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Optically stimulated luminescence of quartz extracted from fired materials has been used for retrospective dosimetry for about 40 years. Quartz sensitivity to thermoluminescence and optically stimulated luminescence can vary over few orders of magnitude. These discrepancies in sensitivity for the quartz originating from different parts of the world are still not yet fully understood. We have extracted quartz from bricks produced by three different companies in the Czech Republic. Quartz was extracted from fired bricks, as well as from the bricks before firing. Significant changes in quartz sensitivity were observed after firing process. Sensitivity can either increase or decrease, depending mainly on the maximum temperature achieved during firing process. For some samples, the sensitivity increased significantly after firing (7 times). Sensitivity also increased after repeated irradiation exposures. On the other hand, there were also samples for which the sensitivity did not increase after repeated cycles of irradiation.

PURPOSE The threat of serious radiation exposures to members of the public from radiological incidents and nuclear events has led to intensive study of a number of emergency dosimetry techniques for purposes of triage. As such, a national laboratory of retrospective dosimetry was established in our institute. The purpose of this work is to provide a summary of the well-established and already implemented retrospective physical dosimetry techniques based on thermoluminescence (TL), optically stimulated luminescence (OSL) and neutron activation including their specifics. Moreover, we present some new results of the experimental work, in which we compared dosimetry potential of various dental repair materials and human teeth. MATERIALS AND METHODS At first, an overview of already established retrospective physical retrospective methods including their main features was compiled. As regards recent research, an experimental comparative study was performed under defined conditions. The materials used were aliquots prepared from both pure and repaired teeth and aliquots of unused dental ceramics of known type. Following irradiation, we compared TL and OSL curves of the materials. We also compared dosimetry characteristics of OSL signal as reproducibility, dose dependence and fading. RESULTS After irradiation, the teeth aliquots of dental enamel and dentin exhibited very low OSL and TL signals compared with aliquots containing some dental repair materials or aliquots of pure dental ceramics. With a few exceptions, the OSL signal of dental enamel and dentin aliquots irradiated to 2 Gy was hardly distinguishable from OSL signal corresponding to unirradiated aliquots. In contrast, aliquots of teeth containing some dental repair material and aliquots of pure dental ceramics provided a well reproducible OSL signal exhibiting linear dose response. All the materials tested exhibited a significant fading of the OSL signal. The loss of OSL signal during the first 24 hours after irradiation was from 20 to 99% of its original value obtained immediately after the irradiation. CONCLUSIONS The already established physical methods of retrospective dosimetry use a spectrum of verified materials and techniques for dose assessment in the aftermath of serious radiological incidents and nuclear events. In the comparative study, we found that the dosimetry potential of teeth in natural state is much worse compared to teeth repaired with dental ceramics or dental cement fillings. Teeth restored with dental repair materials exhibited relatively favorable dosimetry characteristics. However, they can be usable for a dose reconstruction only on condition that the main practical problems connected with fading and optical bleaching were solved.

New operational quantities for external radiation exposure presented by the ICRU brought changes, which can affect the use of current dosemeters. Dosemeters calibrated in the old quantities should be tested, and the results obtained should be analyzed with respect to the new quantities. The difference between the old and new quantities depends primarily on photon energy. This work concerns instruments for area monitoring, which were exposed to reference photon and neutron spectra of mean energies from 65 to 1250 keV and from 0.02 to 10 MeV, respectively. As expected, it was revealed that the current photon dosemeters overestimate the new quantity ambient dose. For the measurements within the energy interval chosen, it seems to be acceptable to implement a correction factor to optimize the response. For the purposes of measurements of photons of lower energies, further research would be needed. To adapt the response of the neutron dosemeter tested, recalibration or redesign can be considered, but no fundamental changes seem to be necessary for the investigated spectra.

The ICRU proposed new operational quantities, which are defined in close relation to effective dose and absorbed dose. Most of the current personal dosemeters were designed to measure personal dose equivalents. Because of differences between the new and old quantities, the existing dosemeters may not be ideal for measurements of the new quantities, personal dose, Hp, and absorbed dose in local skin, Dp local skin. For photon radiation sources, we investigated relative responses of the current personal dosemeters with respect to the measurement of the new quantities. Introduction of the new quantities into practice will require some changes in practical radiation protection. A recalibration of the current dosemeters will be essential for Hp measurements in higher photon energy region (>50 keV). For lower photon energies, a redesign of specific evaluation algorithms will be necessary. For purposes of Dp local skin measurements the dosemeters do not require any fundamental changes.

The unique feature of nuclear accidents with neutron exposure is the induced radioactivity in body tissues. For dosimetry purposes, the most important stable isotopes occurring in human body, which can be activated by neutrons, are 23 Na and 32 S. The respective activation reactions are as follows:23Na(n,γ)24Na and32S(n,p)32P. While sodium occurs in human blood, sulfur is present in human hair. In order to verify the practical feasibility of this dosimetry technique in conditions of our laboratory, samples of human blood and hair were irradiated in a channel of a training reactor VR-1.24Na activity was measured by gamma-ray spectrometry.32P activity in hair was measured by means of a proportional counter. Based on neutron-spectrum calculation, relationships between neutron dose and induced activity were derived for both blood and hair.

We used the hybrid semiconductor pixel detector Timepix as an area dosimeter in mixed neutron-gamma fields. The surface of the detector was covered with several converters based on 6Li, polyethylene, Th and enriched U. We used three different neutron sources for calibration of the device – thermal neutrons from graphite pile, 241Am-Be and 252Cf. The desired neutron component of dosimetry and operational quantities can be determined by counting events under the converters. The segmentation of the Timepix detector and its capability to measure energy deposition of each interacting quantum of ionizing radiation allows a separation of neutron events from X-ray/gamma or electron interaction. Thus, the device can also be used for simultaneous X-ray and gamma dosimetry, where it is in some aspects superior to most of the commercial devices, given its detection threshold of 3–5 keV.

A historical radium (226Ra) needle was found in a building in Prague. The needle was concealed in a wall under a window frame. Ambient dose equivalent rate measured in close proximity to the frame reached up to 2 mSv/h. The place was located between a corridor and a staircase where people normally did not stay; hence, any significant radiation exposure was not suspected. Because of a remarkable history of the building, our speculation was that the needle could have been concealed there during World War II. To verify this assumption, one adjacent brick nearest to the place of the find was removed. The brick was used for retrospective dosimetry based on optically stimulated luminescence (OSL) of quartz extracted from a chosen brick block. Dose rate values inside the brick block were determined by a laboratory reconstruction. The original exposure conditions were simulated using the needle and a brick wall containing thermoluminescence detectors (TLDs). We also performed a computational simulation with the Monte Carlo technique. The simulation provided us a more detailed dose rate distribution inside the brick block. Finally, we compared OSL quartz, TLD, and Monte Carlo results. A good agreement among the results supports the speculation that the radium needle was concealed during World War II.

In the aftermath of an orphan radiation source find, a complex retrospective dose reconstruction can be required to estimate doses of persons who were staying in the vicinity. In retrospective dose reconstructions based on luminescence measurements of quartz extracted from bricks, high sensitivity thermoluminescence detectors (TLD) can be used as an ancillary tool for dose distribution measurements or natural radiation background measurement. We investigated the potential and limits of Al

Introduction: Within an International Atomic Energy Agency (IAEA) co-ordinated research project (CRP), a remote end-to-end dosimetric quality audit for intensity modulated radiation therapy (IMRT)/ volumetric arc therapy (VMAT) was developed to verify the radiotherapy chain including imaging, treatment planning and dose delivery. The methodology as well as the results obtained in a multicentre pilot study and national trial runs conducted in close cooperation with dosimetry audit networks (DANs) of IAEA Member States are presented. Material and methods: A solid polystyrene phantom containing a dosimetry insert with an irregular solid water planning target volume (PTV) and organ at risk (OAR) was designed for this audit. The insert can be preloaded with radiochromic film and four thermoluminescent dosimeters (TLDs). For the audit, radiotherapy centres were asked to scan the phantom, contour the structures, create an IMRT/VMAT treatment plan and irradiate the phantom. The dose prescription was to deliver 4 Gy to the PTV in two fractions and to limit the OAR dose to a maximum of 2.8 Gy. The TLD measured doses and film measured dose distributions were compared with the TPS calculations. Results: Sixteen hospitals from 13 countries and 64 hospitals from 6 countries participated in the multicenter pilot study and in the national runs, respectively. The TLD results for the PTV were all within +/- 5% acceptance limit for the multicentre pilot study, whereas for national runs, 17 participants failed to meet this criterion. All measured doses in the OAR were below the treatment planning constraint. The film analysis identified seven plans in national runs below the 90% passing rate gamma criteria. Conclusion: The results proved that the methodology of the IMRT/VMAT dosimetric end-to-end audit was feasible for its intended purpose, i.e., the phantom design and materials were suitable; the phantom was easy to use and it was robust enough for shipment. Most importantly the audit methodology was capable of identifying suboptimal IMRT/VMAT delivery.

Background and purpose: An audit methodology for verifying the implementation of output factors (OFs) of small fields in treatment planning systems (TPSs) used in radiotherapy was developed and tested through a multinational research group and performed on a national level in five different countries. Materials and methods: Centres participating in this study were asked to provide OFs calculated by their TPSs for 10 × 10 cm2, 6 × 6 cm2, 4 × 4 cm2, 3 × 3 cm2 and 2 × 2 cm2 field sizes using an SSD of 100 cm. The ratio of these calculated OFs to reference OFs was analysed. The action limit was ±3% for the 2 × 2 cm2 field and ±2% for all other fields. Results: OFs for more than 200 different beams were collected in total. On average, the OFs for small fields calculated by TPSs were generally larger than measured reference data. These deviations increased with decreasing field size. On a national level, 30% and 31% of the calculated OFs of the 2 × 2 cm2 field exceeded the action limit of 3% for nominal beam energies of 6 MV and for nominal beam energies higher than 6 MV, respectively. Conclusion: Modern TPS beam models generally overestimate the OFs for small fields. The verification of calculated small field OFs is a vital step and should be included when commissioning a TPS. The methodology outlined in this study can be used to identify potential discrepancies in clinical beam models. Keywords: Dosimetry audit, Small field output factors, Treatment planning system

We present a concept of using Timepix detector for real-time and simultaneous measurements of various external dosimetry and operational quantities in X-ray/gamma fields with broad range of air kerma rates ranging from natural background levels to the order of Gy·h −1 , including intensive pulsed sources used in medicine. Timepix is a hybrid semiconductor detector of ionizing radiation which can visualize tracks of particles interacting in the semiconductor pixelated sensor bump bonded to the Timepix readout chip. Energy deposited in the individual pixels and properties of these tracks enable us to classify the incident radiation and to assign the correct conversion coefficient between a number of detected events and the desired quantity, e.g. an ambient dose equivalent rate. This paper shows calibration measurements of such dosemeter and discusses its properties.

A new dosimetry system was developed in Japan (Chiyoda Technol Corporation). It has been used for purposes of continuous long-term personal dose monitoring of residents in the area affected by the Fukushima Daiichi nuclear plant accident. The system includes a Si-diode based dosemeter, namely D-Shuttle, a small pocket reader, a laboratory table reader and PC with a complementary software application. After insertion of the dosemeter into the pocket reader, the reader's display shows the dose accumulated during the last day and the total dose. In this way, the dose can be checked by the resident anytime. A more detailed dose reconstruction in time can be done in laboratory. We tested this system, and probed its possible usability for first responders that would operate in emergency radiological events. Most of the results were in correspondence with producer's specifications and reference values, but there were several discrepancies observed.

Dental ceramics are radiation sensitive materials and exhibit luminescent properties. Their samples can be potentially used for individual dose assessment in situations where retrospective dosimetry is required. In this work, we investigated dosimetry properties of two leucite glass-based dental ceramics using Optically Stimulated Luminescence (OSL) and Thermoluminescence (TL). We concentrated on characteristics as reproducibility, fading, optical bleaching, minimum detectable dose (MDD), dose response and photon energy response of TL and OSL signals. Both the dental ceramics exhibited very good reproducibility (

Salt (NaCl) represents a radiation sensitive material with a considerable potential for dosimetry in mixed radiation fields of photons and neutrons. In consequence of a gamma radiation exposure, it exhibits a strong luminescence signal following stimulation with blue light. Optically stimulated luminescence (OSL) technique can be used for measurement. Photon dose reconstruction can be done using so-called Single-Aliquot Regenerative-dose protocol. However, a part of OSL signal is caused by NaCl self-irradiation resulting from neutron reactions. This NaCl neutron sensitivity is comparable with neutron sensitivity of TLD-700. Neutron dose can be determined based on neutron activation of NaCl via reaction 23Na(n,γ)24Na. A relation between neutron dose and activity of 24Na can be derived. The total dose is thus determined based on the combination of results of OSL measurements and gamma activity measurements. Practical feasibility of this approach was experimentally verified for salt samples irradiated in a channel of a training reactor.

The radiological incident in Cochabamba (Bolivia, 2002), where members of the general public where exposed to an unshielded Ir-192 radiation source whilst traveling on a bus was replicated here in an attempt to asses and evaluate emerging retrospective dosimetry methodologies using objects of daily life, that are either carried on or close to the human body or can be found in the vicinity of an individual. For this purpose an accidental exposure was simulated under controlled conditions in a secured area and an unshielded radioactive source was placed in the cargo compartment of a bus resembling a Radiological Exposure Device (RED). Water canisters and anthropomorphic phantoms were placed at selected seats on the bus and equipped with personal objects (mobile phones, chip cards) that had reference dosimeters attached to them. At one seat position, additional salt dosimeters and dental ceramics in the phantom were also tested. Two types of 8 h exposures were conducted: one with a source activity similar to the one in Cochabamba (0.65 TBq) and one with a stronger source (1.5 TBq) in order to have more samples with absorbed doses above the detection limit of the different methods. For 43 out of 61 resistor and glass samples from mobile phones, measured doses agreed within error limits with reference doses, but for some materials more research is needed for a more reliable application. In 13 cases outliers with a significant dose over- or underestimation were observed, 10 of these could be identified by combining the results of at least three dose assays. The field test thus evaluated the potential and limitation of retrospective dosimetry using personal objects and demonstrated the importance of using a multi-dosimeter approach to increase robustness of the method.

The International Atomic Energy Agency (IAEA) has a long tradition of supporting development of methodologies for national networks providing quality audits in radiotherapy. A series of co-ordinated research projects (CRPs) has been conducted by the IAEA since 1995 assisting national external audit groups developing national audit programs. The CRP ‘Development of Quality Audits for Radiotherapy Dosimetry for Complex Treatment Techniques’ was conducted in 2009–2012 as an extension of previously developed audit programs. Material and methods. The CRP work described in this paper focused on developing and testing two steps of dosimetry audit: verification of heterogeneity corrections, and treatment planning system (TPS) modeling of small MLC fields, which are important for the initial stages of complex radiation treatments, such as IMRT. The project involved development of a new solid slab phantom with heterogeneities containing special measurement inserts for thermoluminescent dosimeters (TLD) and radiochromic films. The phantom and the audit methodology has been developed at the IAEA and tested in multi-center studies involving the CRP participants. Results. The results of multi-center testing of methodology for two steps of dosimetry audit show that the design of audit procedures is adequate and the methodology is feasible for meeting the audit objectives. A total of 97% TLD results in heterogeneity situations obtained in the study were within 3% and all results within 5% agreement with the TPS predicted doses. In contrast, only 64% small beam profiles were within 3 mm agreement between the TPS calculated and film measured doses. Film dosimetry results have highlighted some limitations in TPS modeling of small beam profiles in the direction of MLC leave movements. Discussion. Through multi-center testing, any challenges or difficulties in the proposed audit methodology were identified, and the methodology improved. Using the experience of these studies, the participants could incorporate the auditing procedures in their national programs.

Salt represents a radiation sensitive material that can be used for dosimetry. The objective of this experimental study was to test a low-cost salt dosemeter that was designed for personnel that are not radiation workers, but can operate in low probability events resulting in a serious external radiation exposure. The dosemeter is based on use of optically stimulated luminescence (OSL) of a common household salt. Attention was concentrated on its energy and angular responses. The dosemeter was fixed to the ICRU slab phantom and irradiated by photons of reference radiation qualities (ISO 4037-1) with mean energies between 33 and 1250 keV. Angular response was investigated for angles of incidence from 0° to 80° for radiation qualities of N-150 (∼118 keV) and S-Cs (∼662 keV). Single-Aliquot Regenerative-dose analytical protocol was employed for dose reconstruction. The results were evaluated with respect to Hp(10) measurement. The salt dosemeter can provide reliable or reasonably conservative Hp(10) estimates in radiation fields where photon energies > 100 keV predominate, radiation incidence angles are from 0° to 80° and also for rotational geometry. Furthermore, a personal dose reconstruction trial was demonstrated. Relative deviation between the measured and reference Hp(10) values was 5.5%. A practical disadvantage of the method is the more demanding analytical protocol.

The recent lowering of the dose limit for the eye lens from occupational exposure aroused interest in respect to the monitoring of doses to the eye lens. Particular eye dosemeters were developed for this purpose, but routinely used common personal dosemeters can be also employed for evaluation of the dose to the eye lens. For comparison purposes, we performed measurements of personal doses of physicians working in conditions of fluoroscopically guided procedures in hospitals. Results obtained for an eye dosemeter and for a whole-body dosemeter were compared. Our results support the opinion, that the use of eye dosemeters is not always necessary and may bring some disadvantages connected with their properties and with the discomfort of wearing them.

Mobile phones and common chip cards are very widespread items that almost everyone owns. They contain some radiation-sensitive materials that can be used for dosimetry based on stimulated luminescence. We investigated and compared reproducibility, dose response and fading of luminescence signal for the particular materials. Subsequently, we performed an experiment of a dose reconstruction using mobile phones and chip cards, which were fixed to a slab phantom and irradiated by a 137Cs radiation source in our laboratory. Doses obtained were compared with reference values. The materials investigated can be used for dosimetry in cases of serious radiation accidents or malevolent acts with radioactive materials, when it is extremely important to identify as quickly as possible individuals who received high-radiation doses.

In the Czech Republic, a more advanced version of postal audit in radiotherapy (RT) is available. It covers dose measurements with thermoluminescent dosemeters (TLD) in more complex conditions of irradiation, when dose distribution is affected by heterogeneities in the irradiated volume. Relative deviation between doses measured with TLDs and doses stated by RT centre should not exceed 3%. During 2015–2017, all Czech RT centres equipped with modern linear accelerators were subjected to this more advanced TLD audit. A total of 70% of participants complied with the limit of 3% in the first round of this audit.

As workers in interventional radiology belong to one of the most occupationally exposed groups, methods for sufficiently accurate quantification of their external exposure are sought. The objective of the authors' experiment was to investigate the relations between eye lens dose and Hp(10), Hp(3) or Hp(0.07) values measured with a conventional whole-body personal thermoluminescence dosemeter (TLD). Conditions of occupational exposure during common interventional procedures were simulated in laboratory. An anthropomorphic phantom represented a physician. The TLDs were fixed to the phantom in different locations that are common for purposes of personal dosimetry. In order to monitor the dose at the eye lens level during the exposures, a special thermoluminescence eye dosemeter was fixed to the phantom's temple. Correlations between doses measured with the whole-body and the eye dosemeters were found. There are indications that personnel in interventional radiology do not need to be unconditionally equipped with additional eye dosemeters, especially if an appropriate whole-body dosimetry system has been already put into practice.

Because retrospective dosimetry utilises commonly occurring materials and objects, it is particularly useful in cases of large-scale radiation accidents or malevolent acts with radioactive materials where casualties are inflicted on the general public and first emergency responders. The aim of this study was to investigate whether retrospective dosemeters can provide dose estimates with comparable accuracy like conventional personal dosemeters. Using an external source of radiation 137 Cs and an anthropomorphic phantom, we simulated serious irradiation of a human body in anterior-posterior and rotational geometries. Retrospective luminescence dosimetry objects, such as mobile phones, dental ceramic and household salt, and conventional personal dosemeters (thermoluminescent and electronic) were fixed to the anthropomorphic phantom. The doses obtained were compared with specific reference values. In most cases, relative deviations between the measured doses and the reference values did not exceed 20%. As the retrospective and conventional dosemeters show no significant differences in laboratory conditions, the retrospective luminescence dosimetry objects represent a very promising tool if handled properly.

International audience; In the framework of the EU-FP7 MULTIBIODOSE project, two protocols using OSL of resistors removed from the circuit board of mobile phones were developed with the aim to use the resistors as fortuitous dosimeters in the event of a large scale radiological accident. This paper presents the results of an interlaboratory comparison carried out under the umbrella of EURADOS. The two aims of this exercise were the validation of the MULTIBIODOSE protocols by a large number of laboratories and the dissemination of the method with the objective of preparing the basis for a network that could increase Europe's response capacity in the case of a mass casualty radiological emergency. Twelve institutes from eleven European countries and one institute from the USA, with various degrees of expertise in OSL dosimetry, took part in the OSL inter-laboratory comparison. Generally, a good agreement within uncertainties was observed between estimated and nominal doses. © 2014 Elsevier Ltd. All rights reserved.

Human hair contains sulfur, which can be activated by fast neutrons. The 32 S(n,p) 32 P reaction with a threshold of 2.5 MeV was used for fast neutron dose estimation. It is a very important parameter for individual dose reconstruction with regards to the heterogeneity of the neutron transfer to the human body. Samples of human hair were irradiated in a radial channel of a training reactor VR-1. 32 P activity in hair was measured both, directly by means of a proportional counter, and as ash dispersed in a liquid scintillator. Based on neutron spectrum estimation, a relationship between the neutron dose and induced activity was derived. The experiment verified the practical feasibility of this dosimetry method in cases of criticality accidents or malevolent acts with nuclear materials.

A Timepix detector covered with polyethylene convertors of different thicknesses is presented as a fast neutron real-time dosemeter. The application of different weighting factors in connection with the position of a signal in a Timepix detector enables one to obtain an energy-dependent signal equal to neutron dose equivalents. A simulation of a Timepix detector covered with polyethylene convertors using monoenergetic neutrons is presented. The experimental set-up of a dosemeter was also produced. The first results of detector response using different fast neutron sources are presented.

Optically Stimulated Luminescence (OSL) and Thermoluminescence (TL) properties of a fluorapatite glass-ceramic have been investigated, with a view to developing a dose assessment technique for medical triage following unplanned exposures of individuals to ionizing radiation. The ceramic is an innovative material used in dental prostheses and restorations. It is strongly sensitive to radiation and the intensity of both the OSL and TL signals are proportional to the absorbed radiation dose. We focused on the optimization of the measuring procedure and investigated characteristics such as reproducibility, fading, minimum detectable dose (MDD), dose response and photon energy response of TL and OSL signals. The dental ceramic exhibited very good reproducibility (

Alumina substrate can be found in electronic components used in portable electronic devices. The material is radiation sensitive and can be applied in dosimetry using thermally or optically stimulated luminescence. Electronic portable devices such as mobile phones, USB flash discs, mp3 players, etc., which are worn close to the body, can represent personal dosemeters for members of the general public in situations of large-scale radiation accidents or malevolent acts with radioactive materials. This study investigated dosimetric properties of alumina substrates and aspects of using mobile phones as personal dosemeters. The alumina substrates exhibited favourable dosimetry characteristics. However, anomalous fading had to be properly corrected in order to achieve sufficient precision in dose estimate. Trial dose reconstruction performed by means of two mobile phones proved that mobile phones can be used for reconstruction of personal doses.

NaCl is a cheap and widely available material. This study investigated the potential of NaCl in the form of a household salt as a retrospective and accident dosemeter using optically stimulated luminescence (OSL). Samples of the investigated household salt were stimulated using blue light of linearly modulated power. Attention was concentrated on sensitivity, dose dependence of the OSL signal, fading, optimisation of the read-out procedure and application of analytical protocols that do not require a specific calibration. A potential of NaCl as a complementary dosemeter within emergency preparedness was considered. The behaviour of the OSL signal observed was found to be favourable for dosimetry.

The National Radiation Protection Institute in Prague is about to use a commercially available multi-element whole-body thermoluminescence dosimeter for its radiation personnel. During the phase of practical verification of the method, the dosimeter was tested, among others, in mixed neutron-photon fields in the area of interim storages for spent nuclear fuel of the Czech nuclear power plant Dukovany. The testing was made with the intention to get information about accuracy of H(p)(10) determination for cases when no site-specific calibration is available or neutron spectra are not known. The measured photon and neutron personal dose equivalents were evaluated and discussed in relation to results obtained by survey meters and neutron spectra measured before.

s / Physica Medica 30 (2014) e1ee15 e14 at the national level with IAEA assistance. The national counterparts conduct the TPS audit at local radiotherapy centres through on-site visits. TPS calculated doses are compared with ion chamber measurements performed in an anthropomorphic phantom for eight test cases per algorithm/beam. The set of pre-defined agreement criteria is used to analyze the performance of TPSs. Results: TPS audit was carried out in sixty radiotherapy centers in eight European countries e Estonia, Hungary, Latvia, Lithuania, Serbia, Slovakia, Poland and Portugal. In total, 190 data sets (combination of algorithm and beam quality) have been collected and reviewed. Dosimetry problems requiring interventionswerediscovered in about10%of datasets. In addition, suboptimal beam modelling in TPSs was discovered in a number of cases. Conclusions: The TPS audit project using the IAEA methodology has verified the treatment planning system calculations for 3D conformal radiotherapy in a group of radiotherapy centres in Europe. It contributed to achieving better understanding of the performance of TPSs and helped to resolve issues related to imaging, dosimetry and treatment planning. DOSIMETRY AUDITS IN RADIOTHERAPY IN THE CZECH REPUBLIC Irena Koniarova, Daniela Ekendahl, Ivana Horakova, Michaela Kapucianova, Vladimir Dufek. National Radiation Protection Institute, Prague, Czech Republic Background: The independent audits in radiotherapy are carried out by the National Radiation Protection Institute as a part of the regulatory authority activity since 1996. The system includes TLD postal audits (external radiotherapy) and on-site audits (external radiotherapy and brachytherapy). TLD audit can be performed in several versions differing in the scope and focus of dose measurements. Basic TLD audit consists in beam calibration check. Each clinically used beam must undergo it at least once per two years. During 1997 e 2013, a total of 1435 beams have been thus controlled. Advanced versions of TLD audit focused on more complex conditions of irradiation (non-reference geometries, MLC fields, small IMRT fields, inhomogeneities) have been performed in the case of a request or research studies. On-site audit is performed after the commissioning of each unit. The absorbed dose to water (or RAKR for brachytherapy), beam quality, output and wedge factors, PDD, MLC positioning, MLC transmission, and dosimetric leaf gap (where applicable) are controlled. Mechanical parameters (isocenter stability, radiation field size, table parameters, etc.) are evaluated as well. A number of 535 megavoltage photon and electron external beams,103 kilovoltage external beams, and 32 brachytherapy sources have been controlled since 1996. 2 proton beams were checked in 2013. Checks of non-dosimetric parameters and imaging functions of TPS with QUASAR phantoms can be performed on request. In addition, 19 departments (23 treatment plans) have been checked using a special pelvic phantom in end-to-end audit for IMRT and IMAT prostate treatment in 2013. Delivered doses to PTV and rectum were measured with ionisation chambers in 3 planes. Planar dose distribution has been verified with EBT2 film. Retrospectively, it was possible to make DVHs analysis and compare all IMRT plans for the pelvic phantom showing common planning practice in the Czech Republic for photon IMRT and proton radiotherapy. Conclusion: The audits revealed several significant errors that might potentially lead to an accident. All results can be analysed retrospectively, showing trends related to chosen indicators. DOSIMETRY AUDITS IN RADIOTHERAPY IN GREECE C.J. Hourdakis, A. Boziari, V. Kamenopoulou. Greek Atomic Energy