EURADOS Working Group Research Articles

EURADOS IC2019exteye- a self-funded intercomparison for extremity and eye lens dosemeters organised by EURADOS working group 2.

The European Radiation Dosimetry Group (EURADOS) has been organising regular, self-funding, external dosimetry intercomparisons (ICs) since 2008. IC2019exteye, for extremity and eye lens dosemeters, attracted 113 systems (68 extremity and 45 eye lens) from 60 institutes with participants from 26 countries around the world. Irradiations were carried out in accredited European irradiation facilities in terms of Hp(0.07)/or Hp(3) in the ranges: photon energy: 16-662keV, beta mean energy 250-1000keV, dose: 0.5mSv to 1Sv, maximum angle of incidence: ±60°. This paper describes the IC2019exteye set-up, irradiation plan and coordination with an overview of the main conclusions. Out of the total of 113 systems, 57 reported results for photons only and 56 reported both photon and beta. In general, the participants showed very satisfactory performances with the medians of all Hp(0.07) and Hp(3) response values very close to unity.

Out-of-Field Doses Produced by a Proton Scanning Beam Inside Pediatric Anthropomorphic Phantoms and Their Comparison With Different Photon Modalities.

Since 2010, EURADOS Working Group 9 (Radiation Dosimetry in Radiotherapy) has been involved in the investigation of secondary and scattered radiation doses in X-ray and proton therapy, especially in the case of pediatric patients. The main goal of this paper is to analyze and compare out-of-field neutron and non-neutron organ doses inside 5- and 10-year-old pediatric anthropomorphic phantoms for the treatment of a 5-cm-diameter brain tumor. Proton irradiations were carried out at the Cyclotron Centre Bronowice in IFJ PAN Krakow Poland using a pencil beam scanning technique (PBS) at a gantry with a dedicated scanning nozzle (IBA Proton Therapy System, Proteus 235). Thermoluminescent and radiophotoluminescent dosimeters were used for non-neutron dose measurements while secondary neutrons were measured with track-etched detectors. Out-of-field doses measured using intensity-modulated proton therapy (IMPT) were compared with previous measurements performed within a WG9 for three different photon radiotherapy techniques: 1) intensity-modulated radiation therapy (IMRT), 2) three-dimensional conformal radiation therapy (3D CDRT) performed on a Varian Clinac 2300 linear accelerator (LINAC) in the Centre of Oncology, Krakow, Poland, and 3) Gamma Knife surgery performed on the Leksell Gamma Knife (GK) at the University Hospital Centre Zagreb, Croatia. Phantoms and detectors used in experiments as well as the target location were the same for both photon and proton modalities. The total organ dose equivalent expressed as the sum of neutron and non-neutron components in IMPT was found to be significantly lower (two to three orders of magnitude) in comparison with the different photon radiotherapy techniques for the same delivered tumor dose. For IMPT, neutron doses are lower than non-neutron doses close to the target but become larger than non-neutron doses further away from the target. Results of WG9 studies have provided out-of-field dose levels required for an extensive set of radiotherapy techniques, including proton therapy, and involving a complete description of organ doses of pediatric patients. Such studies are needed for validating mathematical models and Monte Carlo simulation tools for out-of-field dosimetry which is essential for dedicated epidemiological studies which evaluate the risk of second cancers and other late effects for pediatric patients treated with radiotherapy.

Monte Carlo calculation of organ and effective doses due to photon and neutron point sources and typical X-ray examinations: Results of an international intercomparison exercise

This paper summarizes the results of an intercomparison on the use of the ICRP Reference Computational Phantoms with radiation transport codes, which was organized by EURADOS working group 6. Three exercises are described: exposure to an anterior-posterior (AP) photon point source, exposure to an AP neutron point source, and exposure to two typical medical X-ray examinations. The three exercises received 17, 8 and 8 solutions, respectively. Participants originated from fifteen different countries, and used a wide range of Monte Carlo codes. Due to difficulties in defining the precise source location unambiguously in the exercise description, agreement to within ∼10% of the reference solution was considered satisfactory for a given participant's results. Although some participants provided initial solutions in good agreement with the reference solutions, differences of several tens of percent, or even several orders of magnitude, were exhibited for many of the others. Following feedback and suggestions from the organizers, revised solutions were submitted by some of the participants for the photon exercises; in general, agreement was improved. The overall observations from these three intercomparison exercises are summarized and discussed.

RENEB/EURADOS field exercise 2019: robust dose estimation under outdoor conditions based on the dicentric chromosome assay

Purpose Biological and/or physical assays for retrospective dosimetry are valuable tools to recover the exposure situation and to aid medical decision making. To further validate and improve such biological and physical assays, in 2019, EURADOS Working Group 10 and RENEB performed a field exercise in Lund, Sweden, to simulate various real-life exposure scenarios. Materials and methods For the dicentric chromosome assay (DCA), blood tubes were located at anthropomorphic phantoms positioned in different geometries and were irradiated with a 1.36 TBq 192Ir-source. For each exposure condition, dose estimates were provided by at least one laboratory and for four conditions by 17 participating RENEB laboratories. Three radio-photoluminescence glass dosimeters were placed at each tube to assess reference doses. Results The DCA results were homogeneous between participants and matched well with the reference doses (≥95% of estimates within ±0.5 Gy of the reference). For samples close to the source systematic underestimation could be corrected by accounting for exposure time. Heterogeneity within and between tubes was detected for reference doses as well as for DCA doses estimates. Conclusions The participants were able to successfully estimate the doses and to provide important information on the exposure scenarios under conditions closely resembling a real-life situation.

Recommendations for the use of active personal dosemeters (APDs) in interventional workplaces in hospitals.

Occupational radiation doses from interventional procedures have the potential to be relatively high. The requirement to optimise these doses encourages the use of electronic or active personal dosimeters (APDs) which are now increasingly used in hospitals. They are typically used in tandem with a routine passive dosimetry monitoring programme, with APDs used for real-time readings, for training purposes and when new imaging technology is introduced. However, there are limitations when using APDs. A survey in hospitals to identify issues related to the use of APDs was recently completed, along with an extensive series of APD tests by the EURADOS Working Group 12 on Dosimetry for Medical Imaging. The aim of this review paper is to summarise the state of the art regarding the use of APDs. We also used the results of our survey and our tests to develop a set of recommendations for the use of APDs in the clinical interventional radiology/cardiology settings, and draw attention to some of the current challenges.

A European perspective on dental cone beam computed tomography systems with a focus on optimisation utilising diagnostic reference levels

Cone beam computed tomography (CBCT) has been available since the late 1990s for use in dentistry. European legislation requires optimisation of protection and the use of diagnostic reference levels (DRLs) as well as regular quality control (QC) of the imaging devices, which is well outlined in existing international recommendations. Nevertheless, the level of application is not known. Earlier studies have indicated that few European countries have established DRLs and that patient doses (exposure parameters) have not been properly optimised. The EURADOS Working Group 12—Dosimetry in Medical Imaging undertook a survey to identify existing practices in Member States. Questionnaires were developed to identify equipment types, clinical procedures performed, and exposure settings used. The surveys were circulated to 22 countries resulting in 28 responses from 13 countries. Variations were identified in the exposure factors and in the doses delivered to patients for similar clinical indicators. Results confirm that patient doses are still not properly optimised and DRLs are largely not established. There is a need to promote the importance of performing QC testing of dental CBCT equipment and to further optimise patient exposure by establishment and use of DRLs as a part of a continuous optimisation process.

The 2019-2020 EURADOS WG10 and RENEB Field Test of Retrospective Dosimetry Methods in a Small-Scale Incident Involving Ionizing Radiation.

With the use of ionizing radiation comes the risk of accidents and malevolent misuse. When unplanned exposures occur, there are several methods which can be used to retrospectively reconstruct individual radiation exposures; biological methods include analysis of aberrations and damage of chromosomes and DNA, while physical methods rely on luminescence (TL/OSL) or EPR signals. To ensure the quality and dependability of these methods, they should be evaluated under realistic exposure conditions. In 2019, EURADOS Working Group 10 and RENEB organized a field test with the purpose of evaluating retrospective dosimetry methods as carried out in potential real-life exposure scenarios. A 1.36 TBq 192Ir source was used to irradiate anthropomorphic phantoms in different geometries at doses of several Gy in an outdoor open-air geometry. Materials intended for accident dosimetry (including mobile phones and blood) were placed on the phantoms together with reference dosimeters (LiF, NaCl, glass). The objective was to estimate radiation exposures received by individuals as measured using blood and fortuitous materials, and to evaluate these methods by comparing the estimated doses to reference measurements and Monte Carlo simulations. Herein we describe the overall planning, goals, execution and preliminary outcomes of the 2019 field test. Such field tests are essential for the development of new and existing methods. The outputs from this field test include useful experience in terms of planning and execution of future exercises, with respect to time management, radiation protection, and reference dosimetry to be considered to obtain relevant data for analysis.

Photon dosimetry methods outside the target volume in radiation therapy: Optically stimulated luminescence (OSL), thermoluminescence (TL) and radiophotoluminescence (RPL) dosimetry

Dosimetry methods outside the target volume are still not well established in radiotherapy. Luminescence detectors due to their small dimensions, very good sensitivity, well known dose and energy response are considered as an interesting approach in verification of doses outside the treated region. The physical processes of thermoluminescence (TL), radiophotoluminescence (RPL) and optically stimulated luminescence (OSL) are very similar and can be described in terms of the energy band model of electron-hole production following irradiation.This work is a review of the main dosimetric characteristics of luminescence detectors which were used in experiments performed by EURADOS Working Group 9 for in-phantom measurements of secondary radiation (scattered and leakage photons). TL LiF:Mg,Ti detectors type MTS-7 (IFJ PAN, Poland), types TLD-100 and TLD-700 (Harshaw), OSL Al2O3:C detectors type nanoDot™ (Landauer Inc.) and RPL rod glass elements type GD-352M (Asahi Techno Glass Coorporation) are described. The main characteristics are discussed, together with the readout and calibration procedures which lead to a determination of absorbed dose to water.All dosimeter types used show very good uniformity, batch reproducibility and homogeneity. For improved accuracy, individual sensitivity correction factors should be applied for TL and OSL dosimeters while for RPL dosimeters there is no need for individual sensitivity corrections.The dose response of all dosimeters is linear for a wide range of doses.The energy response of GD-352M type dosimeters (with Sn filter) used for out-of-field measurements is flat for medium and low energy X-rays.The energy dependence for TLDs is low across the range of photon energies used and the energy correction was neglected. A significant over response of Al2O3:C OSLDs irradiated in kilovoltage photon beams was taken into account. The energy correction factor fen was calculated by using the 2006 PENELOPE Monte Carlo code.With suitable calibration, all dosimeter types are appropriate for out-of-field dose measurements as well as for the in-phantom measurements of radiotherapy MV X-rays beams.

EURADOS self-sustained programme of intercomparisons for individual monitoring services

Within EURADOS working group 2, a system for self-sustained intercomparisons for individual monitoring services for external radiation was developed. With the intercomparison results, the participants can show compliance within their quality management system, compare their results with those from other participants and develop plans for improvement of their system. The costs of the exercises are covered by the participants fees. In this programme, the first intercomparison exercise for whole-body dosemeters has been executed in 2008 with 62 participating dosimetry systems from participants across Europe. In general, film systems show the largest deviations, although the results of some participants indicate that it is possible to achieve results with a film system with similar quality as for thermoluminescence dosimetry (TLD) systems. A second intercomparison has been organised for extremity dosemeters in 2009. For 2010 it is planned to organise a second intercomparison for whole-body dosemeters.

EURADOS intercomparison on measurements and Monte Carlo modelling for the assessment of americium in a USTUR leg phantom

A collaboration of the EURADOS working group on 'Internal Dosimetry' and the United States Transuranium and Uranium Registries (USTUR) has taken place to carry out an intercomparison on measurements and Monte Carlo modelling determining americium deposited in the bone of a USTUR leg phantom. Preliminary results and conclusions of this intercomparison exercise are presented here.

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.

Harmonisation (legal, dosimetric, quality aspects) of individual monitoring, and integration of monitoring for external and internal exposures (EURADOS Working Group).

The EURADOS Working Group II on 'Harmonisation of individual monitoring' consists of experts from almost all EU Member States and Newly Associated States (NAS), involved in tasks related to the assessment of doses for internal and external radiation. The final objective is to achieve harmonisation in individual monitoring for occupational exposures. Sub-group 2 activities are focused on investigating how the results from personal dosemeters for external radiation and workplace monitoring and from monitoring for internal exposure can be combined into a complete and consistent system of individual monitoring. Three questionnaires were prepared, covering 'Individual monitoring of external radiation' (Questionnaire 1), 'Internal exposure' (Questionnaire 2) and 'Natural sources of radiation at the workplace' (Questionnaire 3). With the agreement of a 'contact-person', selected in each country, the distribution of the three EURADOS 2002 questionnaires was carried out by e-mail among the dosimetry facilities of 28 European countries. The preliminary results of these actions are presented here.

Results of a Large Scale Neutron Spectrometry and Dosimetry Comparison Exercise at the Cadarache Moderator Assembly

Eurados Working Group 7 recently organised a large-scale comparison of neutron spectrometry and dosimetry measurements at the IPSN/SDOS laboratory of the CEA Cadarache Research Centre in France. A large number of participants took part with a range of instruments including spectrometers, tissue-equivalent proportional counters, personal dosemeters, and survey instruments. The neutron field used for the exercise was a primarily low energy neutron spectrum similar to those which have been measured recently around nuclear facilities. This paper presents the results of the measurements and attempts to draw conclusions about the accuracy attainable with the various devices, their advantages and drawbacks, and potential problems.