International Commission On Radiological Protection Publication Research Articles

39th Lauriston S. Taylor Lecture: Dosimetry of Internal Emitters: Contribution of Radiation Protection Bodies and Radiological Events.

Since the early days of the Manhattan Engineer District, Oak Ridge National Laboratory (ORNL) has served to advance the dosimetry models used to set protection standards for radionuclides taken into the body. Throughout the years, this effort benefited significantly from ORNL staff's active participation in national and international scientific bodies. The first such interaction was in 1946 with the National Committee on Radiation Protection (NCRP), chaired by L.S. Taylor, which led to the 1949 to 1953 series of tripartite conferences of experts from Canada, the United Kingdom, and the United States. These conferences addressed the need for standardization of dosimetry models and led to the establishment of an anatomic and physiologic model called "Standard Man," a precursor of the reference worker defined in Publication 23 of the International Commission on Radiological Protection (ICRP). Standard Man was used in setting the maximum permissible concentrations in air and water published in NBS Handbook 52 and subsequent reports by NCRP and ICRP. K.Z. Morgan, then director of the Health Physics Division at ORNL, participated in the tripartite conferences and subsequently established ORNL as a modeling and computational resource for development of radiation protection standards. ORNL's role expanded with participation in the work of the Medical Internal Radiation Dose (MIRD) Committee of the Society of Nuclear Medicine. Results of interactions with the MIRD Committee are evident in the radiation protection guidance for internal emitters in ICRP Publication 30. The annual limit on intake and derived air concentration values tabulated in Publication 30 were computed by an ORNL-based task group of ICRP Committee 2. A few years after the appearance of Publication 30, the Chernobyl nuclear reactor accident made clear the need to develop standard dosimetry models for pre-adult ages as members of the public. In the late 1980s, ICRP began an effort to extend its reference worker concept to a reference family and develop dosimetric models for application to intake of radionuclides by members of the public. However, the modeling approach underlying the ICRP Publication 30 computational framework was not amenable to age and gender considerations. With support of U.S. federal agencies, ORNL had begun efforts in the early 1980s to develop age- and gender-specific dosimetric models, including physiologically informed biokinetic models and age-specific dosimetric phantoms. ORNL's models and methods became the starting point for the ICRP's series of reports on dose coefficients for radionuclide intake by the public. Currently ICRP Committee 2 is overseeing development of a second generation of post-Chernobyl models and methods, with updates of Publications 30 and 68 soon to appear and new models for members of the public in preparation. The focus of this Lauriston S. Taylor Lecture is to chronicle advancements in the dosimetry of internal emitters with some discussion of models and methods but with due deference to decisions within scientific bodies and stimulated by radiological events.

Radiation Dosimetry of Whole-Body Dual-Tracer 18F-FDG and 11C-Acetate PET/CT for Hepatocellular Carcinoma.

Combined whole-body dual-tracer ((18)F-FDG and (11)C-acetate) PET/CT is increasingly used for staging hepatocellular carcinoma, with only limited studies investigating the radiation dosimetry data of these scans. The aim of the study was to characterize the radiation dosimetry of combined whole-body dual-tracer PET/CT protocols. Consecutive adult patients with hepatocellular carcinoma who underwent whole-body dual-tracer PET/CT scans were retrospectively reviewed with institutional review board approval. OLINDA/EXM 1.1 was used to estimate patient-specific internal dose exposure in each organ. Biokinetic models for (18)F-FDG and (11)C-acetate as provided by ICRP (International Commission on Radiological Protection) publication 106 were used. Standard reference phantoms were modified to more closely represent patient-specific organ mass. With patient-specific parameters, organ equivalent doses from each CT series were estimated using VirtualDose. Dosimetry capabilities for tube current modulation protocols were applied by integrating with the latest anatomic realistic models. Effective dose was calculated using ICRP publication 103 tissue-weighting coefficients for adult male and female, respectively. Fourteen scans were evaluated (12 men, 2 women; mean age ± SD, 60 ± 19.48 y). The patient-specific effective dose from (18)F-FDG and (11)C-acetate was 6.08 ± 1.49 and 1.56 ± 0.47 mSv, respectively, for male patients and 6.62 ± 1.38 and 1.79 ± 0.12 mSV, respectively, for female patients. The patient-specific effective dose of the CT component, which comprised 2 noncontrast whole-body scans, to male and female patients was 21.20 ± 8.94 and 14.79 ± 3.35 mSv, respectively. Thus, the total effective doses of the combined whole-body dual-tracer PET/CT studies for male and female patients were 28.84 ± 10.18 and 23.19 ± 4.61 mSv, respectively. Patient-specific parameters allow for more accurate estimation of organ equivalent doses. Considering the substantial radiation dose incurred, judicious medical justification is required with every whole-body dual-tracer PET/CT referral. Although radiation risks may have less impact for the population with cancer because of their reduced life expectancy, the information is of interest and relevant for both justification, to evaluate risk/benefit, and protocol optimization.

Overview of ICRP Committee 1: radiation effects.

This paper does not necessarily reflect the views of the International Commission on Radiological Protection. The author passed away on 13 November 2015.Committee 1 of the International Commission on Radiological Protection (ICRP) addresses issues pertinent to tissue reactions, risks of cancer and heritable diseases, radiation dose responses, effects of dose rate, and radiation quality. In addition, it reviews data on the effects of radiation on the embryo/fetus, genetic factors in radiation response, and uncertainties in providing judgements on radiation-induced health effects. Committee 1 advises the Main Commission on the biological basis of radiation-induced health effects, and how epidemiological, experimental, and theoretical data can be combined to make quantitative judgements on health risks to humans. The emphasis is on low radiation doses, in the form of detriment-adjusted nominal risk coefficients, where there are considerable uncertainties in terms of the biology and the epidemiology. Furthermore, Committee 1 reviews data from radiation epidemiology studies and publications on the molecular and cellular effects of ionising radiation relevant to updating the basis of the 2007 Recommendations published in ICRP Publication 103 This paper will provide an overview of the activities of Committee 1, the updated work of the Task Groups and Working Parties, and the future activities being pursued.

Overview of ICRP Committee 4: application of the Commission's recommendations.

Committee 4 develops principles and recommendations on radiological protection of people in all exposure situations. The committee meeting in 2014 was hosted by GE Healthcare in Arlington Heights, IL, USA on 27 July-1 August 2014. The programme of work of Committee 4 encompasses several broad areas, including a series of reports covering various aspects of existing exposure situations, leading the efforts of the International Commission on Radiological Protection (ICRP) to update and elaborate recommendations in light of the accident at Fukushima Daiichi nuclear power plant for emergencies and living in contaminated areas, elaborating the underpinnings of the system of radiological protection, and developing focussed reports on specific topic areas in consultation with ICRP's special liaison organisations. Committee 4 has six active Task Groups working on naturally occurring radioactive material; cosmic radiation in aviation; updates of ICRP Publications 109 and 111; ethics of radiological protection; surface and near-surface disposal of solid radioactive waste; and exposures resulting from contaminated sites from past industrial, military, and nuclear activities. In addition, there is a Working Party on tolerability of risk, and ongoing work with the various special liaison organisations of ICRP.

Erratum to: Effective dose to adult patients from 338 radiopharmaceuticals estimated using ICRP biokinetic data, ICRP/ICRU computational reference phantoms and ICRP 2007 tissue weighting factors.

Background: Effective dose represents the potential risk to a population of stochastic effects of ionizing radiation (mainly lethal cancer). In recent years, there have been a number of revisions and updates influencing the way to estimate the effective dose. The aim of this work was to recalculate the effective dose values for the 338 different radiopharmaceuticals previously published by the International Commission on Radiological Protection (ICRP). Method: The new estimations are based on information on the cumulated activities per unit administered activity in various organs and tissues and for the various radiopharmaceuticals obtained from the ICRP publications 53, 80 and 106. The effective dose for adults was calculated using the new ICRP/International Commission on Radiation Units (ICRU) reference voxel phantoms and decay data from the ICRP publication 107. The ICRP human alimentary tract model has also been applied at the recalculations. The effective dose was calculated using the new tissue weighting factors from ICRP publications 103 and the prior factors from ICRP publication 60. The results of the new calculations were compared with the effective dose values published by the ICRP, which were generated with the Medical Internal Radiation Dose (MIRD) adult phantom and the tissue weighting factors from ICRP publication 60. Results: For 79% of the radiopharmaceuticals, the new calculations gave a lower effective dose per unit administered activity than earlier estimated. As a mean for all radiopharmaceuticals, the effective dose was 25% lower. The use of the new adult computational voxel phantoms has a larger impact on the change of effective doses than the change to new tissue weighting factors. Conclusion: The use of the new computational voxel phantoms and the new weighting factors has generated new effective dose estimations. These are supposed to result in more realistic estimations of the radiation risk to a population undergoing nuclear medicine investigations than hitherto available values.

ORGAN AND EFFECTIVE DOSE COEFFICIENTS FOR CRANIAL AND CAUDAL IRRADIATION GEOMETRIES: PHOTONS

With the introduction of new recommendations of the International Commission on Radiological Protection (ICRP) in Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors and the introduction of reference sex-specific computational phantoms. Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision of ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT) and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for photon irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue kerma and absorbed doses for caudal and cranial exposures to photons ranging in energy from 10 keV to 10 GeV have been performed using the MCNP6.1 radiation transport code and the adult reference phantoms of ICRP Publication 110. As with calculations reported in ICRP 116, the effects of charged-particle transport are evident when compared with values obtained by using the kerma approximation. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above ∼30 MeV the cranial and caudal values are greater.

Synchrotron radiation shielding design and ICRP radiological protection quantities

Protection and operational quantities as defined by the International Commission on Radiological Protection (ICRP) and the International Commission on Radiation Units and Measurements (ICRU) are the two sets of quantities recommended for use in radiological protection for external radiation. Since the ’80s, the protection quantities have evolved from the concept of dose equivalent to effective dose equivalent to effective dose, and the associated conversion coefficients have undergone changes. In this work, the influence of three different versions of ICRP photon dose conversion coefficients in the synchrotron radiation shielding calculations of an experimental enclosure has been examined. The versions are effective dose equivalent (ICRP Publication 51), effective dose (ICRP Publication 74), and effective dose (ICRP Publication 116) conversion coefficients. The sources of the synchrotron radiation white beam into the enclosure were a bending magnet, an undulator and a wiggler. The ranges of photons energy from these sources were 10–200 keV for the bending magnet and undulator, and 10–500 keV for the wiggler. The design criterion aimed a radiation leakage less than 0.5 µSv h−1 from the enclosure. As expected, larger conversion coefficients in ICRP Publication 51 lead to higher calculated dose rates. However, the percentage differences among the calculated dose rates get smaller once shielding is added, and the choice of conversion coefficients set did not affect the final shielding decision.

Application of the Commission's recommendations: the 2013-2017 Committee 4 programme of work.

Committee 4 of the International Commission on Radiological Protection (ICRP) is responsible for developing principles, recommendations, and guidance on the protection of people against radiation exposure, and to consider their practical application in all exposure situations. Currently, the Committee's efforts are focused on the completion of a series of future ICRP publications on the implementation of its 2007 Recommendations to the various existing exposure situations. A report on protection against radon exposure was published recently (ICRP Publication 126), and two documents on protection against cosmic radiation in aviation, and naturally occurring radioactive material are under development. The programme of work for the forthcoming 2013-2017 period comprises the update of ICRP Publication 109 on protection of people in emergency exposure situations, and the update of ICRP Publication 111 on protection of people living in long-term contaminated areas after a nuclear accident, as well as the development of a future ICRP publication on the ethics of radiological protection. It also includes the preparation of task groups on the application of the Commission's recommendations for contaminated sites from past activities and for surface and near-surface disposal of radioactive waste. Another important task for Committee 4 will be to develop a reflection on the tolerability of risk from radiation.

Dosimetric models of the eye and lens of the eye and their use in assessing dose coefficients for ocular exposures.

Based upon recent epidemiological studies of ocular exposure, the Main Commission of the International Commission on Radiological Protection (ICRP) in ICRP Publication 118 states that the threshold dose for radiation-induced cataracts is now considered to be approximately 0.5 Gy for both acute and fractionated exposures. Consequently, a reduction was also recommended for the occupational annual equivalent dose to the lens of the eye from 150 mSv to 20 mSv, averaged over defined periods of 5 years. To support ocular dose assessment and optimisation, Committee 2 included Annex F within ICRP Publication 116 . Annex F provides dose coefficients - absorbed dose per particle fluence - for photon, electron, and neutron irradiation of the eye and lens of the eye using two dosimetric models. The first approach uses the reference adult male and female voxel phantoms of ICRP Publication 110. The second approach uses the stylised eye model of Behrens etal., which itself is based on ocular dimensional data given in Charles and Brown. This article will review the data and models of Annex F with particular emphasis on how these models treat tissue regions thought to be associated with stem cells at risk.

Use of effective dose in medicine.

This paper does not necessarily reflect the views of the International Commission on Radiological Protection. The protection quantity 'effective dose' was developed by the International Commission on Radiological Protection (ICRP) for use in the radiological protection of workers and the public. In this context, it is used as a risk-adjusted dosimetric quantity to optimise protection, comparing received or planned doses with constraints, reference levels, and limits expressed in the same quantity. Considering exposures incurred during medical procedures, effective dose can be of practical value for comparing: doses from different diagnostic examinations and interventional procedures; the use of similar technologies and procedures in different hospitals and countries; and the use of different technologies for the same medical examination, provided that the representative patients or patient populations for which the effective doses are derived are similar with regard to age and sex. However, as stated in ICRP Publication 103, '… risk assessment for medical diagnosis and treatment… is best evaluated using appropriate risk values for the individual tissues at risk and for the age and sex distribution of the individuals undergoing the medical procedures'. This topic was explored in a session of the First ICRP Symposium with arguments for and against the use of a new quantity referred to as 'effective risk', and examination of variations in estimated risk for different diagnostic procedures according to the age and sex of the exposed individuals. This paper restates the primary purposes of effective dose, and summarises estimates of variation in individual risk from medical procedures. The authors support the judicious use of effective dose as an indicator of possible risk, but caution against the use of effective risk as compared with the calculation of scientific best estimates of risk with consideration of associated uncertainties.

Overview of ICRP Committee 5.

The International Commission on Radiological Protection (ICRP) established Committee 5 in 2005 in response to the need to provide direct demonstration of environmental protection from radiation in accordance with national law and international agreements. The development of the ICRP system for environmental protection was facilitated by research over the previous decades, as well as by ICRP's evaluation of the ethical and philosophical basis for environmental protection as laid out in ICRP Publication 91. The 2007 Recommendations (Publication 103) incorporated environmental protection as one of the integral elements of the radiation protection system. Over a relatively short time, the system has evolved to incorporate a set of 12 Reference Animals and Plants (RAPs), which is a small enough number to develop comprehensive databases for each RAP, but wide ranging enough to provide some insight into radiation impact and protection against such impact, as appropriate, in terrestrial, freshwater, and marine ecosystems. As necessary, the databases can be used to derive supplementary databases for Representative Organisms typical for a particular exposure situation of concern or under study. The system, to date, details biology of the RAPs (Publication 108); outlines transfer factors for estimation of internal concentrations of radionuclides of environmental significance under different situations (Publication 114); provides further information (Publication 108) on dosimetry, biological effects, and derived consideration reference levels (bands of environmental dose rates where potential detrimental effects may deserve attention); and provides information on application of the system in planned, emergency, and existing exposure situations (Publication 124). Currently, a review of experimental determinations of relative biological effectiveness, to guide derivation of specific weighting factors for use in environmental radiation protection if possible and necessary, is being concluded, as is work on improved dosimetry. Further work in this area involves consolidation of databases, recommendations for derivation of specific databases for Representative Organisms on the basis of the RAP data, and recommendations for application of the system to environmental protection in relation to certain human activities of potential environmental concern. Consideration needs to be made for the wider range of ecosystem effects that may be covered in ecological risk assessments, which incorporate the complete suite of stressors that result from human activity, and their effects, to understand the role of radiation effects in this context.

Radiological protection in computed tomography and cone beam computed tomography.

The International Commission on Radiological Protection (ICRP) has sustained interest in radiological protection in computed tomography (CT), and ICRP Publications 87 and 102 focused on the management of patient doses in CT and multi-detector CT (MDCT) respectively. ICRP forecasted and 'sounded the alarm' on increasing patient doses in CT, and recommended actions for manufacturers and users. One of the approaches was that safety is best achieved when it is built into the machine, rather than left as a matter of choice for users. In view of upcoming challenges posed by newer systems that use cone beam geometry for CT (CBCT), and their widened usage, often by untrained users, a new ICRP task group has been working on radiological protection issues in CBCT. Some of the issues identified by the task group are: lack of standardisation of dosimetry in CBCT; the false belief within the medical and dental community that CBCT is a 'light', low-dose CT whereas mobile CBCT units and newer applications, particularly C-arm CT in interventional procedures, involve higher doses; lack of training in radiological protection among clinical users; and lack of dose information and tracking in many applications. This paper provides a summary of approaches used in CT and MDCT, and preliminary information regarding work just published for radiological protection in CBCT.

Review of the ICRP system of protection: the approach to existing exposure situations.

The International Commission on Radiological Protection (ICRP) system of protection consists of existing, planned, and emergency exposure situations. With the 2007 Recommendations in ICRP Publication 103, a coherent approach has been established that emphasises the optimisation of protection with appropriate constraints or reference levels in each exposure situation. Existing exposure situations pose unique challenges because the source of exposure already exists, and it may not always be possible to control the source directly. This is the case for naturally occurring sources, which are ubiquitous in the environment and vary widely in the magnitude of exposures that may be received by individuals. Decisions on protection strategies must consider a graded, pragmatic, and flexible approach for dealing with exposure of members of the public, and those that may be occupationally exposed while working with naturally occurring sources. Although limits are not applicable, aspects of the management approach for planned exposure situations may be appropriate, depending upon the magnitude of exposures.

US Transuranium and Uranium Registries case study on accidental exposure to uranium hexafluoride

The United States Transuranium and Uranium Registries’ (USTUR) whole-body donor (Case 1031) was exposed to an acute inhalation of uranium hexafluoride (UF6) produced from an explosion at a uranium processing plant 65 years prior to his death. The USTUR measurements of tissue samples collected at the autopsy indicated long-term retention of inhaled slightly enriched uranium material (0.85% 235U) in the deep lungs and thoracic lymph nodes. In the present study, the authors combined the tissue measurement results with historical bioassay data, and analysed them with International Commission on Radiological Protection (ICRP) respiratory tract models and the ICRP Publication 69 systemic model for uranium using maximum likelihood and Bayesian statistical methods. The purpose of the analysis was to estimate intakes and model parameter values that best describe the data, and evaluate their effect on dose assessment. The maximum likelihood analysis, which used the ICRP Publication 66 human respiratory tract model, resulted in a point estimate of 79 mg of uranium for the occupational intake composed of 86% soluble, type F material and 14% insoluble, type S material. For the Bayesian approach, the authors applied the Markov Chain Monte Carlo method, but this time used the revised human respiratory tract model, which is currently being used by ICRP to calculate new dose coefficients for workers. The Bayesian analysis estimated that the mean uranium intake was 160 mg, and calculated the case-specific lung dissolution parameters with their associated uncertainties. The parameters were consistent with the inhaled uranium material being predominantly soluble with a small but significant insoluble component. The 95% posterior range of the rapid dissolution fraction (the fraction of deposited material that is absorbed to blood rapidly) was 0.12 to 0.91 with a median of 0.37. The remaining fraction was absorbed slowly, with a 95% range of 0.000 22 d−1 to 0.000 36 d−1 and a median of 0.000 31 d−1. The effective dose per unit intake calculated using the dissolution parameters derived from the maximum likelihood and the Bayesian analyses was higher than the current ICRP dose coefficient for type F uranium by a factor of 2 or 7, respectively; the higher value of the latter was due to use of the revised respiratory tract model. The dissolution parameter values obtained here may be more appropriate to use for radiation protection purposes when individuals are exposed to a UF6 mixture that contains an insoluble uranium component.

Effective dose to adult patients from 338 radiopharmaceuticals estimated using ICRP biokinetic data, ICRP/ICRU computational reference phantoms and ICRP 2007 tissue weighting factors.

BackgroundEffective dose represents the potential risk to a population of stochastic effects of ionizing radiation (mainly lethal cancer). In recent years, there have been a number of revisions and updates influencing the way to estimate the effective dose. The aim of this work was to recalculate the effective dose values for the 338 different radiopharmaceuticals previously published by the International Commission on Radiological Protection (ICRP).MethodThe new estimations are based on information on the cumulated activities per unit administered activity in various organs and tissues and for the various radiopharmaceuticals obtained from the ICRP publications 53, 80 and 106. The effective dose for adults was calculated using the new ICRP/International Commission on Radiation Units (ICRU) reference voxel phantoms and decay data from the ICRP publication 107. The ICRP human alimentary tract model has also been applied at the recalculations. The effective dose was calculated using the new tissue weighting factors from ICRP publications 103 and the prior factors from ICRP publication 60. The results of the new calculations were compared with the effective dose values published by the ICRP, which were generated with the Medical Internal Radiation Dose (MIRD) adult phantom and the tissue weighting factors from ICRP publication 60.ResultsFor 79% of the radiopharmaceuticals, the new calculations gave a lower effective dose per unit administered activity than earlier estimated. As a mean for all radiopharmaceuticals, the effective dose was 25% lower. The use of the new adult computational voxel phantoms has a larger impact on the change of effective doses than the change to new tissue weighting factors.ConclusionThe use of the new computational voxel phantoms and the new weighting factors has generated new effective dose estimations. These are supposed to result in more realistic estimations of the radiation risk to a population undergoing nuclear medicine investigations than hitherto available values.Electronic supplementary materialThe online version of this article (doi:10.1186/2197-7364-1-9) contains supplementary material, which is available to authorized users.

Evaluation of organ doses and effective dose according to the ICRP Publication 110 reference male/female phantom and the modified ImPACT CT patient dosimetry.

We modified the Imaging Performance Assessment of CT scanners (ImPACT) to evaluate the organ doses and the effective dose based on the International Commission on Radiological Protection (ICRP) Publication 110 reference male/female phantom with the Aquilion ONE ViSION Edition scanner. To select the new CT scanner, the measurement results of the CTDI100,c and CTDI100,p for the 160 (head) and the 320 (body) mm polymethylmethacrylate phantoms, respectively, were entered on the Excel worksheet. To compute the organ doses and effective dose of the ICRP reference male/female phantom, the conversion factors obtained by comparison between the organ doses of different types of phantom were applied. The organ doses and the effective dose were almost identical for the ICRP reference male/female and modified ImPACT. The results of this study showed that, with the dose assessment of the ImPACT, the difference in sex influences only testes and ovaries. Because the MIRD‐5 phantom represents a partially hermaphrodite adult, the phantom has the dimensions of the male reference man including testes, ovaries, and uterus but no female breasts, whereas the ICRP male/female phantom includes whole‐body male and female anatomies based on high‐resolution anatomical datasets. The conversion factors can be used to estimate the doses of a male and a female accurately, and efficient dose assessment can be performed with the modified ImPACT.PACS number: 87.53.LY, 87.57.Q‐, 87.57.‐s

Internal dose to active marrow and endosteum from radioactive iodine.

This study analyses the active marrow and endosteum dose differences between the new International Commission on Radiological Protection (ICRP) male and female reference computational phantoms and the stylised phantom for two thyroid agents. The active marrow and endosteum doses from (131)I and (123)I were calculated for 0-55 % maximum thyroid uptakes using the MCNP-4C Monte Carlo code. The biokinetic models were taken from ICRP Publication 53. To evaluate the absorbed doses to red marrow and endosteum, the deposited energy was determined for the 19 spongiosa regions and 6 medullary cavities and was mass weighted using the mass fractions available in ICRP Publication 116. The results were then compared with the published values given in ICRP Publication 53. The poor anatomic realism of the stylised phantom used in ICRP Publication 53 leads to important dose differences between the ICRP voxel phantoms and the stylised phantom. The influence of the use of different bone material was also investigated. Underestimations of ∼60% were observed for active marrow doses of the stylised phantom compared with reference voxel phantoms. The results highlight the importance of the accuracy of the shape and inter-organ distances of the anthropomorphic model used.

Development of a 9-months pregnant hybrid phantom and its internal dosimetry for thyroid agents.

As a consequence of fetal radiosensitivity, the estimation of internal dose received by a fetus from radiopharmaceuticals applied to the mother is often important in nuclear medicine. A new 9-months pregnant phantom based on magnetic resonance (MR) images tied to the International Commission on Radiological Protection (ICRP) reference voxel phantom has been developed. Maternal and fetal organs were segmented from a set of pelvic MR images of a 9-months pregnant subject using 3D-DOCTORTM and then imported into the 3D modeling software package RhinocerosTM for combining with the adult female ICRP voxel phantom and further modeling. Next, the phantom organs were rescaled to match with reference masses described in ICRP Publications. The internal anatomy of previous pregnant phantom models had been limited to the fetal brain and skeleton only, but the fetus model developed in this study incorporates 20 different organs. The current reference phantom has been developed for application in comprehensive dosimetric study in nuclear medicine. The internal dosimetry calculations were performed for thyroid agents using the Monte Carlo transport method. Biokinetic data for these radiopharmaceuticals were used to estimate cumulated activity during pregnancy and maternal and fetal organ doses at seven different maximum thyroid uptake levels. Calculating the dose distribution was also presented in a sagittal view of the pregnant model utilizing the mesh tally function. The comparisons showed, in general, an overestimation of the absorbed dose to the fetus and an underestimation of the fetal thyroid dose in previous studies compared with the values based on the current hybrid phantom.

Evaluation of effective dose conversion coefficients for Korean adults during medical x-ray examinations up to 150 keV through comparison with ICRP Publication 74 and ICRP Publication 116

A Monte Carlo program for calculating organ doses for patients undergoing medical x-ray examination (PCXMC) was used to calculate effective dose conversion coefficients for Korean adults. Two sets of effective dose results were calculated based on tissue weighting factors recommended in International Commission on Radiological Protection (ICRP) Publications 60 and 103 for monochromatic energy photons of 10, 15, 20, 30, 40, 50, 60, 70, 80, 100 and 150 keV. The results were obtained for monoenergetic photons, since effective dose conversion coefficients recommended in ICRP Publications 74 and 116 were given for monochromatic energies, thereby enabling the comparison of our result to those suggested by the ICRP publications. The areas of comparison include: to observe effects due to changes in tissue weighting factors, modification within Medical Internal Radiation Dose (MIRD) phantoms and differences in phantom types. The phantom employed in the PCXMC program is a modified version of the phantom used in ICRP Publication 74, with additional organs that were added in order to take into account the updated tissue weighting factors given in ICRP Publication 103. Both use MIRD phantoms but our study modified the phantom size to the average physical condition of Korean adults, while ICRP Publication 74 uses the phantom size of the reference man defined in ICRP Publication 23. On the other hand, the effective dose suggested in ICRP 116 was calculated using an entirely different type of phantom: a voxel phantom with the size of reference man. Although significant differences were observed for certain organ doses in the lateral beam directions, differences in the effective doses were within 5% for the anterior–posterior (AP) and posterior–anterior (PA) directions, and within 16% in lateral directions when tissue weighting factors were applied and the variations were adjusted for all three comparisons. The results show that calculation of effective doses for Korean adults using the PCXMC (Caucasian-based phantom) is acceptable for the AP and PA directions, but care should be taken for lateral directions.

水晶体の放射線防護に関する専門研究会中間報告書 (Ⅲ)

Many studies have been internationally reported as part of projects regarding the radiation exposure for the lens of the eye of medical staff members under various conditions, methods of dosimetry and development of dosimeters for the lens of the eye. Recently conducted studies include the Retrospective Evaluation of Lens Injuries and Dose (RELID) of the International Atomic Energy Agency, Occupational Cataracts and Lens Opacities in interventional Cardiology (O’CLOC) study in France, Optimization of Radiation Protection of Medical Staff (ORAMED) project in European countries, and a 20-year prospective cohort study among US radiologic technologists. Given the newly implemented dose limit for the lens of the eye by the International Commission on Radiological Protection (ICRP), we summarized these studies as the necessary information for reconsideration of the Japanese dose limit for the lens of the eye. In addition, this article also covers the exposures for the lens of the eye of clean-up workers in the Chernobyl accident as shown in ICRP Publication 118 and the results of a hearing survey with specialists of the Academy of Medical Science of Ukraine.