Radiation Detriment Research Articles

Accuracy in dosimetry of diagnostic agents: impact of the number of source tissues used in whole organ S value-based calculations

BackgroundDosimetry for diagnostic agents is performed to assess the risk of radiation detriment (e.g., cancer) associated with the imaging agent and the risk is assessed by computing the effective dose coefficient, e. Stylized phantoms created by the MIRD Committee and updated by work performed by Cristy-Eckerman (CE) have been the standard in diagnostic dosimetry. Recently, the ICRP developed voxelized phantoms, which are described in ICRP Publication 110. These voxelized phantoms are more realistic and detailed in describing human anatomy compared with the CE stylized phantoms. Ideally, all tissues should be represented and their pharmacokinetics collected for an as accurate a dosimetric calculation as possible. As the number of source tissues included increases, the calculated e becomes more accurate. There is, however, a trade-off between the number of source tissues considered, and the time and effort required to measure the time-activity curve for each tissue needed for the calculations. In this study, we used a previously published 68Ga-DOTA-TATE data set to examine how the number of source tissues included for both the ICRP voxelized and CE stylized phantoms affected e.ResultsDepending upon the number of source tissues included e varied between 14.0–23.5 μSv/MBq for the ICRP voxelized and 12.4–27.7 μSv/MBq for the CE stylized phantoms. Furthermore, stability in e, defined as a < 10% difference between e obtained using all source tissues compared to one using fewer source tissues, was obtained after including 5 (36%) of the 14 source tissues for the ICRP voxelized, and after including 3 (25%) of the 12 source tissues for the CE stylized phantoms. In addition, a 2-fold increase in e was obtained when all source tissues where included in the calculation compared to when the TIAC distribution was lumped into a single reminder-of-body source term.ConclusionsThis study shows the importance of including the larger tissues like the muscles and remainder-of-body in the dosimetric calculations. The range of e based on the included tissues were less for the ICRP voxelized phantoms using tissue weighting factors from ICRP Publication 103 compared to CE stylized phantoms using tissue weighting factors from ICRP Publication 60.

Sensitivity analysis of parameters and methodological choices used in calculation of radiation detriment for solid cancer

Purpose: Radiation detriment is a concept used by the International Commission on Radiological Protection (ICRP) to quantify the harmful health effects of radiation exposure in humans. The current approach of radiation detriment calculation has been defined in ICRP Publication 103 in 2007. It is determined from lifetime risk of cancer and heritable effects for a composite reference population, taking into account the severity of the disease in terms of lethality, quality of life and years of life lost. Many parameters are used in the calculations and the variation of these parameters can have effects on the cancer detriment, which needs to be investigated.Materials and methods: In this paper, we conducted a sensitivity analysis for examining the impact of 12 different parameters or methodological choices on the calculation of solid cancer detriment, such as the lifetime risk calculation method, survival curve, dose and dose-rate effectiveness factor (DDREF), age-at-exposure, sex, reference population, risk transfer model, latency, attained age, lethality, minimum quality of life factor and relative cancer-free life lost. Sensitivity calculations have been performed systematically for each of 10 solid cancer sites, by changing each one of the parameters in turn.Results: This sensitivity analysis demonstrated a large impact on estimated detriment from DDREF, age-at-exposure, sex and lethality, a noticeable impact of risk transfer model associated to variation of baseline rates, and a limited impact of risk calculation method, survival curve, latency, attained age, quality of life and relative years of life lost.Conclusion: These results could have implications for radiation protection standards, and they should help define priorities for future research in the field of low radiation dose and dose rate research. The present sensitivity analysis is part of a global effort of ICRP to review the bases of radiation detriment calculation and assess potential evolutions to improve the radiation protection system.

Review of airkerma-area product, effective dose and dose conversion coefficients for non-cardiac interventional fluoroscopy procedures.

To provide current data on average air kerma-area product (PKA ) and effective dose (E) for noncardiac interventional fluoroscopy procedures and suggested values of dose coefficients (DCE ) for conversion of PKA to estimates of effective dose. A PubMed literature search covering the time period from 2006 to August 2019 was performed to obtain recent data on PKA , E and DCE for interventional fluoroscopy procedures. There is very wide variation in the reported values of PKA , E, and DCE in the literature. A number of factors are involved in this variability and the resultant uncertainty in average values of these dose quantities. The values of PKA , average E and suggested DCE presented here can be of use for comparison of the radiation detriment from different procedures and may be useful for categorizing detriment within an order of magnitude or so. They do not represent actual or expected radiation dose or detriment from any specific procedure or for a specific patient and should be not be used as such.

Оценка потенциальных радиологических рисков населения при реализации проекта «Прорыв» Госкорпорации «Росатом». Часть 1. Рекомендации МКРЗ

The concept “radiation detriment” has been debated intensively in the pages of the ICRP Publica-tion 103 (2007), new radiation epidemiological data obtained after 2007 have also been brought into discussion. For radiation detriment calculation radiation risk models based on data of the study of Japanese cohort of atomic bombings survivors were used. Models developed for esti-mating radiation risk factors take account of gender and age at exposure. Now ICRP has estimat-ed radiation detriment in specially designed standard population by averaging the estimates based on age at exposure. The concept “radiation detriment” was developed for quantification of the overall harm to health of humans and their offspring from stochastic effects of low-level radi-ation on different parts of the body, reduction in life expectancy and reduced quality of life. In ad-dition, radiation detriment is used to assess effective dose and its standardization for radiological protection. In the paper, the concept “radiation detriment” is assessed with regard to the possibility of extending the area of its application. The applicability of technique for calculation of radiation detriment is possible to be extended with account of Russian health and statistical data, lethality fraction estimates, years of life lost, gender and age. The extended “radiation detriment” will be renamed as “radiological detriment”, that will highlight the possibility of quantifying potential harm to a specific irradiated population. The magnitude of population-based radiological detri-ment may be used not only for matching sources of ionizing radiation by their impact on the standard population, but also for estimating the level of radiological protection of the specific population. The level of radiological detriment may be used for quantification of potential harm to the public health in the implementation of the Rosatom project “Proryv”.

Оценка потенциальных радиологических рисков населения при реализации проекта «Прорыв» Госкорпорации «Росатом». Часть 2. Определение радиологического ущерба

Nuclear power is effective and safe source of electricity. Meanwhile, uranium reserves in the earth's crust will run out in 100 years with the development of traditional nuclear reactors. The Rosatom “Proryv” project implementation will allow multiplying fuel sources for the new genera-tion nuclear power through the closing fuel cycle. Radiation safety of the new nuclear powers should be based on the state of the art Russian national and international regulations, as well as on predicted radiation doses, estimates of potential radiation risks and radiation detriment of the public. Developed methods for computational analysis of possible doses of estimates of radia-tion risks and population-based detriment, associated with atmospheric fallouts of radioactive substances from the BREST-OD-300 reactor, corresponds to the currently recognized approach-es to evaluating safety of nuclear energy facilities. Developed method for radiation detriment es-timating is in accordance with ICRP recommendations. It allows making assessment of radiation-associated health effects for Russian population with account of patients’ quality of life provided by the current health care system. The analysis of possible radiation doses and potential radia-tion risks shows that the upper 95% confidence bound of radiation detriment for the critical group of population in the town of Seversk (girls of 5 years of age) even in the event of beyond design basis accident at the reactor equals 1.1610-5 year-1, and does not exceed the radiation risk limit of 510-5 years-1, established by Russian national radiation safety regulations NRB-99/2009 for the population during normal operation of ionizing radiation sources. In the event of an accidental situation on the Brest-OD-300 reactor, the average estimates of radiation risks for the population living within the 30-km zone around the JSC “Siberian Chemical Combine” will generally remain in the range of negligible risk and will not exceed the level of 10-6 year-1.

Сравнительная оценка безопасности глубинных захоронений радиоактивных отходов открытого и замкнутого топливного циклов: радиологическая миграционная эквивалентность

The article presents analysis of safety of long-lived high level radioactive waste (RW) disposed for permanent storage in a deep geological repository. According to the study protocol it is necessary to estimate the human and environmental health safety of RW, generated in different nuclear fuel cy-cles, during their long-term stay in the repository. To estimate biological effects, RW composition from thermal reactors in open nuclear fuel cycle (“TR”) and from simultaneously operated thermal and fast reactors in closed nuclear cycle (“TR+FR”) in different time after their disposal have been evaluated. It is suggested that RW to be safe to humans and the environment if committed effective doses from RW components including minor actinides and fission products and from natural urani-um are equivalent (radiation equivalence) or lifetime attributable risks of cancer mortality from RW and natural uranium are equivalent (radiological equivalence). For this purpose it is important to evaluate the time of achievement of radiation or radiological equivalence. To evaluate health effect of RW containing radio-nuclides on the public and the environment their migration activity has been evaluated with the use of distribution coefficient and retardation factor. Probable annual effective doses to the public from exposure to the radionuclides released from the repository to the biosphere at different time after the RW disposal have been estimated. Radiation doses to the public following the consumption of water from the well installed on the repository, and lifetime attributable risk (LAR) of cancer mortality associated with the exposure to radionuclides contained in “TR” and ”TR+FR” generated waste have been evaluated. It turned out that LARs of cancer mortality from “TR+FR” radionuclides is lower than LAR from natural uranium, it means that radiological migration equivalence after its achievement will exists until the repository conditions allow, about 1 billion years. We have found that LARs from “TR+FR” waste is about 100 times lower than the negligible level, 10-6, established in the Russian National Radiation Safety Standards (NRB-99/2009). Estimat-ed LAR of cancer mortality from “TR”-generated waste is 360 times higher than LAR from “TR+FR”-generated waste. As evaluated for the waste from TR radiological equivalence will be achieved not earlier than 1 million years after permanent disposal. If RW is generated in the closed cycle estimat-ed LAR value from consumption of well water does not exceed 10-5 year-1, if RW is generated in open fuel cycle, the LAR value is 10-3 year-1, this is socially unacceptable risk. In the first 10 thousand years after the disposal the major dose- and risk-forming radionuclides in the well water will be 241Am, 239Pu и 240Pu. Estimates of radiation detriment from ”TR” generated waste put to the perma-nent deep geological disposal are given in the article.

Mammography Dose Survey Using International Quality Standards

Digital mammography is the current standard for breast cancer screening. The absence of any dosimetric data, the quality standards, and the fear of radiation detriment, sometimes, hampers the smooth introduction of this technology and the launch of breast cancer screening programmes. As the breast cancer screening programmes are in development in Morocco, quality standards have been set in this study, so that any new breast cancer screening service could get started with their first analysis. The purpose of this study was to report the first Moroccan breast dose and to test quality standards compared with European guidelines. A dosimetric study is conducted by calculating mean glandular dose (MGD) for patients' breasts and polymethyl methacrylate (PMMA) for each thickness from recorded radiographic factors and X-ray tube (output and half-value layer) measurements using Dance's model for a digital mammography system. This is carried out to determine the correlation between phantom and patient measurements.The mean MGD for patient data was 1.02 ± 0.5 mGy and the compressed breast thickness was 55 ± 14 mm. For compressed breast thickness range of 50–60 mm, the MGD was 0.94 ± 0.3 mGy and the dose calculated with PMMA phantom for the same range thickness was 1.33 mGy. The results of MGD as a function of PMMA thickness is lower than the achievable limit curve proposed in the European guidelines. The average doses, which depend on the technical parameters of the mammography equipment, are in line with values obtained in European guidelines. In addition, an investigation is needed throughout the Moroccan territory, in the sense of optimization of radiological practices and techniques in mammographic centres aligning with the international recommendations.

Balancing the physics of radiation: Challenges to the system of quantities and units in radiological protection

AbstractIonizing radiation is present in various situations in the contemporary world. Defining the quantities and units for this field is a complex scientific task, especially the quantities used in radiological protection (RP) to estimate the damage caused to individuals exposed to radiation (detriment). This article highlights the lack of consensus in the scientific RP community regarding the quantities and units employed in practice from the perspective of the philosophy of science. The basic concepts related to the system of quantities are presented, followed by the problems and criticisms addressed by experts in the field. Several reasons for these problems are identified. The article discusses the scant interest on the part of philosophy of science in RP. The philosophy of science is still dominated by an analytical–conceptual perspective that pays little attention to the actual influence of certain structures better understood when considered from the institutional viewpoint, which is here exemplified by the International Commission on Radiological Protection (ICRP) and the International Atomic Energy Agency (IAEA).

Impact of updating the non-radiation parameters in the ICRP 103 detriment model

The radiation detriment in ICRP 103 is defined as the product of the organ-specific risk coefficient and the damage that may be associated with a cancer type or hereditary effect. This is used to indicate a weighted risk according to the radiation sensitivity of different organs and the severity of damage that may possibly arise. While the risk refers to radiation exposure parameters, the extent of damage is independent of radiation. The parameters that are not affected by radiation are lethality, impairment of quality of life, and reduced life expectancy, which are considered as quantities associated with the severity of disease or damage. The damage and thus the detriment appear to be mostly affected by lethality, which is the quotient of the age-standardized mortality rate to the incidence rate. The analysis of the detriment presented in this paper focuses on the influence of the lethality on the detriment from 1980 to 2012 in the USA and Germany. While the lethality in this period covering more than three decades has decreased approximately linearly by 30% (both USA and Germany), within the same period the detriment declined only by 13% in the USA and by 15% in Germany. If only based on these two countries, an update on the detriment parameters with reference to 2007, when ICRP 103 was released, would result in a reduced weighted risk, i.e. the radiation detriment would be reduced by 10 to 15% from originally 5.7% per Sv for the whole population to roughly 5% per Sv.

Calculating disability-adjusted life years (DALY) as a measure of excess cancer risk following radiation exposure

This paper has proposed that disability-adjusted life year (DALY) can be used as a measure of radiation health risk. DALY is calculated as the sum of years of life lost (YLL) and years lived with disability (YLD). This multidimensional concept can be expressed as a risk index without a probability measure to avoid the misuse of the current radiation detriment at low doses. In this study, we calculated YLL and YLD using Japanese population data by gender. DALY for all cancers in Japan per 1 Gy per person was 0.84 year in men and 1.34 year in women. The DALY for all cancers in the Japanese baseline was 4.8 in men and 3.5 in women. When we calculated the ICRP detriment from the same data, DALYs for the cancer sites were similar to the radiation detriment in the cancer sites, excluding leukemia, breast and thyroid cancer. These results suggested that the ICRP detriment overestimate the weighting fraction of leukemia risk and underestimate the weighting fraction of breast and thyroid cancer. A big advantage over the ICRP detriment is that DALY can calculate the risk components for non-fatal diseases without the data of lethality. This study showed that DALY is a practical tool that can compare many types of diseases encountered in public health.

İyonize Radyasyon Uygulamaları İçin Güvenlik ve Korunmaya Yönelik Genel Kavramlar

In this study, the concepts for safety and protection in applications of ionizing radiationare presented and the information is given to applications in our country.Radiation irradiation of human activities on interest and the need for applications that are based on three basic requirements is recommended in the system: Justification, Optimization and Dose Limits.According to these principles, no practice involving exposure to radiation should be adopted unless it produces at least sufficient benefit to the exposed individuals or to society to offset the radiation detriment it causes (Justification). In relation to any particular source of radiation within a practice, the dose to any individual from that source should be below an appropriate dose constraint, and all reasonable steps should be taken to adjust the protection so that exposures are as low as reasonably achievable, economic and social factors being taken into account (Optimization). A limit should be applied to the dose received by individual as the result of all the practices (except for medical diagnosis or treatment) to which he or she is exposed (Dose Limits)

Effective dose: a radiation protection quantity

Modern radiation protection is based on the principles of justification, limitation, and optimisation. Assessment of radiation risks for individuals or groups of individuals is, however, not a primary objective of radiological protection. The implementation of the principles of limitation and optimisation requires an appropriate quantification of radiation exposure. The International Commission on Radiological Protection (ICRP) has introduced effective dose as the principal radiological protection quantity to be used for setting and controlling dose limits for stochastic effects in the regulatory context, and for the practical implementation of the optimisation principle. Effective dose is the tissue weighted sum of radiation weighted organ and tissue doses of a reference person from exposure to external irradiations and internal emitters. The specific normalised values of tissue weighting factors are defined by ICRP for individual tissues, and used as an approximate age- and sex-averaged representation of the relative contribution of each tissue to the radiation detriment of stochastic effects from whole-body low-linear energy transfer irradiations. The rounded values of tissue and radiation weighting factors are chosen by ICRP on the basis of available scientific data from radiation epidemiology and radiation biology, and they are therefore subject to adjustment as new scientific information becomes available. Effective dose is a single, risk-related dosimetric quantity, used prospectively for planning and optimisation purposes, and retrospectively for demonstrating compliance with dose limits and constraints. In practical radiation protection, it has proven to be extremely useful.

ICRP and radiation protection of medical staff

Committee 3 (Protection in Medicine) and Committee 4 (Application of Recommendations) of the International Commission on Radiological Protection (ICRP) deal with the protection of medical staff. In the last 10 years, the Committee on Protection in Medicine has been involved in the preparation of 12 publications, some of which include specific recommendations on occupational RP. This paper summarizes the most relevant aspects of these recommendations on RP for medical staff. The most recent publication on Radiation Dose to Patients from Radiopharmaceuticals contains an annex on hand exposure in radio-pharmacies. Radiation detriment from exposure of both radiological staff and other individuals is considered as part of the justification of medical exposures and of the optimization process. ICRP advises on the uncertainty concerning the risk of cataracts and puts particular emphasis on optimization in situations of exposure of the eyes. Some recommendations on staff protection are included in the documents on computed tomography, digital radiology, pregnancy, discharge of patients after therapy and interventional radiology. The contents related to staff RP in the coming publications of the Committee (pediatric, cardiology, and fluoroscopy) are also summarized.

Comparative dose in pediatric radiology: uncertainty, estimates and ballparks

There is an increasing need for all radiologists, particularly pediatric radiologists, to have a good working knowledge of the relative radiation dose of the examinations we perform or supervise. We must be capable of providing such information to our referring physicians, patients and their families, for internal quality-assurance purposes and in the future, perhaps to outside regulatory or advisory bodies. In an ideal world, there would be a universally accepted common dose parameter applicable to all medical examinations involving ionizing radiation. That parameter would be derived with a user-friendly standard methodology that accounted for age and developmental variability and involved minimal extrapolations and assumptions. We do not have such a parameter. Currently, the most practicable common dose assessor is effective dose (ED). Defined by the ICRP and measured in miliSieverts (mSv), ED is the sum of the absorbed doses in all tissues and organs in the radiation field, each multiplied by a tissue-specific weighting factor. It provides an assessment of overall radiation detriment from a non-uniform dose distribution in terms of a uniform or whole-body exposure. The merits of ED are that it allows us to compare the relative dose impact of common radiographic, fluoroscopic, CT and nuclear medicine examinations, enables comparison to annual background radiation, and can be used together with risk models to provide a broad estimate of future excess malignancy risk. However, there are reservations associated with its use in medical imaging, certainly when applied to an individual patient. Calculation involves multiple levels of intrinsic uncertainties, extrapolations and error bars, generating an ED value that is a broader estimate than often appreciated. Expert assessment suggests that we should expect an uncertainty of +/−40%, whether using organ dose and weighting-factor methods; Monte Carlo simulations; or age-, regionand modality-specific conversion factor methods. Systematic and random components to error exist at each stage in calculation, and for all modalities. A few of the many potential contributors include dosimeter thresholds, accuracy, and placement; inter-observer variability in field of view specification with implication on partially included organs; whole-population based (not pediatric) weighting factors that are periodically updated with new epidemiological evidence; console-displayed CT dose parameters based on previously calculated standardized cylindrical phantom doses, the use of Monte Carlo or conversion factor data derived from older CT scanners, and uncertainties in models of radionuclide uptake, distribution and retention. A decade ago, there was a paucity of available ED data for the practicing pediatric radiologist. Isolated publications addressed individual examinations, mostly radiographic and fluoroscopic studies, and there was some dose data from national surveys but rarely providing ED values. Although conversion coefficients were available, they were not widely appreciated beyond physics circles. There was almost no dose data for pediatric CT. Some ED values, when investigated, did not relate to children but to the more extensive, although still not comprehensive or collated, adult-based data. In the years since, publications involving organ dose measurement and ED estimation in pediatric imaging have escalated. The information available to all of us has significantly increased, although there is ongoing debate as to the merits of various approaches and a need to improve the methodology and inconsistencies that especially plague pediatric CT dosimetry. Disclaimer Dr. Thomas has no financial interests, investigational or off-label uses to disclose.

Radiation doses originating from diagnostic procedures during the treatment and follow-upof children and adolescents with malignant lymphoma

Children with malignant lymphoma undergo many diagnostic procedures that involveexposure to ionising radiation. In addition, many, but by no means all, undergo furtherexposure to ionising radiation during radiotherapy. While therapeutic radiation exposuresare prescribed, the extent of radiation exposure arising from diagnostic procedures utilisedin such children is largely unknown. We completed an audit of the radiation doses arisingfrom diagnostic imaging procedures performed in a cohort of children with malignantlymphoma.The cumulative effective radiation dose associated with radiographic and radioisotopicprocedures was derived for 81 children and adolescents with malignant lymphoma duringtheir diagnosis, treatment and follow-up. Thirty-eight of the 42 patients (90%) withHodgkin lymphoma were alive at study termination, with follow-up periods ranging from1.9 to 11.7 years (median 5.3). Thirty-three of the 39 patients (85%) with non-Hodgkinlymphoma were alive at study termination with follow-up periods ranging from 2.4 to 12.3years (median 7.5). The median effective dose was 518 mSv for patients with Hodgkinlymphoma and 309 mSv for those with non-Hodgkin lymphoma. The maximumeffective dose was 1.7 Sv. The principal contributors to the effective dose werecomputed tomography (CT) and nuclear medicine imaging procedures using 67Ga. Protocols for the management of children and adolescents with malignant lymphomashould be reviewed in order to reduce the radiation detriment without loss of essentialdiagnostic information.

Radiation effects analysis in a group of interventional radiologists using biological and physical dosimetry methods

Interventional radiologists and staff members are frequently exposed to protracted and fractionated low doses of ionizing radiation, which extend during all their professional activities. These exposures can derive, due to the effects of direct and scattered radiation, in deterministic effects (radiodermitis, aged skin, cataracts, telangiectasia in nasal region, vasocellular epitelioms, hands depilation) and/or stochastic ones (cancer incidence). A methodology has been proposed for estimating the radiation risk or detriment from a group of six exposed interventional radiologists of the Hospital Universitario La Fe (Valencia, Spain), which had developed general exposition symptoms attributable to deterministic effects of ionizing radiation. Equivalent doses have been periodically registered using TLD’s and wrist dosimeters, H p (10) and H p (0.07), respectively, and estimated through the observation of translocations in lymphocytes of peripheral blood (biological methods), by extrapolating the yield of translocations to their respective dose–effect curves. The software RADRISK has been applied for estimating radiation risks in these occupational radiation exposures. This software is based on transport models from epidemiological studies of population exposed to external sources of ionizing radiation, such as Hiroshima and Nagasaki atomic bomb survivors [UNSCEAR, Sources and effects of ionizing radiation: 2006 report to the general assembly, with scientific annexes. New York: United Nations; 2006]. The minimum and maximum average excess ratio for skin cancer has been, using wrist physical doses, of [ 1.03 × 1 0 − 3 , 5.06 × 1 0 − 2 ], concluding that there is not an increased risk of skin cancer incidence. The minimum and maximum average excess ratio for leukemia has been, using TLD physical doses, of [ 7.84 × 1 0 − 2 , 3.36 × 1 0 − 1 ], and using biological doses, of [ 1.40 × 1 0 − 1 , 1.51], which is considerably higher than incidence rates, showing an excess radio-induced risk of leukemia in the group under study. Finally, the maximum radiological detriment in the group, evaluated as the total number of radio-induced cancers using physical dosimetry, has been of 2.18/1000 person-year (skin and leukemia), and using biological dosimetry of 9.20/1000 PY (leukemia). As a conclusion, this study has provided an assessment of the non-deterministic effects (rate of radio-induced cancer incidence) attributable to the group under study due to their professional activity.

Patient dose in neonatal units

Lung disease represents one of the most life-threatening conditions in prematurely born children. In the evaluation of the neonatal chest, the primary and most important diagnostic study is therefore the chest radiograph. Since prematurely born children are very sensitive to radiation, those radiographs may lead to a significant radiation detriment. Hence, knowledge of the patient dose is necessary to justify the exposures. A study to assess the patient doses was started at the neonatal intensive care unit (NICU) of the University Hospital in Leuven. Between September 2004 and September 2005, prematurely born babies underwent on average 10 X-ray examinations in the NICU. In this sample, the maximum was 78 X-ray examinations. For chest radiographs, the median entrance skin dose was 34 microGy and the median dose area product was 7.1 mGy.cm(2). By means of conversion coefficients, the measured values were converted to organ doses. Organ doses were calculated for three different weight classes: extremely low birth weight infants (<1000 g), low birth weight infants (1000-2500 g) and normal birth weight infants (>2500 g). The doses to the lungs for a single chest radiograph for infants with extremely low birth weights, low birth weights and normal birth weights were 24, 25 and 32 microGy, respectively.

Assessment of patient organ dose in CT virtual colonoscopy for bowel cancer screening

Justification and optimisation form the basic elements for the radiological protection of individuals for medical exposures. Justification includes the assessment of patient organ doses from which radiation risks are deduced. Medical radiation exposures are justified only in the case of a sufficient net benefit. For screening examinations, such as CT virtual colonoscopy, this implies that patient organ doses should be relatively low to minimise the radiation detriment. Image quality should be sufficient to maximise the potential diagnostic benefits. The Medical Exposures Directive places special attention on medical exposures as part of health screening programmes and examinations involving high individual doses to the patient, both of which apply to CT virtual colonoscopy. Technical factors were recorded for a series of patients having virtual colonoscopy on a CT scanner. In addition, the dose-length product was assessed. Patient organ doses were deduced using a CT dose calculation program. The typical effective dose was 7.5 mSv for male patients and 10.2 mSv for female patients. The effective dose is higher for female patients, as some gender-specific organs are irradiated during virtual colonoscopy. Each patient has two series of scans resulting in doses of 15 mSv for male patients and 20 mSv for female patients.

Calculation of organ doses in x-ray examinations of premature babies

Lung disease represents one of the most life-threatening conditions in prematurely born children. In the evaluation of the neonatal chest, the primary and most important diagnostic study is the chest radiograph. Since prematurely born children are very sensitive to radiation, those radiographs may lead to a significant radiation detriment. Knowledge of the radiation dose is therefore necessary to justify the exposures. To calculate doses in the entire body and in specific organs, computational models of the human anatomy are needed. Using medical imaging techniques, voxel phantoms have been developed to achieve a representation as close as possible to the anatomical properties. In this study two voxel phantoms, representing prematurely born babies, were created from computed tomography- and magnetic resonance images: Phantom 1 (1910 g) and Phantom 2 (590 g). The two voxel phantoms were used in Monte Carlo calculations (MCNPX) to assess organ doses. The results were compared with the commercially available software package PCXMC in which the available mathematical phantoms can be downsized toward the prematurely born baby. The simple phantom-scaling method used in PCXMC seems to be sufficient to calculate doses for organs within the radiation field. However, one should be careful in specifying the irradiation geometry. Doses in organs that are wholly or partially outside the primary radiation field depend critically on the irradiation conditions and the phantom model.

Preface, Executive Summary and Glossary

These revised Recommendations for a System of Radiological Protection formally replace the Commission's previous, 1990, Recommendations; and update, consolidate, and develop the additional guidance on the control of exposure from radiation sources issued since 1990. Thus, the present Recommendations update the radiation and tissue weighting factors in the quantities equivalent and effective dose and update the radiation detriment, based on the latest available scientific information of the biology and physics of radiation exposure. They maintain the Commission's three fundamental principles of radiological protection, namely justification, optimisation, and the application of dose limits, clarifying how they apply to radiation sources delivering exposure and to individuals receiving exposure. The Recommendations evolve from the previous process-based protection approach using practices and interventions by moving to an approach based on the exposure situation. They recognise planned, emergency, and existing exposure situations, and apply the fundamental principles of justification and optimisation of protection to all of these situations. They maintain the Commission's current individual dose limits for effective dose and equivalent dose from all regulated sources in planned exposure situations. They reinforce the principle of optimisation of protection, which should be applicable in a similar way to all exposure situations, subject to the following restrictions on individual doses and risks; dose and risk constraints for planned exposure situations, and reference levels for emergency and existing exposure situations. The Recommendations also include an approach for developing a framework to demonstrate radiological protection of the environment.