Radiation Protection Dosimetry - current issue

Patient dose studies: what should be reported?

Martin, C. J. — 2008-06-04

Radiation dosimetry for diagnostic medical exposures

Martin, C. J. — 2008-06-04

The number and complexity of medical procedures using X rays or radioactive materials are both steadily increasing. As a result, the dose from medical exposures now makes up the largest component of the radiation dose to the population in some developed countries. Key developments include the change from film to digital radiography, the increasing sophistication of interventional radiology allowing more complex procedures and the speed and facilities available with multi-slice computed tomography scanners that have extended the range of applications. It is crucial to have accurate dosimetry to monitor the impact of these developments, to ensure that techniques are optimised, and to provide information on health risk that clinicians can consider when justifying exposures. There are two aspects to dosimetry in radiology, assessment of doses to patients and measurement of equipment performance. The techniques that are used will be described, factors that influence doses and that must be considered when making measurements will be discussed, and future developments will be considered.

Neutron microdosimetric response of a gas electron multiplier

Dubeau, J., Waker, A. J. — 2008-06-04

A new high-sensitivity tissue equivalent proportional counter (TEPC) on the basis of the gas electron multiplier (GEM) detector used in high-energy physics experiments has been designed, constructed and tested in a variety of neutron fields. The GEM–TEPC makes use of a lithographically produced strip readout system to achieve the equivalent of a large number of miniature TEPC detector elements. This new device could be used as the basis of an electronic personal dosemeter for gamma and neutron mixed radiation fields.

Automated detection of irradiated food with the comet assay

Verbeek, F., Koppen, G., Schaeken, B., Verschaeve, L. — 2008-06-04

Food irradiation is the process of exposing food to ionising radiation in order to disinfect, sanitise, sterilise and preserve food or to provide insect disinfestation. Irradiated food should be adequately labelled according to international and national guidelines. In many countries, there are furthermore restrictions to the product-specific maximal dose that can be administered. Therefore, there is a need for methods that allow detection of irradiated food, as well as for methods that provide a reliable dose estimate. In recent years, the comet assay was proposed as a simple, rapid and inexpensive method to fulfil these goals, but further research is required to explore the full potential of this method. In this paper we describe the use of an automated image analysing system to measure DNA comets which allow the discrimination between irradiated and non-irradiated food as well as the set-up of standard dose–response curves, and hence a sufficiently accurate dose estimation.

Evaluation of specific absorbed fractions from internal photon sources in ORNL analytical adult phantom

Hakimabad, H. M., Motavalli, L. R. — 2008-06-04

To design a diagnostic or therapeutic irradiation programme, there is a need to estimate the absorbed dose. In this investigation, specific absorbed fractions (SAFs) were calculated based on Cristy and Eckerman's analytical adult phantom, by MCNP4C Monte Carlo code. SAFs were estimated with uncertainty <3%, for about 600 source organ–target organ pairs at 12 photon energies (these data are available at http://www.um.ac.ir/~mirihakim). Then these results were compared with Cristy and Eckerman's, which were based on direct Monte Carlo, reciprocity principle and point source kernel methods. Also, agreements and disagreements between them for different states were discussed.

Indoor radon survey in dwellings of the Kars province, Turkey

Celik, N., Poffijn, A., Cevik, U., Schepens, L. — 2008-06-04

Makrofol Solid State Nuclear Track Detectors were used to study the ²²²Radon concentration in dwellings of the Kars province in Turkey. Radon measurements were done for 3 months in 87 houses, selected as uniformly distributed in the area as possible. All values were seasonally corrected. In order to define the seasonal correction factors, the readings were taken in 12 homes for a 12-month period. A 1:100.000 scale geologic map of the region, prepared and published by the Institute of Mineral Research and Exploration (Ankara, Turkey), was used to present the radon results. Digitising, processing and integrating of the data were performed by using ArcView GIS. The results of the radon measurements in the study area range from 20 to 600 Bq/m³, with 114 Bq/m³ as average value. The results showed that the number of lung cancer deaths attributable to indoor radon exposure was estimated to be ~5.

Confidence limits for Neyman type A-distributed events

2008-06-04

The Neyman type A distribution, a generalised, ‘contagious’ Poisson distribution, finds application in a number of disciplines such as biology, physics and economy. In radiation biology, it best describes the distribution of chromosomal aberrations in cells that were exposed to neutrons, alpha radiations or heavy ions. Intriguingly, no method has been developed for the calculation of confidence limits (CLs) of Neyman type A-distributed events. Here, an algorithm to calculate the 95% CL of Neyman type A-distributed events is presented. Although it has been developed in response to the requirements of radiation biology, it can find application in other fields of research. The algorithm has been implemented in a PC-based computer program that can be downloaded, free of charge, from www.pu.kielce.pl/ibiol/neta.

Variations in occupational exposure to magnetic fields among welders in Malaysia

Man, A.-K., Shahidan, R. — 2008-06-04

This study attempted to estimate the lifelong magnetic field (MF) exposures of a particular group of welders. Exposure was quantified via measurements, observations and interviews. It was found that these welders face a vast range of lifelong MF exposures depending on the welding processes and duration of the welding tasks performed. This may explain the inconsistency in the results of studies of MF exposures on human health. The mere assessing of the MF exposure levels through spot measurements does not give an overall picture of the total amount of exposure received by the welders as some of these workers performed the welding task throughout the day, whereas others performed this as a part of their job. The exposure to various chemicals in the fume may complicate the interpretation of the elevated health risk among the welders.

Effect of an aerosol deposition pattern in the lung on the counting efficiency of a large area germanium detector array

Kramer, G. H., Hauck, B. M. — 2008-06-04

The Human Monitoring Laboratory has extended the use of sliced lungs containing planar sources to simulate heterogeneous radionuclide deposition patterns. This work examined two deposition patterns and their effect on the counting efficiency of low-energy photons. The results have shown that heterogenous distributions can be difficult to detect in some cases and can still lead to large uncertainties (up to a factor of 2.5) in the activity estimate, especially at low photon energies. At higher energies (~60 keV), the effect of the heterogeneous distribution is greatly reduced and errors in the activity estimate reduced to ~25%. The presence of a heterogenous distribution can be detected by comparing the ratio of the individual detector counts with the expected values obtained from measuring multiple lungs sets that contained a homogeneous distribution. The distributions tested in this paper were detectable (at 2) as heterogeneous by two of the four detectors in the counting array.

Direct high-resolution alpha spectrometry from nuclear fuel particles in an outdoor air sample

Pollanen, R., Siiskonen, T. — 2008-06-04

The potential use of direct high-resolution alpha spectrometry to identify the presence of transactinium elements in air samples is illustrated in the case when alpha-particle-emitting radionuclides are incorporated in nuclear fuel particles. Alpha particle energy spectra are generated through Monte Carlo simulations assuming a nuclide composition similar to RBMK (Chernobyl) nuclear fuel. The major alpha-particle-emitting radionuclides, in terms of activity, are ²⁴²Cm, ²³⁹Pu and ²⁴⁰Pu. The characteristics of the alpha peaks are determined by fuel particle properties as well as the type of the air filter. It is shown that direct alpha spectrometry can be readily applied to membrane filter samples containing nuclear fuel particles when rapid nuclide identification is of relevance. However, the development of a novel spectrum analysis code is a prerequisite for unfolding complex alpha spectra.

Assessment of occupational exposure to magnetic fields in high-voltage substations (154/34.5 kV)

Helhel, S., Ozen, S. — 2008-06-04

This work proposes the survey of magnetic field measurements taken in 154/31.5 kV substations in the city of Antalya for occupational exposure assessment. For measurements, three substations have been taken into account, where four occupants are present for each 8 h of shift, which means 12 occupants are present during the day. Operator desks at three different substations read a lowest magnetic field of 0.3 µT at minimum loaded season and reached up to 1 µT at maximum loaded season, which means operators exposed to a magnetic field of ≥ 0.3 µT 8 h d^–1. In switch gear regions, maximum magnetic field reading is 23 µT at minimum loaded season and reached up to 70 µT. Outdoor magnetic field measurement at circuit breaker region goes up to 62 µT with respect to operator heights.

Radionuclide content and associated radiation hazards of building materials and by-products in Baoji, West China

Lu, X., Zhang, X. — 2008-06-04

Seven types of common building materials and by-products of coal-fired power plants collected from Baoji, West China, were analysed for the natural radioactivity of ²²⁶Ra, ²³²Th and ⁴⁰K using gamma ray spectrometry with an NaI(Tl) detector. The average activity concentrations vary from 23.0 to 112.2, 20.2 to 147.5 and 113.2 to 890.8 Bq kg^–1 for ²²⁶Ra, ²³²Th and ⁴⁰K, respectively. The measured activity concentrations for these radionuclides were compared with the data reported from other countries and with the worldwide average activity of soil. As a measure of radiation hazard to the people, the radium equivalent activities, total annual effective dose and activity concentration index were estimated. The radium equivalent activities of the studied samples are below the internationally accepted values. The calculated total annual effective dose and the activity concentration index of seven types of common building materials are <1 mSv y^–1 and 1, respectively. But fly ash and bottom ash exhibit the higher values that exceed and be close to the acceptable values, respectively. This study shows that the measured building materials do not pose any significant source of radiation hazard and are safe for use in the construction of dwellings. Nevertheless, when fly ash and bottom ash are used in dwelling construction, it is important to assess their radiation potential.

Determination of natural radioactivity in drinking water in private dug wells in Akure, Southwestern Nigeria

Ajayi, O. S., Owolabi, T. P. — 2008-06-04

Gamma spectrometry of well water was done to measure the activity concentrations of gamma-emitters ²²⁶Ra and ²²⁸Ra from ²³⁸U and ²³²Th series, respectively, and ⁴⁰K in their waters. Measurements were done using high-purity (HPGe) co-axial detectors (Canberra, GC 2018-7500 ) coupled to Canberra Multichannel Analyser system. Activity concentrations ranged from 0.57 to 26.86, 0.20 to 60.06 and 0.35 to 29.01 Bq l^–1 for ²²⁶Ra, ²²⁸Ra and ⁴⁰K, respectively. Activity concentrations were compared with data from other parts of the world and used to estimate annual effective dose for three age groups. Total annual effective doses from the intake of these radionuclides in the waters ranged from 0.02 to 76.84, 0.02 to 38.80 and 0.05 to 481.60 mSv y^–1 for age group <1, 2–7 and ≥17 y, respectively. These values are considerably higher than both the World Health Organisation and the International Commission on Radiological Protection limits.

Patient dosimetry in interventional cardiology at the University Hospital of Osijek

2008-06-04

The interventional cardiology was recently implemented at the University Hospital of Osijek. Patients' absorbed doses during coronary angiography (CA) and the percutaneous transluminal coronary angioplasty (PTCA) procedures were measured and compared with published data and international standards. All patients undergoing CA or PTCA procedures during a 1-month period were included in the study. Patients' doses are expressed in terms of dose area product (DAP) per procedure. The patients' DAPs ranged from 2.6 to 210 Gy cm² (average of 59 Gy cm²) during CAs, and from 61 to 220 Gy cm² (average of 120 Gy cm²) during PTCAs. Patients' doses during CAs and PTCAs at the University Hospital of Osijek are in good agreement with the published ones. In complex cases, the radiochromic dosimetry films were used to show possible dose distributions across patient's skin. The film dosimetry showed a limitation of using only DAP values for the estimation of skin injuries risk.

Dose level of occupational exposure in China

Tian, Y., Zhang, L., Ju, Y. — 2008-06-04

This paper discusses the dose level of Chinese occupational exposures during 1986–2000. Data on occupational exposures from the main categories in nuclear fuel cycle (uranium enrichment and conversion, fuel fabrication, reactor operation, waste management and research activity, except for uranium mining and milling because of the lack of data), medical uses of radiation (diagnostic radiation, nuclear medicine and radiotherapy) and industrial uses of radiation (industrial radiography and radioisotope production) are presented and summarised in detail. These are the main components of occupational exposures in China. In general, the average annual effective doses show a steady decreasing trend over periods: from 2.16 to 1.16 mSv in medical uses of radiation during 1990–2000; from 1.92 to 1.18 mSv in industrial radiography during 1990–2000; from 8.79 to 2.05 mSv in radioisotope production during the period 1980–2000. Almost all the average annual effective doses in discussed occupations were lower than 5 mSv in recent years (except for well-logging: 6.86 mSv in 1999) and no monitored workers were found to have received the occupational exposure exceeding 50 mSv in a single year or 100 mSv in a five-year period. So the Chinese protection status of occupation exposure has been improved in recent years. However, the average annual effective doses in some occupations, such as diagnostic radiology and coal mining, were still much higher than that of the whole world. There are still needs for further improvement and careful monitoring of occupational exposure to protect every worker from excessive occupational exposure, especially for the workers who were neglected before.

A method for calculation of radiation quantities at all points in gamma radiation calibration fields

2008-06-04

Radiation quantity values at all points of a known distance range of gamma radiation calibration fields were calculated using a mathematical method. The method is based on interpolation using Chi-square test on a set of experimental data at optional points of both collimated and un-collimated calibration set-ups by means of a reference instrument. In comparison with Monte Carlo calculations, the values that were calculated by this method differ by <1% for collimated and 2% for un-collimated calibration set-ups. Consequently, the radiation quantities at all points of gamma radiation calibration field set-ups can accurately be formulated and determined by this method. In addition, all points in the radiation fields can be regarded as test points.

One cubic metre NIST traceable radon test chamber

Kotrappa, P., Stieff, F. — 2008-06-04

With the availability of the National Institute of Standards and Technology (NIST) Radon Emanation Standard with a content of ~5000 Bq of ²²⁶Ra, it is possible to build a flow through a practical radon test chamber. A standard glove box with four gloves and a transfer port is used. Air is pumped through a flow integrator, water jar for humidification and NIST source holder, and into the glove box through a manifold. A derived theoretical expression provides the calculated radon concentration inside the chamber. The calculation includes a derived decay correction due to the large volume and low flow rate of the system. Several calibrated continuous radon monitors and passive integrating electret ion chambers tested in the chamber agreed fairly well with the calculated radon concentrations. The chamber is suitable for handling the calibration of several detectors at the same time.

Effective dose: a useful concept in diagnostic radiology?

Brenner, D., Huda, W. — 2008-06-04

Letters to the Editor

German, U., Weinstein, M., Abraham, A., Alfassi, Z. B. — 2008-06-04

Letters to the Editor

Horowitz, Y. S. — 2008-06-04

Radon transport through concrete and determination of its diffusion coefficient

Nikezic, D., Urosevic, V. — 2008-06-04