Radiation Protection Dosimetry - Advance Access

Response to Letter to the Editor

Horowitz, Y. S. — 2008-07-23

Letter to the Editor

German, U., Weinstein, M., Abraham, A., Alfassi, Z. B. — 2008-07-23

RADIONUCLIDE CONCENTRATIONS IN SOILS OF NORTHERN NAMIBIA, SOUTHERN AFRICA

Oyedele, J. A., Sitoka, S., Davids, I. — 2008-07-22

Activity concentrations of the naturally occurring radionuclides like ²³⁸U, ²³²Th and ⁴⁰K in 400 soil samples collected from four major towns across the northern region of Namibia have been determined using gamma-ray spectrometry with the objective of providing baseline data on the radiation level in the region. The average concentrations of radionuclides in the towns vary from 7.5 ± 2.3 to 14.2 ± 3.3 Bq kg^–1 for ²³⁸U, 5.8 ± 2.6 to 24.9 ± 6.1 Bq kg^–1 for ²³²Th and 52.1 ± 28.7 to 380.1 ± 112.9 Bq kg^–1 for ⁴⁰K. These concentrations were used to calculate the mean absorbed dose rate and the mean annual effective dose in the region. The low value of 21 ± 16 µSv obtained for the mean annual effective dose indicates that the region has normal background radiation.

RECONSIDERATION OF THE MINIMUM DOSE CONSTRAINT FOR PUBLIC EXPOSURES IN RADIOLOGICAL PROTECTION

Hattori, T. — 2008-07-22

By using a probabilistic approach, the effects of the dose distribution of radiation due to man-made radioactive nuclides when added to those of natural background radiation have been studied. These results show that additional exposure to man-made radiation of up to 0.5 mSv y^–1 (as a dose constraint) would not significantly change the distribution of total public doses. Taking into consideration such probabilistic analysis and rationales of derivations of exemption and clearance levels, it can be concluded that the minimum dose constraint that requires optimisation in radiation protection, should be set to 0.1 mSv y^–1, which is one-order magnitude higher than 0.01 mSv y^–1, the current dose criterion for exemption and clearance.

How close is close enough?

McDonald, J. C. — 2008-07-18

PLUTONIUM ISOTOPES IN MARINE SEDIMENTS AND SOME BIOTA FROM THE SUDANESE COAST OF THE RED SEA

Sirelkhatim, D. A., Sam, A. K., Hassona, R. K. — 2008-07-18

Measurements of ^239+240Pu and ²³⁸Pu were carried out on marine biota as well as on sediments from the fringing reefs area extending towards north and south (Flamingo Bay) of PortSudan harbour. The analyses were performed using radiochemical separation and alpha spectrometry. The range of the activity concentrations in marine sediments, in mBq kg^–1 dry weight, was found to be from 5.10 to 82.00 for ^239+240Pu and from 0.89 to 8.63 for ²³⁸Pu. Corresponding activity concentrations of ^239+240Pu and ²³⁸Pu in sediments from the harbours at PortSudan and Sawakin were 53-301 and 8.29-28.6 (PortSudan) and 163-343 and 4.7 (Sawakin), respectively. The higher values for plutonium in marine algae suggest their suitability as an indicator species for monitoring purposes. The results obtained are generally lower than those found by other studies and show that the Red Sea environment is mildly affected by plutonium contamination. Activity ratios of plutonium isotopes confirm that the existence of plutonium in the Red Sea is mainly due to atmospheric global fallout.

VARIATION OF SOIL RADON CONCENTRATIONS IN SOUTHERN ONTARIO

Chen, J., Ly, J., Bergman, L., Wierdsma, J., Klassen, R. A. — 2008-07-17

Radon has been identified as the second leading cause of lung cancer after tobacco smoking. Information on indoor radon concentrations is required to assess the lung cancer burden due to radon exposure. However, radon data in highly populated southern Ontario are very limited. Since radon in soil is believed to be the main source of radon in homes, measurements of soil gas radon concentrations can be used to estimate variations in radon potential of indoor environments. This study reports a transect survey of natural background variation in soil radon levels across southern Ontario. The results indicate that radon risk could be high in some areas of southern Ontario.

MITIGATION OF THREE WATER SUPPLIES WITH HIGH RADON EXPOSURE TO THE EMPLOYEES

Ringer, W., Simader, M., Bernreiter, M., Kaineder, H. — 2008-07-17

A comprehensive survey to determine the occupational radiation exposure in water supplies and spas was conducted in the federal state of Upper Austria. The study comprises 45 water supplies. The limit for radon exposure of 6 MBq h m^–3 was exceeded by two water supplies (WS 33 and WS 42). In one water supply (WS 29), the level of 2 MBq h m^–3 was exceeded. These water supplies were mitigated. Prior to mitigation the main radon sources were identified. Mitigation measures were: evacuation of the outlet air of the vaporiser by means of a fan, installation of a fan in the exhaust air duct of the compensating reservoir, sealing of drain shafts and mechanical ventilation of the office. In all water supplies, the radon exposure was reduced to below 0.8 MBq h m^–3 at a cost of approx. 750 to 1000.

A STUDY OF INDOOR RADON LEVELS IN RURAL DWELLINGS OF EZINE (CANAKKALE, TURKEY) USING SOLID-STATE NUCLEAR TRACK DETECTORS

Orgun, Y., Altinsoy, N., Sahin, S. Y., Ataksor, B., Celebi, N. — 2008-07-11

Indoor radon activity level and radon effective dose (ED) rate have been carried out in the rural dwellings of Ezine (Çanakkale) during the summer season using Radosys-2000, a complete set suitable to radon concentration measurements with CR-39 plastic alpha track detectors. The range of radon concentration varied between 9 and 300 Bq m^–3, with an average of 67.9 (39.9 SD) Bq m^–3. Assuming an indoor occupancy factor of 0.8 and 0.4 for the equilibrium factor of radon indoors, it has been found that the ²²²Rn ED rate in the dwellings studied ranges from 0.4 to 5.2 mSv y^–1, with an average value of 1.7 (1.0) mSv y^–1. There is a possibility that low radon concentrations exist indoors during the summer season in the study area because of relatively high ventilation rates in the dwellings. A winter survey will be needed for future estimation of the annual ED.

COMPARISON OF RADIATION DOSE TO PATIENT AND STAFF FOR TWO INTERVENTIONAL CARDIOLOGY UNITS: A PHANTOM STUDY

Mesbahi, A., Mehnati, P., Keshtkar, A., Aslanabadi, N. — 2008-07-11

The purpose of this investigation was to measure the patient and staff dose during routine interventional cardiology procedures for an image intensifier-based and a flat detector system using a water phantom. The Integris BH3000 image intensifier-based (Philips) and the Axiom Artis flat detector-based (Siemens) angiography units were used in this study. The accuracy of tubes potential and irradiation timers and also internal dosimeters were verified and confirmed. A water phantom with a thickness of 18 cm was used for patient and staff dose measurements. For the Philips system, phantom entrance dose rates were 2.77 and 38.97 µGym² s^–1 during fluoroscopy and cineangiography. The respective dose rates for the Siemens were 1.98 and 13.46 µGym² s^–1. Phantom entrance dose rate was 28.5 and 65% higher for the Philips system during fluoroscopy and cineangiography, respectively. Comparing the scattered dose rates at the operator location showed that the flat detector-based Siemens system delivers five times lower dose to the operator in comparison with the image intensifier-based Philips unit. The results suggest that the decrease in received dose of the patient and staff is achievable using the flat detector system. In addition, application of lead curtain and glass is recommended to lower the cardiologist dose especially for the image intensifier-based Philips system.

STATISTICAL APPROACHES TO FORECAST GAMMA DOSE RATES BY USING MEASUREMENTS FROM THE ATMOSPHERE

Jeong, H.-J., Hwang, W.-T., Kim, E.-H., Han, M.-H. — 2008-07-11

In this paper, the results obtained by inter-comparing several statistical techniques for estimating gamma dose rates, such as an exponential moving average model, a seasonal exponential smoothing model and an artificial neural networks model, are reported. Seven years of gamma dose rates data measured in Daejeon City, Korea, were divided into two parts to develop the models and validate the effectiveness of the generated predictions by the techniques mentioned above. Artificial neural networks model shows the best forecasting capability among the three statistical models. The reason why the artificial neural networks model provides a superior prediction to the other models would be its ability for a non-linear approximation. To replace the gamma dose rates when missing data for an environmental monitoring system occurs, the moving average model and the seasonal exponential smoothing model can be better because they are faster and easier for applicability than the artificial neural networks model. These kinds of statistical approaches will be helpful for a real-time control of radio emissions or for an environmental quality assessment.

LONG-TERM FADE STUDY OF THE DT-702 LiF: Mg,Cu,P TLD

2008-07-11

LiF thermoluminescent dosemeters (TLDs) are used by the US Navy to record radiation exposure of personnel. The Model DT-648 LiF:Mg,Ti TLD has been replaced by a new Model DT-702 LiF:Mg,Cu,P TLD. The DT-648 was used for many years and has undergone extensive testing to identify its pre- and post-irradiation fade operating characteristics. Studies have shown that the addition of copper increases the thermoluminesence sensitivity of the TLD for improved low-level radiation monitoring. This study evaluates various fading characteristics of the new copper-doped dosemeter using current equipment for processing of TLDs and calibrating to a National Institute of Standards and Technology standard source. The 57-week study took place at the Naval Dosimetry Center, Bethesda, MD, USA. TLDs were stored for various lengths of time before and after being exposed to a National Institute of Standards and Technology calibrated radiation sources. TLDs were then processed using current US Navy instructions and the resulting dose compared with the calibrated exposure. Both loss of signal and loss of sensitivity were evaluated. The results of this study have shown that the DT-702 TLD has no statistically significant change in sensitivity or change in signal with up to 57 weeks of pre- or post-irradiation time. The results of this study will increase the accuracy of exposure record keeping for the Navy and will allow longer issue periods. This will increase flexibility with international and domestic shipping procedures, as well as reduce workload requirements for dosimetry processing.

OBITUARY

2008-07-04

ICRP PUBLICATION 103: RECOMMENDATIONS OF THE ICRP

Charles, M. W. — 2008-07-04

VERTICAL DISTRIBUTIONS AND GAMMA DOSE RATES OF 40K, 232Th, 238U AND 137Cs IN THE SELECTED FOREST SOILS IN IZMIR, TURKEY

Karadeniz, O., Yaprak, G. — 2008-07-01

This paper presents the results obtained from a radioecological study carried out in the selected forest sites of Izmir, Turkey. The levels of gamma-emitting radionuclides, ⁴⁰K, ²³²Th, ²³⁸U and ¹³⁷Cs, in soils were determined using gamma spectroscopy. The activity profile for ⁴⁰K, ²³²Th and ²³⁸U exhibits a uniform distribution with respect to depth. The depth distribution of ¹³⁷Cs activity was established by fitting the experimental points to an exponential or a Gaussian function. About 42–97% of the ¹³⁷Cs deposition was found in the first 10 cm of soil even after 18 y from Chernobyl accident. The dose-rate and annual-effective dose received from external irradiation were quantified. It is indicated that ¹³⁷Cs from the fallout plays a less role in external radiation exposures in forest sites of Izmir than in potential exposures from naturally occurring radionuclides accounted for by soil.

Science and Anti-Science

McDonald, J. C. — 2008-06-30

ETHICS AND POLICY: DEALING WITH PUBLIC ATTITUDES

Sheehan, M. — 2008-06-30

The current trend towards ethical scrutiny and oversight is very much a social trend. Many of the results of this trend are perfectly reasonable but some go harmfully too far. In this paper, caution is advocated about public attitudes and social trends. Although there is often a degree of truth in them, there is an inevitable simplification of the issues involved. The more specific danger for the professions is to think that public attitudes and social trends simply deliver ‘the ethical’. In this context a more adequate account of ethics is considered—one that is relevant for professions like radiology confronting the demands of ethical scrutiny and oversight. The paper concludes with some suggestions about how to incorporate the important aspects of public attitudes and social trends without being subservient to them.

EXPERIMENTAL EVALUATION OF PCXMC AND PREPARE CODES USED IN CONVENTIONAL RADIOLOGY

2008-06-27

The objective of this study is to evaluate the precision of dose-calculation computer codes used in our laboratory (PCXMC and PREPARE) for organ dose evaluation. Measurements of entrance and organ dose were performed using ionisation chamber and thermoluminescence dosimetry. To obtain a mean dose of organ, we have used the Rando–Alderson phantom. The results showed that computed and measured doses correlate well (within 28%) in 60% of the samples. The percentage shows that the computed doses correlate with the experimental doses rather well for PCXMC software than PREPARE. Although the two programs are based on the Monte-Carlo method, their calculations differ. PCXMC carries out a simulation of the trajectory of the photon, whereas PREPARE provides interpolated values. Our experimental results are close to the values given by the PCXMC, a program which takes into account the weight, the height of the patient and field dimensions.

PRELIMINARY OSL STUDIES ON BEIGE SEPIOLITES

Bulur, E. — 2008-06-26

Radiation-induced luminescence signals in beige sepiolite samples were investigated using optically stimulated luminescence. A thermally stable, light-sensitive radiation-induced signal was detected, and radiation dose response and thermal properties of this signal were studied. The thermal stability and dose sensitivity of the signal implies the potential of the material for dating and retrospective radiation dosimetry.

COMPARATIVE STUDY OF IMAGE QUALITY FOR MSCT AND CBCT SCANNERS FOR DENTOMAXILLOFACIAL RADIOLOGY APPLICATIONS

2008-06-26

The image quality of four cone-beam computed tomography (CBCT) scanners dedicated for dentomaxillofacial imaging and one multi-slice computed tomgoraphy (MSCT) scanner was compared. For the MSCT scanner, a clinical and a low-dose protocol for oral indications were evaluated. The image quality was assessed by dedicated software that allows an automated analysis of accuracy measurements and evaluation of metal artefacts on two image quality phantoms. Bone was segmented with sub-millimetre accuracyin all scanners.

THE US RADON PROBLEM, POLICY, PROGRAM AND INDUSTRY: ACHIEVEMENTS, CHALLENGES AND STRATEGIES

Angell, W. J. — 2008-06-26

US radon research, policy and programs have stalled since their start in the late 1980s and early 1990s. In 2005, more homes had radon above the US Environmental Protection Agency (EPA) Reference Level than anytime in history since more homes were added to the housing stock that had indoor radon concentrations exceeding 150 Bq m^–3 than had been mitigated. Funding for the US radon program has declined two-thirds from 1997 to 2007. Despite impressive goals for radon reduction, EPA lacks sound progress indicators especially in new construction radon control systems. School radon reduction has been at a standstill since the early 1990s. There has been no significant radon risk reduction in low-income sectors of the population. There is need for effective partnerships between the public and private sectors of the US radon professional communities as well as with the international programs and professionals.

RADIOLOGICAL SIGNIFICANCE OF BEACH SAND USED FOR CLIMATOTHERAPY FROM SAFAGA, EGYPT

Uosif, M. A. M., El-Taher, A., Abbady, A. G. E. — 2008-06-25

As a part of national survey to evaluate natural radioactivity in the environment, concentration levels of radioactivity were analysed for sand samples from Safaga, Egypt, which is an ideal area for climatotherapy of psoriasis. Gamma dose rates of three beaches in Safaga were measured. The values ranged from 195.1 to 210.7 nGy h^–1. The activity concentrations (Bq kg^–1) of radionuclides ²³⁸U series, ²³²Th series and ⁴⁰K in three different sand profiles (0–5, 5–10, 10–15, 15–25 and 25 – 40 cm) were measured using gamma-ray spectrometry. The annual effective doses were 259 µSv y^–1 for Minveila, 255 µSv y^–1 for Ganet Safaga and 239 µSv y^–1 for Masab El-Ghazel beaches. The dose rates, radium equivalent activities and external hazard indices were evaluated and compared with the international data. These results may contribute to the determination of absorbed dose rate reference levels in Red Sea Coast at Safaga city.

RADIATION PROTECTION IN EDUCATIONAL INSTITUTIONS: NCRP REPORT 157

Kearfott, K. J. — 2008-06-25

ESTIMATION OF HEALTH HAZARDS RESULTING FROM A RADIOLOGICAL TERRORIST ATTACK IN A CITY

2008-06-13

In recent years, the concern for protection of urban populations against terror attacks involving radiological, biological or chemical substances has attracted increasing attention. It sets new demands to decision support and consequence assessment tools, where the focus has traditionally been on accidental exposure. The aim of the present study was to illustrate issues that need to be considered in evaluating the radiological consequences of a ‘dirty bomb’ explosion. This is done through a worked example of simplified calculations of relative dose contributions for a specific ‘dirty bomb’ scenario leading to atmospheric dispersion of ⁹⁰Sr contamination over a city area. Also, the requirements of atmospheric dispersion models for such scenarios are discussed.

Delft Conference Proceedings Editorial 2008: safety and efficacy for new techniques and imaging using new equipment to support European legislation

Faulkner, K., Zoetelief, J., Schultz, F.W., Guest, R. — 2008-06-13

CONVERSION COEFFICIENTS FOR THE ESTIMATION OF EFFECTIVE DOSES IN INTRAORAL AND PANORAMIC DENTAL RADIOLOGY FROM DOSE-AREA PRODUCT VALUES

2008-06-11

Conversion coefficients for the estimation of effective doses in intraoral and panoramic dental radiology from dose-area product (DAP) values were determined by measuring organ-absorbed doses and the corresponding DAP values. Measurements were performed for all standard intraoral radiological projections and standard panoramic examination at different exposure parameters. Organ-absorbed doses were measured using thermoluminescent detectors and an adult anthropomorphic phantom specially designed for dosimetric study in dental radiology. Different techniques for the calculation of effective doses were evaluated. Conversion coefficients derived from this study range from 0.008 to 0.132 µSv mGy^–1 cm^–2 for intraoral radiography and 0.055 to 0.238 µSv mGy^–1 cm^–2 for panoramic radiography.

EXPOSURE TO LOW LEVEL GSM 935 MHZ RADIOFREQUENCY FIELDS DOES NOT INDUCE APOPTOSIS IN PROLIFERATING OR DIFFERENTIATED MURINE NEUROBLASTOMA CELLS

Moquet, J., Ainsbury, E., Bouffler, S., Lloyd, D. — 2008-06-10

The aim of this study was to investigate whether radiofrequency (RF) fields characteristic of mobile phones at non-thermal levels can induce apoptosis in murine neuroblastoma (N2a) cells in both proliferating and differentiated states. Cells were exposed continuously for 24 h to one of the three 935-MHz RF signals: global system for mobile communication (GSM) basic, GSM talk and a continuous wave, unmodulated signal; all at a specific energy absorption rate of 2 W kg^–1. The measured increase in temperature of the cells due to the RF fields was around 0.06°C. At a number of time points between 0 and 48 h post-exposure, the cells were assessed for apoptosis under a fluorescence microscope using three independent assays: Annexin V, caspase activation and in situ end-labelling. No statistically significant differences in apoptosis levels were observed between the exposed and sham-exposed cells using the three assays at any time point post-exposure. These data suggest that RF exposures, characteristic of GSM mobile phones, do not significantly affect the apoptosis levels in proliferating and differentiated murine neuroblastoma cell line N2a.

OCCUPATIONAL RADIATION EXPOSURE DUE TO NORM IN A RARE-EARTH COMPOUNDS PRODUCTION FACILITY

Haridasan, P.P., Pillai, P.M.B., Tripathi, R.M., Puranik, V.D. — 2008-06-10

In India, rare-earth compounds are produced from the beach sand mineral monazite. Caustic digestion of the mineral followed by selective acid extraction is the method used to separate composite rare-earth fraction. The composite rare-earth chloride contains low levels of natural radionuclides and is the starting material for individual rare-earth compounds which have wide applications. Activity concentrations in composite rare-earth compounds such as chlorides, fluorides, carbonates and oxides of Ce, Nd, Pr, Sm, Gd, etc. are presented in this paper. The external gamma exposure rates and airborne activity due to thorium and thoron progeny in the occupational environment are studied. The activity levels in liquid effluent are presented. The potential individual occupational dose is estimated to be 1.9 mSv per annum.

DOSE RECONSTRUCTION FOR AN OCCUPATIONAL COHORT AT THE SAVANNAH RIVER NUCLEAR FACILITY: EVALUATION OF A HYBRID METHOD

Hamra, G., Nylander-French, L. A., Richardson, D. — 2008-06-10

The Savannah River Site (SRS) is the only nuclear facility in the United States that produces tritium, a radioactive isotope of hydrogen. The purpose of the study was to derive annual tritium dose estimates for SRS employees through the development of a job-exposure matrix. The proposed method is unique in that along with qualitative information on job, area and time of employment, it utilises recorded annual whole-body dose measures, when available, in order to estimate doses from tritium intakes of the monitored workers. Using information from 75 253 dose measures for the period 1954–1978, the average proportion of the whole-body dose that was due to tritium intake was calculated; these proportions were allowed to vary by job, area and time period. This information was used to assign tritium dose levels for 43 590 employment-years. The collective estimated tritium dose was 4319 mSv compared with the total known tritium dose of 17 382 mSv. The correlation (R²) of estimated tritium dose with known tritium dose was 0.68.

THE IAEA'S ACTIVITIES IN RADIOLOGICAL PROTECTION IN DIGITAL IMAGING

Rehani, M. M. — 2008-06-03

The success achieved to minimise the radiation exposure to staff to levels much below the prescribed dose limits encourages a similar approach in patient protection where dose limits do not exist but where reference levels are provided. A number of radiation injuries among patients have been reported, per capita dose is increasing and medical exposure has become the largest contributor to population dose. The International Atomic Energy Agency (IAEA) has supported a number of research projects, produced a wide range of guidance publications, conducted over 60 training courses in the past 5 y, produced for free dissemination training CDs on radiation protection and established a dedicated Web site on the radiological protection of patients (http://rpop.iaea.org). The number of countries that is currently receiving assistance in this field exceeds 80, as compared to about half a dozen 5 y ago. Significant results on patient dose management, demonstrating dose reduction of more than 30% while maintaining image quality, have been made available through IAEA projects.

FLUENCE TO ABSORBED FOETAL DOSE CONVERSION COEFFICIENTS FOR PHOTONS IN 50 KEV-10 GEV CALCULATED USING RPI-P MODELS

Taranenko, V., Xu, X. G. — 2008-06-02

Radiation protection of pregnant females and the foetus against ionising radiation is of particular importance to radiation protection due to high foetal radiosensitivity. The only available set of foetal conversion coefficients for photons is based on stylised models of simplified anatomy. Using the RPI-P series of pregnant female and foetus models representing 3-, 6- and 9-month gestation, a set of new fluence to absorbed foetal dose conversion coefficients has been calculated. The RPI-P anatomical models were developed using novel 3D geometry modelling techniques. Organ masses were adjusted to agree within 1% with the ICRP reference data for a pregnant female. Monte Carlo dose calculations were carried out using the MCNPX and Penelope codes for external 50 keV–10 GeV photon beams of six standard configurations. The models were voxelised at 3-mm voxel resolution. Conversion coefficients were tabulated for the three gestational periods for the whole foetus and brain. Comparison with previously published data showed deviations up to 120% for the foetal doses at 50 keV. The discrepancy can be primarily ascribed to anatomical differences. Comparison with published data for five major mother organs is also provided for the 3-month model. Since the RPI-P models exhibit a high degree of anatomical realism, the reported dataset is recommended as a reference for radiation protection of the foetus against external photon exposure.

RADON RISK IN ALPINE REGIONS IN AUSTRIA: RISK ASSESSMENT AS A SETTLEMENT PLANNING STRATEGY

Gruber, V., Baumgartner, A., Seidel, C., Maringer, F. J. — 2008-06-02

Soil gas radon measurements complement indispensable and well-established radon indoor measurements in Austria. Radon in soil gas is a result of geochemical conditions as well as of geology, mineralogy, geophysics and meteorology. Therefore, geological factors can help to predict potential indoor radon concentrations via soil gas. Soil gas radon measurements in well-defined geological units give an estimate of local and regional radon hazards and build the basis for radon risk maps, which could be used for land-use planning and urban development. The creation of maps makes an important contribution to health care. For this purpose, several research projects were carried out in Austria. On the one hand, a study was already conducted in Lower Austria to determine the influence of meteorological and soil physical parameters on radon concentrations in soil gas and to evaluate soil gas radon concentrations with a radon emanation and migration model. On the other hand, radon measurements on different geomorphologic formations in the Austrian Alps, which are potential settlement areas, are of special interest.

DOSIMETRIC MODELS USED IN THE ALPHA-RISK PROJECT TO QUANTIFY EXPOSURE OF URANIUM MINERS TO RADON GAS AND ITS PROGENY

2008-05-29

The European project Alpha-Risk aims to quantify the cancer and non-cancer risks associated with multiple chronic radiation exposures by epidemiological studies, organ dose calculation and risk assessment. In the framework of this project, mathematical models have been applied to the organ dosimetry of uranium miners who are internally exposed to radon and its progeny as well as to long-lived radionuclides present in the uranium ore. This paper describes the methodology and the dosimetric models used to calculate the absorbed doses to specific organs arising from exposure to radon and its progeny in the uranium mines. The results of dose calculations are also presented.

DOSIMETRIC AUDITS OF PHOTON BEAMS IN RADIATION THERAPY CENTRES IN RIO DE JANEIRO, BRAZIL

2008-05-24

Data related to 11 y of high-energy photon radiotherapy beam dosimetry are presented and analysed. Dosimetric evaluations were carried out using water phantoms and thimble ionisation chambers and are part of the radiation protection regulatory licensing process for medicine facilities of Brazilian government. Measurements were done at reference conditions for a standard absorbed dose of 100 cGy [cGy (=1 rad)]. The absolute per cent deviation between the measured and presumed delivered doses should not exceed the tolerance level of ±3%. The first dosimetry survey from 1996 to 1998 showed a situation that was an object of concern. Deviations of 22 and 18.7% could be measured, although small deviations were also obtained. After 1998, the improvement in dosimetry quality control by the radiotherapy centres became clear, with most of the deviations situated within the ±3% range. The decrease in the measured deviations presents the effective success of the Institute of Radiation Protection and Dosimetry audit programme for the improvement in the control of radiotherapy photon beams in Rio de Janeiro. Also, it is possible to recommend to Brazilian regulatory organisation a decrease in the tolerance level for dosimetric deviations in order to achieve a more precise dose delivered to patients in radiotherapy centres.

MOBILITY DETERMINATION OF LEAD ISOTOPES IN GLASS FOR RETROSPECTIVE RADON MEASUREMENTS

2008-05-24

In retrospective radon measurements, the 22-y half life of ²¹⁰Pb is used as an advantage. ²¹⁰Pb is often considered to be relatively immobile in glass after alpha recoil implanted by ²²²Rn progenies. The diffusion of ²¹⁰Pb could, however, lead to uncertain wrong retrospective radon exposure estimations if ²¹⁰Pb is mobile and can escape from glass, or lost as a result of cleaning-induced surface modification. This diffusion was studied by a radiotracer technique, where ²⁰⁹Pb was used as a tracer in a glass matrix for which the elemental composition is known. Using the ion guide isotope separator on-line technique, the ²⁰⁹Pb atoms were implanted into the glass with an energy of 39 keV. The diffusion profiles and the diffusion coefficients were determined after annealing at 470–620°C and serial sectioning by ion sputtering. In addition, the effect of surface cleaning on diffusion was tested. From the Arrhenius fit, the activation enthalpy (H) was determined, which is equal to 3.2 ± 0.2 eV, and also the pre-exponential factor D₀, in the order of 20 m²s^–1. This result confirms the assumption that over a time period of 50 y ²⁰⁹Pb (and ²¹⁰Pb) is effectively immobile in the glass. The boundary condition obtained from the measurements had the characteristic of a sink, implying loss of ²⁰⁹Pb in the topmost surface at high temperatures.

RADIOACTIVITY CONCENTRATION IN SOIL SAMPLES IN THE SOUTHERN PART OF THE WEST BANK, PALESTINE

Dabayneh, K. M., Mashal, L. A., Hasan, F. I. — 2008-05-24

The activity concentrations of naturally occurring radioactive materials such as ²³⁸U, ²³²Th and ⁴⁰K were measured for 38 soil samples collected from diverse zones in the southern area of West Bank, Palestine using gamma-ray spectroscopy. The measured activities of ²³⁸U, ²³²Th and ⁴⁰K were found to range from 32.9 to 104.7, 14.5 to 76.6 and 297 to 962 Bq kg^–1 with averages value of 68.7, 48.0 and 630 Bq kg^–1, respectively. The obtained values of activity concentrations are higher than the world average of 35, 30 and 500 Bq kg^–1 for ²³⁸U, ²³²Th and ⁴⁰K, respectively. The measured ¹³⁷Cs activity concentration was found to range from 1.8 to 36.1 Bq kg^–1 with an average value of 8.5 Bq kg^–1. The detected activities were attributed to the fallout of ¹³⁷Cs, which is the only man-made radionuclide. The calculated average of the total gamma-radiation dose rate of natural radionuclides, ¹³⁷Cs and cosmic radiation is 121.4 nGy h^–1. The radium equivalent activity (R_aeq), dose rate (D_r), external hazard index (H_ex) and radioactivity level index (I) in all samples are presented. Some values were found to be in the range of worldwide values, whereas others were above the worldwide values.

ACTIVITY CONCENTRATIONS AND MEAN ANNUAL EFFECTIVE DOSE FROM GAMMA-EMITTING RADIONUCLIDES IN THE LEBANESE DIET

2008-05-24

Since the primary factor contributing to the internal effective dose in the human organism is contaminated food, the control of radionuclides in food represents the most important means of protection. This study was conducted to determine the levels of the dietary exposure of the Lebanese population to gamma-emitting radioisotopes. The activity concentrations of gamma-emitting radioisotopes have been measured in food samples that represent the market basket of an adult urban population in Lebanon. The artificial radionuclide ¹³⁷Cs was measured above detection limits in only fish, meat and milk-based deserts. The most abundant natural radionuclide was ⁴⁰K (31–121 Bq kg^–1), with the highest content in fish and meat samples. The annual mean effective dose contributed by ⁴⁰K in the reference typical diet was estimated equal to 186 µSv y^–1, a value reasonably consistent with findings reported by several other countries.

HISTORY OF THE MEASUREMENT OF RADON IN CENTRAL BOHEMIA

Burian, I., Otahal, P. — 2008-05-24

It is a little surprising, but radon has been measured by our Institute for >50 y. In the first phase this was carried out in underground mines (up to the present day) but more and more attention has been paid to domestic dwellings and NORM workplaces. The number of the measurements (grab sampling underground, SSNTDs application) was relatively high. To the routine work of the Institute is added research and calibration for radon measuring organisations. Since the formation of the Czech Republic, our previous institution was reformed by the State Office for Nuclear Safety and is one of the two organisations whose main task is, among others, radon measurement.

INTERCOMPARISON OF ACTIVE PERSONAL DOSEMETERS IN INTERVENTIONAL RADIOLOGY

2008-05-24

The use of active personal dosemeters (APD) in interventional radiology was evaluated by Working Group 9 (Radiation protection dosimetry of medical staff) of the CONRAD project, which is a Coordination Action supported by the European Commission within its sixth Framework Programme. Interventional radiology procedures can be very complex and they can lead to relatively high doses to personnel who stand close to the primary radiation field and are mostly exposed to radiation scattered by the patient. For the adequate dosimetry of the scattered photons, APDs must be able to respond to low-energy [10–100 keV] and pulsed radiation with relatively high instantaneous dose rates. An intercomparison of five APD models deemed suitable for application in interventional radiology was organised in March 2007. The intercomparison used pulsed and continuous radiation beams, at CEA-LIST (Saclay, France) and IRSN (Fontenay-aux-Roses, France), respectively. A specific configuration, close to the clinical practice, was considered. The reference dose, in terms of H_p(10), was derived from air kerma measurements and from the measured and calculated energy distributions of the scattered radiation field. Additional Monte Carlo calculations were performed to investigate the energy spectra for different experimental conditions of the intercomparison. The results of this intercomparison are presented in this work and indicate which APDs are able to provide a correct response when used in the specific low-energy spectra and dose rates of pulsed X-rays encountered in interventional radiology.

A PIXEL DETECTOR-BASED SINGLE PHOTON-COUNTING SYSTEM AS FAST SPECTROMETER FOR DIAGNOSTIC X-RAY BEAMS

2008-05-16

Recent advances in semiconductor pixel detectors and read-out electronics allowed to build the first prototypes of single photon-counting imaging systems that represent the last frontier of digital radiography. Among the advantages with respect to commercially available digital imaging systems, there are direct conversion of photon energy into electrical charge and the effective rejection of electronic noise by means of a thresholding process. These features allow the photon-counting systems to achieve high imaging performances in terms of spatial and contrast resolution. Moreover, the now available deep integration techniques allow the reduction of the pixel size and the improvement of the functionality of the single cell and the read-out speed so as to cope with the high fluxes found in diagnostic radiology. In particular, the single photon-counting system presented in this paper is based on a 300-µm thick silicon pixel detector bump-bonded to the Medipix2 read-out chip to form an assembly of 256 x 256 square pixels at a pitch of 55 µm. Each cell comprises a low-noise preamplifier, two pulse height discriminators and a 14-bit counter. The maximum counting rate per pixel is 1 MHz. The chip can operate in two modalities: it records the events with energy above a threshold (single mode) or between two energy thresholds (window mode). Exploiting this latter feature, a possible application of such a system as a fast spectrometer is presented to study the energy spectrum of diagnostic beams produced by X-ray tubes.

ANALYTICAL SHIELDING CALCULATIONS FOR A PROTON THERAPY FACILITY

Avery, S., Ainsley, C., Maughan, R., McDonough, J. — 2008-05-16

The University of Pennsylvania is building a proton therapy facility in collaboration with Walter Reed Army Medical Center. The proposed facility has four gantry rooms, a fixed beam room and a research room, and will use a cyclotron as the source of protons. In this study, neutron shielding considerations for the proposed proton therapy facility were investigated using analytical techniques and Monte Carlo simulated neutron spectra. Neutron spectra calculations were done using the GEANT4 (v6.2) simulation code for various materials: water, carbon, iron, nickel and tantalum to estimate the neutron production at proton beam energies of 100, 175 and 250 MeV. Dose equivalent calculations were performed using analytical methods at various critical points within the facility, by folding the GEANT4 produced neutron spectra with dose equivalent rate data from the National Council on Radiation Protection and Measurements (NCRP) Report #144.

OVERVIEW OF DOUBLE DOSIMETRY PROCEDURES FOR THE DETERMINATION OF THE EFFECTIVE DOSE TO THE INTERVENTIONAL RADIOLOGY STAFF

2008-05-14

In interventional radiology, for an accurate determination of effective dose to the staff, measurements with two dosemeters have been recommended, one located above and one under the protective apron. Such ‘double dosimetry’ practices and the algorithms used for the determination of effective dose were reviewed in this study by circulating a questionnaire and by an extensive literature search. The results indicated that regulations for double dosimetry almost do not exist and there is no firm consensus on the most suitable calculation algorithms. The calculation of effective dose is mainly based on the single dosemeter measurements, in which either personal dose equivalent, directly, (dosemeter below the apron) or a fraction of personal dose equivalent (dosemeter above the apron) is taken as an assessment of effective dose. The most recent studies suggest that there might not be just one double dosimetry algorithm that would be optimum for all interventional radiology procedures. Further investigations in several critical configurations of interventional radiology procedures are needed to assess the suitability of the proposed algorithms.

EVALUATION OF THE POPULATION DOSE TO THE UK POPULATION FROM THE NATIONAL HEALTH SERVICE BREAST SCREENING PROGRAMME

Faulkner, K., Wallis, M.G, Neilson, F, Whitaker, C.J. — 2008-05-14

In the United Kingdom National Health Service Breast Screening Programme (NHSBSP), women aged between 50 and 70 y are invited for mammography every 3 y. Screening histories for each woman, over four screening rounds, were analysed. Data from five screening programmes were used to select 57 425 women into the study. Cases were selected on the basis of being between the ages of 50 and 53 at the start of the NHSBSP (i.e. between 1989 and 1992). Assessment of the outcome for each screening round for each woman involved assigning a simple outcome code. Each of the possible pathways through the four screening rounds was analysed. This comprises of 500 possible pathways. This data enabled the following information to be determined: (i) The number of times a woman attended the screening programme. (ii) The number of women referred for assessment at each screening round. This information may be used to deduce the population dose to this group of women averaged over four screening rounds. Patient doses have been monitored since the programme's inception and are typically 4.5 mGy for two-view screening. It is possible to determine the mean glandular dose received by this cohort of women over four screening rounds by multiplying the number of examinations by the mean glandular dose for a typical woman. Allowance has to be made for the number of projections taken at each screening round. Once a woman has been screened, she may be invited back for further assessment if an abnormality is found on her mammogram. A stereotactic attachment is used to determine where to place the biopsy device. Although the dose received during a normal screening mammogram is well known, the dose for a stereotactic procedure and other assessment procedures is less well known, partly because only a small part of the breast is directly irradiated during stereotaxis. However, the woman may have multiple exposures during this stage. A prospective survey of doses was completed to deduce the mean glandular dose at the first assessment stage and during stereotaxis. Numbers of films, including magnification films taken at first-stage assessment were established in the North East of England and Scotland by means of a postal survey. Average total mean glandular dose was deduced using previous survey data for the screening programme and a multiplying factor to allow for magnification film dose. On average 1.6 full field and 0.15 collimated contact films are taken for each woman (with 2.25 and 0.75 mGy film^–1), 1.0 full field and 0.9 collimated magnification views. The mean magnification film dose to the assessed breast was 5.0 and 1.7 mGy for a collimated magnification film. A survey of 134 women at screening centres in the North East of England was performed to deduce the mean glandular dose from digital stereotaxis which is almost universally used in breast screening. A typical woman received a dose to the assessed breast of 4.5 mGy with a range of 1.3–17 mGy. This data may be used to deduce the total mean glandular dose over four screening rounds including the assessment stages. The estimated mean glandular dose to a typical woman invited to the screening programme is ~16 mGy, when allowance for attendance rate and assessment rate over each screening round is made. The mean glandular dose to the population is ~4700 Sv y^–1.

THE PERFORMANCE EVALUATION OF GAMMA- AND NEUTRON-SENSITIVE SUPERHEATED EMULSION (BUBBLE) DETECTORS

Vaijapurkar, S. G., Senwar, K. R., Hooda, J. S., Parihar, A. — 2008-05-12

The superheated emulsion (bubble) detectors have been developed at Defence Laboratory, Jodhpur (DLJ), India, for measurement of gamma doses. The developed detectors have been tested at Radiation Safety and System Division (RSSD), Bhabha Atomic Research Center (BARC), Mumbai (India) and DLJ having ISO-17025 accredited facility for testing and calibration of Radiation Monitors. A series of experiments were conducted to determine the gamma and neutron sensitivity of these detectors, i.e. batch homogeneity, reproducibility, dose equivalent rate effect, gamma/neutron dose equivalent response, gamma/neutron energy response and change in gamma sensitivity as a function of temperature. All the results were within ±20% of themselves. It is observed that the response of the detector is dependent upon temperature. The recommended ideal working temperature range of the detector is 20–28°C, but a temperature correction is required beyond ~30ºC. The temperature compensation may be possible up to 45°C in improved version using specially prepared reversible thermo-sensitive polymer gel. The detector may have applications in radio-diagnosis, R&D laboratories, and health physics as well as an indicator of gamma radiation for dirty bomb to be useful for first responder in any radiological emergency.

INDOOR RADON CONCENTRATIONS IN ADANA, TURKEY

Degerlier, M., Celebi, N. — 2008-05-10

The indoor radon concentration in Adana, Turkey was measured in living rooms of 52 houses during winter 2005 and 57 houses during summer 2005. Forty-four houses were selected for both winter and summer researches for estimating seasonal variations. Indoor radon concentrations were measured seasonally over hotter and colder 2 months over the whole year, using CR-39 passive nuclear track radon detectors. The radon concentrations were ranged from 15 to 97 Bq m^–3 on January–February 2005 for 60 d and from 5 to 70 Bq m^–3 on June–July 2005 for 60 d. The average summer concentration measured was 25.8 Bq m^–3 and the average winter concentration was 48.9 Bq m^–3 in 44 houses that observed seasonal variations. The differences between winter and summer periods were ranged from 1 to 77 Bq m^–3. The average value in both winter and summer periods is 37 Bq m^–3 in 44 houses that observed seasonal variations. This value is below the worldwide indoor radon concentration distribution of 46 Bq m^–3. The annual effective dose equivalent from ²²²Rn was 0.9 mSv y^–1.

IEC STANDARDS FOR RADIOLOGICAL EQUIPMENT: ISSUES FOR THE INDUSTRY AND FOR END USERS

Malone, J. F., Bischoff, N. — 2008-05-10

The International Electrotechnical Commission (IEC) is a global standard organisation established under the Presidency of Lord Kelvin in 1906. All medical equipment standards in IEC are dealt with by Technical Committee (TC) 62, and within this, Medical Imaging Equipment Standards are developed under the guidance of Subcommittee (SC) 62B. In September 2005, a special meeting of a Steering Group of IEC SC 62B was held to review X-ray standards and to identify an approach to new standards in this field. The agenda for new standards arising from this was definitively established and consolidated, concentrating on whole systems, with the aspiration of returning later to acceptance test and QA standards. A liaison was also established between SC 62B and SENTINEL. In addition, it was decided to review SC 62B's liaisons with the International Atomic Energy Agency and International Commission on Radiological Protection and some national/international professional bodies.

ASSESSMENT OF PERFORMANCE OF A NEW DIGITAL IMAGE INTENSIFIER FLUOROSCOPY SYSTEM

Dimov, A., Vassileva, J. — 2008-05-10

The aim of this study is to assess the physical properties of a recently installed digital fluoroscopy unit, Axiom Iconos R200 unit (Siemens, Germany), including image quality and patient dose. Image quality parameters and patient doses were measured at various fields of view (FOV) and frame rates. The entrance surface dose rate (ESDR) was measured using standard 30 x 30 cm² polymethylmethacrylate (PMMA) phantom with different thicknesses. The ESDR was measured using a 20 cm PMMA and largest FOV ranged from 1.1 to 8.2 mGy min^–1 for different frame rates available. The low-contrast sensitivity varied from 1.8 to 6.6%, as the limiting spatial resolution changes from 1.25 to 2.24 ln mm^–1 for the different magnifications, frame rates and phantom thicknesses. This study shows the weak points of the standard quality control protocols. The additional image quality and dose assessments revealed the existing potential for optimisation of the system.

ASSESSMENT OF PATIENT ORGAN DOSE IN CT VIRTUAL COLONOSCOPY FOR BOWEL CANCER SCREENING

Schopphoven, S., Faulkner, K., Busch, H. P. — 2008-05-03

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.

REVIEW OF EXISTING ISSUES AND PRACTICES WITH RESPECT TO IRRADIATION OF PATIENTS AND STAFF DURING PREGNANCY

Schreiner-Karoussou, A. — 2008-05-02

A number of ethical issues concerning the irradiation of patients and staff during pregnancy are presented and discussed. A review of existing practices in 13 European countries was carried out, by sending a questionnaire to each country. From the review, it was found that the existing practices with respect to irradiation of patients and staff during pregnancy in various European countries vary enormously. There is no harmonisation on this issue at a European level. From the review of practices, a number of conclusions were drawn.

EFFECT OF BACKGROUND RADIATION ON THE LOWER LIMIT OF DETECTION FOR EXTENDED DOSEMETER ISSUE PERIODS

Romanyukha, A., King, D., Benevides, L. A. — 2008-04-30

An extension of dosemeter issue period brings significant economic and logistic benefits. Therefore, it is desirable to have an extended period as long as possible without significant loss of the quality of dose measurements. There are many studies devoted to the investigation of fading or reduction of the dose accumulated in dosemeters with time. However, this is one of many critical factors that need's to be taken into account when extending the dosemeter issue period. Background radiation is also a critical factor that needs to be appropriately accounted. In this report, a new approach has been suggested for evaluating the effect of background radiation on the lower limit of detection (LLD) of occupational radiation dose. This approach is based on the data collected from control dosemeters that are routinely used for subtraction of background radiation from occupational dose measurements. The results show that for LiF:Mg,Cu,P thermoluminescence dosemeters, variations in background radiation have a higher impact on the LLD than dose fading and the absolute value of background radiation. Although there is no significant dose fading in LiF:Mg,Cu,P for a dosemeter issue period up to 1 y, variations in background radiation during this period of time can significantly increase photon LLDs (up to 700 µSv) for workers operating in an environment of variable radiation background.

MONTE-CARLO CALCULATIONS OF PARTICLE FLUENCES AND NEUTRON EFFECTIVE DOSE RATES IN THE ATMOSPHERE

Matthia, D., Sihver, L., Meier, M. — 2008-04-30

Monitoring of radiation exposure of aircrew is a legal requirement for many airlines in the EU and a challenging task in dosimetry. Monte-Carlo simulations of cosmic particles in the atmosphere can contribute to the understanding of the corresponding radiation field. Calculations of secondary neutron fluences in the atmosphere produced by galactic cosmic rays together with the resulting neutron-effective dose rates are shown in this paper and compared with results from the AIR project. The PLANETOCOSMICS package based on GEANT4 and two models for the local interstellar spectra of galactic cosmic rays have been used for the calculations. Furthermore, secondary muon fluences have been computed and are compared with CAPRICE measurements.

CHANGING FROM IMAGE INTENSIFIER TO FLAT DETECTOR TECHNOLOGY FOR INTERVENTIONAL CARDIOLOGY PROCEDURES: A PRACTICAL POINT OF VIEW

Bokou, C., Schreiner-Karoussou, A., Breisch, R., Beissel, J. — 2008-04-29

A small-scale internal audit has been used to evaluate the impact of the use of a dynamic flat panel detector in the clinical routine in the National Interventional Cardiology Centre in Luxembourg. The parameters tested during commissioning and constancy control of an X-ray system, the introduction of new clinical protocols, the patient and the personal staff dosimetry were considered. The technical parameters tested by the hospital physicist stay the same as for the image intensifier. No innovative protocols have been adopted due to the existence of the flat panel detector. A reduction in dose was noted after the installation of a flat detector, due mostly to the continuing education of the interventional cardiologists as well as the initial calibration of the radiological system. The understanding of the X-ray system and its possibilities is vital for the optimisation of clinical procedures in patient and staff exposure.

ORGANISATIONAL ASPECTS OF MAMMOGRAPHY SCREENING IN DIGITAL SETTINGS: FIRST EXPERIENCES OF LUXEMBOURG

2008-04-29

Luxembourg has been conducting a breast cancer screening programme since 1992, like a large number of other European countries, as early detection and treatment of breast cancer have been proven to reduce mortality. The majority of these screening programmes are based on analogue X-ray technology and have optimised their organisation of transporting, archiving and reading with respect to films. Last decade is marked by enormous developments in digital mammography. Different technologies such as flat panel-, computed radiography- and scanning systems became available. Digital mammography is expected to have a major impact on quality and organisation of breast cancer screening programmes. Screening programmes are now faced with a huge challenge of incorporating the digital technology, including implementation of electronic image exchange, conception of new electronic workflow, establishing adapted quality assurance programmes and training of radiologists and technical personnel. Initial experiences of the Luxembourg approach in organising digital mammography screening and its quality assurance are reported.

AN OVERVIEW ON EXTREMITY DOSIMETRY IN MEDICAL APPLICATIONS

2008-04-29

Some activities of EURADOS Working Group 9 (WG9) are presently funded by the European Commission (CONRAD project). The objective of WG9 is to promote and co-ordinate research activities for the assessment of occupational exposures to staff at workplaces in interventional radiology (IR) and nuclear medicine. For some of these applications, the skin of the fingers is the limiting organ for individual monitoring of external radiation. Therefore, sub-group 1 of WG9 deals with the use of extremity dosemeters in medical radiation fields. The wide variety of radiation field characteristics present in a medical environment together with the difficulties in measuring a local dose that is representative for the maximum skin dose, usually with one single detector, makes it difficult to perform accurate extremity dosimetry. Sub-group 1 worked out a thorough literature review on extremity dosimetry issues in diagnostic and therapeutic nuclear medicine and positron emission tomography, interventional radiology and interventional cardiology and brachytherapy. Some studies showed that the annual dose limits could be exceeded if the required protection measures are not taken, especially in nuclear medicine. The continuous progress in new applications and techniques requires an important effort in radiation protection and training.

PERFORMANCE MEASUREMENTS OF MAMMOGRAPHIC SYSTEMS

Bor, D., Akyol, O., Olgar, T. — 2008-04-29

Performance measurements of 30 mammographic installations were carried out in order to see the current level of image quality and breast doses.The half of the systems tested in this survey indicated automatic exposure control and beam collimation problems. Film processing and dark room conditions were not optimum for the majority of the installations. Image quality phantoms were exposed by the user and team of the survey at each visited center. Lower breast doses were obtained at equal image qualities for the radiographs of the team indicating the importance of adequate handling of some exposure parameters. Corrective actions were suggested to each installation and necessary guidance was advised for the implementation of routine quality control activities.

ANALYSIS AND IMPROVEMENT OF CYCLOTRON THALLIUM TARGET ROOM SHIELD

Hajiloo, N., Raisali, G., Aslani, G. — 2008-04-25

Because of high neutron and gamma-ray intensities generated during bombardment of a thallium-203 target, a thallium target-room shield and different ways of improving it have been investigated. Leakage of neutron and gamma ray dose rates at various points behind the shield are calculated by simulating the transport of neutrons and photons using the Monte Carlo N Particle transport computer code. By considering target-room geometry, its associated shield and neutron and gamma ray source strengths and spectra, three designs for enhancing shield performance have been analysed: a shielding door at the maze entrance, covering maze walls with layers of some effective materials and adding a shadow-shield in the target room in front of the radiation source. Dose calculations were carried out separately for different materials and dimensions for all the shielding scenarios considered. The shadow-shield has been demonstrated to be one suitable for neutron and gamma dose equivalent reduction. A 7.5-cm thick polyethylene shadow-shield reduces both dose equivalent rate at maze entrance door and leakage from the shield by a factor of 3.

FUZZY LOGIC BASED ELF MAGNETIC FIELD ESTIMATION IN SUBSTATIONS

Kosalay, I. — 2008-04-24

This paper examines estimation of the extremely low frequency magnetic fields (MF) in the power substation. First, the results of the previous relevant research studies and the MF measurements in a sample power substation are presented. Then, a fuzzy logic model based on the geometric definitions in order to estimate the MF distribution is explained. Visual software, which has a three-dimensional screening unit, based on the fuzzy logic technique, has been developed.

EXPOSURES TO 222RN FROM CONSUMPTION OF UNDERGROUND MUNICIPAL WATER SUPPLIES IN PAKISTAN

Manzoor, F., Alaamer, A. S., Tahir, S. N. A. — 2008-04-24

This paper presents the results of radon (²²²Rn) concentration measurements in municipal supply drinking water in metropolitan Lahore city of Pakistan and evaluation of consequent radiological effects. In this respect, water samples were collected in all nine municipal towns of Lahore city and analysed employing a high-resolution gamma spectrometric system. Radon concentration varied from 2.0 ± 0.3 to 7.9 ± 2.1 Bq l^–1. Mean value of annual effective dose for an individual consumer was assessed to be 16.5 ± 12.8 µSv y^–1. ²²²Rn mean concentration measured in this study is comparable with the reported values for drinking water determined worldwide and found to be less than the limit of 100 Bq l^–1 recommended by the World Health Organisation for public water supplies. The results of this study may be helpful in establishing background levels of radon in drinking water that could be used not only to distinguish additional contributions when a contamination event occurs but also to implement water quality standards by the concerned authorities to maintain radioactive contamination free drinking water supplies for the population.

COUNT-RATE ANALYSIS FROM CLINICAL SCANS IN PET WITH LSO DETECTORS

2008-04-24

The purpose of optimising the acquisition parameters in positron emission tomography is to improve the quality of the diagnostic images. Optimisation can be done by maximising the noise equivalent count rate (NECR) that in turn depends on the coincidence rate. For each bed position the scanner records coincidences and singles rates. For each patient, the true, random and scattered coincidences as functions of the single count rate(s) are determined by fitting the NEMA (National Electrical Manufacturers Association) 70 cm phantom count rate curves to measured clinical points. This enables analytical calculation of the personalised PNECR [pseudo NECR(s)] curve, linked to the NECR curve. For central bed positions, missing activity of ~70% is estimated to get maximum PNECR (PNECR_max), but the improvement in terms of signal-toz-noise ratio would be ~15%. The correlation between patient weight and PNECR_max is also estimated to determine the optimal scan duration of a single bed position as a function of patient weight at the same PNEC. Normalising the counts at PNECR_max for the 70 kg patient, the bed duration for a 90 kg patient should be 230 s, which is ~30% longer. Although the analysis indicates that the fast scanner electronics allow using higher administered activities, this would involve poor improvement in terms of NECR. Instead, attending to higher bed duration for heavier patients may be more useful.

REVIEW OF EXISTING ISSUES, ETHICS AND PRACTICES IN GENERAL MEDICAL RESEARCH AND IN RADIATION PROTECTION RESEARCH

Schreiner-Karoussou, A. — 2008-04-24

A literature review was carried out in relation to general medical research and radiation protection research. A large number of documents were found concerning the subject of ethics in general medical research. For radiation protection research, the number of documents and the information available is very limited. A review of practices in 13 European countries concerning general medical research and radiation protection research was carried out by sending a questionnaire to each country. It was found that all countries reviewed were well regulated for general medical research. For research that involves ionising radiation, the UK and Ireland are by far the most regulated countries. For other countries, there does not seem to be much information available. From the literature review and the review of practices, a number of existing ethical issues were identified and exposed, and a number of conclusions were drawn.

EFFECTIVE DOSE ASSESSMENT FOR WORKERS IN CAVES IN THE CZECH REPUBLIC: EXPERIMENTS WITH PASSIVE RADON DETECTORS

Thinova, L., Burian, I. — 2008-04-24

The new RAMARN system for radon volume activity measurement was developed in 2003 and has been in use since then. RAMARN system consists of a plastic chamber that is conically cylindrical in shape and about 0.5 l in volume; a bare Kodak LR 115 is located on the bottom of this diffusion chamber. The size was chosen to avoid the influence of deposited decay products of radon. Kodak has a spectrometric character—the tracks are visualized only for alphas with energies between 1 and 3 MeV that touch the foil; thus the effective volume has a lens shape. The response therefore corresponds to diffused radon and half of ²¹⁸Po born by radon gas decay. The experiments described below were conducted as one part of a routine methodology control, focused on classifying worker irradiation from natural ionizing radiation sources in show caves and in caves used for speleotherapy.

INVESTIGATION AND REMEDIATION OF HOUSES AFFECTED BY RADON PHENOMENA CONNECTED WITH EARLIER EXPLORATION OF SILVER AND URANIUM ORE

Cechak, T., Moucka, L., Jiranek, M., Fronka, A., Thinova, L. — 2008-04-24

The sources of gamma radiation inside buildings affected by earlier silver and uranium mining activities are discussed. Possibilities how to reduce gamma dose rates from building materials were studied on several houses located in the old mining town Jáchymov. Results of the efficiency analysis are presented. Experience obtained up to now indicates that it is almost impossible to reduce the gamma dose rates in such buildings to the level corresponding with the natural background, because some of the gamma radiation sources cannot be completely removed from the building structures.