Collective Dose Research Articles

The impact of pediatric-specific dose modulation curves on radiation dose and image quality in head computed tomography.

The volume of CT examinations has increased with resultant increases in collective dose values over the last decade. To analyze the impact of the tube current and voltage modulation for dose values and image quality of pediatric head CT examinations. Head CT examinations were performed on anthropomorphic phantoms and four pediatric age categories before and after the introduction of dedicated pediatric curves for tube voltage and current modulation. Local diagnostic reference levels were calculated. Visual grading characteristic image quality evaluation was performed by four pediatric neuroradiologists and image noise comparisons were performed. Pediatric-specific modulation curves demonstrated a 49% decrease in mean radiation dose for phantom examinations. The local diagnostic reference levels (CTDIvol) for clinical examinations decreased by 52%, 41%, 46% and 40% for newborn, 5-, 10- and 15-year-old patients, respectively. Visual grading characteristic image quality was maintained for the majority of age categorizations (area under the curve = 0.5) and image noise measurements did not change (P = 0.693). Pediatric-specific dose modulation curves resulted in an overall mean dose reduction of 45% with no significant differences in subjective or objective image quality findings.

Dose assessment of radionuclides dispersion from Bushehr nuclear power plant stack under normal operation and accident conditions

Assessment of individual and collective doses around the unit-1 of Bushehr nuclear power plant (BNPP-1) site during normal nuclear reactor operation and under reactor accident conditions which are essential for safety and environmental analyses is presented in this paper. Release of radioactive materials to the environment following a design basic accident (DBA) (e.g. LBLOCA) is evaluated using HOTSPOT health physics computer code. In the normal operation conditions, atmospheric dispersion of radioactive material is calculated using CAP88-PC code. These codes utilize a Gaussian dispersion air transport plume model to simulate the atmospheric dispersion of radionuclides in different atmospheric stability classes and various wind speeds and directions. To calculate the doses under normal operation using CAP88 code, the surrounding area of the BNPP-1 within a radius of 30 km is gridded into 12 concentric rings and 16 sectors and the distribution of population and data of agricultural products are calculated for each grid. The meteorological data on atmospheric stability conditions, wind speed and the frequency distribution of wind direction based on data collected near the reactor site are also analyzed and applied. The results illustrate that the maximum total effective dose equivalent (TEDE) and committed effective dose equivalent (CEDE) values for personnel and public around the BNPP-1 site are lower than the annual effective dose limits for workers and public in normal operation and under accident conditions. Also, the results of the radiological impacts of the BNPP-1 in normal and accidental radioactive materials releases are compared with the dose values given in the Final Safety Analysis Report (FSAR) of the BNPP-1.

I Am Confused About the Cancer Risks Associated With CT: How Can We Summarize What Is Currently Known?

AJR:205, July 2015 A typical CT examination may involve 5–15 mSv of effective dose. The current data do not provide conclusive evidence regarding risk from a couple of CT examinations, though a minority of patients have undergone enough CT examinations to make some associated risk probable [8]. The question arises: Is there newer scientific information that warrants increasing the level of concern and intensifying the controversy? The answer is no. According to an International Commission on Radiological Protection (ICRP) report published in 2007 [9], “the estimates of cancer risk attributable to radiation exposure have not changed greatly in the past 17 years.” The ICRP has adjusted tissue weighting factors primarily to estimate additional risks for breasts and less risk for gonads, but the overall whole-body risk coefficient has changed only marginally. Then what is the cause for controversy? One reason is that the bounds of evidence are overstepped by extreme positions on both sides of the controversy. The ICRP clearly states that “the calculation of the number of cancer deaths based on collective effective doses from trivial individual doses should be avoided” [9]. According to ICRP, the collective effective dose quantity is an instrument for optimization, for comparing radiologic technologies and protection procedures, predominantly in the context of occupational exposure and group risk management. Collective effective dose is not intended as a tool for epidemiologic risk assessment, and it is inappropriate to use it in risk projections. The aggregation of very low doses to groups of individuals over extended time periods is misleading for individual risk projections [9]. Much as projections for cancer risk may be useful for policy planning, for strategic developments in managing radiation protection, they should not be used to characterize individual risk. I Am Confused About the Cancer Risks Associated With CT: How Can We Summarize What Is Currently Known?

Comparison of Five Developed Algorithms to Estimate Staff Effective Dose in Interventional Cardiology: Are They Interchangeable?

Introduction: Interventional procedures are becoming substantial contributors to collective radiation dose due to their increasing rate of application. This study examined the relationships between effective dose data derived from five developed algorithms (Netherlands Commission on Radiation Dosimetry (NCS) and National Council on Radiation Protection and Measurements (NCRPs) algorithms for single dosimetry and Niklason, NCRPd and Clerinx algorithms for double dosimetry) to assess whether they can be used interchangeably in the assessment of staff effective dose in interventional cardiology. Material and Methods: The study population consisted of thirteen radiation workers (eight cardiologists, two technicians and three nurses) were involved in cardiac interventional procedures. Effective doses with thermoluminescence dosemeters were estimated for the duration of two months using five algorithms. The linear correlation and Bland-Altman analysis were performed to assess relationships and the agreement between effective doses calculated by the algorithms respectively. Results and Conclusion: We found significant correlation coefficients between the all effective doses calculated using the algorithms. Comparisons of two algorithms showed significant differences between estimated effective doses ( p 0� 05). Limit of agreements were wide (NCS vs. NCRPd: −0.406 to 0.280 mSv and NCS vs. Niklason: −0.035 to 0.401 mSv, respectively) and considerable disagreement was found between these algorithms and despite strong correlations, should not be used interchangeably for assessment of effective dose.

Modeling of the radiation doses during dismantling of RBMK-1500 reactor emergency core cooling system large diameter pipes

Personnel radiation safety is one of the most important issues during the dismantling of nuclear installations. In this paper, results of modeling radiation doses during the dismantling of the large diameter pipes from the emergency core cooling system of RBMK-1500 reactor at Ignalina NPP are presented. The effective doses to the workers are modeled for four dismantling alternatives in order to propose the optimal dismantling approach. The impacts of the cutting technology and individual respiration protection on effective doses are analyzed. The total effective personnel doses are obtained by summing the effective personnel doses from various sources of exposure, i.e., direct radiation from radioactive equipment, internal radiation due to inhalation and ingestion of radioactive aerosols, and direct radiation from radioactive aerosols arising during hot cutting. The collective effective doses and their uncertainties are analyzed using VISIPLAN and MATLAB codes.

Radiological mapping of the area around two research reactors in Islamabad

This study presents survey of gamma radiation exposure around Pakistan Institute of Nuclear Science and Technology (PINSTECH). PINSTECH hosts two research reactors, two isotope production plants and several radiochemistry laboratories. Dose measurement was performed in thirty villages around PINSTECH. The average outdoor absorbed dose rate in air was 59 ± 16 nGy h−1. The average annual outdoor dose rate due to terrestrial gamma-rays was 71.4 ± 20.0 μSv y−1. The annual collective effective dose equivalent was 415 man-Sv and the estimated excess life-time cancer risk was 7.3 × 10−4. The study revealed that inhabitants living in the area surrounding PINSTECH were radiologically safe.

Análise dos registros de dose ocupacional externa no Brasil

Brazil, a continental country, with actually more than 150,000 workers under individual monitoring for ionizing radiation, has implemented in 1987 a centralized system for storage of external occupational dose. This database has been improved over the years and is now a web-based information system called Brazilian External Occupational Dose Management Database System - GDOSE. This paper presents an overview of the Brazilian external occupational dose over the years. The estimated annual average effective dose shows a decrease from 2.4 mSv in 1987 to about 0.6 mSv, with a remarkable reduction from 1987 to 1990. Analyzing by type of controlled practice, one sees that the medical radiology is the area with the largest number of users of individual monitors (60%); followed by educational practices (9%) and industrial radiography (8%). Additionally to photon whole body monitoring; neutron monitors are used in maintenance (36%), reactor (29%) and education (27%). Extremity monitors are mainly used in education (27%), nuclear medicine (22%) and medical radiology (19%). In terms of collective dose, the highest value is also found in medical radiology, but the highest average dose value is received by interventional radiology IOE. Nuclear medicine, radiotherapy and research practices present average annual effective dose higher than 1 mSv. However, some dose values higher than 500 mSv registered in the data base give false information. They are not realistic. This should be better analyzed in the future to improve the analysis of the trends of external occupational dose in Brazil.

Integral Indices of the Radiological Effect of Open and Closed Fuel Cycle Objects on the General Population

The collective dose is examined as an integral characteristic of the radiological effect of nuclear fuel cycle enterprises on the general population. A relation is obtained for evaluating the ecological factor, which takes account of the specifics of radionuclides from the standpoint of their migration capacity and the particularities of dose load formation. The ecological factors are calculated for 241Am, 242mAm, 242Am, 243Am, 242Cm, 243Cm, 244Cm, 245Cm, 246Cm, 247Cm, 248Cm, 237Np, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, 244Pu, 235U, 236U, and 238U. Links where the activity of the daughter radionuclides was taken as equal to the activity of long-lived precursors are singled out in the decay chains of the actinides. The dynamics of the yearly collective dose for the general population, formed by individual actinides with activity 1 Bq in the emissions and their decay products, for a long period of time is calculated. The results are suitable for performing comparative radioecological assessments of enterprises in open and closed nuclear fuel cycles.

Collective effective dose in Europe from X-ray and nuclear medicine procedures.

Population doses from radiodiagnostic (X-ray and nuclear medicine) procedures in Europe were estimated based on data collected from 36 European countries. For X-ray procedures in EU and EFTA countries (except Liechtenstein) the collective effective dose is 547,500 man Sv, resulting in a mean effective dose of 1.06 mSv per caput. For all European countries included in the survey the collective effective dose is 605,000 man Sv, resulting in a mean effective dose of 1.05 mSv per caput. For nuclear medicine procedures in EU countries and EFTA (except Liechtenstein) countries the collective effective dose is 30,700 man Sv, resulting in a mean effective dose of 0.06 mSv per caput. For all European countries included in the survey the collective effective dose is 31,100 man Sv, resulting in a mean effective dose of 0.05 mSv per caput.

Collective effective dose from diagnostic radiology in Ukraine.

The frequencies and effective doses for the most common X-ray diagnostic examinations in Ukraine were assessed in the frame of the European Commission (EC) Study on European Population Doses from Medical Exposure (Dose Datamed 2). The average effective doses for all radiographic procedures were estimated using the ODS-60 software (Finland). The estimation of the effective doses for the chest film fluorography was carried out from the results of own representative measurements with thermoluminescent (TL) dosimetry and a standard Alderson-Rando phantom. The effective doses for fluoroscopy procedures were assessed using the Russian guidelines for estimation of effective doses. For all other X-ray examinations and procedures [computed tomography (CT), angiography and interventional procedures], typical effective dose values were taken from the EC Guidance RP154. The most frequently performed in Ukraine is chest film fluorography, with 389 examinations per 1000 population annually, reflecting in the greatest contribution to the total collective effective dose (CED) of 428 mSv per 1000 population (44 %). The total frequency and CED from all X-ray diagnostic examinations and procedures were estimated to be 1218 examinations and 1060 mSv per 1000 populations, respectively. The expected additional cancer risk from X-ray diagnostic examinations and interventional procedures is 2680 cases per year, with 1200 of them due to the contribution of chest fluorography. The main important action in radiation protection of patients in diagnostic radiology is the organisation of the monitoring of patient doses for different types of X-ray diagnostic examinations and replacement of chest film fluorography with digital X-ray systems.

Romanian medical exposure to ionising radiation in 2012

Medical exposure, the main source of artificial exposure, shows an increasing trend in the last years, manifested both by increasing the number of examinations with ionising radiation and by increasing the patient dose level. Annual results obtained for medical exposure to ionising radiation based on the data collected from Romanian hospitals are useful for the update of the national database and optimisation of diagnostic procedures in radiology and nuclear medicine. Medical exposure level is expressed in terms of annual collective dose and is evaluated from annual frequencies and the average effective dose per procedure for different types of radiological and nuclear medicine procedures. The Romanian hospitals reported during 2012 a number of 5,505,792 radiological examinations and 17,088 diagnostic procedures of nuclear medicine. Based on the data reported, the average effective doses and their contributions to the collective dose were evaluated. The main contributions to the collective dose of the radiological procedures are registered for CT abdomen and pelvis region, followed by thorax CT and head CT examinations. The next positions are fluoroscopic examination of the thorax and gastrointestinal disease and radiographic examination of the lumbar spine and thorax, which in spite of their low effective dose have an important contribution to the collective dose due to the large number of examinations. For nuclear medicine procedures, major contributions to collective dose are given by bone scintigraphy, followed by PET-CT and thyroid scintigraphy.

Tectonic and radioactivity impacts of 238U on groundwater-based drinking water at Gosa and Lugbe areas of Abuja, North Central Nigeria

Tectonic contribution of activity level of 238U in groundwater-based drinking water in Gosa and Lugbe areas of Abuja was measured using inductively coupled plasma mass spectrometry (ICP-MS). The highest activity level of 2736 µBq L−1 reported in Lugbe borehole, whereas the lowest value of 443 µBq L−1 reported at Gosa borehole. The inhabitants permanently used water from the boreholes for daily consumption. The group receives 5.55 × 10−5 mSv of the annual collective effective dose due to 238U in drinking water. The radiological risks of 238U in the water samples were found to be low, typically in magnitude of 10−7 with cancer mortality value of 1.03 × 10−7 and morbidity value of 1.57 × 10−7. The chemical toxicity risk of 238U in drinking water over a lifetime consumption has a mean value of 4.0 × 10−3 μg kg−1 day−1. It could be that the human risk due to 238U content in groundwater supplies from ingestion may likely be the chemical toxicity of 238U as a heavy metal rather than radiological risk. Significantly, Lugbe subsurface may have developed some fractions of granitic strata that contributed to the distribution of radioactive of 238U in tectonically weak zones.

Cone beam CT for dental and maxillofacial imaging: dose matters.

The widespread use of cone-beam CT (CBCT) in dentistry has led to increasing concern regarding justification and optimisation of CBCT exposures. When used as a substitute to multidetector CT (MDCT), CBCT can lead to significant dose reduction; however, low-dose protocols of current-generation MDCTs show that there is an overlap between CBCT and MDCT doses. More importantly, although the 3D information provided by CBCT can often lead to improved diagnosis and treatment compared with 2D radiographs, a routine or excessive use of CBCT would lead to a substantial increase of the collective patient dose. The potential use of CBCT for paediatric patients (e.g. developmental disorders, trauma and orthodontic treatment planning) further increases concern regarding its proper application. This paper provides an overview of justification and optimisation issues in dental and maxillofacial CBCT. The radiation dose in CBCT will be briefly reviewed. The European Commission's Evidence Based Guidelines prepared by the SEDENTEXCT Project Consortium will be summarised, and (in)appropriate use of CBCT will be illustrated for various dental applications.

National diagnostic reference level initiative for computed tomography examinations in Kenya.

The purpose of this study was to estimate the computed tomography (CT) examination frequency, patient radiation exposure, effective doses and national diagnostic reference levels (NDRLs) associated with CT examinations in clinical practice. A structured questionnaire-type form was developed for recording examination frequency, scanning protocols and patient radiation exposure during CT procedures in fully equipped medical facilities across the country. The national annual number of CT examinations per 1000 people was estimated to be 3 procedures. The volume-weighted CT dose index, dose length product, effective dose and NDRLs were determined for 20 types of adult and paediatric CT examinations. Additionally, the CT annual collective effective dose and effective dose per capita were approximated. The radiation exposure during CT examinations was broadly distributed between the facilities that took part in the study. This calls for a need to develop and implement diagnostic reference levels as a standardisation and optimisation tool for the radiological protection of patients at all the CT facilities nationwide.

Radiological Impacts and Regulation of Rare Earth Elements in Non-Nuclear Energy Production

Energy industries account for a significant portion of total rare earth usage, both in the US and worldwide. Rare earth minerals are frequently collocated with naturally occurring radioactive material, imparting an occupational radiological dose during recovery. This paper explores the extent to which rare earths are used by various non-nuclear energy industries and estimates the radiological dose which can be attributed to these industries on absolute and normalized scales. It was determined that typical rare earth mining results in an occupational collective dose of approximately 0.0061 person-mSv/t rare earth elements, amounting to a total of 330 person-mSv/year across all non-nuclear energy industries (about 60% of the annual collective dose from one pressurized water reactor operated in the US, although for rare earth mining the impact is spread out over many more workers). About half of the collective dose from non-nuclear energy production results from use of fuel cracking catalysts for oil refining, although given the extent of the oil industry, it is a small dose when normalized to the energy equivalent of the oil that is used annually. Another factor in energy industries’ reliance on rare earths is the complicated state of the regulation of naturally occurring radiological materials; correspondingly, this paper also explores regulatory and management implications.

Estimated collective effective dose to the population from radiological examinations in Slovenia.

BackgroundThe aim of the study was to systematically evaluate population exposure from diagnostic and interventional radiological procedures in Slovenia.MethodsThe study was conducted in scope of the “Dose Datamed 2” project. A standard methodology based on 20 selected radiological procedures was adopted. Frequencies of the procedures were determined via questionnaires that were sent to all providers of radiological procedures while data about patient exposure per procedure were collected from existing databases. Collective effective dose to the population and effective dose per capita were estimated from the collected data (DLP for CT, MGD for mammography and DAP for other procedures) using dose conversion factors.ResultsThe total collective effective dose to the population from radiological in 2011 was estimated to 1300 manSv and an effective dose per capita to 0.6 mSv of which approximately 2/3 are due to CT procedures.ConclusionsThe first systematic study of population exposure to ionising radiation from radiological procedures in Slovenia was performed. The results show that the exposure in Slovenia is under the European average. It confirmed large contributions of computed tomography and interventional procedures, identifying them as the areas that deserve special attention when it comes to justification and optimisation.

On effective dose for radiotherapy based on doses to nontarget organs and tissues.

The National Council for Radiation Protection and Measurement (NCRP) published estimates for the collective population dose and the mean effective dose to the population of the United States from medical imaging procedures for 1980/1982 and for 2006. The earlier report ignored the effective dose from radiotherapy and the latter gave a cursory discussion of the topic but again did not include it in the population exposure for various reasons. This paper explains the methodology used to calculate the effective dose in due to radiotherapy procedures in the latter NCRP report and revises the values based on more detailed modeling. This study calculated the dose to nontarget organs from radiotherapy for reference populations using CT images and published peripheral dose data. Using International Commission on Radiological Protection (ICRP) 60 weighting factors, the total effective dose to nontarget organs in radiotherapy patients is estimated as 298 ± 194 mSv per patient, while the U.S. population effective dose is 0.939 ± 0.610 mSv per person, with a collective dose of 283,000 ± 184,000 person Sv per year. Using ICRP 103 weighting factors, the effective dose is 281 ± 183 mSv per patient, 0.887 ± 0.577 mSv per person in the U.S., and 268,000 ± 174,000 person Sv per year. The uncertainty in the calculations is largely governed by variations in patient size, which was accounted for by considering a range of patient sizes and taking the average treatment site to nontarget organ distance. The methods used to estimate the effective doses from radiotherapy used in NCRP Report No. 160 have been explained and the values updated.

Increasing Radiation Doses from Computed Tomography versus Diagnostic Reference Levels: How Compliance Are We?

Aim: To assess the radiation dose received in a clinical/real life setting by patients visiting selected radiological centres in Enugu, Enugu State, southeast of Nigeria for diagnostic computed tomography (CT) scans of the heads and thus assess compliance to the diagnostic Original Research Article Chiegwu et al.; BJMMR, 9(9): 1-15, 2015; Article no.BJMMR.15123 2 reference levels (DRL). Study Design: A prospective cross-sectional survey design. Place and Duration of Study: CT Units of University of Nigeria Teaching Hospital, Memfys Hospital for Neurosurgery and Conquest Medical Imaging Limited in Enugu, Enugu State, Nigeria between April 2012 and January 2013. Materials and Method: Radiation doses absorbed by 98 patients (60 males and 38 females, age range 3-65years) that presented for CT scans of the head at the study centres were prospectively measured using lithium fluoride thermoluminescent dosimeter, LiF-TLD (TLD-100) chips. The mean absorbed dose, mean effective dose, collective dose and the per caput dose with their standard deviations were obtained. Results: The mean absorbed dose was 4.315 ± 3.815mSv (range 1.005-17.607mSv) and the mean effective dose was 2.244±1.984 mSv. In children (0-15years) the mean absorbed dose was 5.604±4.904mSv and mean effective dose, 2.914±2.278 mSv and these doses were higher than that of the adults. The annual collective dose was 224.40±198.4 person-mSv and the annual per caput dose was 5.9 x 10 -7 mSv. The calculated mean organ effective doses were 0.147±0.056mSv, 0.884±0.334mSv, 0.147±0.056mSv, 0.3540±0.134mSv and 0.147±0.056mSv for the brain, eye lenses, thyroid gland, red bone marrow and breast respectively. Conclusion: TLD chip were used to assess patients’ radiation dose in a clinical setting. The overall mean effective dose (2.244mSv) was in compliance with the recommended DRL. The radiation dose received correlated positively with the tube current (mA) and number of images obtained but negatively with the scan time, patients’ head AP dimension and age. Radiation risks from CT can be reduced through justification of the procedure and dose optimization.

Estimation of the collective ionizing dose in the Portuguese population for the years 2011 and 2012, due to nuclear medicine exams

ObjectivesIn 2009–2010 a Portuguese consortium was created to implement the methodologies proposed by the Dose Datamed II (DDM2) project, aiming to collect data from diagnostic X-ray and nuclear medicine (NM) procedures, in order to determine the most frequently prescribed exams and the associated ionizing radiation doses for the Portuguese population. The current study is the continuation of this work, although it focuses only on NM exams for the years 2011 and 2012. Material and methodsThe annual frequency of each of the 28 selected NM exams and the average administered activity per procedure was obtained by means of a nationwide survey sent to the 35 NM centres in Portugal. ResultsThe results show a reduction of the number of cardiac exams performed in the last two years compared with 2010, leading to a reduction of the annual average effective dose of Portuguese population due to NM exams from 0.08mSv±0.017mSv/caput to 0.059±0.011mSv/caput in 2011 and 0.054±0.011mSv/caput in 2012. Portuguese total annual average collective effective dose due to medical procedures was estimated to be 625.6±110.9manSv in 2011 and 565.1±117.3manSv in 2012, a reduction in comparison with 2010 (840.3±183.8manSv). ConclusionsThe most frequent exams and the ones that contributed the most for total population dose were the cardiac and bone exams, although a decrease observed in 2011 and in 2012 was verified. The authors intend to perform this study periodically to identify trends in the annual Portuguese average effective dose and to help to raise awareness about the potential dose optimization.

Prediction of External Exposure during Dismantling of Steam Generator

The decommissioning of nuclear power plants is in the Slovak Republic an actual issue. In 2015 started the second decommissioning stage of nuclear power plant V1 in Jaslovské Bohunice. This stage involves the dismantling and segmentation of activated (reactor pressure vessel, reactor internals) and contaminated parts (steam generators, pressurizer). From this reason it is necessary to investigate the radiation situation in the vicinity of the component to be cut. The presented results show that during remote dismantling the exposure is small (compared with the fragmentation tasks). Moreover, when the pre-dismantling decontamination with decontamination factor of 100 is applied, the total collective effective dose is below the yearly limit of 20 mSv for workers.