NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Sixty-third Session, Supplement No. 46. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. Scientific Annexes Annex A. Medical radiation exposures Annex B. Exposures of the public and workers from various sources of radiation INTROdUCTION 1. In the course of the research and development for and the application of atomic energy and nuclear technologies, a number of radiation accidents have occurred. Some of these accidents have resulted in significant health effects and occasionally in fatal outcomes. The application of technologies that make use of radiation is increasingly widespread around the world. Millions of people have occupations related to the use of radiation, and hundreds of millions of individuals benefit from these uses. Facilities using intense radiation sources for energy production and for purposes such as radiotherapy, sterilization of products, preservation of foodstuffs and gamma radiography require special care in the design and operation of equipment to avoid radiation injury to workers or to the public. Experience has shown that such technology is generally used safely, but on occasion controls have been circumvented and serious radiation accidents have ensued. 2. Reviews of radiation exposures from accidents have been presented in previous UNSCEAR reports. The last report containing an exclusive chapter on exposures from accidents was the UNSCEAR 1993 Report [U6]. 3. This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices. Its conclusions are to be seen in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation. 4. The Committee's evaluations of public, occupational and medical diagnostic exposures are mostly concerned with chronic exposures of …

sources and effects of ionizing radiation

Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. This paper gives a detailed description of the design and development of GATE by the OpenGATE collaboration, whose continuing objective is to improve, document and validate GATE by simulating commercially available imaging systems for PET and SPECT. Large effort is also invested in the ability and the flexibility to model novel detection systems or systems still under design. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at http:/www-lphe.epfl.ch/GATE/. Two benchmarks developed for PET and SPECT to test the installation of GATE and to serve as a tutorial for the users are presented. Extensive validation of the GATE simulation platform has been started, comparing simulations and measurements on commercially available acquisition systems. References to those results are listed. The future prospects towards the gridification of GATE and its extension to other domains such as dosimetry are also discussed.

/pdf/gate-a-simulation-toolkit-for-pet-and-spect-i05cuwekfu.pdf

GATE : a simulation toolkit for PET and SPECT

Preface Abstract 1. Basis of ICRP Reference Values 2. Summary of Reference Values 3. Embryo and Fetus 4. Total Body 5. Respiratory System 6. Alimentary System 7. Circulatory and Lymphatic Systems 8. Urogenital System 9. Skeletal System 10. Integumentary System 11. Additional Organs and Tissues 12. Pregnant Woman: Anatomical and Physiological Changes 13. Elemental Composition of the Body Reference

Basic anatomical and physiological data for use in radiological protection : reference values

The objective of this study was to develop anatomically correct whole body human models of an adult male (34 years old), an adult female (26 years old) and two children (an 11-year-old girl and a six-year-old boy) for the optimized evaluation of electromagnetic exposure. These four models are referred to as the Virtual Family. They are based on high resolution magnetic resonance (MR) images of healthy volunteers. More than 80 different tissue types were distinguished during the segmentation. To improve the accuracy and the effectiveness of the segmentation, a novel semi-automated tool was used to analyze and segment the data. All tissues and organs were reconstructed as three-dimensional (3D) unstructured triangulated surface objects, yielding high precision images of individual features of the body. This greatly enhances the meshing flexibility and the accuracy with respect to thin tissue layers and small organs in comparison with the traditional voxel-based representation of anatomical models. Conformal computational techniques were also applied. The techniques and tools developed in this study can be used to more effectively develop future models and further improve the accuracy of the models for various applications. For research purposes, the four models are provided for free to the scientific community.

/pdf/the-virtual-family-development-of-surface-based-anatomical-47u5t3e6am.pdf

The Virtual Family—development of surface-based anatomical models of two adults and two children for dosimetric simulations

This report presents detailed information on age- and gender-related differences in the anatomical and physiological characteristics of reference individuals. These reference values provide needed input to prospective dosimetry calculations for radiation protection purposes for both workers and members of the general public. The purpose of this report is to consolidate and unify in one publication, important new information on reference anatomical and physiological values that has become available since Publication 23 was published by the ICRP in 1975. There are two aspects of this work. The first is to revise and extend the information in Publication 23 as appropriate. The second is to provide additional information on individual variation among grossly normal individuals resulting from differences in age, gender, race, or other factors. This publication collects, unifies, and expands the updated ICRP reference values for the purpose of providing a comprehensive and consistent set of age- and gender-specific reference values for anatomical and physiological features of the human body pertinent to radiation dosimetry. The reference values given in this report are based on: (a) anatomical and physiological information not published before by the ICRP; (b) recent ICRP publications containing reference value information; and (c) information in Publication 23 that is still considered valid and appropriate for radiation protection purposes. Moving from the past emphasis on ‘Reference Man’, the new report presents a series of reference values for both male and female subjects of six different ages: newborn, 1 year, 5 years, 10 years, 15 years, and adult. In selecting reference values, the Commission has used data on Western Europeans and North Americans because these populations have been well studied with respect to antomy, body composition, and physiology. When appropriate, comparisons are made between the chosen reference values and data from several Asian populations. The first section of the report provides summary tables of all the anatomical and physiological parameters given as reference values in this publication. These results give a comprehensive view of reference values for an individual as influenced by age and gender. The second section describes characteristics of dosimetric importance for the embryo and fetus. Information is provided on the development of the total body and the timing of appearance and development of the various organ systems. Reference values are provided on the mass of the total body and selected organs and tissues, as well as a number of physiological parameters. The third section deals with reference values of important anatomical and physiological characteristics of reference individuals from birth to adulthood. This section begins with details on the growth and composition of the total body in males and females. It then describes and quantifies anatomical and physiological characteristics of various organ systems and changes in these characteristics during growth, maturity, and pregnancy. Reference values are specified for characteristics of dosimetric importance. The final section gives a brief summary of the elemental composition of individuals. Focusing on the elements of dosimetric importance, information is presented on the body content of 13 elements: calcium, carbon, chloride, hydrogen, iodine, iron, magnesium, nitrogen, oxygen, potassium, sodium, sulphur, and phosphorus.

https://journals.sagepub.com/doi/pdf/10.1016/S0146-6453%2803%2900002-2

Basic anatomical and physiological data for use in radiological protection: reference values ICRP Publication 89: Approved by the Commission in September 2001

PREFACE MAIN POINTS EXECUTIVE SUMMARY 1. INTRODUCTION 2. Quantities used in radiation protection for external exposure 3. Determination of organ absorbed doses OF the ICRP/ICRU REFERENCE phantomS 4. Conversion coefficients for external exposure 5. Relationships between dose conversion coefficients For operational and protection quantities References Annex A - Effective dose conversion coefficients Annex B - Organ absorbed dose conversion coefficients for photons Annex C - Organ absorbed dose conversion coefficients for neutrons Annex D - Skeletal fluence-to-dose response functions - Photons Annex E - Skeletal fluence-to-dose response functions - Neutrons Annex F - Conversion coefficients for the eye lens Annex G - Special considerations for assessing the local skin equivalent dose Annex H - Effective dose for superior hemisphere semi isotropic irradiation for aircraft crew dosimetry Annex I - Methods used for evaluation of reference data

Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures

Voxel phantoms are human models based on computed tomographic or magnetic resonance images obtained from high-resolution scans of a single individual. They consist of a huge number of volume elements (voxels) and are at the moment the most precise representation of the human anatomy. The purpose of this paper is to introduce the GSF voxel phantoms, with emphasis on the new ones and highlight their characteristics and limitations. The GSF voxel family includes at the moment two paediatric and five adult phantoms of both sexes, different ages and stature and several others are under construction. Two phantoms made of physical calibration phantoms are also available to be used for validation purposes. The GSF voxel phantoms tend to cover persons of individual anatomy and were developed to be used for numerical dosimetry of radiation transport but other applications are also possible. Examples of applications in patient dosimetry in diagnostic radiology and in nuclear medicine as well as for whole-body irradiations from idealized external exposures are given and discussed.

https://iopscience.iop.org/article/10.1088/0031-9155/47/1/307/pdf

The GSF family of voxel phantoms.

New organ equivalent dose conversion coefficients are presented for whole body irradiation with monoenergetic photons of energies between 10 keV and 10 MeV for idealized geometries and seven adult male and female voxel models. The geometries are broad parallel photon beams in anterior–posterior, posterior–anterior, left- and right-lateral direction and a full 360° rotation around the body length axis. Dose differences between the different voxel models are below approximately 30% for some organs and geometries in the energy range between 60 and 200 keV, but they can be up to 100% or more in single cases, due to differences in stature and individual anatomical details. For low photon energies, the differences may amount to hundreds of per cent. Extensive comparisons of the dose conversion coefficients with respective values calculated using mathematical body models revealed various degrees of unrealistic positioning of single organs in the latter models. Examples are the kidneys, spleen and stomach that are located too superficially in the mathematical models. Over- or underestimations of several tens of per cent may, thus, occur for the mathematical models, compared to the voxel models considered. In contrast to previous assumptions, when the mathematical models have been used to establish reference organ dose conversion coefficients, it can be concluded that they do not properly represent a large population of individuals.

https://iopscience.iop.org/article/10.1088/0031-9155/47/14/301/pdf

Organ dose conversion coefficients for external photon irradiation of male and female voxel models

The purpose of this work is to examine the effects of patient size on radiation dose from CT scans. To perform these investigations, we used Monte Carlo simulation methods with detailed models of both patients and multidetector computed tomography (MDCT) scanners. A family of three-dimensional, voxelized patient models previously developed and validated by the GSF was implemented as input files using the Monte Carlo code MCNPX. These patient models represent a range of patient sizes and ages (8 weeks to 48 years) and have all radiosensitive organs previously identified and segmented, allowing the estimation of dose to any individual organ and calculation of patient effective dose. To estimate radiation dose, every voxel in each patient model was assigned both a specific organ index number and an elemental composition and mass density. Simulated CT scans of each voxelized patient model were performed using a previously developed MDCT source model that includes scanner specific spectra, including bowtie filter, scanner geometry and helical source path. The scan simulations in this work include a whole-body scan protocol and a thoracic CT scan protocol, each performed with fixed tube current. The whole-body scan simulation yielded a predictable decrease in effective dose as a function of increasing patient weight. Results from analysis of individual organs demonstrated similar trends, but with some individual variations. A comparison with a conventional dose estimation method using the ImPACT spreadsheet yielded an effective dose of 0.14 mSv mAs(-1) for the whole-body scan. This result is lower than the simulations on the voxelized model designated 'Irene' (0.15 mSv mAs(-1)) and higher than the models 'Donna' and 'Golem' (0.12 mSv mAs(-1)). For the thoracic scan protocol, the ImPACT spreadsheet estimates an effective dose of 0.037 mSv mAs(-1), which falls between the calculated values for Irene (0.042 mSv mAs(-1)) and Donna (0.031 mSv mAs(-1)) and is higher relative to Golem (0.025 mSv mAs(-1)). This work demonstrates the ability to estimate both individual organ and effective doses from any arbitrary CT scan protocol on individual patient-based models and to provide estimates of the effect of patient size on these dose metrics.

https://iopscience.iop.org/article/10.1088/0031-9155/52/9/017/pdf

Estimating radiation doses from multidetector CT using Monte Carlo simulations: effects of different size voxelized patient models on magnitudes of organ and effective dose

Purpose: A recent work has demonstrated the feasibility of estimating the dose to individual organs from multidetector CT exams using patient-specific, scanner-independent CTDIvol-to-organ-dose conversion coefficients. However, the previous study only investigated organ dose to a single patient model from a full-body helical CT scan. The purpose of this work was to extend the validity of this dose estimation technique to patients of any size undergoing a common clinical exam. This was done by determining the influence of patient size on organ dose conversion coefficients generated for typical abdominal CT exams.

Methods: Monte Carlo simulations of abdominal exams were performed using models of 64-slice MDCT scanners from each of the four major manufacturers to obtain dose to radiosensitive organs for eight patient models of varying size, age, and gender. The scanner-specific organ doses were normalized by corresponding CTDIvol values and averaged across scanners to obtain scanner-independent CTDIvol-to-organ-dose conversion coefficients for each patient model. In order to obtain a metric for patient size, the outer perimeter of each patient was measured at the central slice of the abdominal scan region. Then, the relationship between CTDIvol-to-organ-dose conversion coefficients and patient perimeter was investigated for organs that were directly irradiated by the abdominal scan. These included organs that were either completely (“fully irradiated”) or partly (“partially irradiated”) contained within the abdominal exam region. Finally, dose to organs that were not at all contained within the scan region (“nonirradiated”) were compared to the doses delivered to fully irradiated organs.

Results: CTDIvol-to-organ-dose conversion coefficients for fully irradiated abdominal organs had a strong exponential correlation with patient perimeter. Conversely, partially irradiated organs did not have a strong dependence on patient perimeter. In almost all cases, the doses delivered to nonirradiated organs were less than 5%, on average across patient models, of the mean dose of the fully irradiated organs.

Conclusions: This work demonstrates the feasibility of calculating patient-specific, scanner-independent CTDIvol-to-organ-dose conversion coefficients for fully irradiated organs in patients undergoing typical abdominal CT exams. A method to calculate patient-specific, scanner-specific, and exam-specific organ dose estimates that requires only knowledge of the CTDIvol for the scan protocol and the patient’s perimeter is thus possible. This method will have to be extended in future studies to include organs that are partially irradiated. Finally, it was shown that, in most cases, the doses to nonirradiated organs were small compared to the dose to fully irradiated organs.

/pdf/the-feasibility-of-patient-size-corrected-scanner-aynioo3u43.pdf

Maria Zankl

Papers

Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures

The GSF family of voxel phantoms.

Organ dose conversion coefficients for external photon irradiation of male and female voxel models

Estimating radiation doses from multidetector CT using Monte Carlo simulations: effects of different size voxelized patient models on magnitudes of organ and effective dose

The feasibility of patient size-corrected, scanner-independent organ dose estimates for abdominal CT exams.