Dose Conversion Coefficients for External Photons Based on ICRP 1990 Recommendations

Monte Carlo calculations were performed to estimate the effective doses E for external photons based on the recent proposals in the ICRP 1990 Recommendations. Twelve photon energies between 17 keV and 8.5 MeV and eleven irradiation geometries were selected to be applicable to many exposure conditions encountered in the working and living environment. A MIRD-based unisex phantom was used in conjunction with the Monte Carlo transport code MORSE-CG. The results were presented as a form of dose conversion coefficients transforming the air kerma or fluence in free air to the effective dose. These coefficients were given in graphical and tabular forms. Analyses of organs' fractional contribution to E showed that the gonadal exposure has generally a great contribution for all the geometries except the incidence from above. A comparison of conversion coefficients with other results gave a reasonably satisfactory agreement. Finally, the ambient dose equivalent H ^*(10), one of the operational quantities proposed by the ICRU, was found to give conservative estimates of E for most of the irradiation geometries considered, but it gives a considerable overestimate of E at the incidences from above and below.     

External Radiation Conversion Coefficients using Radiation Weighting Factor and Quality Factor for Neutron and Proton from 20 MeV to 10 GeV

Conversion coefficients from neutron and proton fluences to effective dose are calculated in the range of incident neutron energy from 20 MeV to 10 GeV. Two different versions of effective dose are treated, respectively calculated using: (a) the radiation weighting factor wR, and (b) the Q-L relationship given in ICRP 60. Monte Carlo calculations are performed applying the HETC-3STEP and the MORSE-CG/KFA in the HERMES code system. The calculations are based on a modified MIRDS anthropomorphic phantom, which is irradiated in anterior-posterior and posterior-anterior directions of beam. For effective dose calculation using the Q-L relationship, a database was compiled and added to the HETC-3STEP, to derive the average quality factor. The effective dose derived using wR proved to overestimate that obtained with the Q-L relationship by about 80% at 10 GeV incident neutron energy in the case of conversion from neutron fluence. For proton fluence, the corresponding overestimation reaches a maximum factor of 4.     

外照射情况下有效剂量（E）与有效剂量当量（HE）的比较

ＩＣＲＰ第６０号出版物引入了对外照射辐射剂量学的几个重大变化,６０号出版物推荐的辐射加权方法和基本防护量的技术规格与２６号出版的推荐有很大的不同,本文依据ＩＣＲＰ第７４号出版物给出的数据和讨论,对在各种照射几何条件下对不同能量的光子,中子及电子辐射场计算的有效剂量（Ｅ）与有效剂量当量（ＨＥ）的数值差别作了评述。     

中国成年女性精细乳房模型的建立及其在外照射防护中的应用

乳腺是对辐射致癌最敏感的器官之一,2007年国际放射防护委员会(ICRP)将乳腺的组织权重因子由0.05提升为0.12,使乳腺剂量的准确评估变得更为重要。本文利用数学建模方法建立了精细乳房模型,包括输乳窦、输乳管、小叶和脂肪组织,模型体素化后与中国成年女性参考人体素模型进行了融合。利用该模型计算了光子AP照射时乳腺腺体的剂量转换系数,并与原来模型的计算结果进行对比。结果显示,光子能量较低时两个模型的计算结果相差30%,光子能量在0.03 MeV以上时差别不大。     

Relations Between the Effective Dose and the Indications of an Individual Dosimeter in Anisotropic Photon Fields

The effective dose, the personal dose equivalent, and the indications of an individual dosimeter are calculated, using the ROBOT computer program (Monte Carlo method), for the conditions of irradiation of an anthropomorphic heterogeneous ICRP phantom with wide beams of 40 keV–11 MeV photons for all solid angles. In anisotropic photon fields, the dosimeter indications satisfactorily estimate the personal dose equivalent. The dependence of the ratio of the effective dose to the indications of an individual dosimeter on the irradiation conditions is analyzed. It is noted that the individual dosimeter indications are not conservative when the phantom is irradiated from the back half-space. It is shown that for wide photon beams the ratio of the effective dose to the dosimeter indications determined neglecting the scattering of radiation inside the working room is an upper limit of the indicated ratio calculated taking scattering into account.     

女性蹲姿曲面模型光子外照射剂量研究

基于中国女性参考人曲面模型建立女性蹲姿曲面模型,采用蒙特卡罗方法,针对6种标准光子外照射几何,计算光子能量0.01～10 MeV范围内21个能量点的器官吸收剂量转换系数和有效剂量转换系数,并与直立姿势的剂量数据进行了对比。结果表明:两种姿势中某些器官的吸收剂量转换系数在前后、后前以及侧向照射方式下差异较大。其中,后前照射方式下,光子能量为0.03 MeV时,乳腺的吸收剂量转换系数比直立姿势高115.1%。在不同照射方式下,大部分能量点的有效剂量转换系数的差异在10%范围内。转换系数的差异主要是由于胳膊和腿位置的改变,以及蹲姿时因身体前倾造成器官在照射方向上厚度发生改变而产生的。     

Calculation of Effective Doses for External Neutrons

Monte Carlo calculations of the effective dose, on the basis of 1CRP Publication 60, were performed for external neutrons from thermal energy to 18.3 MeV for five irradiation geometries: AP, PA, RLAT, ROT and ISO. A unisex anthropomorphic phantom and the MORSE-CG code were used in conjunction with a nuclear data set based on the JENDL-3 library. The effective dose was found to be superior to the effective dose equivalent, the former quantity, for neutrons below about 1 MeV and inferior above this energy for all the geometries. The ambient dose equivalent based on the new Q-L relationship proposed in the Publication was found not necessarily to give a conservative estimate of the effective dose for the AP and PA geometries. The results obtained here were in good agreement with those calculated with a different computer code and a different nuclear data set.     

中国参考人系列模型的建立及外照射剂量学特征的研究

为探讨不同人种、不同姿势及新的组织权重因子对人体剂量学的影响,建立了基于GBZ/T200的中国参考人系列模型（包括立姿、坐姿、走姿的男女模型）;结合蒙特卡罗程序计算得到不同射线能量、6种标准照射方式下的器官吸收剂量和有效剂量。结果表明,基于不同权重因子和不同种族参考模型可得到不同的有效剂量,尤其是低能阶段的差异较为明显;姿势的改变使得器官剂量和有效剂量有所变化,主要由于器官之间的屏蔽作用,体现在相对立姿时坐姿前后照射的有效剂量减小和走姿左右照射的有效剂量增加。进行辐射剂量学评估时,在低能阶段不同的影响因素对结果有较大的影响,而高能时不太明显,因此在进行医学影像等复杂辐射场的辐射防护工作时应注重实际情况的考虑。     

确定X线诊断中人体剂量的实验研究

本文介绍了在 X 线诊断照射中受检者所受剂量的一种估算方法。对自行设计制作的非均匀人体模型进行了实验,测定了几种 X 线诊断时体模内的吸收剂量;并应用 ICRP 第26号出版物所推荐的权重因子,估算了有效剂量当量与体表射线入射口的照射量之比值。     

Dose conversion coefficients for Chinese reference adult male and female voxel phantoms from idealized neutron exposures

A whole-body voxel phantom called CRAF representing the Chinese adult female was constructed in this study from color photographs. The CRAF has a height of 160 cm and a weight of 54 kg with 80 organs and tissues, including almost all organs required in the ICRP Publication 103. Masses of all organs in CRAF are consistent with the Chinese reference data within 1%. Our research group has previously developed a Chinese reference adult male phantom called CRAM, which has a height of 170 cm and a weight of 60 kg with 80 tissues and organs. A new set of fluence-to-dose conversion coefficients based on the Chinese reference adult voxel phantoms CRAM and CRAF are presented for six idealized external neutron exposures from 10^?8 MeV to 20 MeV. The calculation of organ-absorbed doses and effective doses were performed with the Monte Carlo transport code MCNPX 2.4. The resulting dose conversion coefficients were compared with those published in ICRP Publication 116, which represents the reference Caucasian. It was observed that the two sets of organ-absorbed dose conversion coefficients agreed well for most organs in ROT and ISO geometry; however, considerable deviations were found in some organs in AP, PA, RLAT and LLAT exposures. Organ-absorbed dose coefficients difference showed good agreement with the difference of organ depth distribution between Chinese and ICRP phantoms. For neutrons with energies above 2 MeV, the effective dose conversion coefficients of Chinese reference adult are almost identical to those of ICRP Publication 116 in AP, PA, ROT and ISO geometries, while are generally 15% higher than those of ICRP Publication 116 from lateral geometries. When energies range from 10^?8 MeV to 1 MeV, differences are within 10% in AP (–5%), PA (–8%) and ROT (4%) geometries; however, relatively large discrepancies are shown in lateral and ISO geometries, with differences of 15% for LLAT, 20% for RLAT and 12% for ISO, respectively.     

Calculations of Effective Dose and Ambient Dose Equivalent Conversion Coefficients for High Energy Photons

The conversion coefficients from photon fluence to ambient dose equivalent, H* (10) and effective doses were calculated for photons up to 10 GeV. A Monte Carlo code EGS4 was used for these calculations and secondary particle transports were considered. The calculated ambient dose equivalents were compared to the calculated effective doses. The comparison shows that the ambient dose equivalents at 1 cm depth, H* (10) underestimate the effective doses at the energy above 5MeV. H* (10) is not suitable operational quantity since it does not provide reasonable estimation of effective dose. It is difficult to define the operational quantity which can be consistently used for photons from low energy to high energy above 10 MeV. Instead of operational quantities, the maximum effective dose in various irradiation geometries can be used for shielding design calculations.     

NRC修订10 CFR Part 20的技术问题及其启示

介绍了美国核管理委员会在ICRP 2007年建议书出版后的联邦法规10 CFR Part 20修订中涉及的技术细节问题及其解决方案。提出在我国现行辐射防护相关法规的审管实践中需要注意以下问题：①在当量剂量和有效剂量的辐射权重因子和组织权重因子更新后,应评估对当量剂量和有效剂量的影响;②剂量约束的设置并在其取值时对行业间辐射状况差异的考虑;③胚胎和胎儿的剂量限制。     

X,γ射线外照射有效剂量当量

国际放射防护委员会(ICRP)提出在辐射防护中采用有效剂量当量,本文对能量在62keV 至10MeV 范围内的 X、γ射线,在不同的照射几何条件下,计算了有效剂量当量与自由空气场照射量或个人剂量仪读数的比值,并讨论了有关的应用问题。     

Implementation of Japanese Male and Female Tomographic Phantoms to Multi-particle Monte Carlo Code for Ionizing Radiation Dosimetry

Japanese male and female tomographic phantoms, which have been developed for radio-frequency electromagnetic-field dosimetry, were implemented into multi-particle Monte Carlo transport code to evaluate realistic dose distribution in human body exposed to radiation field. Japanese tomographic phantoms, which were developed from the whole body magnetic resonance images of Japanese average adult male and female, were processed as follows to be implemented into general purpose multi-particle Monte Carlo code, MCNPX2.5. Original array size of Japanese male and female phantoms, 320x160x866 voxels and 320x160x804 voxels, respectively, were reduced into 320x160x433 voxels and 320x160x402 voxels due to the limitation of memory use in MCNPX2.5. The 3D voxel array of the phantoms were processed by using the built-in repeated structure algorithm, where the human anatomy was described by the repeated lattice of tiny cube containing the information of material composition and organ index number. Original phantom data were converted into ASCII file, which can be directly ported into the lattice card of MCNPX2.5 input deck by using in-house code. A total of 30 material compositions obtained from International Commission on Radiation Units and Measurement (ICRU) report 46 were assigned to 54 and 55 organs and tissues in the male and female phantoms, respectively, and imported into the material card of MCNPX2.5 along with the corresponding cross section data. Illustrative calculation of absorbed doses for 26 internal organs and effective dose were performed for idealized broad parallel photon and neutron beams in anterior-posterior irradiation geometry, which is typical for workers at nuclear power plant. The results were compared with the data from other Japanese and Caucasian tomographic phantom, and International Commission on Radiological Protection (ICRP) report 74. The further investigation of the difference in organ dose and effective dose among tomographic phantoms for other irradiation geometries should be carried out by employing additional tomographic phantoms to find out the dosimetric difference of Asian human phantoms from Caucasian-based phantoms.     

ICRU 95号报告:外照射实用量及其对剂量学的影响（英文）

国际放射防护委员会(ICRP)提出了“防护量”这一概念。最常用的防护量,即有效剂量E,用于设定照射限值,并在实用辐射防护中使用,以实现最优化原则。然而,有效剂量不是一个可测量的量,基于此国际辐射单位与测量委员会(ICRU)为外照射的剂量测定提出了一个可测量的量,即实用量,用于估计有效剂量。目前使用的实用量定义于20世纪80年代,当时核工业是职业辐射防护的主要关注点。当前,在其他辐射领域,特别是高能辐射,实用量的不足之处变得很明显：可能高估或低估有效剂量。因此,ICRU和ICRP在全面研究的基础上,为外照射的剂量测定提出了新的实用量,以克服上述缺点。实用量的新定义与防护量(包括有效剂量)的定义更具相关性,特别是使用了相同的仿真体模。当前提出的实用量通过缩小防护量与实用量之间的定义差异简化了辐射防护量体系,并从整体上改进了对有效剂量的估计。本文讨论了提出的新实用量对实际剂量测定的影响。     

有效剂量当量在医疗照射剂量评价中的应用

自从国际放射防护委员会(ICRP)采用有效剂量当量(H_E)作为辐射防护基本限值量以来,H_E较好地解决了非均匀照射时的剂量表达问题。尽管对接受医疗照射的受检者使用 H_E 并不是 ICRP本来的意图。但是为了便于统一比较,把 H_E 谨慎地扩展应用到诊断检查的医疗照射剂量评价中又是可取的。本文以北京 X 线诊断的医疗照射剂量评价为例,说明用 Drexler,G.等给出的考虑性别差异的组织权重因子所计算的加权剂量当量与 H_E 的差别很小。     

Conversion from Tooth Enamel Dose to Organ Doses for Electron Spin Resonance Dosimetry

Conversion from tooth enamel dose to organ doses was analyzed to establish a method of retrospective individual dose assessment against external photon exposure by electron spin resonance (ESR) dosimetry. Dose to tooth enamel was obtained by Monte Carlo calculations using a modified MIRD-type phantom with a teeth part. The calculated tooth enamel doses were verified by measurements with thermo-luminescence dosimeters inserted in a physical head phantom. Energy and angular dependences of tooth enamel dose were compared with those of other organ doses. Additional Monte Carlo calculations were performed to study the effect of human model on the tooth enamel dose with a voxel-type phantom, which was based on computed tomography images of the physical phantom. The data derived with the modified MIRD-type phantom were applied to convert from tooth enamel dose to organ doses against external photon exposure in a hypothesized field, where scattered radiation was taken into account. The results indicated that energy distribution of photons incident to a human body is required to evaluate precisely an individual dose based on ESR dosimetry for teeth.     

Relative biological effectiveness (RBE), quality factor (Q), and radiation weighting factor (w(R)). A report of the International Commission on Radiological Protection

The effect of ionising radiation is influenced by the dose, the dose rate, and the quality of the radiation. Before 1990, dose-equivalent quantities were defined in terms of a quality factor, Q(L), that was applied to the absorbed dose at a point in order to take into account the differences in the effects of different types of radiation. In its 1990 recommendations, the ICRP introduced a modified concept. For radiological protection purposes, the absorbed dose is averaged over an organ or tissue, T, and this absorbed dose average is weighted for the radiation quality in terms of the radiation weighting factor, w(R), for the type and energy of radiation incident on the body. The resulting weighted dose is designated as the organ- or tissue-equivalent dose, H(T). The sum of the organ-equivalent doses weighted by the ICRP organ-weighting factors, w(T), is termed the effective dose, E. Measurements can be performed in terms of the operational quantities, ambient dose equivalent, and personal dose equivalent. These quantities continue to be defined in terms of the absorbed dose at the reference point weighted by Q(L). The values for w(R) and Q(L) in the 1990 recommendations were based on a review of the biological and other information available, but the underlying relative biological effectiveness (RBE) values and the choice of w(R) values were not elaborated in detail. Since 1990, there have been substantial developments in biological and dosimetric knowledge that justify a re-appraisal of w(R) values and how they may be derived. This re-appraisal is the principal objective of the present report. The report discusses in some detail the values of RBE with regard to stochastic effects, which are central to the selection of w(R) and Q(L). Those factors and the dose-equivalent quantities are restricted to the dose range of interest to radiation protection, i.e. to the general magnitude of the dose limits. In special circumstances where one deals with higher doses that can cause deterministic effects, the relevant RBE values are applied to obtain a weighted dose. The question of RBE values for deterministic effects and how they should be used is also treated in the report, but it is an issue that will demand further investigations. This report is one of a set of documents being developed by ICRP Committees in order to advise the ICRP on the formulation of its next Recommendations for Radiological Protection. Thus, while the report suggests some future modifications, the w(R) values given in the 1990 recommendations are still valid at this time. The report provides a scientific background and suggests how the ICRP might proceed with the derivation of w(R) values ahead of its forthcoming recommendations.     

Estimating internal dose coefficients of short-lived radionuclides in accordance with ICRP 2007 recommendations

For radiation protection in high-energy accelerator facilities, internal dose coefficients of short-lived radionuclides were estimated using the dosimetric methodology in accordance with the International Commission on Radiological Protection (ICRP) 2007 Recommendations. A computational program was developed for estimating the dose coefficients. The program was verified by confirming whether it could reproduce the dose coefficients provided by ICRP for intakes of representative radionuclides. In addition, the estimated dose coefficients of short-lived radionuclides were compared to the values generated by Dose and risk CALculation software (DCAL), which is based on a dosimetric methodology that is in accordance with the ICRP 1990 Recommendations, to discuss the reasons why the dose coefficients were changed by the revision of the dosimetric methodologies. The comparison revealed a decreasing trend of dose coefficients in the case of inhalation upon revision of the dosimetric methodologies. By contrast, in the case of ingestion, the dose coefficients tended to increase.     

一例239Pu内污染者的剂量评价

ICRP66、67号出版物中对内照射剂量估算中使用的呼吸道模型和Pu在人体内代谢模式进行了较大的修改。本文应用ICRP66、67号出版筇的推荐的Pu在人体内的代谢模型及参数及新呼吸道模型,估算了一例^239Pu内污染者的摄入量和待积有效剂量。