electrons, besides neutrons and photons, incorporating the EGS4 electron modules. The code, which is currently being benchmarked, is intended for use in the field of radiation protection and dosimetry.     

Managing patient dose in multi-detector computed tomography(MDCT). ICRP Publication 102

Computed tomography (CT) technology has changed considerably in recent years with the introduction of increasing numbers of multiple detector arrays. There are several parameters specific to multi-detector computed tomography (MDCT) scanners that increase or decrease patient dose systematically compared to older single detector computed tomography (SDCT) scanners. This document briefly reviews the MDCT technology, radiation dose in MDCT, including differences from SDCT and factors that affect dose, radiation risks, and the responsibilities for patient dose management. The document recommends that users need to understand the relationship between patient dose and image quality and be aware that image quality in CT is often higher than that necessary for diagnostic confidence. Automatic exposure control (AEC) does not totally free the operator from selection of scan parameters, and awareness of individual systems is important. Scanning protocols cannot simply be transferred between scanners from different manufacturers and should be determined for each MDCT. If the image quality is appropriately specified by the user, and suited to the clinical task, there will be a reduction in patient dose for most patients. Understanding of some parameters is not intuitive and the selection of image quality parameter values in AEC systems is not straightforward. Examples of some clinical situation shave been included to demonstrate dose management, e.g. CT examinations of the chest, the heart for coronary calcium quantification and non-invasive coronary angiography, colonography, the urinary tract, children, pregnant patients, trauma cases, and CT guided interventions. CT is increasingly being used to replace conventional x-ray studies and it is important that patient dose is given careful consideration, particularly with repeated or multiple examinations.     

Effect of gamma irradiation on a polymer electrolyte: Variation in crystallinity, viscosity and ion-conductivity with dose

PEO(1 − x)NH₄ClO₄(x) samples with x = 0.18 are irradiated with gamma doses varying up to 50 kGy. DSC and XRD studies indicate, in general, a decrease in crystallinity with dose. Measurement of viscosity of aqueous solutions of the irradiated samples at the same concentration, shows that there is overall chain scission on irradiation, though there is evidence of some cross-linking also at higher doses. This is corroborated by FTIR measurements. The ion-conductivity shows a strong increase for irradiation dose 35 kGy. This suggests that there is a possibility of improving polymer electrolyte properties on gamma irradiation.     

Space radiation dosimetry in low-Earth orbit and beyond

Space radiation dosimetry presents one of the greatest challenges in the discipline of radiation protection. This is a result of both the highly complex nature of the radiation fields encountered in low-Earth orbit (LEO) and interplanetary space and of the constraints imposed by spaceflight on instrument design. This paper reviews the sources and composition of the space radiation environment in LEO as well as beyond the Earth's magnetosphere. A review of much of the dosimetric data that have been gathered over the last four decades of human space flight is presented. The different factors affecting the radiation exposures of astronauts and cosmonauts aboard the International Space Station (ISS) are emphasized. Measurements made aboard the Mir Orbital Station have highlighted the importance of both secondary particle production within the structure of spacecraft and the effect of shielding on both crew dose and dose equivalent. Roughly half the dose on ISS is expected to come from trapped protons and half from galactic cosmic rays (GCRs). The dearth of neutron measurements aboard LEO spacecraft and the difficulty inherent in making such measurements have led to large uncertainties in estimates of the neutron contribution to total dose equivalent. Except for a limited number of measurements made aboard the Apollo lunar missions, no crew dosimetry has been conducted beyond the Earth's magnetosphere. At the present time we are forced to rely on model-based estimates of crew dose and dose equivalent when planning for interplanetary missions, such as a mission to Mars. While space crews in LEO are unlikely to exceed the exposure limits recommended by such groups as the NCRP, dose equivalents of the same order as the recommended limits are likely over the course of a human mission to Mars.