Analysis of EURADOS neutron intercomparison results according to new ISO standards criteria

The European Radiation Dosimetry Group has carried out several different types of intercomparison (IC) exercises in the past that qualify as proficiency tests for different dosimetry systems and types of radiation. The first neutron dosemeter IC was held in 2012 (IC2012n) and was followed by a second in 2017/2018 (IC2017n). In sum, 31 Individual Monitoring Services (IMSs) entered 34 dosimetry systems in IC2012n, and 32 IMSs entered 33 dosimetry systems for IC2017n. Such exercises provided a rare opportunity to see how neutron dosemeters perform. For the IC2012n exercise, there were no applicable performance standards for neutron personal dosemeters. ISO/TC85/SC2 updated the ISO Standard 14146 in 2018 (ISO 14146:2018. Radiation protection-Criteria and performance limits for the periodic evaluation of dosimetry services) to include neutron dosimetry. It was thus possible to analyse the IC2017n exercise in accordance with the requirements given by this new standard. It is now of interest to reanalyse the results of IC2012n to quantify any modifications to the conclusions.

EURADOS STRATEGIC RESEARCH AGENDA 2020: VISION FOR THE DOSIMETRY OF IONISING RADIATION

Since 2012, the European Radiation Dosimetry Group (EURADOS) has developed its Strategic Research Agenda (SRA), which contributes to the identification of future research needs in radiation dosimetry in Europe. Continued scientific developments in this field necessitate regular updates and, consequently, this paper summarises the latest revision of the SRA, with input regarding the state of the art and vision for the future contributed by EURADOS Working Groups and through a stakeholder workshop. Five visions define key issues in dosimetry research that are considered important over at least the next decade. They include scientific objectives and developments in (i) updated fundamental dose concepts and quantities, (ii) improved radiation risk estimates deduced from epidemiological cohorts, (iii) efficient dose assessment for radiological emergencies, (iv) integrated personalised dosimetry in medical applications and (v) improved radiation protection of workers and the public. This SRA will be used as a guideline for future activities of EURADOS Working Groups but can also be used as guidance for research in radiation dosimetry by the wider community. It will also be used as input for a general European research roadmap for radiation protection, following similar previous contributions to the European Joint Programme for the Integration of Radiation Protection Research, under the Horizon 2020 programme (CONCERT). The full version of the SRA is available as a EURADOS report (www.eurados.org).

EURADOS education and training activities

This paper provides a summary of the Education and Training (E&T) activities that have been developed and organised by the European Radiation Dosimetry Group (EURADOS) in recent years and in the case of Training Courses over the last decade. These E&T actions include short duration Training Courses on well-established topics organised within the activity of EURADOS Working Groups (WGs), or one-day events integrated in the EURADOS Annual Meeting (workshops, winter schools, the intercomparison participants' sessions and the learning network, among others). Moreover, EURADOS has recently established a Young Scientist Grant and a Young Scientist Award. The Grant supports young scientists by encouraging them to perform research projects at other laboratories of the EURADOS network. The Award is given in recognition of excellent work developed within the WGs' work programme. Additionally, EURADOS supports the dissemination of knowledge in radiation dosimetry by promoting and endorsing conferences such as the individual monitoring (IM) series, the neutron and ion dosimetry symposia (NEUDOS) and contributions to E&T sessions at specific events.

EURADOS IC2012N: FURTHER INFORMATION DERIVED FROM AN EURADOS INTERNATIONAL COMPARISON OF NEUTRON PERSONAL DOSEMETERS

In 2012, the European Radiation Dosimetry Group (EURADOS) performed an intercomparison for neutron dosemeters that are intended to measure personal dose equivalent, Hp(10). A total of 31 participants registered with 34 dosimetry systems. The irradiation tests were chosen to provide the participants with useful information on their dosimetry systems, i.e. linearity, reproducibility, responses for different energies and angles and to simulated workplace fields. This paper gives details of the extensive information derived from the exercise.

EURADOS strategic research agenda: vision for dosimetry of ionising radiation

Since autumn 2012, the European Radiation Dosimetry Group (EURADOS) has been developing its Strategic Research Agenda (SRA), which is intended to contribute to the identification of future research needs in radiation dosimetry in Europe. The present article summarises-based on input from EURADOS Working Groups (WGs) and Voting Members-five visions in dosimetry and defines key issues in dosimetry research that are considered important for the next decades. The five visions include scientific developments required towards (a) updated fundamental dose concepts and quantities, (b) improved radiation risk estimates deduced from epidemiological cohorts, (c) efficient dose assessment for radiological emergencies, (d) integrated personalised dosimetry in medical applications and (e) improved radiation protection of workers and the public. The SRA of EURADOS will be used as a guideline for future activities of the EURADOS WGs. A detailed version of the SRA can be downloaded as a EURADOS report from the EURADOS website (www.eurados.org).

EURADOS IC2012N: EURADOS 2012 intercomparison for whole-body neutron dosimetry

The European Radiation Dosimetry Group (EURADOS) IC2012n intercomparison for neutron dosemeters intended to measure personal dose equivalent, Hp(10), was performed in 2012. A total of 31 participants (27 individual monitoring services from Europe, 2 from Japan, 1 from Israel and 1 from USA) registered with 34 dosimetry systems. Participation was restricted to passive or active neutron dosemeters routinely used in individual monitoring of radiation workers. The dosimetry systems were based on thermoluminescence, polyallyldiglycol carbonate, optically stimulated luminescence, fission track detection and silicon diodes (electronic devices). The irradiation tests were chosen to provide the participants with useful information on their dosimetry systems, i.e. linearity, reproducibility, responses for different energies and angles and to simulated workplace fields. The paper will report and discuss the first analysis of the results of the EURADOS IC2012n intercomparison.

Hp(3)/Φ conversion coefficients for neutrons: discussion on the basis of the new ICRP recommended limit for the eye lens

The new recommendation issued by the International Commission on Radiological Protection (ICRP) introducing a 20-mSv annual dose limit for the eye lens stimulated an interesting debate among the radiation protection community. In the present work the problem of estimating Hp(3) for neutron realistic workplace spectra is treated, employing the recently published Hp(3)/Φ conversion coefficients with the aim of establishing a workplace-dependent relationship between Hp(10) and Hp(3). The results demonstrate that, whilst the two quantities can differ by less than 10 %, in general, Hp(10) cannot be considered a conservative estimate of Hp(3).

Air kerma to HP(3) conversion coefficients for photons from 10 keV to 10 MeV, calculated in a cylindrical phantom

In the framework of the ORAMED project (Optimization of RAdiation protection for MEDical staff), funded by the European Union Seventh Framework Programme, different studies were aimed at improving the quality of radiation protection in interventional radiology and nuclear medicine. The main results of the project were presented during a final workshop held in Barcelona in January 2011, the proceedings of which are available in the open literature. One of the ORAMED tasks was focused on the problem of eye-lens photon exposure of the medical staff, a topic that gained more importance especially after the ICRP decision to lower the limiting equivalent dose to 20 mSv per year. The present technical note has the scope, besides briefly summarising the physical reasons of the proposal and the practical implications, to provide, in tabular form, a set of air kerma to Hp(3) conversion coefficients based on the adoption of a theoretical cylindrical model that is well suited for reproduction of the mass and the shape of a human head.

ENEA extremity dosemeter based on LiF(Mg,Cu,P) to evaluate Hp(3,alpha)

Recent epidemiological studies suggest a rather low-dose threshold (<0.5 Gy) for the induction of a cataract of the eye lens. Some other studies even assume that there is no threshold at all. Therefore, protection measures have to be optimised and current dose limits for the eye lens may be reduced in the future. ICRP Publication 103 on H(p)(d), in §(136), reads that '… a depth d = 3 mm has been proposed for the rare case of monitoring the dose to the lens of the eye. In practice, however, H(p)(3) has rarely been monitored and H(p)(0.07) can be used for the same monitoring purpose… '. As recommended on the EU 'Technical recommendations for monitoring individuals occupationally exposed to external radiation', a test on the ENEA TL extremity dosemeter is herein reported. The results within the actual EU founded Optimization of RAdiation protection for MEDical staff (ORAMED) Project, whose WP2 is aimed at the quantity H(p)(3) and eye lens dosimetry in practice, are taken into account. The paper summarises the main aspects of the study carried out at ENEA-Radiation Protection Institute (Bologna, Italy) to provide practical solutions (in the use and the design) to evaluate the response of the ENEA TL extremity dosemeter in terms of H(p)(3).

Eye lens dosimetry: task 2 within the ORAMED project

The ORAMED (Optimization of RAdiation protection for MEDical staff) project is funded by EU-EURATOM within the 7° Framework Programme. Task 2 of the project is devoted to study the dose to the eye lens. The study was subdivided into various topics, starting from a critical revision of the operational quantity H(p)(3), with the corresponding proposal of a cylindrical phantom simulating as best as possible the head in which the eyes are located, the production of a complete set of air kerma to dose equivalent conversion coefficients for photons from 10 keV to 10 MeV, and finally, the optimisation of the design of a personal dosemeter well suited to respond in terms of H(p)(3). The paper presents some preliminary results.

The new EC technical recommendations for monitoring individuals occupationally exposed to external radiation

The purpose of the European Commission technical recommendations (TR) for monitoring individuals occupationally exposed to external radiation is to provide guidance on those aspects of the implementation of the European Union Parliament and Council Directives directly related to individual monitoring of external radiation, and to encourage harmonisation thereof. They are mainly aimed at the management and staff of IM services but also at manufacturers, laboratories supplying type-testing services, national authorities trying to harmonise approval procedures, and government bodies to harmonise regulations and guidance. The TR main topics are: objectives and aims of IM for external radiation; dosimetry concepts; accuracy requirements; calibration, type testing and performance testing; approval procedures; quality assurance and quality control; and dose record keeping. Attention is paid to particular aspects, such as wide energy ranges for the use of personal dosemeters, pulsed fields and non-charged particle equilibrium; and use of active personal dosemeters. The TR give proposals towards achieving harmonisation in IM and the eventual mutual recognition of services and of dose results.

Personal dosimetry in terms of HP(3): Monte Carlo and experimental studies

Hp(3) has been defined as the operational quantity for eye lens dosimetry. Hp(3)/ka conversion coefficients were evaluated at the GSF (Germany) in a 30x30x15 cm3 4-elements ICRU slab phantom for various energies and incident angles through Monte Carlo. The ISO report 12,794 suggests to employ a PMMA water filled phantom, of the same dimensions, for dosemeter calibration in terms of Hp(3). The present paper briefly summarises the main aspects of a study carried out at ENEA-Radiation Protection Institute (Bologna, Italy) to provide practical procedures for the calibration of dosemeters in terms of Hp(3). Tabulations of a new set conversion coefficients and air kerma backscatter factors are provided as a function of energy and incident angle. The paper demonstrates that a more accurate approach to the dosimetric assessment in terms of Hp(3) could be rather simply introduced employing a reduced phantom.

Standards, documents of relevance and directives in individual monitoring: is European individual monitoring in compliance with standards?

Individual monitoring services (IMS) in Europe do not comply with the same legal or approval requirements. Anyway, a degree of harmonisation existing in individual monitoring practices in Europe has been achieved mainly thanks to documents as standards or international recommendations, which with different weight represent invaluable vehicles of condensed information transfer. However, implementation of standards is not straightforward and harmonisation is not directly a consequence. Somehow, 'harmony' is needed also in standards: IEC and ISO standards, on performance requirements for dosemeters sometimes have different approaches (i.e. performance criteria). Moreover, standards do not all refer to reliability, and therefore being in compliance with standards does not by itself assure that dose results are reliable. Standards are not the only reference documents for an IMS. EURADOS working group on 'Harmonisation of Individual Monitoring in Europe', who has been active in the years 2001-2004, suggested a classification of publication on individual monitoring, distinguishing between standards and documents of relevance, which can be both national and international. None of the two categories are mandatory unless specified in legislation. The Council Directive 96/29/EURATOM and its implementation in each EU Member States has fostered harmonisation of the approach (i.e. approval of dosimetric services) and of the reference quantities for individual monitoring within EU, but national legislation still allow substantial differences in individual monitoring from country to country.

Aspects of harmonisation of individual monitoring for external radiation in Europe: conclusions of a EURADOS action

Following the publication of the EU Council Directive 96/29, EURADOS coordinated two working groups (WGs) for promoting the process of harmonisation on individual monitoring of occupationally exposed persons in Europe. An overview of the major findings of the second WG is presented. Information on the technical and quality standards and on the accreditation and approval procedures has been compiled. The catalogue of dosimetric services has been updated and extended. An overview of national regulations and standards for protection from radon and other natural sources in workplaces has been made, attempting to combine the results from individual monitoring for external, internal and workplace monitoring. A first status description of the active personal dosemeters, including legislative and technical information, and their implementation has been made. The importance of practical factors on the uncertainty in the dose measurement has been estimated. Even if a big progress has been made towards harmonisation, there is still work to be done.

The implementation in routine of the ENEA new personal photon dosemeter

The ENEA photon dosemeter, introduced in 1995, consisting of two differently filtrated LiF(Mg,Cu,P) detectors, has been modified recently. The ABS (acrylonitrile butadiene styrene) plastic support has been replaced by a new aluminium card supporting the same two detectors (LiF(Mg,Cu,P) GR200). The new card, fully developed at the ENEA-Radiation Protection Institute (which is going to be patented), can now be processed through a Harshaw Model 6600 Automated TLD Reader, a hot gas reader. This paper reports the results of the individual calibration of approximately 60,000 LiF(Mg,Cu,P) GR200 detectors inserted on the new aluminium cards. Before the implementation in routine of the new cards, the reader has been characterised. Steps and tests to be made to use the card in routine (i.e. reader stability, linearity, reproducibility, etc.) are reported. The whole dosimetric system now combines the very good performances of the Harshaw Model 6600 reader and that of LiF(Mg,Cu,P) thermoluminescent material.

The ENEA neutron personal dosimetry service

The ENEA Radiation Protection Institute has been operating the only neutron personal dosimetry service in Italy since the 1970s. Since the 1980s the service has been based on PADC (poly allyl diglycol carbonate) for fast neutron dosimetry, while thermal neutron dosimetry has been performed using thermoluminescence (TL) dosemeters. Since the service was started, a number of aspects have undergone evolution. The latest and most important changes are as follows: in 1998 a new PADC material was introduced in routine, since 2001 TL thermal dosimetry has been based on LiF(Mg,Cu,P) [GR-200] and (7)LiF(Mg,Cu,P) [GR-207] detectors and since 2003 a new image analysis reading system for the fast neutron dosemeters has been used. Herein an updated summary of how the service operates and performs today is presented. The approaches to calibration and traceability to estimate the quantity of H(p)(10) are mentioned. Results obtained at the performance test of dosimetric services in the EU member states and Switzerland sponsored by the European Commission and organised by Eurados in 1999 are reported. Last but not least, quality assurance (QA) procedures introduced in the routine operation to track the whole process of dose evaluation (i.e. plastic QA, acceptance test, test etching bath reproducibility and 'dummy customer' (blind test) for each issuing monitoring period) are presented and discussed.

Batch homogeneity of LiF(Mg,Cu,P)-GR200 and LiF(Mg,Cu,P)-MCP-NS TL detectors for use as extremity dosemeters at ENEA personal dosimetry service

The results of a study of two commercially available LiF(Mg,Cu,P) TL materials, a GR200 detector and a MCP-Ns thin detector, are described in order to use these phosphors for individual monitoring for the extremities. After a dosimetry system has been type tested, the implementation routine is not straightforward. Additional tests and software modification are needed to make the routine system work comply with the type test results. Not often can literature be found on the steps required to implement the results in a routine study. This paper reports the results of the individual calibration of about 15 000 extremity dosemeters, 12 000 containing a GR200 detector and 3000 an MCP-Ns thin detector. It describes the experimental procedure followed in order to assure reproducibility and stability of the results with proper accuracy and reliability. In particular, this is the first time that results on homogeneity of such a large batch of MCP-Ns detectors are reported.

The ENEA criticality accident dosimetry system: a contribution to the 2002 international intercomparison at the SILENE reactor

The present paper summarises the activity carried out at the ENEA Radiation Protection Institute for updating the methodologies employed for the evaluation of the neutron and photon dose to the exposed workers in case of a criticality accident, in the framework of the 'International Intercomparison of Criticality Accident Dosimetry Systems' (Silène reactor, IRSN-CEA-Valduc June 2002). The evaluation of the neutron spectra and the neutron dosimetric quantities relies on activation detectors and on unfolding algorithms. Thermoluminescent detectors are employed for the gamma dose measurement. The work is aimed at accurately characterising the measurement system and, at the same time, testing the algorithms. Useful spectral information were included, based on Monte Carlo simulations, to take into account the potential accident scenarios of practical interest. All along this exercise intercomparison a particular attention was devoted to the 'traceability' of all the experimental and computational parameters and therefore, aimed at an easy treatment by the user.

Implementation of standards for individual monitoring in Europe

A large number of standards are available for radiation protection and individual monitoring purposes. They are published by various organisations, international and national. Moreover, the increasing policy of "Quality" applied to individual monitoring requires the implementation of standards on Quality Assurance (QA) both in technical and management aspects of a dosimetric service. Implementation of standards is not mandatory; therefore, varying degrees of implementation can be found in different European countries. However, for a number of good reasons, a degree of harmonisation within the European Union (EU) of the requirements and procedures for individual monitoring would be desirable. Harmonisation as applied to dosimetric services does not mean that they should all follow exactly the same procedures, but that they should aim to meet the same general requirements, and their results should be comparable. This article aims to compile information on the use of all standards applied within individual monitoring practices, be it on the calibration of dosemeters or on the QA procedures to be applied to the overall dose evaluation process. Both "technical standards" and "quality standards" will be discussed. A list of documents of relevance to subjects such as recommendations and requirements in the field of individual monitoring, whose application could help in the harmonisation of procedures, will also be given. As it is agreed that implementation of quality standards is a relevant framework within which harmonisation can be achieved, guidance on the implementation of quality standards in a dosimetric service is given. Accreditation and approval of dosimetric services will be of relevance in the process of harmonisation of individual monitoring within the EU. In this article, a discussion of various procedures and the meaning of both forms of recognition is also provided. Although most of the text applies to the monitoring of internal and external exposure to ionising radiation, the emphasis of this practical guidance is on monitoring for external radiation with passive dosemeters.

A personal neutron monitoring system based on CR-39 recoil proton track detectors: assessment of Hp(10) using image process algorithms

At the Individual Monitoring Service (IMS) of the ENEA Institute for Radiation Protection (IRP), the Hp(10) fast neutron dosemeter consists of a CR-39 (PADC, poly allyl diglycol carbonate) recoil protons track detector. The tracks across the detector surface are magnified through a chemical etching procedure and counted by a semi-automated system which consists of a microscope, a camera and a PC. A new analysis system, based on the National Instruments vision tools, was developed. The track area distribution for each reading field is recorded and numerical algorithms were developed in order to correct the energy dependence of the response and to recognise the tracks due to the background. This improves the dose evaluation system in terms of accuracy and discrimination or the background.

CR-39 acceptance test and optimisation for fast neutron dosimetry applications

The ENEA fast neutron dosemeter is based on a planar PADC (poly allyl diglycol carbonate) placed in a polyethylene holder. The CR-39 (registered trademark of PPG Industries Inc.) material, produced by Intercast Europe S.p.A., has been used in the routine of the Individual Monitoring Service (IMS) since 1998. Since then, acceptance tests on average sheet background track density and sheet neutron sensitivity have been made on new batches as a quality control within a quality assurance programme of the IMS of ENEA-Institute for Radiation Protection (IRP). Dosemeters were irradiated with a 241Am-Be source at ENEA-IRP and processed through a chemical etching procedure (pre-etching with 40% KOH water solution 6.25 N and 60% ethyl alcohol at 70 degrees C followed by 12 h of etching in 6.25 N KOH water solution). In this paper we present the analysis of acceptance testing data for more than 30 sheets of CR-39 plastic produced in 1998, 1999 and 2000. Moreover, we compare the performance of sheets of CR-39 of standard composition with that of sheets of CR-39 with the addition of DOP (dioctylphthalate), in different concentrations, on the hasis of average background density, neutron sensitivity and background fluctuation that limit the lower detectable dose. This study demonstrates the need for acceptance tests to assure the quality of the dosimetric performance of these dosemeters, which is considerably dependent on the quality of the CR-39 plastic.

Pilot study on the application of computerised glow curve analysis in TL based personal dosimetry services

Preliminary results of an inter-laboratory collaborative work on the application of computerised glow curve analysis to TL personal dosimetry are presented. Very simple analysis methods have proved to be useful for the evaluation of glow curves similar to those encountered in the dosimetric control of radiation workers. A first result obtained in the study has been the possibility of simplifying the TL working procedures by eliminating pre-annealing or pre-heating steps employed in conventional systems to avoid low temperature peaks. The presence of these unwanted peaks can be detected by the computerised evaluation methods, discriminating their contribution to the dosimetric TL data.

Energy dependence of TLD-300 response from 6 keV up to 1250 keV

The energy dependence of the response function S(E), of CaF2:Tm (TLD-300) thermoluminescent material (3.2 x 3.2 x 0.90 mm3 ribbons) was measured from 6 keV up to 1250 keV (60Co) using 55Fe, 137Cs and 60Co gamma ray sources as well as X ray ISO reference beams. To the best knowledge of the authors the data for energies below 45 keV are reported for the first time. The S(E) function was also calculated in the energy range from 1 keV up to 20 MeV and compared with the experimental data relative to the total glow curve. The comparison shows good agreement from 1250 keV down to 40 keV. At lower energy the discrepancy increases. This is interpreted in terms of the X ray attenuation within the thickness of TLD-300. Finally, measurements point out the effects of different reading and annealing treatments on the measured function S(E).

ENEA personal dosemeters for assessing Hp(10) and Hp(0.07)

Although, at present, neither Italian legislation nor technical protocols require that personal dosimetry is performed to assess Hp(d), the ENEA Individual Monitoring Service (IMS) is able to supply thermoluminescence (TL) whole-body and extremity dosemeters for photon and beta fields, based on LiF(Mg,Cu,P) detectors and these have been fully developed at the ENEA Institute for Radiation Protection (IRP). All irradiation tests have been performed with ISO phantoms and ISO recommended reference radiations at the ENEA-IRP Secondary Standard Dosimetry Laboratory. The whole-body dosemeter contains two LiF(Mg,Cu,P) (GR200) detectors that are filtered differently. One is filtered on both sides by 290 mg.cm-2 mass per area (270 mg.cm-2 Al + 20 mg.cm-2 plastic protective layer); the other is filtered on both sides by a plastic layer of 20 mg.cm-2 mass per area. In photon radiation fields, the maximum uncertainty due to the energy dependence of the response, is +/- 4% for Hp(0.07) in the energy range 13 keV to 202 keV, and +/- 15% for Hp(10) in the range 13 keV to 1.25 MeV. The dosemeter response in terms of Hp(d,alpha) in beta fields has been investigated recently. The results of a EURADOS trial performance test for photon and beta fields are reported and discussed in this paper. The extremity dosemeter currently used at ENEA IMS consists of a GR200 detector glued on a kapton strip identified by a bar code. Its response in terms of Hp(0.07,alpha) has been measured recently and the results are given. Moreover, different dosemeter assemblies have been tested to compare the performances in photon and beta fields. Therefore, the following three constructions have been prepared: (1) an MCP-Ns (8.5 mg.cm-2 mass per area) detector with a Mylar filter of 0.5 mg.cm-2 mass per area; (2) a polyethylene filter of 12 mg.cm-2 mass per area; and (3) a GR200 (210 mg.cm-2 mass per area) detector with a Mylar filter of 0.5 mg.cm-2. Finally, a brief discussion on international and Italian requirements for personal monitoring is given.

Harmonisation and dosimetric quality assurance in individual monitoring for external radiation

The current situation amongst Member States is that there are widely differing national requirements for dosimetric services and for dosemeter performance. It is clear that with the free movement of workers within the European Union (EU) and the requirements for individual dosimetry given in Council Directive 96/29 EURATOM, a degree of harmonisation of requirements and procedures of EU Member States would be desirable. A EURADOS action group, made up of members from each of the EU Member States plus Switzerland, was set up with the overall objectives of consolidating within the EU the quality of individual monitoring using personal dosemeters and assisting movement towards harmonised procedures. An outline of the work of the action group is given and the term 'harmonisation' is discussed.

Present status of approval procedures in the EU member states and Switzerland

The European Union Council Directive 96/29/EURATOM requires that 'individual monitoring shall be ... based on individual measurements which are established by an approved dosimetric service' and that 'Each Member State shall make arrangements to recognise, as appropriate, the capacity of ... approved dosimetric services'. At present, approval of dosimetric services does not have the same meaning within EU Member States and Switzerland. In some countries, service and dosemeter approval is clearly separated, in some others only one of the two is supposed to be tested, and in others no approval is required. Dosimetric requirements and criteria are based on different international documents (e.g. IEC, ISO, ANSI, CEC report) or national specific rules. Approval frequency can be once, every 2 or more years. Approval can be based on either evaluation of technical and management reports, irradiation tests, inspection on-site or the three steps together. In most cases, approval involves photon dosimetry while beta and neutron dosimetry test procedures are not as well established. However, comparisons may lead to some convergent evolution of procedures and to a greater degree of harmonisation and quality consolidation.

Radiation dose to the testes after 131I therapy for ablation of postsurgical thyroid remnants in patients with differentiated thyroid cancer

Radioiodine-131 is used in differentiated thyroid cancer (DTC) for ablation of postsurgical thyroid remnants and destruction of metastases. The question may be raised of whether 131I treatment of DTC in male patients may give an irradiation dose to the testes that could impair fertility. Few data in the literature concern the dose absorbed by the testes after 1311 therapy for DTC. Because 131I kinetics may be altered by the hypothyroid condition commonly present at the time of treatment and by the radioiodinated iodoproteins released by the damaged thyroid tissue, the dose values reported in the International Commission on Radiological Protection (ICRP) tables for euthyroid men may not be appropriate. To clarify this problem, three male subjects undergoing 131I therapy for ablation of thyroid remnants shortly after thyroidectomy for DTC were studied.

METHODS

The mean administered activity was 1256 MBq, and the duration of the study was 2 wk. The gamma dose was measured by thermoluminescent dosimeters (TLDs) applied to the lower poles of the testes. Correction factors were calculated for the distance of the TLD from the center of the testes and for attenuation by the testes of the gamma rays reaching the TLD. After correction, the gamma dose to the testes ranged from 21 to 29 mGy. The gamma dose calculated by the Medical Internal Radiation Dose (MIRD) method from blood and urine samples was similar (18-20 mGy) to that measured by TLDs. The beta dose was estimated by the MIRD method from blood activity and testicular volume and ranged between 14 and 31 mGy.

RESULTS

The total (beta and gamma) doses to testes were 30, 33 and 43 microGy/MBq in the three subjects.

CONCLUSION

These values are close to those derived from the ICRP tables (26-37 microGy/MBq 131I) for euthyroid subjects. The present data indicate that significant irradiation is delivered to the testes after the administration of the 131I ablative dose to thyroidectomized patients. The relevance of the radiation absorbed by testes on fertility remains to be established.

[Volume of the irradiated small intestine during pelvic radiotherapy. Comparison of various calculation methods]

In pelvic irradiation, the small bowel portion included in the planning treatment volume is one of the major factors of acute enteropathy. Three different methods are used to calculate the bowel volume: Gallagher's grid method and two systems based on specific algorithms using CT data. We compared the results of these different methods in a series of nine patients submitted to treatment volume planning simulation for pelvic irradiation, after oral barium administration. The small bowel volumes were calculated with the grid method on orthogonal radiographs. About one hour later, the patients were submitted to CT for radiotherapy planning. The small bowel regions to be irradiated were drawn manually on all CT slices on a Varian Cadplan 2.62 console. Two different algorithms were used to calculate the small bowel volumes: one of them based on polyhedral and the other on cylindric approximation. The average volumes, the variance and the determination coefficient with linear and polynomial regression were in substantial statistical agreement in the three series; the correlation index between the grid and the CT methods ranged 0.84-0.87. Therefore, the authors believe that enteric side-effects can be correlated with the irradiated small bowel volume, independent of the calculation method.