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In the field of Electron spin resonance (ESR) dosimetry variety of materials are being investigated for the purpose of dose reconstruction of the victims of radiological and nuclear accidents. One of the desirable properties of ESR dosimeter is energy independence since the radiation accidents are mostly caused by the mixed radiation sources. Soda-lime glass has been proven to be a good ESR dosimeter in the dose range above 2 Gy by using the ESR signal amplitudes, but below 2 Gy the radiation induced signal is overlapping with the intrinsic ESR signal. It was shown [1, 2] that in the range below 2 Gy is possible to reconstruct the dose from the soda-lime glass samples by using the g-value dose dependence of ESR signals. All irradiated soda-lime samples exhibit ESR spectra that can be decomposed to inhomogeneous background signal (BKS) with associated gBKS value, and homogeneous radiation induced signal (RIS) with associate gRIS value. The effective g- value of the irradiated sample is combination of these two. In this study, the dependence of g-effective value on the radiation energy of the ESR signal was investigated. The g-effective value has exponential dependence on the dose as shown before [1, 2]. The samples were irradiated with gamma sources of different energies, X-ray source of energy 39.40 keV and Co-60 source of the mean energy 1.25 MeV in the dose range from 0.1 – 10.0 Gy. All irradiations were performed in IBA Dosimetry Laboratory and the ESR readout was performed on the Bruker Magnettech ESR5000 spectrometer in the Laboratory for Electron Spins Spectroscopy at the Ruđer Bošković Institute. As a conclusion, the preliminary study shown that the g-values of the samples are independent on the energy of radiation source for the energies used in this research.

The security risk of R/N events have increased through the years due to the raised use of ionising radiation in hospitals, the nuclear research or industry, and, unfortunately, also to the threat of malicious or terrorist attacks with radiological materials. Radiation victims, i.e. people not carrying conventional dosimeters can be exposed to doses of ionising radiation which requires individual dose estimates to support classifications for convenient medical triage in large scale accidents. The current golden standard is the biological dosimetry, that is based on high cost techniques taking at least several days for the dose estimation. Therefore, the development of physical methods is the focus of the research to complement biodosimetry. Significant efforts have been made on the dose assessment from the objects that could be found at the location of the event, i.e., on fortuitous dosimeters. The optical luminescence technique has been successfully applied to various materials. Before establishing protocols regarding such objects and materials, they should be studied by determining their doseresponse and reliability. In this purpose, we combine the use of a low-cost portable Photo-Stimulated Luminescence (PSL) reader with the selection of cheap materials that contain salt: salty snacks and coastal sand [1]. The proposed method for determining the dose from such dosimeters is based on the use of a reader also applied for determining irradiated food [2] and therefore widely spread in many countries, and available for mass application. Until now, the two laboratories involved in the BioPhyMeTRE project, fully funded by NATO Science for Peace and Security Programme (Grant G5684), collected interesting and promising results on salty snacks and coastal sand [2]. These results encourage the use of blue light stimulation which provided a better response compared to infrared light and were not influenced by the difference in dose rates applied by the two Institutes. Furthermore, the different approach for determination of the detection limit were used and discussed.

Introduction: In retrospective dosimetry, for the radiation and nuclear (R/N) emergency if uncontrolled radiation affected many people or the environment, the information about radiation doses allows for the prediction of the biomedical consequences. Therefore, when professional dosimeters are not available, objects of everyday use can be applied as dosimeters. In such cases, the method of optically stimulated luminescence (OSL) has proved very promising. Methods: The salt, following the exposure to ionizing radiation, exhibits a particularly high OSL response compared with many other materials. In this study, radiation sensitivity of salty crackers available on the market was monitored with two PSL systems in two physical dosimetry laboratories (ISS, Italy and RBI, Croatia) using the validated PSL methods. The response at two stimulation 890 nm and 470 nm have been compared. Results: The results indicate that salty snacks can be used in accident dosimetry. The stimulation by 470 nm has better response, but for both stimulations detect absorbed doses are below 100 mGy. Conclusion: The obtained data, showed good agreement between both laboratory OSL readout suggesting additional benefit to the use of salty crackers in the retrospective dosimetry. The study was supported by NATO Science for Peace and Security Programme, grant No. G5684.

In case of Radiological and Nuclear (R/N) emergencies, the early knowledge on the individual radiation absorbed dose is of paramount importance for sorting out unaffected subjects from those requiring medical intervention. Retrospective dosimetry by using biological and physical methods aims to prioritize the selection of over-exposed individuals for a rapid triage-dose assessment. In this context, the BioPhyMeTRE project focuses on the validation of innovative biological and physical methods allowing a rapid screening/triage of potential victims, by using inexpensive and user-friendly analytical procedures and devices. The biological method combines the two most standardized biodosimetry methods into a single one and the physical technique concerns the use of a low-cost, portable mini photo-luminescence reader for the individual dose assessment by using personal objects that civilians wear or carry every day. Next to the experimental work, the project includes training for the transfer of knowledge and skills among the partners, inter-laboratory exercises for the validation of the analytical procedures and disseminations of the results. The preliminary results of these activities are here reported.

Introduction: The project entitled “Novel biological and physical methods for triage in radiological and nuclear (R/N) emergencies” (BioPhyMeTRE) has been recently approved within the NATO Science for Peace and Security Programme. The project focuses on innovative biological and physical dosimetry methods allowing a rapid screening/triage of potential victims by using inexpensive and user- friendly analytical procedures and devices. Methods: In the “BioPhyMeTRE” project, a multi- parametric approach, by both biological and physical dosimetry methods, is used. The biological method combines the two most standardised biodosimetry methods into a more exhaustive “two-in-one” assay. The physical method focuses on the use of a low cost, portable mini photo-luminescence reader for the individual dose assessment by using personal objects. Results: The novel biological and physical methods have been developed and partially tested by the laboratories participating in the project. The biological combined protocol offers the advantage of simultaneous scoring of chromosome aberrations and micronuclei on the same slide, it is therefore time-saving and inexpensive. The physical method system, designed and commercialized for irradiated food analysis, allows rapid measurements, is transportable and usable in site, even by not skilled operators. Both methods will be validated through the set- up of calibration curves and inter-laboratory comparisons to verify their reliability for triage in R/N emergencies. Moreover, automation systems for the novel biological protocol will be evaluated. Conclusion: The biological and physical dosimetry methods proposed in the “BioPhyMeTRE” project, once they have been fully developed and validated, could represent useful tools for the categorization of subjects overexposed to ionising radiation in R/N emergencies.

Dozimetrija primjenom spektroskopije elektronske spinske rezonancije (ESR) utemeljena je na detekciji radikala nastalih pri izlaganju ionizirajućem zračenju. Metoda ima široku primjenu u kemiji, fizici, biologiji i mnogim interdisciplinarnim područjima, a važnost joj raste i u području retrospektivne dozimetrije. U retrospektivnoj dozimetriji važna je brza rekonstrukcija nepoznate apsorbirane doze kod žrtve slučajne radiološke ili nuklearne nesreće. Pomoću spektroskopije ESR apsorbirana doza se određuje direktnim mjerenjem radikala nastalih u materijalu pronađenom u blizini žrtve ili na samoj žrtvi zračenja. Lijevana kalcijeva natrijeva silikatna stakla masovno se primjenjuju u građevinskoj i automobilskoj industriji, te su stoga potencijalno dobar retrospektivni dozimetar. U ovom istraživanju lijevana kalcijeva natrijeva silikatna stakla su upotrijebljena kao detektori malih doza zračenja metodom spektroskopije ESR. Prema dosadašnjim istraživanjima lijevano natrijevo kalcijevo silikatno staklo ima dobar odziv u širokom rasponu doza, s donjom granicom detekcije 2 Gy. U ovom radu, ispitan je ESR odziv uzoraka lijevanoga natrijeva kalcijeva silikatnog stakla ozračenih dozama u rasponu od 0,2–20,0 Gy. Mjerenja su pokazala da se ESR spektar ozračenih uzoraka sastoji od dvije vrste signala i to signala nastalih kao posljedica zračenja (engl. radiation-induced signal, RIS) i signala koji ne nastaju zračenjem, odnosno pozadinskih signala (engl. background signal, BKS). U rasponu niskih doza zračenja do 2 Gy, udio RIS ESR signala manji je od udjela BKS ESR signala, te se stoga RIS ESR signal preklapa s BKS ESR signalom. Ovo otežava određivanje apsorbirane doze standardnim metodama rekonstrukcije temeljenih na doznoj ovisnosti vrh-vrh amplitude IPP (engl. peak-to-peak amplitude) RIS signala. U ovom radu ispitana je promjena položaja g-vrijednosti ESR spektralne linije ozračenih uzoraka u odnosu na g-vrijednost BKS spektralne linije koja je mjerljiva i u rasponu doza nižim od 2 Gy. Nadalje, pokazano je da IPP amplitude RIS i BKS signala imaju različitu temperaturnu ovisnost te da je rast signala obrnuto proporcionalan s temperaturom. Razlika u temperaturnoj ovisnosti ova dva signala omogućuje preciznije očitanje g-vrijednosti pri nižim temperaturama. Rezultati ovih istraživanja pokazali su se upotrebljivim za odvajanje BKS od RIS signala u rasponu malih doza čime doprinose poboljšanju u detekciji malih doza zračenja nakon neplaniranog izlaganja ionizirajućem zračenju te u slučajevima nepoznatog broja izloženih osoba. U tu svrhu metoda je testirana na uzorku ozračenom nepoznatom dozom te je pokazana mogućnost očitanja vrijednosti doze zračenja koja je znatno niža od do sada mogućeg očitanja u uzorcima lijevanoga natrijeva kalcijeva silikatnog stakla. The electron spin resonance (ESR) method is widely used in the field of chemistry, physics, biology and many interdisciplinary fields, and the application is growing also in the field of retrospective dosimetry. ESR detection of dosimetric signals originating from radicals induced under the influence of ionizing radiation allows to determine the dose absorbed by the casualties following catastrophic, large-scale radiological events. The ESR technique have been applied to a wide range of radiological studies, including nuclear bomb detonation (e.g., Hiroshima and Nagasaki), nuclear power plant accidents (e.g., Chernobyl), radioactive pollution (e.g., Mayak plutonium facility), and in the future could include terrorist events involving the dispersal of radioactive materials. For retrospective dosimetry, immediate action to evaluate dose to individuals following radiation exposure is required to assess deterministic biological effects and to enable rapid medical triage. The triage dose levels are differently defined in the literature and for purpose of this study triage levels defined in MULTIBIODOSE project have been used. Low triage dose level is less than 1 Gy when it is unlikely to develop symptoms of acute radiation syndrome (ARS) and no immediate care is required. The medium level implies doses 1-2 Gy when victim may experience mild or delayed ARS symptoms and follow-up care may be necessary and high for the doses higher than 2 Gy when moderate to urgent care may be required. The retrospective dosimetry measurement techniques aim to perform direct dose evaluations for individuals who, as members of the public, are most unlikely to be carrying a dosimeter for radiation monitoring purposes in the event of a radiation incident. Hence attention has focused on biological or physical materials they may have in their possession that could be used as surrogate dosimeters. For ESR measurements this includes material within the body (such as bone or tooth enamel) requiring invasive procedures, a materials collected non-invasively (such as clippings taken from finger- or toenails) and artefacts within their personal belongings (such as clothing, fabrics, plastics, glass, sugar, touch screens of mobile phones). The use of electron spin resonance (ESR) on detection of ionizing radiation-induced radicals in different types of glasses is a well-established technique in radiation dosimetry. Nowadays, the float glass is the most widely used form of glass and makes more up to other types 96% of output. Float soda lime silicate glass is used principally in building and automotive industries. It is used in various application such as in car glass, windows, doors, sun roofs, copy v machines, computers, etc. This is very useful for retrospective dosimetry since it is easily found at places of the nuclear and radiological mass-casualty incidents and possible terrorist events involving the dispersal of radioactive materials. As a retrospective dosemeter, the float soda-lime glass has proven to possess many required qualities due to the specific radiation-induced ESR signal with a linear dose response (generally ascribed to an oxygen hole center) and the detection limit (DL) of 2 Gy. Additionally, ESR signal decay is about 10 up to 35% at room temperature during the first 24–48 h after irradiation, after which the signal remains stable. A major effort in recent years has been devoted to improving the lower detection limit for retrospective dosimetry purposes because the useful low dose radiation induced signal (RIS) is superimposed over the background signal, BKS. Regarding triage dose levels several methods for correct determination of dosimetric signal magnitude in retrospective ESR dosimetry have been proposed in the literature. Deconvolution method is based on mathematical simulation of BKS and RIS that approximates measured spectra. The approach based on the best fit of the experimental spectrum with a set of Gaussian lines, spectrum-simulated lines, and experimental reference spectra is used in intercomparison organized among participants of European Radiation Dosimetry Group (EURADOS). For the retrospective dosimetry purposes, the widely used method is ESR spectrum subtraction approach based on background ESR signal subtraction from ESR signal of irradiated samples. Also, there are other techniques like selective saturation method and second derivative method. The subject of investigation presented in this disertation is ESR dosimetry of transparent float soda-lime glass in the low dose range, 0.2-20.0 Gy, for retrospective dosimetry purposes. Investigation of the ESR spectrum of the float soda-lime glass in the low dose range shown that it consists of two main components, background signal, BKS, and ionising radiation induced signal, RIS. In the low dose range ESR spectrum of the RIS in float soda-lime glass overlaps with the ESR spectrum of the BKS. Therefore, in the low dose range, the dose reconstruction by the established methods based on the dose dependence of peak to peak amplitudes, IPP, of RIS and BKS is very difficult and ambiguous. For the purpose of improvement of dose reconstruction in the range 0-10 Gy, we have investigated the ESR parameters of two components (RIS and BKS) of soda-lime glass ESR spectrum irradiated in the Co-60 beam. After establishing the exact g-values of the BKS and ESR signal of irradiated samples at the position of maximum amplitude, we have investigated the change of g-effective, geff, combination of the two reference signals g-values, value of ESR signal of irradiated samples and observed regular change of geff value of spectral lines after vi increasing the gamma irradiation dose. This change is measurable even in the dose range below 2 Gy, which is published detection limit of the float soda-lime samples. The experiment shown that the geff value does not depends on temperature. Furthermore, it is shown that the IPP amplitude of RIS signal exhibits different temperature dependence than IPP amplitude of BKS signal and that both IPP amplitudes increase linearly with the temperature decrease. At the low dose regime combination of the observed dose dependence of the geff value and temperature dependence of the IPP amplitudes of irradiated and non-irradiated float soda-lime samples, indicate that performing ESR measurements at the lower temperature can increase sensitivity of dose reading. From obtained results according to the proposed model, it can be concluded that the geff value dose dependence is useful tool in dose reconstruction and decomposing of RIS and BKS signal. This enables contribution to the improvement of the detection limit in the low dose range, 0-10 Gy. The method is tested on a sample irradiated with unknown, blind, dose and the application of the geff value analysis proved the improvement of the detection limit of the float soda-lime samples.

The g-effective value exhibits strong dependence on the dose in soda-lime glass samples, and yet its value remains unchanged with the temperature and 2 h after irradiation. According to the results, g-effective value approach is useful tool in dose reconstruction.

Dosimetry services using Panasonic dosimeters have been put in a difficult position after the introduction of the new eye lens dose limit for Hp(3) prescribed by the Euratom BSS Directive and the recommendations by the IAEA to monitor the eye lens dose for exposed workers working in non-uniform radiation fields. There are currently no commercially available eye lens dosimeters holders that could fit Panasonic TLD pellets. Therefore, inexpensive, waterproof and comfortable holders have been designed and 3D printed to fit Panasonic Li2B4O7 but also other producers’ single dosimeter element. The Panasonic Li2B4O7 is a tissue equivalent TLD material with quite a horizontal energy response and well documented characteristics. The eye lens dosimeter consists of an acrylonitrile butadiene styrene (ABS or ABS+) plastic holder with a quadratic slot for a TLD pellet with approximately 3 mm front filtration. After the insertion of the pellet, the slot part was covered by a heat-shrink tube and shortly heated with a hot air to wrap. The dosimeter is to be worn fixed to a headband, close to either eye, on the side of the head. The energy and angular response of a new holder with a single Panasonic UD- 807ATN TLD element were tested in the Secondary Standard Dosimetry Laboratory of the Ruder Boskovic Institute (RBI-SSDL). The testing was performed using a cylinder phantom with a 20 cm diameter and 20 cm height, water-filled with PMMA walls for radiation qualities, R, narrow beam series, defined in ISO 4037-1, N-30, N-60, N-100, as the reference R, N-120, and S-Cs at 0˚, +30˚, +60˚ and +75˚ (due to bilateral symmetry of the dosimeter). Applied conversion coefficients hpK(3 ; R, α)cyl from air kerma to Hp(3) for different R and angles of incidence in Sv/Gy were taken from R. Behrens, Radiat.Prot.Dosim. 151, 450 (2012). A total of 100 dosimeters in groups of 5 were irradiated in 20 separate irradiations with a Hp(3) value of 2 mSv. Measurement results for energy/angular response for all radiation qualities used were within IEC 62387:2012 limits: 0, 71 ≤ response ≤ 1, 67. Further testing shall include exposure to IEC 61267 RQR spectra for selected angles. Furthermore, the stability of the ABS+ plastic holder itself under the influence of irradiation was investigated by electron spin resonance (ESR) spectroscopy. Continuous wave (CW) ESR spectra were recorded on a Varian E-109 X-band (≈9.5 GHz) spectrometer equipped with a Bruker ER 4111 VT variable- temperature unit with a flow of N2 gas. The concentration of radicals, intrinsic and radiation induced, was monitored before and after the radiation process. Both the shape of the ESR spectra and the signal intensities indicated that the ABS+ holders were stable for the dose range required in the application. According to all testing results, the new holder is suitable for use in eye lens dosimetry in IR and IC.

In this research project we are investigating electron paramagnetic resonance (EPR) dosimetry of transparent float soda-lime glass in the dose range below 20 Gy for retrospective dosimetry purposes. Since it is easily found in the places of nuclear and radiological mass- casualty incidents and possible terrorist events involving the dispersal of radioactive materials, it is useful for retrospective dosimetry. Previous investigations of glasses demonstrated good behavior of soda-lime glass as a retrospective dosimeter but mostly in the high dose range. The detection in the dose range from 0-8 Gy is essential regarding the medical treatment of casualties, to discriminate the acute radiation syndrome treatment from long- term surveillance within a clinically relevant time period. Medical treatment of radiological casualties depends on the received doses According to the literature the casualties whose radiation dose is most amenable to treatment will be those who receive between 2 and 6 Gy. It is well known that low dose limit in EPR dosimetry of glasses is dependent on the background signal. The background signal (BKS) of the soda-lime glass is competing with the radiation induced signal (RIS) for the doses below 6 Gy. According to previous research the BKS can be attributed to transition-group ions, ferromagnetic precipitates, photo-induced centers as well as mechanical induced defects. The calibration dose-EPR intensity curve of float soda – lime glass in the low dose regime gives inaccurate answer of the unknown dose. In this research project we are investigating other physical parameters at low dose regime that influence EPR spectrum and that could increase sensitivity of dose reading in low dose range.

ESR response of g irradiated soda-lime glass in low dose range were studied for retrospective dosimetry goals [1]. In this range overlapping of background signal (BKS) with radiation induced signal (RIS) inhibit dose reconstruction. Use of combination of the intensities and areas below the ESR curve and g shifts of RIS and BKS, was found useful for improving detection limit.

The measurements of the five potential scenarios, some of which include misuse of X-ray device and handling the opposite of what the prescribed by regulations governing this area were performed. The highest patient dose was measured at the position of the thyroid, but in reality (given the number of exposures, ie. the number of dental images per month), this dose is 20-30 times lower. As expected, the highest dose was measured at the extremities (fingers) which adheres to the sensor and the annual dose received in this way is four times higher than the prescribed limits. The maximum effective dose was measured in a scenario where, also incorrectly, beam of the X- ray unit was directed directly to the operator. For scenarios in which the operator during the exposure stands at the back of the X-ray tube is not measured elevated doses (except for the case of adherence to the sensor). The dosimeter, which is mounted to the hand of the X-ray machine during operation, does not show an increased effective dose. Abiding by the principles of radiation protection when using intraoral dental X-ray unit, it is not possible to get out of the dose limits prescribed by law. Effective, but also the equivalent dose received by the patient during the exposure of the teeth are low as about 50 μSv per radiograph (equivalent dose of thyroid).

Common use of ionizing radiation in industry as well as health service stimulates the need for searching of the suitable radiation-sensitive materials, which can be used during unexpected exposition to radiation. A fast and reliable retrospective dosimetry method is very important for the prediction of health effects following an exposure. Electron paramagnetic resonance (EPR) glass dosimetry is a promising way to estimate radiation dose. However, the available studies give rather different results, especially in low dose range. Therefore, soda lime glass samples have been tested as potential dosimeters for low gamma doses using electron paramagnetic resonance (EPR). Radiation-induced EPR signals detected in powder samples and plates were compared. Basic dosimetric properties of the radiation-sensitive substances were studied, namely dose response, fading of the EPR signals and values of minimum detectable doses (MDDs). The variability of background signal (BKG) intensity was found as main factor causing the inaccuracy of radiation dose reconstruction in low dose range.

Dosimetry in diagnostic radiology requires the use of specialized instrumentation, the design and performance of which must be matched to the needs of the clinical situation. These instruments have to be calibrated to be traceable to national or international standards. The IAEA ensures traceability of radiation measurements through the IAEA/WHO network of Secondary Standards Dosimetry Laboratories (SSDLs) and Secondary Standard Dosimetry Laboratory at Ruđer Bošković Institute (RBI/SSDL) is a member of the network. Calibrations are performed in compliance with TRS457 [1] which is the code of practise for calibrations in diagnostic radiology. Calibrations are performed in the X ray field in different beam qualities. The qualities at RBI/SSDL are established according to IEC 61267 [2]. Calibrations should be performed in radiation fields with air kerma rate within the sensitive volume of the detector not to vary more than 5% according to standard 4037-1 [4]. Uniformity of radiation field is influenced by spectral distribution of x-rays, finit focus dimensions, Heel effect and aging of anode. Our aim was to investigate uniformity and dose profiles of IEC 61267[2] RQT-8, RQT-9 and RQT-10 radiation qualities. These qualities simulate the unattenuated beam used in CT diagnostic radiology. Establishment of these qualities requires establishment of radiation qualities RQR IEC 61267[2] which are used for measurements in the radiation beam as emerging from the x-ray source assembly. Such radiation qualities are, for example, applied for determining characteristics of patient supports in case the patient support is situated in between the x-ray source assembly and the patient. When these qualities are established, copper filtration is added to generate RQT qualities.

Mjerna nesigurnost metode za mjerenje osobnog doznog ekvivalenta napravljena je na ThermoFisher Scientific (Harshaw) sustavu (čitač model 6600 te TLD LiF:Mg, Ti), prema „Guide to the expression of uncertainty in measurement“ (GUM) smjernicama. U ovom radu dan je pregled komponeti koje ulaze u izračun mjerne nesigurnosti tzv. „fish-bone“ pristupom. Za potrebe budžeta mjerne nesigurnosti napravljen je tipni test prema zahtjevima norme HRN IEC 61066:2007. Sama mjerenja, kao i izračun mjerne nesigurnosti, napravljeni su za osobni dozni ekvivalent Hp(10) kao i za osobni dozni ekvivalent Hp(0, 07) (na dubini kože). Tipni test uključuje testove za linearnu, energijsku i kutnu ovisnost, aditivnost i slabljenje signala („fading“). Rezultati su izraženi kao proširena mjerna nesigurnost pouzdanosti 95% (faktor prekrivanja od 1, 96), koja je dobivena kombinacijom obje utjecajne veličine, nesigurnosti tipa A i B. Mjerenja su provedena kroz 20 mjeseci, a za potrebe ispitivanja korišteno je više od 500 TL detektora/dozimetara. Dozimetri su ozračeni u Sekundarnom standardnom dozimetrijskom laboratoriju Instituta Ruđer Bošković (SSDL) energijama od 33 keV do 1, 33 MeV.