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Funding Information: This work was supported by EFRE (K-Regio project FAENOMENAL, Grant No. EFRE 2016-4) and the Austrian Science Fund FWF (Project No. P31149, I4130). This work was also supported by Fundação para a Ciência e a Tecnologia (FCT-MCTES), Radiation Biology and Biophysics Doctoral Training Programme (RaBBiT, PD/00193/2012); Applied Molecular Biosciences Unit - UCIBIO (UIDB/04378/2020) and CEFITEC Unit (UIDB/00068/2020); and scholarship Grant No. PD/BD/114447/2016 to J.A., F. Zappa acknowledges support from the Brazilian agency CNPq. K.v.H. kindly acknowledges the award of a LFUI guest professorship. The demand for nanoscale materials of ultra-high purity and narrow size distribution is addressed. Clusters of Au, C60, H2O, and serine are produced inside helium nanodroplets using a combination of ionization, mass filtering, collisions with atomic or molecular vapor, and electrostatic extraction, in a specific and novel sequence. The helium droplets are produced in an expansion of cold helium gas through a nozzle into vacuum. The droplets are ionized by electron bombardment and subjected to a mass filter. The ionic and mass-selected helium droplets are then guided through a vacuum chamber filled with atomic or molecular vapor where they collide and "pick up" the vapor. The dopants then agglomerate inside the helium droplets around charge centers to singly charged clusters. Evaporation of the helium droplets is induced by collisions in a helium-filled radio frequency (RF)-hexapole, which liberates the cluster ions from the host droplets. The clusters are analyzed with a time-of-flight mass spectrometer. It is demonstrated that using this sequence, the size distribution of the dopant cluster ions is distinctly narrower compared to ionization after pickup. Likewise, the ion cluster beam is more intense. The mass spectra show, as well, that ion clusters of the dopants can be produced with only few helium atoms attached, which will be important for messenger spectroscopy. All these findings are important for the scientific research of clusters and nanoscale materials in general. publishersversion published

A goal of whole body counting (WBC) is the estimation of the total body burden of radionuclides disregarding the actual position within the body. To achieve the goal, the detectors need to be placed in regions where the photon flux is as independent as possible from the distribution of the source. At the same time, the detectors need high photon fluxes in order to achieve better efficiency and lower minimum detectable activities. This work presents a method able to define the layout of new WBC systems and to study the behaviour of existing ones using both detection efficiency and its dependence on the position of the source within the body of computational phantoms.

When measuring the internally deposited activity in the bone of a subject, the placement of the detector is critical. This study reports the simulated counting efficiencies for three counting geometries, the skull, knee and shin, using 13 different voxel phantoms. It shows that the range of counting efficiencies for a given geometry is large for the studied phantoms, especially at low energies. Skull counting offers higher efficiency for low energies such as the 17 keV compared to knee counting or shin counting, but this advantage disappears when the energy is higher such as at 185 keV. This work also shows that the calibration phantom may greatly impact the accuracy of the activity estimate in bone counting, with uncertainties increasing greatly as the photon energy is reduced. Estimating the activity of a radionuclide in bone from direct counting has large uncertainties, and the dose calculated from a skeleton measurement would need careful analysis and, if possible, supporting data from other bioassay measurements.

The nuclear workers of the Mayak Production Association had regular check-ups including medical diagnostic X-ray examinations since start of the production lines in 1948. Doses from diagnostic examinations need to be considered in reconstruction of occupational doses of the workers with electron paramagnetic resonance (EPR) of tooth enamel. The numbers and types of examinations of an individual worker can be assessed from the Mayak PA archives but no information was available on doses delivered to teeth by a single specific examination. Of the twenty one applied examination procedures only three affected the teeth, these being X-ray examinations of teeth, skull and cervical spine. For these three kinds of examinations operational procedures and operating modes of X-ray units were compiled from the archive and photon spectra were obtained from a catalog of spectral data for diagnostic X-rays. Entrance doses in air kerma were calculated using the fluence of photon spectra and absorbed dose in tooth enamel for various tooth positions and exposure geometry was then calculated using dose conversion coefficients obtained from Monte Carlo simulations. Doses were calculated for examinations in 1948–2000. Except for examination of the skull, absorbed doses in enamel of incisors were found to be about twice as large as in enamel of molars. In the period before 1970 the largest mean absorbed doses in tooth enamel were due to X-ray examination of teeth, with 64 mGy and 34 mGy calculated for incisors and molars, respectively. In the same period the lowest mean doses were due to X-ray examination of the skull, with 11 mGy and 12 mGy calculated for incisors and molars, respectively. In the period from 1970 to 2000, largest mean doses in enamel were due to X-ray examination of cervical spine, with 23 mGy and 12 mGy calculated for incisors and molars, respectively.

The estimation of the fluence-to-effective dose conversion coefficients used especially for aircrew dosimetry is an important issue, since the geometrical conditions of aircrew exposure are considered not to be represented by the standard irradiation geometries such as the anterior-to-posterior (AP) and isotropic (ISO) geometries. We therefore calculated the dose conversion coefficients for neutrons and protons based on the ICRP 2007 Recommendations for three additional irradiation geometries: semi-isotropic irradiation from the upper hemisphere, and geometries closely representing the geometrical situations of aircrew exposure for two different flight conditions. The calculation was performed by the PHITS code coupled with the ICRP/ICRU adult reference computational phantoms. It was found from the calculation that (1) the conversion coefficients for the irradiation geometries closely representing the geometrical situations of aircrew exposure agree better with the corresponding data for the isotropic irradiation than those for the semi-isotropic irradiation; (2) the error associated with the assumption of the isotropic irradiation in the aircrew dosimetry is less than only 1% for conventional flight conditions. These findings indicate the adequacy of the use of dose conversion coefficients for the isotropic irradiation geometry in aircrew dosimetry.

Recent epidemiological studies suggest a rather low dose threshold (below 0.5 Gy) for the induction of a cataract of the eye lens. Some other studies even assume that there is no threshold at all. Therefore, protection measures have to be optimized and current dose limits for the eye lens may be reduced in the future. Two questions arise from this situation: first, which dose quantity is related to the risk of developing a cataract, and second, which personal dose equivalent quantity is appropriate for monitoring this dose quantity. While the dose equivalent quantity H(p)(0.07) has often been seen as being sufficiently accurate for monitoring the dose to the lens of the eye, this would be questionable in the case when the dose limits were reduced and, thus, it may be necessary to generally use the dose equivalent quantity H(p)(3) for this purpose. The basis for a decision, however, must be the knowledge of accurate conversion coefficients from fluence to equivalent dose to the lens. This is especially important for low-penetrating radiation, for example, electrons. Formerly published values of conversion coefficients are based on quite simple models of the eye. In this paper, quite a sophisticated model of the eye including the inner structure of the lens was used for the calculations and precise conversion coefficients for electrons with energies between 0.2 MeV and 12 MeV, and for angles of radiation incidence between 0 degrees and 45 degrees are presented. Compared to the values adopted in 1996 by the International Commission on Radiological Protection (ICRP), the new values are up to 1000 times smaller for electron energies below 1 MeV, nearly equal at 1 MeV and above 4 MeV, and by a factor of 1.5 larger at about 1.5 MeV electron energy.

The fluence to organ-dose and effective-dose conversion coefficients for neutrons and protons with energies up to 100 GeV was calculated using the PHITS code coupled to male and female adult reference computational phantoms, which are to be released as a common ICRP/ICRU publication. For the calculation, the radiation and tissue weighting factors, w(R) and w(T), respectively, as revised in ICRP Publication 103 were employed. The conversion coefficients for effective dose equivalents derived using the radiation quality factors of both Q(L) and Q(y) relationships were also estimated, utilizing the functions for calculating the probability densities of the absorbed dose in terms of LET (L) and lineal energy (y), respectively, implemented in PHITS. By comparing these data with the corresponding data for the effective dose, we found that the numerical compatibilities of the revised w(R) with the Q(L) and Q(y) relationships are fairly established. The calculated data of these dose conversion coefficients are indispensable for constructing the radiation protection systems based on the new recommendations given in ICRP103 for aircrews and astronauts, as well as for workers in accelerators and nuclear facilities.

This communication briefly summarises the results obtained from the 'International comparison on MC modeling for in vivo measurement of Americium in a knee phantom' organised within the EU Coordination Action CONRAD (Coordinated Network for Radiation Dosimetry) as a joint initiative of EURADOS working groups 6 (computational dosimetry) and 7 (internal dosimetry). Monte Carlo simulations using the knee voxel phantom proved to be a viable approach to provide the calibration factor needed for in vivo measurements.

Only a few reports of congenital meatal atresia and microtia have been published. Dominant as well as recessive inheritance has been suggested. We report a family with five affected members in two generations. An irregularly dominant transmission seems to be the most likely explanation.

Human exposure to space radiation implies two kinds of risk, both stochastic and deterministic. Shielding optimisation therefore represents a crucial goal for long-term missions, especially in deep space. In this context, the use of radiation transport codes coupled with anthropomorphic phantoms allows to simulate typical radiation exposures for astronauts behind different shielding, and to calculate doses to different organs. In this work, the FLUKA Monte Carlo code and two phantoms, a mathematical model and a voxel model, were used, taking the Galactic Cosmic Rays (GCR) spectra from the model of Badhwar and O'Neill. The time integral spectral proton fluence of the August 1972 Solar Particle Event (SPE) was represented by an exponential function. For each aluminium shield thickness, besides total doses the contributions from primary and secondary particles for different organs and tissues were calculated separately. More specifically, organ-averaged absorbed doses, dose equivalents and a form of 'biological dose', defined on the basis of initial (clustered) DNA damage, were calculated. As expected, the SPE doses dramatically decreased with increasing shielding, and doses in internal organs were lower than in skin. The contribution of secondary particles to SPE doses was almost negligible; however it is of note that, at high shielding (10 g cm(-2)), most of the secondaries are neutrons. GCR organ doses remained roughly constant with increasing Al shielding. In contrast to SPE results, for the case of cosmic rays, secondary particles accounted for a significant fraction of the total dose.

Astronauts' exposure to the various components of the space radiation field is of great concern for long-term missions, especially for those in deep space such as a possible travel to Mars. Simulations based on radiation transport/interaction codes coupled with anthropomorphic model phantoms can be of great help in view of risk evaluation and shielding optimisation, which is therefore a crucial issue. The FLUKA Monte Carlo code can be coupled with two types of anthropomorphic phantom (a mathematical model and a ''voxel'' model) to calculate organ-averaged absorbed dose, dose equivalent and ''biological'' dose under different shielding conditions. Herein the ''biological dose'' is represented by the average number of ''Complex Lesions'' (CLs) per cell in a given organ. CLs are clustered DNA breaks previously calculated by means of event-by-event track structure simulations at the nm level and integrated on-line into FLUKA, which adopts a condensed-history approach; such lesions have been shown to play a fundamental role in chromosome aberration induction, which in turn can be correlated with carcinogenesis. Examples of calculation results will be presented relative to Galactic Cosmic Rays, as well as to the August 1972 Solar Particle Event. The contributions from primary ions and secondary particles will be shown separately, thus allowing quantification of the role played by nuclear reactions occurring in the shield and in the human body itself. As expected, the SPE doses decrease dramatically with increasing the Al shielding thickness; nuclear reaction products, essentially due to target fragmentation, are of minor importance. A 10 g/cm2 Al shelter resulted to be sufficient to respect the 30-day limits for deterministic effects recommended for missions in Low Earth Orbit. In contrast with the results obtained for SPEs, the calculated GCR doses are almost independent of the Al shield thickness, and the GCR doses to internal organs are not significantly lower than the skin doses. Furthermore, nuclear interactions play a much larger role for GCR than for SPE doses.

Astronauts’ exposure to space radiation is of high concern for long-term missions, especially for those in deep space such as possible travels to Mars. In these cases shielding optimization is a crucial issue, and simulations based on radiation transport codes and anthropomorphic model phantoms can be of great help. In this work the FLUKA Monte Carlo code was coupled with two anthropomorphic phantoms (a mathematical model and a “voxel” model) to calculate organ-averaged dose, dose equivalent and “biological dose” in the various tissues and organs following exposure to the August 1972 Solar Particle Event and to Galactic Cosmic Rays under different shielding conditions. The “biological dose” was characterized by the average number of induced “Complex Lesions” (CLs) per cell in a given organ or tissue, where CLs are clustered DNA breaks which can play an important role in chromosome aberration induction. Separate calculation of the contributions from secondary hadrons – in particular neutrons – with respect to primary particles allowed us to quantify the role played by nuclear interactions occurring in the shield and in the human body. Specifically for GCR, the contributions from the different components of the incident primary spectra were calculated separately as well. As expected, the SPE doses showed a dramatic decrease with increasing Al shielding. Furthermore, for SPEs internal organs received much lower doses with respect to skin, and nuclear interactions were found to be of minor importance. A 10 g/cm 2 Al storm shelter turned out to be sufficient to respect the NCRP limits for 30-days LEO missions in case of a SPE similar to the August 1972 event. In contrast with SPEs, GCR absorbed doses remained roughly constant with increasing Al shielding. The organ-averaged dose equivalent and biological dose showed a (slight) decrease starting from a shield thickness of 2 g/cm 2 , probably due the lower LET of projectile fragments.

Distributions of absorbed dose and DNA clustered damage yields in various organs and tissues following the October 1989 solar particle event (SPE) were calculated by coupling the FLUKA Monte Carlo transport code with two anthropomorphic phantoms (a mathematical model and a voxel model), with the main aim of quantifying the role of the shielding features in modulating organ doses. The phantoms, which were assumed to be in deep space, were inserted into a shielding box of variable thickness and material and were irradiated with the proton spectra of the October 1989 event. Average numbers of DNA lesions per cell in different organs were calculated by adopting a technique already tested in previous works, consisting of integrating into "condensed-history" Monte Carlo transport codes--such as FLUKA--yields of radiobiological damage, either calculated with "event-by-event" track structure simulations, or taken from experimental works available in the literature. More specifically, the yields of "Complex Lesions" (or "CL", defined and calculated as a clustered DNA damage in a previous work) per unit dose and DNA mass (CL Gy-1 Da-1) due to the various beam components, including those derived from nuclear interactions with the shielding and the human body, were integrated in FLUKA. This provided spatial distributions of CL/cell yields in different organs, as well as distributions of absorbed doses. The contributions of primary protons and secondary hadrons were calculated separately, and the simulations were repeated for values of Al shielding thickness ranging between 1 and 20 g/cm2. Slight differences were found between the two phantom types. Skin and eye lenses were found to receive larger doses with respect to internal organs; however, shielding was more effective for skin and lenses. Secondary particles arising from nuclear interactions were found to have a minor role, although their relative contribution was found to be larger for the Complex Lesions than for the absorbed dose, due to their higher LET and thus higher biological effectiveness. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

This paper describes the construction of an adult male voxel model named "Golem" intended to be used for Monte Carlo simulations to calculate dosimetric quantities for radiation protection considerations. The model was segmented from whole-body medical image data of a living person who was 38 years old and had external dimensions close to those of the ICRP Reference Man. The segmentation process using dedicated image processing hard- and software is described and the resulting model is characterised with respect to weight and height of the total body, organ and tissue masses and red bone marrow distribution. A comparison with the respective data for ICRP Reference Man and three further voxel models is presented. Golem was found to agree reasonably well with Reference Man, so that he can be used for the assessment of "representative" body doses.

Computational human phantoms have been widely used to estimate organ doses and other dosimetric quantities related to the human body where direct measurements are difficult to perform. In recent years, voxel phantoms (voxel = volume element) based on computed tomographic (CT) data of real persons have been constructed which provide a realistic description of the human anatomy. A CT phantom of a Japanese male adult with an average body size was developed as the first Asian voxel phantom. The segmented phantom consists of more than 100 regions enabling the calculation of doses for various parts of the body. The bone marrow distribution was precisely modelled according to the CT values. The EGS4 Monte Carlo transport code was combined with the phantom to calculate organ doses for external exposure due to photons and electrons up to 1 TeV. The calculated organ doses were compared with respective data using MIRD-type mathematical phantoms. In some cases, significant discrepancies in doses were observed, demonstrating the necessity of sophisticated models for accurate dose calculations.

This work presents conversion coefficients per air kerma free-in-air for the personal dose equivalent, Hp(10), calculated according to its definition by the International Commission on Radiation Units and Measurements as a quantity in the human body. The values were calculated using Monte Carlo methods for various dosimeter positions in the trunk of a voxel model of an adult male, and they are given for various directions of incidence of broad parallel photon beams with energies between 10 keV and 10 MeV. It is shown that the numerical values of the personal dose equivalent depend on the exact position of the dosimeter, with maximum differences between 12% and 80%, depending on the beam geometry. It is further shown that the recommended calibration quantity Hp slab(10), which has been used in ICRP Publication 74 and ICRU Report 57 in the absence of data in the human body to approximate personal dose equivalent, does represent the latter quantity in a sensible way for some, but not all, beam geometries. Comparison of the values for the personal dose equivalent of this work with effective dose revealed that Hp(10) is a conservative estimate or close approximation of E for most irradiation geometries and photon energies.

X ray projection data (see Part I) and GSF phantoms ADAM and EVA were used as input for the GSF Monte Carlo transport code to calculate hitherto unavailable dose conversion coefficients (DCCs) for common projections in arteriography of the lower limbs. These DCCs served to estimate organ equivalent doses and effective dose in a study of 455 patients. The effective dose caused by percutaneous needle puncture arteriography of one leg was on average I mSv, by Seldinger catherisation for arteriography of both legs 4 mSv, and by intravenous digital subtraction arteriography (DSA) 5 mSv, For needle puncture and Seldinger arteriography the effective dose attributable to fluoroscopy was about 50% for male and 60% for female patients. The contribution of DSA was between 15 and 35%, that of cut films between 17 to 28%, depending on gender and procedure. The effective dose in intravenous arteriography was mainly due to DSA (91-93%).

The radiation risk from ionising radiation in different organs and tissues of the human body may he quantified using equivalent dose. As organ doses usually cannot be measured directly in patients, it is necessary to establish suitable conversion coefficients between organ doses and measurable dose quantities. For this purpose, computer codes, often based on Monte Carlo techniques, simulating the radiation transport in material are commonly used together with computational models of the human body. Most computational body models in use are mathematical models, in which mathematical expressions representing simple geometrical bodies are used to describe idealised arrangements of body organs. Additionally, tomographic models were developed in recently ears which use computed tomographic data of real persons to provide three-dimensional representations of the body. Using these computational models, numerous studies concerning organ and tissue doses from diagnostic radiology were performed. Organ dose conversion coefficients from various types examinations are available in the literature. In some of these studies, the influence of single technical exposure conditions (e.g tube v oltage. filtration, field size and location and focus-to-skin distance) on organ and tissue doses was examined. Additionally, the tomographic models enable the assessment of the influence of moderate vanations of the patient size on organ doses. They, therefore, improve the applicability of data for deriving doses to individual patients.

Specific Absorbed Fractions (SAF), which specify the fraction of the energy emitted by radioactivity in a given organ which is absorbed in the source organ itself and in other organs, are a prerequisite for the calculation of dose from internally deposited radioactive emitters. Extensive calculations of SAFs for monoenergetic photon sources were performed using Monte Carlo photon transport codes together with voxel anthropomorphic models based on computed tomographic data of real persons of various ages. These models offer greater realism with respect to organ topology than the mathematical phantoms commonly used up to now. Selected results are compared with those from the literature derived using the Oak Ridge mathematical phantoms. Some general results of other authors were confirmed by the present results, whereas for some source-target organ combinations discrepancies of up to one or two orders of magnitude were found, depending on photon energy and the location and masses of the organs involved. Agreement for the different model types of the organ absorbed doses per administered activity for radionuclides was found to be much better than that of the SAF values.

Effective dose, an indicator of the stochastic effect of radiation, has been widely used in dose evaluation in the environment. Though conversion factors have been used to obtain E from the air kerma or air absorbed dose, the variation of the conversion factors due to the change of exposure conditions has not been sufficiently investigated. This report documents an investigation of the variation of the effective dose per air kerma for environmental gamma rays depending on the exposure conditions using anthropomorphic phantoms and Monte Carlo calculations, taking into account the precise angular and energy distributions of the environmental gamma rays incident on the human body. As causes of the variation, posture of human bodies, biases of environmental source distributions, and body size were considered. The variation of effective dose in a prone position compared with that in a standing position was found to be within 30%. The bias of environmental sources causes the effective dose per air kerma to vary by 20% at maximum, but in some cases for low-energy gamma rays the variation was found to be up to 40% due to the change in the energy spectrum. The effective dose for a new born infant was estimated to be higher than that for an adult by a maximum of 80-90% for low-energy gamma rays from anthropogenic sources because of a lower shielding effect of the smaller body. The variation of the effective dose equivalent shows a similar tendency to the effective dose. Consequently, this study made it possible to estimate the uncertainties of effective dose and effective dose equivalent evaluated from air kerma or absorbed dose in air using the standard available conversion factors.

To improve the final concept for a high-level radioactive waste (HAW) disposal in geological salt formations, plans have been developed in Germany for a full scale testing of an underground repository. As a main part of this so-called HAW project, the testwise emplacement of 30 vitrified highly radioactive canisters was planned in test galleries at the 800 m level of the Asse salt mine near Braunschweig, Germany. An attempt should be made to correlate the changes induced to the salt with the amount of energy deposited there. This paper provides absorbed dose rate and photon fluence rate distributions in rock salt around these highly radioactive canisters, containing the radionuclides 137Cs and 90Sr, and around a single canister containing radioactive material of a lower activity level (INHAW experiment). The data given were calculated using a Monte Carlo method simulating photon transport in complex geometries of differently composed materials. The aim of these calculations was to enable determination of the dose absorbed in any arbitrary sample of salt 1 m around the canisters to be further examined in the future with sufficient reliability for safety considerations. The geometry of the test arrangement, the materials involved, the calculational method and selected results are shown.

PURPOSE Estimation of radiogenic risks for patient and radiologist in chemoembolisation of hepatocellular carcinoma (HCC) and laser angioplasty of the pelvic arteries. METHODS In 5 chemoembolisations of HCC (4 males, one female) and 6 laser angioplasties of the pelvic arteries (5 males, one female) the surface doses received by patient and operator were measured using thermoluminescent dosimeters in standardised positions. The organ doses of the patient were derived by conversion factors employed on the measured surface doses. Effective dose was determined according to the recommendations of ICRP 60. RESULTS The risk of lethal malignant disease and genetic disorder derived from the doses in the patient was found to be of the magnitude of 10(-4)-10(-5). The thresholds for transient erythema of the skin and depression of hematopoiesis can be reached after high expositions. A theoretical maximum of 700 laser angioplasties of the pelvic arteries allowable in one year was calculated based on the dose to the operator's left hand. For chemoembolisation of HCC, the dose to the left eye lens would reach the yearly maximum after approximately 1000 procedures. Remarkable risks for malignant disease of skin and thyroid as well as detectable opacities of the eye lens can occur after frequent interventions for many years. CONCLUSIONS Because of the lower life expectancy the patient's risk for stochastic effect can be seen as minimal. No clinically relevant deterministic effects will occur. In the case of frequent interventions, the dose absorbed by the radiologist is likely to exceed the prescribed dose limit and to cause remarkable risk for stochastic and non-stochastic effects after many years.

In the 1990 Recommendations of the International Commission on Radiological Protection, the risk-weighted quantity "effective dose equivalent" was replaced by a similar quantity, "effective dose." Among other alterations, the selection of the organs and tissues contributing to the risk-weighted quantity and their respective weighting factors were changed, including a modified definition of the so-called "remainder." Close consideration of this latter definition shows that it causes certain ambiguities and unexpected effects which are dealt with in the following. For several geometries of external photon irradiation, the numerical differences of two possible methods of evaluating the remainder dose from the doses to ten single organs, namely as arithmetic mean or as mass weighted average, are assessed. It is shown that deviation from these averaging procedures, as prescribed for those cases where a remainder organ receives a higher dose than an organ with a specified weighting factor, causes discontinuities in the energy dependence of the remainder dose and, consequently, also non-additivity of this quantity. These problems are discussed, and it is shown that, although the numerical consequences for the calculation of the effective dose are small, this unsatisfactory situation needs clarification. One approach might be to abolish some of the ICRP guidance relating to the appropriate tissue weighting factors for the remainder tissues and organs and to make other guidance more precise.

This paper presents effective and organ dose conversion coefficients for members of the public due to environmental external exposures, calculated using the ICRP adult male and female reference computational phantoms as well as voxel phantoms of a baby, two children and four adult individual phantoms--one male and three female, one of them pregnant. Dose conversion coefficients are given for source geometries representing environmental radiation exposures, i.e. whole body irradiations from a volume source in air, representing a radioactive cloud, a plane source in the ground at a depth of 0.5 g cm⁻², representing ground contamination by radioactive fall-out, and uniformly distributed natural sources in the ground. The organ dose conversion coefficients were calculated employing the Monte Carlo code EGSnrc simulating the photon transport in the voxel phantoms, and are given as effective and equivalent doses normalized to air kerma free-in-air at height 1 m above the ground in Sv Gy(-1). The findings showed that, in general, the smaller the body mass of the phantom, the higher the dose. The difference in effective dose between an adult and an infant is 80-90% at 50 keV and less than 40% above 100 keV. Furthermore, dose equivalent rates for photon exposures of several radionuclides for the above environmental exposures were calculated with the most recent nuclear decay data. Data are shown for effective dose, thyroid, colon and red bone marrow. The results are expected to facilitate regulation of exposure to radiation, relating activities of radionuclides distributed in air and ground to dose of the public due to external radiation as well as the investigation of the radiological effects of major radiation accidents such as the recent one in Fukushima and the decision making of several committees.

To estimate the risk resulting from exposures to ionizing radiation, the organ and tissue doses should be assessed. A convenient method is the calculation of these doses using representations of the human body, called models or phantoms, together with computer codes simulating the transport of radiation in the body. Most commonly used are mathematical phantoms whose external and internal volumes are defined by simple geometric bodies. More recently, phantoms constructed from computed tomographic data of real persons were introduced as an improvement. These phantoms present advantages concerning the location and shape of the organs, in particular the hard bone and bone marrow, whose distribution can be assessed with high resolution. So far, three of these phantoms were constructed at the GSF, a fourth is under process. The construction technique is described, and some calculational results of organ doses due to external photon irradiation are presented.

Recent epidemiological studies suggest a rather low dose threshold (below 0.5 Gy) for the induction of a cataract of the eye lens. Some other studies even assume that there is no threshold at all. Therefore, protection measures have to be optimized and current dose limits for the eye lens may be reduced in the future. Two questions arise from this situation: first, which dose quantity is related to the risk of developing a cataract, and second, which personal dose equivalent quantity is appropriate for monitoring this dose quantity. While the dose equivalent quantity H(p)(0.07) has often been seen as being sufficiently accurate for monitoring the dose to the lens of the eye, this would be questionable in the case when the dose limits were reduced and, thus, it may be necessary to generally use the dose equivalent quantity H(p)(3) for this purpose. The basis for a decision, however, must be the knowledge of accurate conversion coefficients from fluence to equivalent dose to the lens. This is especially important for low-penetrating radiation, for example, electrons. Formerly published values of conversion coefficients are based on quite simple models of the eye. In this paper, quite a sophisticated model of the eye including the inner structure of the lens was used for the calculations and precise conversion coefficients for electrons with energies between 0.2 MeV and 12 MeV, and for angles of radiation incidence between 0 degrees and 45 degrees are presented. Compared to the values adopted in 1996 by the International Commission on Radiological Protection (ICRP), the new values are up to 1000 times smaller for electron energies below 1 MeV, nearly equal at 1 MeV and above 4 MeV, and by a factor of 1.5 larger at about 1.5 MeV electron energy.

The current dose coefficients for internal dose assessment of occupationally exposed persons and the general public were derived using the methodology of the International Commission on Radiological Protection (ICRP), which is similar to the Medical Internal Radiation Dose (MIRD)-type methodology. One component of this methodology is the mathematical representation of the human body (so-called MIRD-type phantoms) developed at the Oak Ridge National Laboratory for calculations of photon specific absorbed fractions (SAFs). Concerning the beta emissions, it is assumed in general that they irradiate only the organ where the radionuclide resides, whereas for walled organs, a fixed fraction of the emitted energy is absorbed within the wall. For the active marrow and bone surface targets, absorbed fractions were explicitly provided in ICRP Publication 30. The ICRP Publications 66 and 100 contain further detailed energy-dependent absorbed fraction data for the airways and the segments of the alimentary tract. In the present work, the voxel phantoms representing the reference male and female adults, recently developed at the Helmholtz Zentrum Munchen-German Research Center for Environmental Health (HMGU) in collaboration with the Task Group DOCAL of ICRP Committee 2, were used for the Monte Carlo computation of photon as well as electron SAFs. These voxel phantoms, being constructed from computed tomography (CT) scans of individuals, are more realistic in shape and location of organs in the body than the mathematical phantoms; therefore, they provide photon SAFs that are more precise than those stemming from mathematical phantoms. In addition, electron SAFs for solid and walled organs as well as tissues in the alimentary tract, the respiratory tract, and the skeleton were calculated with Monte Carlo methods using these phantoms to complement the data of ICRP Publications 66 and 100 that are confined to self-irradiation. The SAFs derived for photons and electrons are then used to calculate the dose coefficients of the beta emitters 141Ce, 144Ce, 95Zr, and 90Sr. It is found that the differences of the dose coefficients due to the revised SAFs are much larger for injection and ingestion than for inhalation. The equivalent doses for colon and ingestion with the new voxel-based SAFs are significantly smaller than the values with the MIRD-type photon SAFs and simplifying assumptions for electrons. For lungs and inhalation, no significant difference was observed for the equivalent doses, whereas for injection and ingestion, an increase of the new values is observed.

The emission of radiation from a contaminated body region is connected with the dose received by radiosensitive tissue through the specific absorbed fractions (SAFs) of emitted energy, which is therefore an essential quantity for internal dose assessment. A set of SAFs were calculated using the new adult reference computational phantoms, released by the International Commission on Radiological Protection (ICRP) together with the International Commission on Radiation Units and Measurements (ICRU). Part of these results has been recently published in ICRP Publication 110 (2009 Adult reference computational phantoms (Oxford: Elsevier)). In this paper, we mainly discuss the results and also present them in numeric form. The emission of monoenergetic photons and electrons with energies ranging from 10 keV to 10 MeV was simulated for three source organs: lungs, thyroid and liver. SAFs were calculated for four target regions in the body: lungs, colon wall, breasts and stomach wall. For quality assurance purposes, the simulations were performed simultaneously at the Helmholtz Zentrum München (HMGU, Germany) and at the Institute for Radiological Protection and Nuclear Safety (IRSN, France), using the Monte Carlo transport codes EGSnrc and MCNPX, respectively. The comparison of results shows overall agreement for photons and high-energy electrons with differences lower than 8%. Nevertheless, significant differences were found for electrons at lower energy for distant source/target organ pairs. Finally, the results for photons were compared to the SAF values derived using mathematical phantoms. Significant variations that can amount to 200% were found. The main reason for these differences is the change of geometry in the more realistic voxel body models. For electrons, no SAFs have been computed with the mathematical phantoms; instead, approximate formulae have been used by both the Medical Internal Radiation Dose committee (MIRD) and the ICRP due to the limitations imposed by the computing power available at this time. These approximations are mainly based on the assumption that electrons are absorbed locally in the source organ itself. When electron SAFs are calculated explicitly, discrepancies with this simplifying assumption are notable, especially at high energies and for neighboring organs where the differences can reach the same order of magnitude as for photon SAFs. © 2010 Institute of Physics and Engineering in Medicine.

Zusammenfassung In einem Alderson-Rando-Rumpfphantom wurden bei einer Ganzkorpertomographie (125 kV, 2.2 mm Al + 0.4 mm Cu, 122 Schichten) und bei 60 Co-Ganzkorperbestrahlungen (ap und pa) Gewebedosismessungen mit TLD an 28 Targetpositionen ausgefuhrt. Aus den CT-Daten wurde auserdem ein dreidimensionales Voxel-Phantom konstruiert, das aus 8 verschiedenen Medien bestand und Monte-Carlo-Simulationen der gleichen Ganzkorpertomographie und Ganzkorperbestrahlungen erlaubte. Der resultierende Unterschied zwischen gemessenen und berechneten Gewebedosen an den einzelnen Targetpositionen variierte zwischen - 15 % und + 15 %; sein mittlerer Betrag war stets kleiner als 5 %. Diese Untersuchung erbringt somit eine direkte und detaillierte experimentelle Prufung und Bestatigung von Dosisberechnungen mithilfe dreidimensionaler Voxeiphantome.

Zusammenfassung Organdosisberechnungen nach der Monte-Carlo-Methode erfordern fur jeden Punkt des Korpers die Festlegung der Zugehorigkeit zu einem bestimmten Gewebe oder Organ. In mathematischen Phantomen werden diese Organe durch einfache geometrische Formen wie z. B. Ellipsoide dargeslellt, in tomographischen Phantomen („Voxel-Phantomen“) werden Form und Lage der Organe aus CT-Schnittserien realer Patienten abgeleitet. Als Beispiel wurden die Knochenmarksdosen bei Ganzkorperbestrahlung eines 7-jahrigen Kindes mit Co-60 zur Leukamietherapie berechnet; in den verschiedenen Bereichen des Skeletts ergaben sich Werte zwischen 8.9 und 13.5 Gy (bei einer angestrebten Dosis von 12 Gy).

There is a large number of optimization strategies for optimal relation between information and exposure in mammographic imaging procedures. This is especially due to the specific situations in screening programs. However, the variety of possibilities like breast CT, tomosynthesis absorption with photon counting or with energy integrating detectors and phase contrast mammography results in very difficult comparisons about pros and cons of different techniques. Simulation methods based on Monte-Carlo methods would be a useful tool for first approaches. However, such a simulateion approach requires suitable and useful phantoms of the female breast in typical imaging conditions. Voxel phantoms of real breasts would be an optimal solution. Mammographic specimen of female breasts from corps have been compressed and than fixated while being compressed as in a general mammographic application. Such kinds of specimen have been scanned using a flat panel imager system a holding unit and a rotation table. By that CT images could be gained with relatively low radiation qualities. These data sets have been transformed by segmentation into high resolution voxel models. We performed Monte-Carlo simulations of using such phantoms for simulating absorption based imaging procedures including monoenergetic and standard spectra images using EGSnrc and Geant4 codes to proof the feasibility of such phantoms and simulations in order to obtain a tool for radiation protection optimization.

Automatic tube current modulation is meanwhile a standard procedure in modern CT devices to save radiation dose. The implementation of this method into Monte Carlo organ-dose calculations is described. A comparison of conversion coefficients obtained with and without tube current modulation is performed. A standard reliable procedure to compute conversion coefficients for any CT examination is to combine the pre-computed coefficients obtained in axial scans appropriately. The applicability of this procedure was validated for the case with tube current modulation, too.

Radiation dose estimates are needed for assessment of the risk to patients associated with the use of radiopharmaceuticals both for comparison with the possible benefit of an investigation and to help giving adequate information to the patient. With respect to the physical aspects, one of the most crucial requirements is to establish values of socalled Specific Absorbed Fractions (SAF) which specify the fraction of penetrating energy emitted by radioactivity in a given organ which is absorbed in the source organ itself and in other organs. Until recently, photon SAFs were calculated on the basis of MIRD-type mathematical anthropomorphic phantoms and a whole range of data exists covering all ages. For electrons, the radiation was assumed to be absorbed entirely in the source region, except when the source was part of the skeleton or when the source is in the contents of a walled organ. For this work, photon SAFs and electron SAFs were derived with the Monte Carlo code EGSnrc for the new reference male and female voxel-based phantoms adopted by the ICRP. The present results of electron SAFs show that the previously applied assumption of electrons being fully absorbed in the source organ itself presents an over-simplification at higher energies. For organs in close vicinity, such as liver and stomach wall, high-energetic electrons escaping from the source organ may result in cross-fire SAF values that can reach the same order of magnitude as those from photons. Examples of organ absorbed doses per nuclear transformation will be given for some radiopharmaceuticals. The impact of the new electron SAFs used for the calculation of the absorbed doses instead of the previously used assumption, will be discussed.

Introduction: Connecting the emission of radiation from a contaminated body region with the dose received by a radio-sensitive tissue, the specific absorbed fraction (SAF) of energy is an essential element of internal dose assessment. Here is reported a set of specific absorbed fractions calculated using the male and female reference computational phantoms recently published by the International Commission on Radiological Protection (ICRP). This work was performed simultaneously at the Helmholtz Zentrum Munchen (HMGU, Germany) and IRSN (France) for quality assurance purpose. The results were then compared to the SAF values for mathematic phantoms.

Organ doses for babies, children and adults and doses to foetuses from environmental gamma rays were calculated using Monte Carlo codes. Firstly, gamma ray fields in the air-over-ground geometry were simulated, neglecting the disturbance of the radiation field by the human body. The exposure modes considered were semi-infinite homogeneous volume sources in the air, infinite plane sources at a depth of 0.5 g.cm −2 in the ground and homogeneous volume sources of a natural radionuclides in the ground. The results of the simulation of the gamma ray transport in the air-over-ground geometry were used as sources irradiating the anthropomorphic phantoms : an 8 week old baby, a seven year old child and two «reference» adult phantoms of a male and a female. the doses to foetuses were estimated from the dose to the uterus of the adult female. Dose conversion factors normalised to source intensity and air kerma were calculated for monoenergetic sources (15 keV to 10 MeV) and natural and artificial radionuclides

The personal dose, H d , relative to the effective male dose equivalent H Em , was assessed for various target geometries by means of a male phantom mathematical model which was a modification of the ADAM phantom. Irradiation projections were both sagittal and lateral. Whole-body photon irradiation was simulated by Monte Carlo calculations for a point source at distances of 50 and 350 cm from the phantom. Data for H Em were calculated for nine energies between 26 and 1250 keV and normalised against dosemeter readings, when the dosemeter was placed at conventionally used locations. The ratios H Em :H d for each dosemeter location are presented as a function of photon energy, irradiation geometry and source to skin distance