Individual monitoring for internal exposure in Europe and the integration of dosimetric data

The European Radiation Dosimetry Group, EURADOS, established a working group consisting of experts whose aim is to assist in the process of harmonisation of individual monitoring as part of the protection of occupationally exposed workers. A catalogue of facilities and internal dosimetric techniques related to individual monitoring in Europe has been completed as a result of this EURADOS study. A questionnaire was sent in 2002 to services requesting information on various topics including type of exposures, techniques used for direct and indirect measurements including calibration and sensitivity data and the methods employed for the assessment of internal doses. Information relating to Quality Control procedures for direct and indirect measurements, Quality Assurance Programmes in the facilities and legal requirements for ‘approved dosimetric services' were also considered. A total of 71 completed questionnaires were returned by internal dosimetry facilities in 26 countries. This results in an overview of the actual status of the processes used in internal exposure estimation in Europe. In many ways harmonisation is a reality in internal dose assessments, especially when taking into account the measurements of the activity retained or excreted from the body. However, a future study detailing the estimation of minimum detectable activity in the laboratories is highly recommended. Points to focus on in future harmonisation activities are as follows: the process of calculation of doses from measured activity, establishment of guidelines, similar dosimetric tools and application of the same ICRP recommendations. This would lead to a better and more harmonised approach to the estimation of internal exposures in all European facilitie

Thermoluminescent detectors applied in individual monitoring of radiation workers in Europe—a review based on the EURADOS questionnaire

Among the activities of EURADOS Working Group 2 formed by experts from several European countries is the harmonisation of individual monitoring as part of radiation protection of occupationally exposed persons. Here, we provide information about thermoluminescent detectors (TLDs) applied by the European dosimetric services and the dosimetric characteristics of dosemeters in which these detectors are applied. Among 91 services from 29 countries which responded to the EURADOS questionnaire, 61 apply dosemeters with TLDs for the determination of personal dose equivalent Hp(10) for photons and beta radiation, and 16 services use TLDs for neutron albedo dosemeters. Those most frequently used are standard lithium fluoride TLDs (mainly TLD-100, TLD-700, Polish MTS-N and MTS-7, Russian DTG-4), high-sensitive lithium fluoride (GR-200, MCP-N) and lithium borate TLDs. Some services use calcium sulphate and calcium fluoride detectors. For neutron dosimetry, most services apply pairs of LiF:Mg,Ti TLDs with 6Li and 7Li. The characteristics (energy response) of individual dosemeters are mainly related to the energy response of the detectors and filters applied. The construction of filters in dosemeters applied for measurements of Hp(10) and their energy response are also reviewe

Workplace monitoring for exposures to radon and to other natural sources in Europe: integration of monitoring for internal and external exposures

Part of the action of the EURADOS working group (European Radiation Dosimetry Group) on ‘Harmonisation of Individual Monitoring in Europe' was to investigate how the results from personal dosemeters for external radiation, from monitoring for internal exposure and from workplace monitoring, can be combined into a complete and consistent system of individual monitoring. To facilitate this work, the ‘EURADOS questionnaire Q3' relating to radon and other natural sources of radiation in the workplace was distributed to relevant institutes across Europe. A total of 24 countries replied to the questionnaire. This study offers an important overview on actual regulations, national standards and reference levels for protection of employees from radon and other natural sources in different workplace scenarios. Information was also collected on individual monitoring and area monitoring to determine individual doses in workplaces with elevated levels of natural radiation. The article discusses in detail the results obtained showing by country the reference level in workplaces for radon gas and other natural sources. In both instances, exposures in mines, other underground workplaces, industry workplaces/waterworks, offices, schools and day-care homes were considered. The resultant data clearly indicate that there is a need for harmonisation among countries, not least in the areas of regulation and use of reference levels in the workplac

Some clinical applications of MTS-type TLD detectors

An important part of any QA programme for radiotherapy is verification, in vitro or in vivo, of calculated doses and dose distributions. We studied the clinical applicability of LiF:MG, Ti sintered TL detectors produced, as type MTS-N, by the Institute of Nuclear Physics in Kraków (INP). These are solid pellets of diam 4.5mm and 0.8mm thickness. The TL reader was a modified planchet-type 770A, also produced at the INP, with linear heating and computerised glow curve recording.For analysis of in vivo applications, we measured, in a water phantom, the dose at 14 points aroud the Standard gynaecological applicator of our SELECTRON LDR/MDR afterloading unit with Cs-137 pellets and compared the measured values with doses calculated at these points by the in-house developed SELKOM computer code used for planning gynaecological brachytherapy at the Centre of Oncology in Kraków (COK). Agreement to within 5% was stated.To demonstrate the applicability of MTS dosemeters in calibration dosimetry, we studied the accuracy, stability and reproducibility of a batch of 100 detectors over several readout cycles at doses ranging from 0.5 to 2.5 Gy. At 1 Gy, the relative standard deviation of Individual Calibration Factors (ICF) over six readout cycles did not exceed 2.5% indicating that the error of dose estimation using individual MTS detectors should not exceed 2%.In an intercomparison of Co-60 beams at the COK and at Louvain performed with MTS detectors agreement to within less than 0.5% was found with an accuracy better than 1%.This work is partly supported by KBN Polish State Committee for Scientific Research, Research Project No. 8T11E02908

Analysis of time-profiles with in-beam PET monitoring in charged particle therapy

Background: Treatment verification with PET imaging in charged particle therapy is conventionally done by comparing measurements of spatial distributions with Monte Carlo (MC) predictions. However, decay curves can provide additional independent information about the treatment and the irradiated tissue. Most studies performed so far focus on long time intervals. Here we investigate the reliability of MC predictions of space and time (decay rate) profiles shortly after irradiation, and we show how the decay rates can give an indication about the elements of which the phantom is made up. Methods and Materials: Various phantoms were irradiated in clinical and near-clinical conditions at the Cyclotron Centre of the Bronowice proton therapy centre. PET data were acquired with a planar 16x16 cm$^2$ PET system. MC simulations of particle interactions and photon propagation in the phantoms were performed using the FLUKA code. The analysis included a comparison between experimental data and MC simulations of space and time profiles, as well as a fitting procedure to obtain the various isotope contributions in the phantoms. Results and conclusions: There was a good agreement between data and MC predictions in 1-dimensional space and decay rate distributions. The fractions of $^{11}$C, $^{15}$O and $^{10}$C that were obtained by fitting the decay rates with multiple simple exponentials generally agreed well with the MC expectations. We found a small excess of $^{10}$C in data compared to what was predicted in MC, which was clear especially in the PE phantom.Comment: 9 pages, 5 figures, 1 table. Proceedings of the 20th International Workshop on Radiation Imaging Detectors (iWorid2018), 24-28 June 2018, Sundsvall, Swede

Individual monitoring for internal exposures in Europe: Conclusions of an EURADOS action

Once the EC Directive 96/29 has been implemented into national regulation across Europe, the coordination of dosimetry laboratories for the monitoring of occupational exposures becomes the principal aim to achieve. Within this framework the European Radiation Dosimetry Group, EURADOS, carried out an Action on ‘Harmonisation of Individual Monitoring' (2000-2004) to promote coordination in the field of individual monitoring of occupational exposures throughout Europe. With reference to internal exposures, the main aims were the completion of a catalogue of internal dosimetry services and an inventory of methods and techniques used for individual monitoring at European internal dosimetry facilities. At the end of this EURADOS Action, a report was published in Radiation Protection Dosimetry in 2004. The information collected related to various topics: the equipments used for the measurement of internal exposures, calibration and sensitivity data, the methods applied for the assessment of internal doses, Quality Control procedures, Quality Assurance Programmes in the facilities and legal requirements. The information to be presented here will give a general overview of the actual status of individual monitoring for internal exposures in Europ

A catalogue of dosemeters and dosimetric services within Europe—an update

The catalogue of dosemeters and dosimetric services within the European Union (EU) Member States and Switzerland that was issued by EURADOS in the year 2000 has been updated and extended with information on dosimetric services in the new EU Member States and Bulgaria, Croatia, Romania, Serbia and Montenegro, and Ukraine. The total number of dosimetric services in these European countries is now estimated to be about 200. The present catalogue is based on information collected from 90 European dosimetric services, among which 34 questionnaires from 32 services were obtained over the years 2001-2004 for the first time. This article assesses and updates the present use of personal dosemeters and the extent to which occupationally exposed persons in Europe are monitored with dosemeters able to measure the operational quantity—personal dose equivalent, HP(d). The perspective of joining EU by the new countries accelerated the implementation of the EU Basic Safety Standard Directive to their national regulations. As a result, all newly investigated services reported their ability to measure HP(d). The catalogue provides information on the dosemeters, dose calculation and background subtraction algorithms, calibration methods, energy and angular response, and performanc

24. Validation of conformal radiotherapy treatment planning systems using an antro-pomorphic phantom and thermoluminescence dosimetry

Within the requirements of a Quality Assurance programme in a radiotherapy department, the ability of a treatment planning system (TPS) to accurately calculate dose distributions under realistic conditions encountered in radiotherapy (RT) should be validated. This may be accomplished by thermoluminescence (TL) dosimetry in simulated treatment of antropomorphic phantoms. In our radiotherapy department, several planning systems are used concurrently in 3D conformal treatment of larger volumes (with irregular fields obtained via individual shielding or multileaf collimation) and of very small volumes (stereotactic technique), by external megavoltage photon beams. Realistic 3D treatment plans were prepared using CadPlan, Theraplan and BrainLab TPS for treating volumes in an Alderson phantom, which was prepared for topometry (CT-scanned) and irradiated in fully simulated conditions of patient RT. Suitably selected TL detectors (some custom-produced for these measurements), were placed inside and around the treated volumes in the phantom. For every photon beam applied (Co-60, 6 MV or 9 MV) the TL detectors, individually corrected, were calibrated in a standard solid phantom against ionisation chamber dosimetry. For irradiation of larger volumes, standard MTS-N (LiF:Mg,Ti) detectors were used. For stereotactic irradiation of small volumes in the head (6 MV) special miniature thermoluminescent LiF:Mg,Ti and LiF:Mg,Cu,P were developed. The technique of detector calibration, preparation of Alderson phantom for simulated RT, detector readout and interpretation of the measured versus calculated values of dose at measurement points inside the phantom, will be described