Showing papers in "Radiation Protection Dosimetry in 2004"

A comprehensive study of natural gamma radioactivity levels and associated dose rates from surface soils in cyprus.

Abstract: A survey was carried out to determine activity concentration levels and associated dose rates from the naturally occurring radionuclides 2 3 2 Th, 2 3 8 U and 4 0 K, in the various geological formations of Cyprus, by means of high-resolution gamma ray spectrometry. A total of 115 representative soil samples were collected from all over the bedrock surface of the island, based on the different lithological units of the study area, sieved through a fine mesh, sealed in 1000 ml plastic Marinelli beakers and measured in the laboratory with respect to gamma radioactivity for a counting time of 18-h each. From the measured spectra, activity concentrations were determined for 2 3 2 Th (range from 1.0 x 10 - 2 to 39.8 Bq kg - 1 ), 2 3 8 U (from 1.0 × 10 - 2 to 39.3 Bq kg - 1 ) and 4 0 K (from 4.0 x 10 - 2 to 565.8 Bq kg - 1 ). Gamma absorbed dose rates in air outdoors were calculated to be in the range from 1.1 x 10 - 2 to 51.3 nGy h - 1 , depending on the geological features, with an overall mean value of 8.7 nGy h - 1 and a standard deviation of 8.4 nGy h - 1 . This value is by a factor of about seven below the corresponding population-weighted world-averaged value of 60 nGy h - 1 and one of the lowest that has been reported from similar investigations worldwide. Assuming a 20% occupancy factor, the corresponding effective dose rates outdoors equivalent to the population were calculated to be between 1.3 x 10 - 2 and 62.9 μSv y - 1 , with an arithmetic mean value of 10.7 μSv y - 1 and a standard deviation of 10.3 μSv y - 1 .

The variation in biological effectiveness of X-rays and gamma rays with energy.

Abstract: The ICRP has attributed the same relative risk for all low-LET (linear energy transfer) radiations, including X and gamma radiations of all energies. However, very low energy X-rays are expected to be more biologically effective, per unit absorbed dose, than high energy X-rays or gamma rays due to the production of lower energy secondary electrons, with a correspondingly higher LET. This increase in relative biological effectiveness (RBE) is also seen experimentally for a range of biological end-points, however, a wide range of RBE values have been reported. The assessment of risks is particularly important due to the use of low energy X-rays for mammography screening. A review of the published data on the variation in biological effectiveness with energy is presented here.

The energy spectrum of cosmic-ray induced neutrons measured on an airplane over a wide range of altitude and latitude.

Abstract: Crews of high-altitude aircraft are exposed to radiation from galactic cosmic rays (GCRs). To help determine such exposures, the Atmospheric Ionizing Radiation Project, an international collaboration of 15 laboratories, made simultaneous radiation measurements with 14 instruments on a NASA ER-2 high-altitude airplane. The primary instrument was a sensitive extended-energy multisphere neutron spectrometer. Its detector responses were calculated for energies up to 100 GeV using the radiation transport code MCNPX 2.5.d with improved nuclear models and including the effects of the airplane structure. New calculations of GCR-induced particle spectra in the atmosphere were used to correct for spectrometer counts produced by protons, pions and light nuclear ions. Neutron spectra were unfolded from the corrected measured count rates using the deconvolution code MAXED 3.1. The results for the measured cosmic-ray neutron spectrum (thermal to >10 GeV), total neutron fluence rate, and neutron dose equivalent and effective dose rates, and their dependence on altitude and geomagnetic cut-off agree well with results from recent calculations of GCR-induced neutron spectra.

Measurement of radioactivity in the soil of Bahawalpur division, Pakistan.

Abstract: Bahawalpur is the largest division of the Punjab province in Pakistan. It is larger than many countries of the world. Gamma activity from the naturally occurring radionuclides namely 226Ra, 232Th, the primordial radionuclide 40K and the artificial radionuclide 137Cs was measured in the soil of the Bahawalpur division using gamma spectrometry technique. The mean activity of 226Ra, 232Th, 40K and 137Cs were found to be 32.9 +/- 0.9, 53.6 +/- 1.4, 647.4 +/- 14.1 and 1.5 +/- 0.2 Bq kg(-1), respectively. The mean radium equivalent activity Raeq, external hazard index, internal hazard index and terrestrial absorbed dose rate for the area under study are 158.5 +/- 4.1 Bq kg(-1), 0.4, 0.5 and 77.32 nGy h(-1), respectively. The annual effective dose equivalent to the public was found to be 0.5 mSv.

Cosmic radiation exposure of aircraft crew: compilation of measured and calculated data.

Abstract: The aim of the working group has been to bring together, in particular from European research groups, the available, preferably published, experimental data and results of calculations, together with detailed descriptions of the methods of measurement and calculation. The purpose is to provide a dataset for all European Union Member States for the assessment of individual doses and/or to assess the validity of different approaches, and to provide an input to technical recommendations by the Article 31 group of experts and the European Commission. The radiation protection quantity of interest is effective dose, E (ISO), but the comparison of measurement results obtained by different methods or groups, and comparison of measurement results and the results of calculations, is done in terms of the operational quantity ambient dose equivalent, H*(10). The final report giving the results of the investigations will be published by the European Commission Directorate General Transport and Energy. This paper gives a preview of the report.

Peripheral neutron and gamma doses in radiotherapy with an 18 MV linear accelerator

Abstract: More and more attention is being given in radiotherapy to the doses received by organs other than the target organ. With increasing survival time of the patients, the risks of secondary malignancies need to be lowered as much as possible. So total body doses are worth estimating in radiotherapy. The introduction of intensity modulated radiotherapy (IMRT) needs an increase in the number of monitor units given to the patient. So there is a risk of increasing the peripheral doses using this technique. Another aspect, mostly neglected, is the neutron peripheral dose that occurs when LINAC energies above 8 MeV are used. We did measurements for both gammas and neutrons with an 18 MV Varian accelerator for a prostate cancer treatment. The measurements were done both free-in-air, at different depths in a plexi-phantom, and using a Rando-Alderson phantom. Effective doses for the total body outside the treatment area are estimated using these measurements.

Radiation protection aspects of the cosmic radiation exposure of aircraft crew.

Abstract: Aircraft crew and frequent flyers are exposed to elevated levels of cosmic radiation of galactic and solar origin and secondary radiation produced in the atmosphere, the aircraft structure and its contents. Following recommendations of the International Commission on Radiological Protection in Publication 60, the European Union introduced a revised Basic Safety Standards Directive, which included exposure to natural sources of ionising radiation, including cosmic radiation, as occupational exposure. The revised Directive has been incorporated into laws and regulations in the European Union Member States. Where the assessment of the occupational exposure of aircraft crew is necessary, the preferred approach to monitoring is by the recording of staff flying times and calculated route doses. Route doses are to be validated by measurements. This paper gives the general background, and considers the radiation protection aspects of the cosmic radiation exposure of aircraft crew, with the focus on the situation in Europe.

Dose rate assessment of terrestrial gamma radiation in the Delta region of Nigeria

Abstract: In situ gamma spectroscopy has been employed to characterise natural radiation in the soil at 32 locations in the Delta region of Nigeria. The outdoor gamma dose rates in the air due to 40K, 238U and 232Th in the soil were 1.5 +/- 0.9 nGy h(-1), 6.9 +/- 1.6 nGy h(-1) and 16.3 +/- 3.1 nGy h(-1) respectively. The estimated total annual outdoor effective dose to the people in the region was 31.6 microSv y(-1).

Mini-TEPCs for radiation therapy.

Abstract: A mini-tissue-equivalent proportional-counter (TEPC) has been constructed to study the possibility to manufacture mini-counters without field-shaping tubes for radiation therapy. The mini-TEPC can be assembled with and without field-shaping tubes. It can be equipped with a mini-alpha source for a precise lineal energy calibration. After the positive conclusions of this study, a slim TEPC has been designed and constructed. The slim TEPC has an external diameter of only 2.7 mm. It has been tested with therapeutic proton beams and gamma ray sources.

Fast neutrons produced by nuclear fragmentation in treatment irradiations with 12C beam.

Abstract: In the framework of the heavy-ion tumour therapy project at GSI we investigated the nuclear fragmentation of 200 AMeV carbon ions stopping in a 12.78-cm thick water absorber. Fast neutrons and charged particles emerging from the target were registered at forward angles between 0 degrees and 30 degrees with a DeltaE-E-telescope consisting of an NE102 and a BaF2 scintillator. We obtained neutron energy spectra and angular distributions and derived the neutron yield in the energy range from 10 to 500 MeV in the forward hemisphere. In addition, we performed fragmentation measurements in actual patient treatment irradiations. The resulting angular distributions of neutrons and charged particles as well as their yields are similar to those obtained with the water absorber.

The annual effective dose from natural sources of ionising radiation in Canada.

Abstract: A review and analysis of published information combined with the results of recent gamma ray surveys were used to determine the annual effective dose to Canadians from natural sources of radiation. The dose due to external radiation was determined from ground gamma ray surveys carried out in the cities of Toronto, Ottawa, Montreal and Winnipeg and was calculated to be 219 microSv. A compilation of airborne gamma ray data from Canada and the United States shows that there are large variations in external radiation with the highest annual outdoor level of 1424 microSv being found in northern Canada. The annual effective inhalation dose of 926 microSv from 222Rn and 220Rn was calculated from approximately 14,000 measurements across Canada. This value includes a contribution of 128 microSv from 222Rn in the outdoor air together with 6 microSv from long-lived uranium and thorium series radionuclides in dust particles. Based on published information, the annual effective dose due to internal radioactivity is 306 microSv. A program developed by the Federal Aviation Administration was used to calculate a population-weighted annual effective dose from cosmic radiation of 318 microSv. The total population-weighted average annual effective dose to Canadians from all sources of natural background radiation was calculated to be 1769 microSv but varies significantly from city to city, largely due to differences in the inhalation dose from 222Rn.

Recent advances of nanodosimetry.

Abstract: The early damage to genes and cells due to ionizing radiation is initiated by the overlay of the track structure of charged particles and of the structure of radiosensitive sub-cellular volumes. As a result of this overlay, a specified number of ionizations (the ionization cluster size) is formed per primary particle. Therefore, one of the aims of nanodosimetry is to determine ionization cluster-size distributions in nanometric volumes of liquid water, as a substitute to sub-cellular structures. After a short description of the main aspects of cluster-size formation by charged particles, an overview of the advanced measuring techniques that use millimetric target volumes filled with a low-pressure gas to simulate nanometric target volumes at unit density is given. Afterwards, physical principles are discussed which are applicable to convert ionization cluster-size distributions measured in gases into those for liquid water. Finally, a tentative possibility is proposed of how to relate parameters derived from cluster-size distributions in liquid water to parameters derived from radiation-induced radiobiological experiments.

Radiation protection dosimetry for diagnostic radiology patients.

Abstract: The radiation protection of patients undergoing medical X-ray examinations is governed by the principles of justification and optimisation. Radiation dosimetry is required to inform medical practitioners of the levels of exposure and hence the risks from the diagnostic procedures that they have to justify and to assist the operators of X-ray imaging equipment to determine whether their procedures are optimised. This paper describes the main dosimetric methods that have been developed to meet these requirements. Suitable radiation risk projection models are used to predict the risks to patients in the UK from computed tomography examinations, as a function of age at exposure and sex, and show that the lifetime risk of fatal cancer can reach 1 in 1000 for children. The concept of 'diagnostic reference levels' as an aid to the optimisation of medical exposures is described, and progress in implementing them in the UK is reported.

Increasing film-focus distance (ffd) reduces radiation dose for x-ray examinations

Abstract: Increasing film-focus distance (FFD) from the traditional 100 cm has been shown to be an effective method of reducing dose whilst maintaining image quality. In particular, previous work increasing the FFD from 100 to 130 cm for lumbar spine examinations demonstrated an effective dose reduction of 44%. Objective. The current study continues on from this work by investigating the dose-reducing efficacy of this FFD change for pelvis X-ray examinations. Materials and methods. Dose measurements at 100 and 130 cm using thermoluminescent dosemeters were undertaken using an anthropomorphic phantom and patients. Image quality was assessed using CEC anatomical criteria and psychophysical tests. Results. The results showed that increasing the FFD results in a reduction in effective dose of 33%, with no change in image quality. The data provided in this and previous studies demonstrate the need for rapid implementation of this simple cost-effective procedure across imaging departments, leading to an important reduction in collective dose. Conclusion. The CEC recommendation of using 115 cm FFD for a number of procedures, although useful compared with 100 cm, undervalues by a factor between 2 and 3 the potential of this dose-reducing tool.

The effects of ionisation density on the thermoluminescence response (efficiency) of LiF:Mg,Ti and LiF:Mg,Cu,P

Abstract: In this paper, the various models dealing with the effects of ionisation density on the thermoluminescence (TL) response (efficiency) of TL LiF dosemeters are discussed. These include (i) the Unified Interaction Model (UNIM), which models photon/electron linear/supralinear dose response; (ii) the Extended Track Interaction Model (ETIM), which models heavy charged particle (HCP) TL fluence response; (iii) Modified Track Structure Theory (MTST), which models relative HCP TL efficiencies; and (iv) Microdosimetric Target Theory (MTT), which models both relative HCP efficiencies and photon energy response.

Adult reference levels in diagnostic and interventional radiology for temporary use in Switzerland.

Abstract: This work aims at establishing a set of diagnostic reference levels (DRLs) for various types of examinations performed in diagnostic and interventional radiology. The average doses for 257 types of radiological examinations were established during the 1998 nationwide survey on the exposure of the Swiss population by radiodiagnostics. They were calculated using appropriate dosimetric models and average technical parameters. The DRLs were derived from the average doses using a multiplying factor of 1.5. The DRLs obtained were rounded and compared to the data reported in the literature. The results are in most cases comparable to the DRLs determined by the 3rd-quartile method. These discrepancies registered in some cases, particularly for complex examinations, can be explained by significant differences in the protocols and/or the technical parameters used. A set of DRLs is proposed for a large number of examinations to be used in Switzerland as temporary values until a national dosimetric database is set up.

Recent advances in dosimetry using the optically stimulated luminescence of Al2O3:C.

Abstract: This paper presents an overview of some very recent developments in optically stimulated luminescence (OSL) dosimetry using aluminium oxide (Al 2 O 3 :C), with special emphasis given to the work of the research group at Oklahoma State University. Some of the advances are: (i) the development of a real-time optical fibre system for in viva dosimetry applied to radiotherapy; (ii) the development of a fibre dosimetry system for remote detection of radiological contaminants in soil; (iii) the characterisation of Al 2 O 3 :C in heavy charged particle fields and the study of ionisation density dependence of the OSL from Al 2 O 3 :C; and (iv) fast and separate assessment of beta and gamma components of the natural dose rate in natural sediments. These achievements highlight the versatility of the OSL technique associated with the high-sensitivity of Al 2 O 3 :C for the development of new dosimetry applications.

Quasi-monoenergetic neutron reference fields in the energy range from thermal to 200 MeV.

Abstract: Well-characterised neutron fields are a prerequisite for the investigation of neutron detectors. Partly in collaboration with external partners, the PTB neutron metrology group makes available for other users neutron reference fields covering the full energy range from thermal to 200 MeV. The specification of the neutron fluence in these beams is traceable to primary standard cross sections.

Excess radiation absorbed doses from non-optimised radioiodine treatment of hyperthyroidism.

Abstract: Radioiodine therapy is often the method of choice for treatment of hyperthyroidism because it is considered safe, is relatively inexpensive, and is convenient for the patient and except for occasional hypothyroidism, almost without side effects. Even though radioiodine treatment has been performed for over 50 years, the method of treatment differs from country to country and even from hospital to hospital within the same country. To illuminate such differences 187 radioiodine treatments for Graves' disease at Malmo University Hospital in Sweden have been analysed. Comparative dose calculations were carried out assuming that the individual patients had also been treated according to a number of other protocols in current use. The results show that the protocol used for calculating the administered activity in radioiodine therapy is far from optimised in many hospitals. Following the protocols where the absorbed dose to the thyroid is calculated without any uptake measurements after administration of a test activity, most of the patients were treated with an unnecessarily high activity, as a mean factor of 2.5 times too high and in individual patients up to eight times too high, leading to an unnecessary radiation exposure both for the patient, the family and the public. This is not in accordance with generally accepted radiation protection principles. Using higher activity than necessary will also prolong the patient's stay at the hospital and thus increase the costs for the care. Unnecessarily high activity will also necessitate more long-lasting radiation protection restriction relative to family members when the patient is back home.

Active personal dosemeters for individual monitoring and other new developments.

Abstract: In this paper, we will present a first (but not complete) status description of active personal dosemeters (APDs) and their implementation in European countries. In modern radiation protection practices, APDs are becoming absolutely necessary operational tools for satisfying the ALARA principle. Despite their success, they are relatively new for individual monitoring of workers. Regulation, legal requirements and calibration procedures are different in European member states. A catalogue of commercially available and prototype devices is presented. Improvement on devices and in implementation of calibration method are expected in the forthcoming years. End-user feedback experience and requirements are reported.

Activity concentrations and mean annual effective dose of foodstuffs on the island of Tenerife, Spain

Abstract: A total of 26 different food types and 12 elaborated diets were analysed by low-level gamma spectrometry to measure their content of 238U(234Th), 228Ra(228Ac), 226Ra(214Pb), 210Pb, 137Cs and 40K. The concentrations of these radionuclides measured in some imported foodstuffs were compared with those measured in some locally produced ones. Moreover, the concentrations found in the analysed foodstuffs and composite diets were compared with the data available in literature from other locations, such as Egypt, Brazil, Poland and Hong Kong. 40K contributed highest to the daily dose produced by the intake of comestibles. The largest 40K concentrations were measured in the chickpeas and beans with 380 +/- 30 and 380 +/- 20 Bq kg(-1) fresh weights, respectively. The artificial radionuclide 137Cs was measured only above detection limits in the potatoes and sweet potatoes. A mean annual effective dose of 362 microSv with a standard deviation of 110 microSv was calculated from the composite diets.

Development of software for internal dose calculation from bioassay measurements.

Abstract: Recently developed biokinetic models of ICRP permit increasingly realistic descriptions of the behaviour of radionuclides in the human body. This, however, has made the interpretation of bioassay data extremely difficult. Thus computer programs for implementing these models are in need, but very few are available. The present work describes personal-computer-based software, MONDAL2 (monitoring to dose calculation ver. 2), that enables users to estimate intake activity and the resulting effective doses from bioassay measurements for both workers and members of the public. This software runs on Microsoft Windows 95, 98, Millennium edition, 2000 or XP. If the system is to be fully copied to a hard disk, hard disk space of 23 MB is required. This software is distributed by the National Institute of Radiological Sciences free of charge.

Comparative dosimetry of BEIR VI revisited.

Abstract: The BEIR VI Committee applied recent developments in the comparative dosimetry of radon exposures in mines and homes to evaluate the so-called K-factor used to extrapolate the excess relative risk of lung cancer determined for underground uranium miners to exposures in homes. This paper describes methodological aspects of these developments that were specified ambiguously in the BEIR VI report. Specifically, in the section dealing with dosimetry (Appendix B of the BEIR VI report), the K-factor was unusually defined in terms of exposure to radon gas (K(gas)), and not in terms of exposure to potential alpha energy (K). An incorrect value of unity was calculated for K(gas). This implies a value of 0.44 for K. In this paper, we describe how application of the ICRP Publication 66 lung and dosimetric models to evaluate the regional lung dose per unit exposure to potential alpha-energy in mines and homes yields the value of K = unity. This confirms the BEIR VI Committee's choice of K = 1 for application in their risk extrapolation model. The paper also reviews the use of doses to specific sub-cellular targets in the evaluation of K. This yields a somewhat greater divergence in the corresponding estimates of K, but again an overall average value of K = unity. The paper describes the methods used to calculate alpha particle hit probabilities for specific subcellular targets, and the resulting estimates of single- and multiple-hit probabilities obtained for exposures in mines and homes, as a function of the respective exposure rates.

A European satellite-derived UV climatology available for impact studies.

Abstract: This paper presents a satellite-derived climatology of the surface UV radiation, intended to support impact studies on the environment and human health. As of today, the dataset covers the period from 1 January 1984 to 31 August 2003, with daily dose maps covering Europe with a spatial resolution of 0.05 degrees. A comparison between the modelled erythemal daily dose and measurements in Ispra yields an r.m.s. value with a relative difference of 29% and a bias of 3%. The seemingly large dispersion is, however, due to a restricted number of days for which the relative difference is very high. The climatological dataset documents systematic patterns in the geographical distribution of the surface UV radiation due to cloudiness, altitude and snow. It also shows a large year-to-year variability in monthly doses of upto +/-50% in spring and +/-30% in summer.

Developing a virtual reality application for training nuclear power plant operators: setting up a database containing dose rates in the refuelling plant.

Abstract: Operators in Nuclear Power Plants can receive high doses during refuelling operations. A training programme for simulating refuelling operations will be useful in reducing the doses received by workers as well as minimising operation time. With this goal in mind, a virtual reality application is developed within the framework of the CIPRES project. The application requires doses, both instantaneous and accumulated, to be displayed at all times during operator training. Therefore, it is necessary to set up a database containing dose rates at every point in the refuelling plant. This database is based on radiological protection surveillance data measured in the plant during refuelling operations. Some interpolation routines have been used to estimate doses through the refuelling plant. Different assumptions have been adopted in order to perform the interpolation and obtain consistent data. In this paper, the procedures developed to set up the dose database for the virtual reality application are presented and analysed.

Evaluation of indoor gamma radiation dose in dwellings.

Abstract: The use of materials containing naturally occurring radionuclides for house construction may enhance the natural radiation background to which some population groups are exposed. External exposure results from gamma emitter radionuclides existing in the walls, floor and ceiling. Mathematical models can be used to predict external dose rates inside a room, provided the compartment geometry and the radionuclide concentration activities are known. This paper presents a methodology and a computer code for theoretical evaluation of indoor external gamma doses in the air. The room was modelled as three pairs of rectangular slabs of finite thickness. Doses were evaluated by applying a photon transport model, taking into account self-absorption and radiation build-up. Calculations were performed for K, 2 2 6 Ra and 2 3 2 Th, considering concrete walls. The results obtained show good agreement with those reported in the literature. Dose conversion factors are presented in a practical manner, ready to use for radiological impact screening.

Task-specific monitoring of nuclear medicine technologists' radiation exposure

Abstract: Many studies have demonstrated that the exposure of nuclear medicine technologists arises primarily from radioactive patients rather than from preparation of radiopharmaceuticals. However, in order to devise strategies to reduce staff exposure, it is necessary to identify the specific tasks within each procedure that result in the highest radiation doses. An ESM Eberline FH41B-10 radiation dosemeter, which records the ambient dose equivalent rate, was used to monitor the radiation exposure of a technologist and to record the dose rate in microSv per hour every 32 s throughout a working day. The technologist recorded the procedures that were being performed so that the procedures that resulted in higher doses could be identified clearly. The measured doses clearly showed that the major contributions to the technologist's dose were the following: (1) transferring incapacitated patients from the imaging table to a hospital trolley; (2) difficult injections without syringe shields; and (3) setting up patients for gated myocardial scans. The average dose to the technologist from transferring patients after a bone scan was 0.54 microSv, 40% of the total dose of 1.3 microSv for the complete bone scan procedure. The average dose received injecting 900 MBq of 99Tcm-HDP using a tungsten syringe shield was 0.57microSv, but the highest dose was 1.6 microSv, in a patient in whom the injection was difficult. A 0.5 mm lead apron was found to reduce the dose when setting up a patient for a gated stress 99Tcm-sestamibi myocardial scan by approximately a factor of 2. The average dose per patient for this task was reduced from 1.1 to 0.6 microSv. It is recommended that staff waiting for assistance with patient transfers stand away from the patient, that tungsten syringe shields be used for all radiopharmaceutical injections and that a 0.5 mm lead apron be worn when attending patients containing high activities of 99Tcm radiopharmaceuticals, such as those having myocardial imaging.

Assessment of aircrew radiation exposure by further measurements and model development.

Abstract: A methodology is presented for collecting and analysing exposure measurements from galactic cosmic radiation using a portable equipment suite and encapsulating these data into a semi-empirical model/Predictive Code for Aircrew Radiation Exposure (PCAIRE) for the assessment of aircrew radiation exposure on any flight over the solar cycle. The PCAIRE code has been validated against integral route dose measurements at commercial aircraft altitudes during experimental flights made by various research groups over the past 5 y with code predictions typically within a20% of the measured data. An empirical correlation, based on ground-level neutron monitoring data, is detailed further for estimation of aircrew exposure from solar particle events. The semi-empirical models have been applied to predict the annual and career exposure of a flight crew member using actual flight roster data, accounting for contributions from galactic radiation and several solar energeticparticle events over the period 1973‐2002.

Radiation dose to premature infants in neonatal intensive care units in Kuwait.

Abstract: Entrance surface dose (ESD) and effective dose (E) to premature infants were estimated at three neonatal intensive care units in Kuwait for three standard X-ray examinations--abdominal, chest and skull X rays using a simple water phantom. The ESD was found to vary between 58 and 102 microGy for abdominal X rays, between 51 and 102 microGy for chest X rays and between 58 and 145 microGy for skull examinations. These doses are comparable to the entrance skin doses published elsewhere. The E-values were estimated using normalised organ dose dataset from the National Radiological Protection Board. The E-values for abdominal, chest and skull examinations were in the ranges of 30-46, 20-36 and 8-18 microSv per examination, respectively. The risk of developing childhood cancers from each of the three examinations was estimated to be in the range (9-117) x 10(-6) for infants undergoing 25 of these X-ray examinations during their stay in the NIC unit.

238U, 226Ra, 210Po concentrations of bottled mineral waters in Hungary and their committed effective dose.

Abstract: Nowadays the consumption of bottled mineral waters has become very popular. The average consumption of these is 0.36 l d - 1 per person in Europe. A considerable segment of the population drinks almost only mineral water as drinking water, which is about 1 l d - 1 . As is known, some kinds of mineral waters contain naturally occurring radionuclides in higher concentration than the usual drinking (tap) water. The WHO (1993) legislation concerning the drinking waters does not include the mineral waters. In our work, the oncentrations of 2 2 6 Ra, 2 3 8 U and 2 1 0 Po were determined in mineral waters available in Hungary. To determine the 2 2 6 Ra concentration the emanation method was used. The 2 3 8 U and 2 1 0 Po concentrations were determined by alpha spectrometry using semiconductor detector. The dose contribution was calculated using the radionuclide concentrations and the dose conversion factors from the Basic Safety Standard IAEA (1995), for 1 l d - 1 mineral water consumption. In some cases the calculated doses were considerable higher than the limit for drinking waters. Especially for children the doses can be remarkably high.