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[en] Human beings are continuously exposed to ionising radiation originating from natural or artificial sources. Uranium-238 and Thorium-232 found in building materials are important sources of radon and thoron in the indoor environment. The concentration levels of radon, thoron and thoron progeny were measured in mud-walled, metallic or iron sheet-walled and stone-walled modern houses in Kilimambogo region, Kenya for 3 months. Radon and thoron concentration levels were measured using passive radon–thoron discriminative monitors (RADUET), while thoron progeny concentrations as the equilibrium equivalent thoron concentration (EETC) were measured using thoron progeny monitors. The mean radon concentration levels in mud, metallic and stone-walled dwellings were 67 ± 11, 60 ± 10 and 75 ± 10 Bq m⁻³, respectively. The mean thoron concentration levels in the corresponding dwellings were 195 ± 36, 71 ± 24 and 161 ± 31 Bq m⁻³, respectively, while EETCs were 12 ± 2, 3 ± 1 and 7 ± 1 Bq m⁻³, respectively. The annual effective doses for radon were 1.3 ± 0.2, 1.1 ± 0.1 and 1.4 ± 0.2 mSv y⁻¹ in mud, metallic and stone-walled houses while those from thoron estimated from EETC were 2.4 ± 0.4, 0.5 ± 0.1 and 1.5 ± 0.2 mSv y⁻¹ in the corresponding houses, respectively. (author)

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[en] In 2007, the European Commission (EC) commissioned a group of experts to undertake the revision of Report Radiation Protection (RP) 91, written in 1997, on 'Criteria for acceptability of radiological (including radiotherapy) and nuclear medicine installations' The revised draft report was submitted to the EC. Before publication, the EC issued this document for public consultation and has commissioned the same group of experts to consider the comments of the public consultation in further improving the revised report. The EC intends to publish the final report under its Radiation Report Series with the number RP 162. This paper introduces the project and presents the methodology adopted to devise the criteria of acceptability/suspension levels for nuclear medicine equipment. (authors)

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[en] Whole-body counting (WBC) is a method for measuring and determining the body burden of gamma-emitting radionuclides. The Research Institute for Industrial and Sea Hygiene, Saint-Petersburg, Russia, has designed a human whole-body phantom, IRINA, to be used for calibrations of WBC systems. We have created voxel phantoms of the IRINA phantoms in a lying geometry, in a total of six voxel phantoms, for usages of Monte Carlo (MC) simulations. All the six voxel phantoms are now available through the Nordic Nuclear Safety Research web site together with a detailed description of the method used to create them. IRINA consists of a number of polyethylene blocks, called scatterers (density 0.95 g cm"3) and radionuclide sources. The scatterers come in two sizes: 110 x 165 x 55 mm"3 and 110 x 165 x 25 mm"3. Two vertical channels, aimed for the insertion of the rod-shaped sources, run parallel to each scatterer's height (165 mm). The scatterers can be assembled to represent six different human bodies, who are either laying down, sitting or sitting bending: a 1-y-old with mass of 12 kg, a 6-y-old with mass of 24 kg, a 14-y-old with mass of 50 kg and an adult with mass of 70, 90 and 110 kg, respectively. Voxel phantoms are commonly created by segmentation of CT or MRI image sets of the real-life phantom, which is a favourable technique for complex geometries such as the human anatomy. This gives a three-dimensional array, whose dimension is determined by millimetre/pixel and slice thickness, where each element defines the position and material composition of a voxel in the xyz-space. However, the less-complicated structure of the IRINA phantom made it possible to construct the voxel phantoms without using segmentation of CT or MRI image sets. Instead, the voxel phantoms were created in MATLAB"R, which is a strong computational tool for matrix manipulations. The dimensions of a large scatterer are related by 2:3:1. Each scatterer was divided into six unit cubes, with sides of 55 mm. Each unit cube was further separated into slices of 9 x 9 voxels, thus measuring 6.1 x 6.1 x 55 mm"3. The sizes were chosen so that the voxel in the middle of each unit cube defined the channel in which a rod source could be placed. The smaller scatterers were not separated into unit cubes but treated as single units with slices consisting of 9 x 4 voxels. Analogous to construction using building blocks, the six IRINA voxel phantoms were modelled by stacking unit cubes and smaller scatterers. The MATLAB"R method has three advantages: (1) no need of CT or MRI systems, (2) geometries are not limited by the scan dimensions of a CT or MRI and (3) the voxel size can easily be optimised to the phantom modelled. To provide a generic IRINA voxel phantom, with respect to MC code, the same file structure as in the ICRP computational phantoms of the Reference Man and Reference Female was used: the voxel phantom contains an array of voxel identification numbers, in ASCII format, with the same orientation in the xyz-space as the ICRP phantoms. Each identification number tells whether the voxel is part of a scatterer, air or a channel in which a rod source can be placed. Each channel has its own identification number to enable a wide range of possible voxelised source distributions. Each IRINA voxel phantom comes with a documentation showing the position of each channel. (authors)

[en] Switzerland's participation in the REMPAN network for preparedness of health sector to medical interventions and provision of technical assistance in the event of radiation emergencies began only a few years ago. However, it is a collaboration that is very important to us. The rarity of radiation emergencies requiring clinical care of irradiated persons makes it challenging for a small country to develop and set up its own structure dedicated to managing of over-exposed persons and to maintain a technical competence in this field. Thus, the solution of networking, allowing each country to benefit from experience and international assistance, is a good and cost-efficient opportunity for Switzerland. Preparing for radiation emergencies and developing relevant national capacities is an obligation for each country under the International Health Regulations, knowing that the use of ionising radiation is a part of every day's economical, medical, industrial and research activities, even when a country does not possess nuclear technology. In this respect, the revision of the Swiss national legislation on radiation protection, which was approved in April 2017 by the Swiss Federal Council and came into force on 1 January 2018, calls for the maintenance of expertise and knowledge concerning the treatment of persons over-exposed to ionising radiation. Our participation in the WHO's REMPAN network fits well within this framework. These proceedings of the 15. Coordination meeting of WHO REMPAN, which address the update of current knowledge on medical care in the event of a radiological or nuclear accidents, will be interesting to many readers globally and will allow to share information and strengthen the international cooperation in the area of radiation emergency preparedness

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[en] In the author's clinical affiliation in Helsinki, Finland, multiple positron emission tomography (PET) procedures with approximately 10 different fluorine-18 or Ga-68-tracers are carried out. Because of the location, there are also patients who cross national borders or who go to the airports, where they may trigger highly sensitive radiation monitors at security check points. Therefore, a certificate is automatically given for administered radioactivity even for PET tracers; if possible security checks are going to take place on the same day. A 57-year-old man was administered with 326 MBq (8.81 mCi) fluoro-18-methylcholine (FCH) at 12:50 p.m. for a whole-body PET/computed tomography study. The next morning at 7:00 a.m. when he entered his work place at a nuclear power plant, all alarms sounded. His radioactivity level was measured to be 0.35 MBq (9.5 μCi) i.e. approximately of 1/930 original activity. The nuclear power plant was informed about the origin of the activity, and all later measurements demonstrated kBq. Radiation safety measurements are extremely sensitive in nuclear power plants, and the person did not have a certificate because the radiation safety check should have happened on the following day. The physical half-life (t_1_/_2) of fluorine-18 is 110 minutes, and the time difference between these activity measurements was 18.2 hours, i.e. 9.73 half-lives. The measured activity was very close with that of physical decay indicating that the activity measured on the next morning might have been overestimated. FCH has urinary excretion and also biological half-life is essential part of effective half-life, especially because this person did not have any sites of pathologic uptakes. This event demonstrates that extremely low radioactivity, <10 μCi, can be detected, in this case for supersensitive nuclear safety reasons. Nuclear medicine community has to keep this in mind while handling in a daily routine 1000- to 10?000-fold activity levels as compared with the levels that can be detected by radiation monitors at check points. (authors)