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Proposed physical dosimetry methods for emergency dosimetry in radiological, mass-casualty incidents include both thermoluminescence (TL) and optically stimulated luminescence (OSL). Potential materials that could feasibly be used for TL and OSL dosimetry include clothing, shoes and personal accessories. However, the most popular target of study has been personal electronics, especially different components from smartphones. Smartphones have been a focus because they are widely available and, in principle, may be viewed as surrogates for commercial TL or OSL dosimeters. The components of smartphones that have been studied include surface mount devices (such as resistors, capacitors and inductors) and glass materials, including front protective glass, display glass and (with more modern devices) back protective glass. This paper reviews the most recent developments in the use of TL and OSL with these materials and guides the way to future, and urgently needed, research.

Large-scale radiological accidents or nuclear terrorist incidents involving radiological or nuclear materials can potentially expose thousands, or hundreds of thousands, of people to unknown radiation doses, requiring prompt dose reconstruction for appropriate triage. Two types of dosimetry methods namely, biodosimetry and physical dosimetry are currently utilized for estimating absorbed radiation dose in humans. Both methods have been tested separately in several inter-laboratory comparison exercises, but a direct comparison of physical dosimetry with biological dosimetry has not been performed to evaluate their dose prediction accuracies. The current work describes the results of the direct comparison of absorbed doses estimated by physical (smartphone components) and biodosimetry (dicentric chromosome assay (DCA) performed in human peripheral blood lymphocytes) methods. For comparison, human peripheral blood samples (biodosimetry) and different components of smartphones, namely surface mount resistors (SMRs), inductors and protective glasses (physical dosimetry) were exposed to different doses of photons (0–4.4 Gy; values refer to dose to blood after correction) and the absorbed radiation doses were reconstructed by biodosimetry (DCA) and physical dosimetry (optically stimulated luminescence (OSL)) methods. Additionally, LiF:Mg,Ti (TLD-100) chips and Al2O3:C (Luxel) films were used as reference TL and OSL dosimeters, respectively. The best coincidence between biodosimetry and physical dosimetry was observed for samples of blood and SMRs exposed to γ-rays. Significant differences were observed in the reconstructed doses by the two dosimetry methods for samples exposed to x-ray photons with energy below 100 keV. The discrepancy is probably due to the energy dependence of mass energy-absorption coefficients of the samples extracted from the phones. Our results of comparative validation of the radiation doses reconstructed by luminescence dosimetry from smartphone components with biodosimetry using DCA from human blood suggest the potential use of smartphone components as an effective emergency triage tool for high photon energies.

Results are presented from measurements of radiophotoluminescence (RPL), optical absorption (OA) and electron paramagnetic resonance (EPR) on Ag-doped alkali-phosphate glass. The build-up phenomenon for RPL is followed during and after irradiation. Reversal of this build-up is induced via exposure to ultra-violet light (UV) at a wavelength of 254 nm and changes to the RPL emitting centers and the EPR spectra are followed during and after UV exposure. The experimental results indicate that Ag2+ centers may be the main centers responsible for RPL emission in the orange region of the spectrum, peaking around 630 nm. Computer simulations of the rate equations describing the suggested charge transfer processes occurring during irradiation, build-up and UV exposure qualitatively support these conclusions.

Motivated by the search of new materials for optically stimulated luminescence (OSL) dosimeters, magnesium aluminum spinels with different Mg:Al ratios were investigated. Powders were prepared via the co-precipitation method with Mg:Al ratios 1:2 (stoichiometric), 1.5:2 (MgO-rich) and 1:3 (Al2O3-rich) and calcined at 1000 °C in air for 2 h. A higher level of structural disorder was found in the powders than in the single crystal as determined by X-ray diffraction and Raman spectroscopy measurements, while the same luminescence centers were present in all materials as shown by X-ray induced radioluminescence measurements. Among the different Mg:Al ratios, stoichiometric spinel presented superior OSL dose response, being linear within 0.16 Gy and 2 Gy, presenting 1% reproducibility of the dosimetric response after repeated exposure to the same dose, having the least fading, and with a minimum detectable absorbed dose (MDD) of 0.65 mGy.

A non-destructive, high-sensitivity, dose-reconstruction method is proposed and tested using optically stimulated luminescence (OSL) from protective back-glasses from modern smartphones. A custom-made OSL reader, capable of accommodating the entire phone, has been built for this purpose and preliminary results are reported. The back-glass is stimulated using several light-emitting diodes (LEDs) while a radiation-induced OSL signal is detected with a high-sensitivity photomultiplier tube. A set of appropriate filters is used for separation of stimulation and emission light. The sensitivity of the system was tested for different wavelengths (colors) of stimulation light. A maximum sensitivity was observed using so-called Royal Blue LEDs, with stimulation centered at a wavelength of 447.5 nm. The following dosimetric properties have been studied: (1) background and radiation-induced OSL curves; (2) dose-response curves for several back-glasses from different phones and the corresponding values of the minimum detectable doses; and (3) fading of the OSL signal with time after irradiation. Background (BG) OSL signals were negligible in all tested phones except one (an iPhone 11), in which the BG signal was equivalent to a dose of ~157 mGy. However, the BG OSL had a different decay-curve shape compared to that of the radiation-induced signal (RIS). This difference in shape allows the two signals to be distinguished and separated. Strong, radiation-induced OSL signals were observed in all glasses after irradiation, but with significant variability in sensitivity among the different phones. The dose-response relationships for all phones were linear in the range 0–2.7 Gy when the OSL signals were measured at the same effective time after irradiation. Values of the minimum detectable doses were in the range 0.2–4.3 mGy for the different phones when measured 3 min after exposure. Fading of the OSL signal was observed for storage times up to 11 days after irradiation and was best-fitted by a power function. Dose recovery tests were carried out on two phones intentionally exposed to a dose of 266 mGy and their OSL measured 6 and 7 days, respectively, after irradiation. During these periods the phones were kept in their original cases but were used as usual for calls, messages, internet surfing, etc. Fading-corrected OSL doses were determined to be 199 mGy and 220 mGy, respectively, which are within 25% of the nominal value.

EPR signals of different origin have been tested in human finger- and toe-nails with an X-band EPR technique for different conditions of nail storage. Three different signals were identified, namely a singlet at g = 2.005, a doublet at g = 2.004 with a splitting constant A = 1.8 mT, and an anisotropic signal at g1 = 2.057, g2 = 2.029 and g3 = 2.003 (positions of local extrema). All EPR spectra from nails, whether irradiated or mechanically stressed, can be described as a superposition of these three signals. The singlet is responsible for the background signal (BG), is the main component of radiation-induced signals (RIS) for low doses (100 Gy or lower) and also contributes to mechanically-induced signals (MIS). This signal is quite stable under vacuum storage, but can be reduced almost to zero by soaking in water. The behavior of this signal under ambient conditions depends on many factors, such as absorbed dose, air humidity, and ambient illumination intensity at the place of storage. The doublet arises after exposure of nails to high (few hundreds Gy and higher) doses or after mechanical stress of samples. Depending on how this signal was obtained, it may have bulk or surface locations with quite different stability properties. The surface-located doublet (generated on the nail edges during cutting or clipping) is quite unstable and decays over about two hours for samples stored at ambient conditions and within several seconds for samples immersed in water. The volume-distributed doublet decays within a few minutes in water, several hours at ambient conditions and several days in vacuum. The anisotropic signal may also be generated by both ionizing radiation and mechanical stress; this signal is quite stable in vacuum and decays over several days at ambient conditions or a few tens of minutes in water. The reference lines for the above-described three EPR signals were obtained and a procedure of spectra deconvolution was developed and tested on samples exposed to both ionizing radiation and mechanical stress.

Samples of Gorilla ® glass (Corning ® ) from several touchscreen mobile phones were prepared and analyzed using phototransferred thermoluminescence (PTTL) in an attempt to retrospectively assess radiation doses absorbed by the glass for potential applications in emergency dosimetry. Samples of glass were prepared by cleaning and cutting into small pieces. Glow curves were recorded after irradiation to different doses, pre-heating to a given temperature, and exposure to ultraviolet (UV) light (365 nm) for various times. The dependencies of the thermoluminescence signals so-obtained on the pre-heat temperature and the duration of UV light exposure were studied. The stability of the PTTL signals was also studied for samples stored under ambient conditions. The PTTL signals were quite stable with little change after storage over several days. Dose response curves (PTTL versus initial applied dose) were linear up to ∼20 Gy. Values of minimum detectable dose (MDD) evaluated using PTTL were determined for samples from different phone brands. A non-radiation-induced, UV-light-stimulated TL signal was also observed as a result of the UV exposure. Variability in the strength of this signal and in the PTTL sensitivity of the various glasses leads to a variation in, and places limits on, the obtained values for the MDD. Typical MDD values were found to range between 0.1 Gy and 5 Gy. A method for accounting for the UV-induced signal is suggested involving pre-heating to high temperatures (550 °C). An exploratory test of a suggested protocol for evaluating dose from smartphones using PTTL is described and the results are compared with those obtained using optically stimulated luminescence (OSL) and thermoluminescence (TL) methods from other phone components.

We examine the optical absorption spectra of a variety of LiF materials, variously doped with Mg, Cu and/or P. Both single crystal LiF (from various sources) and LiF:MCP-N sintered pellets are examined. We follow the growth of the individual absorption bands as a function of high, gamma-photon doses and high, beta-particle doses. Detailed deconvolution of the spectra, measured at room temperature following irradiation also at room temperature, allows for the behavior of the individual OA peaks to be analyzed. We also examine the post-irradiation step annealing of the spectrum by progressively heating the samples to high temperatures. We compare the data so obtained with the shape of the thermoluminescence glow curve recorded from these same materials. F, F2, F3, F3+, F3− and F4 centers are identified, along with impurity-related and possible Li-colloid absorption features. The various OA bands grow with dose (1 kGy–700 kGy) and the annealing behaviors of the various absorption features are discussed.

Several modifications are proposed for emergency dosimetry with different components of mobile phones. Two dosimetric techniques have been exploited, namely optically stimulated luminescence (OSL) from surface mount resistors (SMRs) and integrated circuits (ICs), and electron paramagnetic resonance (EPR) from samples of protective glass (PG). For OSL with SMRs, it was found that fading of the corresponding radiation-induced signal (RIS) is variable among the resistors of different brands and depends also on the value of the administered dose. In the case of ICs, the effect of sample sensitization with an increase in the accumulated dose was compensated by preheating the samples to some selected temperature. An approach based on the matrix spectra deconvolution of EPR spectra was proposed and tested for EPR dosimetry using smartphone protective glasses.

Mueller matrices were measured for natural (or reference) samples of human nails and samples irradiated by a 2 Gy ionizing radiation dose. The elements of the total Mueller matrix as a function of scattering angle were measured in backscattering mode at a wavelength of 632.8 nm. Several types of depolarizing Mueller matrix decompositions, namely, Ossikovsky, Williams, and Chipman, were calculated as a function of scattering angle for each nail sample. A comparative analysis of the sensitivity of the Mueller matrix decompositions in relation to the problem of emergency dose assessment in nails was performed.

Modern techniques for detection of covert nuclear material requires some combination of real time measurement and/or sampling of the material. More common is real time measurement of the ionizing emission caused by radioactive decay or through the materials measured in response to external interrogation radiation. One can expose the suspect material with various radiation types, including high energy photons such as x rays or with larger particles such as neutrons and muons, to obtain images or measure nuclear reactions induced in the material. Stand-off detection using imaging modalities similar to those in the medical field can be accomplished, or simple collimated detectors can be used to localize radioactive materials. In all such cases, the common feature is that some or all of the nuclear materials have to be present for the measurement, which makes sense; as one might ask, "How you can measure something that is not there?" The current work and results show how to do exactly that: characterize nuclear materials after they have been removed from an area leaving no chemical trace. This new approach is demonstrated to be fully capable of providing both previous source spatial distribution and emission energy grouping. The technique uses magnetic resonance for organic insulators and/or luminescence techniques on ubiquitous refractory materials similar in theory to the way the nuclear industry carries out worker personnel dosimetry. Spatial information is obtained by acquiring gridded samples for dosimetric measurements, while energy information comes through dose depth profile results that are functions of the incident radiation energies.

Olive oil is proposed as a medium for storage of nails in the time between nail harvesting and electron paramagnetic resonance (EPR) measurements to minimise the decay of the radiation-induced EPR signals (RIS). The behaviours of three main EPR signals, namely, RIS, mechanically induced and the background signals (MIS and BG, respectively), were studied for storage in olive oil. The properties of the MIS and BG signals were very similar to those previously observed for the storage in a vacuum. The RIS singlet slightly increased during the first day of storage and then remained practically unchanged at least for 6 days. Dose recovery test revealed that doses at the level 2 Gy may be reconstructed with an accuracy of about ±20%.

A method is presented for analyzing complex thermoluminescence (TL) glow curves from disordered materials using aluminosilicate glass as an example. The method is first described using simulated TL glow curves, firstly by assuming a Gaussian distribution of trap depths Et and a fixed frequency factor s, and secondly by assuming distributions of both Et and s. The method is able to reproduce the input distributions for both Et and s with a high degree of accuracy. The method is then applied to the measured TL from an aluminosilicate glass sample. A series of glow curves is recorded at different heating rates and the method is first applied to each glow curve separately, and Et and s distributions are obtained; four different trapping sites are revealed within the material, each with distributions in Et and s. Good self-consistency is obtained at each of the different heating rates. The lowest temperature TL peak shows signs of fading at the lowest heating rates used. The method is then applied to a “pseudo” TL curve consisting of the sum of all individual glow curves obtained at the different heating rates as a simple way to fit all curves recorded at the different heating rates simultaneously. The results obtained are consistent with those obtained by fitting the glow curves individually.

Protective glasses from the back of modern smartphones were tested as potential emergency dosimeters using optically stimulated luminescence (OSL). The glasses were shown to exhibit several favorable dosimetric properties including a strong sensitivity to radiation, a linear dose-response relationship from 0.1 to 8 ​Gy, a 3% reproducibility, and a minimum detectable dose in the low tens of milligray, even after significant fading. The OSL signal was observed to lose ~78% and ~90% of the original intensity over 1 ​h and 1 week, respectively; however, a fading curve was developed to correct for any such signal loss. A dose-recovery test demonstrated that reconstructed doses were capable of accuracies within 20%.

Chips from credit cards issued by the major US banks have been tested with optically stimulated luminescence (OSL) as potential materials for use in emergency radiation dosimetry. The following dosimetric properties have been studied: (1) OSL decay curves from both irradiated and unirradiated samples; (2) dose-response characteristics of the OSL and values of minimum detectable doses; (3) fading of the OSL signal with time after irradiation. No OSL was detected in unexposed samples while prominent signals were observed after irradiation. It was found that the shape of the OSL signals can be fitted by a combination of an exponentially decaying function and a power function. The dose-response relationship was linear in the range 0–7 Gy if the OSL signals were measured at the same effective time after irradiation and normalized to the response to a test dose. Dose recovery tests demonstrated that the doses can be reconstructed with an accuracy ±20% if the OSL measurements are conducted within 7 days after exposure and the corresponding OSL doses are corrected for fading.

ntroduction L-a-alanine has aroused considerable interest for use in radiation ESR dosimetry. In this work, we examined the energy response of alanine ESR films in the low energy X-photon energy range between 1 keV and 40 keV. Dose measurements through a reference ionization chamber and a semiconductor detection system were also performed to complement ESR measurements. Methods Commercial alanine ESR films were used. All ESR signal measurements were also done using an XBand (9.7 GHz) Bruker spectrometer. The dosimeters were irradiated at the "Livio Scarsi" Laboratory (LAX) of the University of Palermo, where X-ray beams in the 1–40 keV energy range are produced using a Seifert SN60 tube. Reference dosimetry measurements were made using a plane parallel chamber with thin polyethylene membranes. X-ray fluxes and energy spectra were measured with an innovative system based on semiconductor detectors (CdTe, Si) and digital pulse processing (DPP) electronics. Results The response of alanine to low-energy X-rays was characterized experimentally. The response as function of dose, the dependence of the ESR signal on the photon energy as well as the stability of the signal with time were investigated. Comparison of the ESR response to high energy photons was also carried out. The relative effectiveness is lower if compared to high-energy photons. Conclusion Alanine dosimeters show very interesting dosimetric features also for these low-energy X-ray beams. To our knowledge, these data have not been previously reported and they may be extremely relevant, e.g., when mapping the high-gradient treatment fields used in microbeam radiation therapy (MRT) with synchrotron radiation.

Existing data on intercomparisons involving biodosimetry or physical dosimetry methods are analyzed and the results interpreted regarding their efficacy in triage in emergency dosimetry following mass casualty radiological events. The biodosimetry technique examined is dicentric chromosome aberrations (DCA). The physical dosimetry techniques include electron paramagnetic resonance (EPR) of biological material (teeth) and physical material (smartphone screen glass), and optically stimulated luminescence (OSL) of electronic components (surface mount resistors) from mobile phones. Issues relating to calibration and interpretation of the data are discussed. An important conclusion of the analysis is that more research is critically needed to interpret the efficacy of the various methods. Included in this needed research are intercomparisons of the various methods in controlled experiments and the need to harmonize protocols.

Several table vitamins, minerals and L-lysine amino acid have been preliminarily tested as potential emergency dosemeters using electron paramagnetic resonance (EPR) and optically stimulated luminescence (OSL) techniques. Radiation-induced EPR signals were detected in samples of vitamin B2 and L-lysine while samples of multivitamins of different brands as well as mineral Mg demonstrated prominent OSL signals after exposure to ionizing radiation doses. Basic dosimetric properties of the radiation-sensitive substances were studied, namely dose response, fading of the EPR or OSL signals and values of minimum measurable doses (MMDs). For EPR-sensitive samples, the EPR signal is converted into units of dose using a linear dose response and correcting for fading using the measured fading dependence. For OSL-sensitive materials, a multi-aliquot, enhanced-temperature protocol was developed to avoid the problem of sample sensitization and to minimize the influence of signal fading. The sample dose in this case is also evaluated using the dose response and fading curves. MMDs of the EPR-sensitive samples were below 2 Gy while those of the OSL-sensitive materials were below 500 mGy as long as the samples are analyzed within 1 week after exposure.

Human finger- and toenails have been tested with an X-band EPR technique for different conditions of nail storage. The main radiation-induced signal at g=2.005 demonstrated good stability if the samples were stored in a vacuum at room temperature after nail harvesting and irradiation. On the basis of this phenomenon, a new protocol is proposed to use the nails as possible emergency EPR dosimeters. The dosimetry protocol was tested on laboratory-exposed samples and demonstrated the ability to recover doses in the region 0-10 Gy with an estimated uncertainty of approximately 0.3-0.4 Gy for doses in the range < 2 Gy, increasing to 0.6-0.7 Gy for doses in the range 5-10 Gy.

A non-destructive, optically stimulated luminescence (OSL) technique was tested on samples of back protective glasses from modern smartphones for possible application in post-exposure radiation triage following a radiological accident. Excitation light from a green-wavelength laser was directed to the samples using an optical fiber; the same optical fiber was used to direct the emission light from the sample to a photomultiplier tube. Excitation and emission beams were separated using a combination of a dichroic mirror, optical filters, and time resolution. It was found that all tested samples fell into two different categories. Category 1 included Gorilla Glass 3 (GG3) and Gorilla Glass 4 (GG4) samples, while Category 2 included samples from Gorilla Glass 5 (GG5) glass. The radiation sensitivity of samples from Category 1 was about one order of magnitude higher than that of Category 2 glass. Minimum detectable doses determined for the pulse OSL mode were about 1 Gy and 10 Gy for Categories 1 and 2, respectively, for samples measured immediately after irradiation. Fading of the OSL signal measured in the CW-OSL mode was ~75% and ~84% one day after irradiation and ~82% and ~88% over one week for Categories 1 and 2, respectively. It was concluded that the back glasses demonstrate a feasible line of future research for potential use as emergency OSL dosimeters, provided they were covered by an opaque cover both during and after an emergency exposure and are then analyzed within a few days following the incident.

A model for RPL emission from Ag-doped alkali phosphate glasses is examined in which the RPL is emitted from Ag2+-pairs and Ag2+ ions. Simultaneous, non-linear, differential rate equations are introduced to describe the flow of charge during irradiation using this model, including the interaction between Ag+ and Ag0 centers to form Ag2+-pairs. The simulation results show that the RPL centers grow nonlinearly during irradiation due to the effect of the build-up process. The simulations are compared with experimental real-time measurements of RPL emission, both during and immediately after irradiation. The conclusion is reached that the model examined is able to qualitatively describe the experimental results.

The feasibility of using radiophotoluminescence from Ag-doped alkali-phosphate glass as an in-situ, sub-surface environmental radiation monitor is examined. GD-302M glass from Chiyoda Technol Corporation was attached to the end of a silica optical fiber inside a stainless-steel probe and inserted into soil to a depth of ~1 m. Radiophotoluminescence (RPL) from the GD-302M detectors was stimulated along the fiber using a 355 nm pulsed laser and RPL emission was directed along the same fiber and detected by a photomultiplier tube. Restrictions on the average laser power to be used in the experiments were observed due to the creation of an RPL signal for a zero-dose sample, or depletion of the radiation-induced signal from an irradiated sample. Short (1 s), low-frequency (1 kHz) laser stimulation rendered such effects negligible, while providing sufficient sensitivity to enable measurements of environmental doses of ~100 μGy.

The build-up of radiophotoluminescence (RPL) from Ag-doped alkali-phosphate glass (from Chiyoda Technol Corporation, Japan) was measured both during and immediately following irradiation. The post-irradiation build-up curve was measured at several different temperatures and could be described by the sum of two exponential functions of time. The two processes are thermally activated, with activation energies of 0.45 eV and 0.17 eV, and their relative contributions were observed to behave in opposite senses as the temperature increases. Thermal quenching of the RPL signal with increasing temperature was also observed. The real-time RPL signal during irradiation could be described by the convolution of an intrinsic growth function and the build-up curve. A model is proposed wherein Ag2+-pairs and Ag2+ centers contribute to the RPL signal. A set of non-linear differential equations was written to describe the build-up process and numerical solution of these equations yielded simulated results which qualitatively matched the observed experimental data.

Ag-doped phosphate glass from Chiyoda Technol Corp. was tested as a potential high-dose dosimeter. Several tens of glass samples were irradiated to different doses in the range 0–300 kGy and measured using radiophotoluminescence (RPL), optical absorption (OA), thermoluminescence (TL) and electron paramagnetic resonance (EPR) techniques. While RPL and TL signals from such glass saturated at the doses of about 1 kGy, OA and EPR (associated with Ag2+ centers) responses demonstrated a monotonic increase with dose up to the maximum tested dose 300 kGy. Fading of the Ag2+-related EPR signal was about 7% at 4 months and about 10% at 10 months after irradiation; no change was observed for OA measured one month after irradiation. It is concluded that with proper calibration, Ag-doped glass may be used for dose assessment in high-dose applications.

Electron Paramagnetic Resonance (EPR) and Thermoluminescence (TL) signals have been studied in samples of Gorilla® Glass (GG) from different smartphones as well as some online stores and vendors. Background, radiation-induced and ultraviolet-induced signals were compared between the samples. Significant variability of both EPR and TL signals (in shape and intensity) was observed between samples from different screens as well as over the surface of the same screen, from the same phone. Both the EPR and TL background signals appear to be due to UV exposure during phone manufacture; some phones have higher EPR and TL signals around the edge of the screen, indicating more UV exposure at the edge than in the center. EPR and TL signals in the same GG samples appear correlated: they decayed over the same temperature region; and both hole- and electron-related EPR and TL signals were made up of stable and unstable components (at room temperature).

In this article, optically stimulated luminescence (OSL) data are presented from integrated circuits (ICs) extracted from mobile phones. The purpose is to evaluate the potential of using OSL from components in personal electronic devices such as smart phones as a means of emergency dosimetry in the event of a large-scale radiological incident. ICs were extracted from five different makes and models of mobile phone. Sample preparation procedures are described, and OSL from the IC samples following irradiation using a (90)Sr/(90)Y source is presented. Repeatability, sensitivity, dose responses, minimum measureable doses, stability and fading data were examined and are described. A protocol for measuring absorbed dose is presented, and it was concluded that OSL from these components is a viable method for assessing dose in the days following a radiological incident.

The OSL dosimetry technique with teeth has been validated against the EPR dosimetry technique through a measurement comparison performed on the same teeth. The OSL reconstructed doses were found to be in agreement with corresponding EPR doses. Minimum measurable doses for the OSL technique were estimated to be in the range 0.9–1.5 Gy for measurements made within 24 h post-exposure if OSL signals are collected from 6 teeth at the same time. These values satisfy the requirements for emergency triage dosimetry. The fading of tooth OSL signals correlated with fading of radiation-induced EPR signals observed at g = 2.0115 that are attributed to CO 3 - radicals. OSL sensitivity can be enhanced if more teeth from the same individual will be used for the signal accumulation.

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.

Several commonplace materials were studied as possible emergency optically stimulated luminescence (OSL) dosimeters. The materials included: paper currency (banknotes) and coins of different denomination and from different countries; plastic cards of different types (credit and debit cards, driver's license cards, membership cards, etc.), parts and details of clothing and shoes as well as samples of different fabrics. The samples displayed significant variability in their OSL properties. They differed in the intensity of the initial ‘native’ signal; the bleaching time of the OSL signal; the sensitivity to light of different wavelengths; the fading rate of OSL signals, etc. Procedures of OSL analysis were proposed to account for this variety. Values of the minimum measurable dose (MMD) were below 2 Gy for most tested samples if OSL measurements were conducted within one week of exposure and the samples were kept in dark since exposure (except samples of shoes that were kept under environmental light). The OSL signals in banknotes appear to originate from compounds containing aluminum, silicon, calcium and titanium – these elements were detected using X-ray microanalysis. For coins, the source of the OSL signals is speculated to be small particles of quartz, which were detected on the coins' surfaces. The X-ray microanalysis spectra from fabrics and shoes revealed sodium, aluminum, titanium, iron and nickel as elements that appeared to be responsible for the radiation sensitivity of those samples. It was concluded that, under certain constrained circumstances, paper and metallic money, personal plastic cards, clothing and shoes could be used as emergency OSL dosimeters in triage applications.

Thermoluminescence and phototransferred thermoluminescence measurements of protective glass from smartphones are described. Samples of Gorilla Glass were examined from nine different manufacturers and 40 different phone models. Additionally, 12 glasses believed to be original equipment manufacturer replacements, as well as three glass samples from U.S. finishers, were also studied. Altogether, 99 different Gorilla Glass samples were examined. The radiation-induced thermoluminescence signal produced glow curve shapes specific to the Gorilla Glass generations and could be used to distinguish between them. A background thermoluminescence (and phototransferred thermoluminescence) signal was found in all unirradiated samples. Its intensity and shape were found to be dependent on the Gorilla Glass generation, phone manufacturer, and phone model. The background signal was demonstrated to be produced by ultraviolet light exposure; the shape of the background signal was able to be reproduced by the combined exposure to a broad-spectrum solar simulator and a 302 nm ultraviolet light source. The background signal intensity was found to vary with the location from which it was taken on the glass. It was also found to be dependent on the depth within the Gorilla Glass due to absorption of the ultraviolet light as it traversed the medium. Removal of the glasses’ surface layers was found to be an inadequate method for removing the background signal. In some samples, the background signal intensity was large enough to significantly contribute to the total thermoluminescence (and phototransferred thermoluminescence) signal; therefore, a matrix deconvolution method was introduced to separate the background signal and radiation-induced signal. This method was found to enable dose reconstruction using the radiation-induced signal alone.

International audience; Purpose: RENEB, ‘Realising the European Network of Biodosimetry and Physical Retrospective Dosimetry,’ is a network for research and emergency response mutual assistance in biodosimetry within the EU. Within this extremely active network, a number of new dosimetry methods have recently been proposed or developed. There is a requirement to test and/or validate these candidate techniques and inter-comparison exercises are a well-established method for such validation. Materials and methods: The authors present details of inter-comparisons of four such new methods: dicentric chromosome analysis including telomere and centromere staining; the gene expression assay carried out in whole blood; Raman spectroscopy on blood lymphocytes, and detection of radiation-induced thermoluminescent signals in glass screens taken from mobile phones. Results: In general the results show good agreement between the laboratories and methods within the expected levels of uncertainty, and thus demonstrate that there is a lot of potential for each of the candidate techniques. Conclusions: Further work is required before the new methods can be included within the suite of reliable dosimetry methods for use by RENEB partners and others in routine and emergency response scenarios. © 2016 Crown Copyright. Published by Informa UK Limited, trading as Taylor & Francis Group.

International audience; Biological and physical retrospective dosimetry are recognised as key techniques to provide individual estimates of dose following unplanned exposures to ionising radiation. Whilst there has been a relatively large amount of recent development in the biological and physical procedures, development of statistical analysis techniques has failed to keep pace. The aim of this paper is to review the current state of the art in uncertainty analysis techniques across the 'EURADOS Working Group 10- Retrospective dosimetry' members, to give concrete examples of implementation of the techniques recommended in the international standards, and to further promote the use of Monte Carlo techniques to support characterisation of uncertainties. It is concluded that sufficient techniques are available and in use by most laboratories for acute, whole body exposures to highly penetrating radiation, but further work will be required to ensure that statistical analysis is always wholly sufficient for the more complex exposure scenarios. © Crown copyright 2017.

This paper reviews recent research on the application of the physical dosimetry techniques of electron paramagnetic resonance (EPR) and luminescence (optically stimulated luminescence, OSL, and thermoluminescence, TL) to determine radiation dose following catastrophic, large-scale radiological events. Such data are used in dose reconstruction to obtain estimates of dose due to the exposure to external sources of radiation, primarily gamma radiation, by individual members of the public and by populations. The EPR and luminescence techniques 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. In this review we examine the application of these techniques in ‘emergency’ and ‘retrospective’ modes of operation that are conducted on two distinct timescales. For emergency dosimetry immediate action to evaluate dose to individuals following radiation exposure is required to assess deterministic biological effects and to enable rapid medical triage. Retrospective dosimetry, on the other hand, contributes to the reconstruction of doses to populations and individuals following external exposure, and contributes to the long-term study of stochastic processes and the consequential epidemiological effects. Although internal exposure, via ingestion of radionuclides for example, can be a potentially significant contributor to dose, this review is confined to those dose components arising from exposure to external radiation, which in most studies is gamma radiation. The nascent emergency 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 issued 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 EPR measurements, in particular, this includes material within the body (such as bone or tooth biopsy) requiring invasive procedures, but also materials collected non-invasively (such as clippings taken from finger- or toenails) and artefacts within their personal belongings (such as electronic devices of which smart phones are the most common). For luminescence measurements, attention has also focused on components within electronic devices, including smartphones, and a wide range of other personal belongings such as paper and other polymer-based materials (including currency, clothing, bank cards, etc.). The paper reviews progress made using both EPR and luminescence techniques, along with their current limitations. For the longer-established approach of retrospective dosimetry, luminescence has been the most extensively applied method and, by employing minerals found in construction materials, it consequently is employed in dosimetry using structures within the environment. Recent developments in its application to large-scale radiation releases are discussed, including the atomic bomb detonations at Hiroshima and Nagasaki, fallout from the Chernobyl reactor and atmospheric nuclear bomb tests within the Semipalatinsk Nuclear Test Site and fluvially transported pollution within the Techa River basin due to releases from the Mayak facility. The developments made in applying OSL and TL techniques are discussed in the context of these applications. EPR measurements with teeth have also provided benchmark values to test the dosimetry models used for Chernobyl liquidators (clean-up workers), residents of Semipalatinsk Nuclear Tests Sites and inhabitants of the Techa River basin. For both emergency and retrospective dosimetry applications, computational techniques employing radiation transport simulations based on Monte Carlo code form an essential component in the application of dose determinations by EPR and OSL to dose reconstruction problems. We include in the review examples where the translation from the physical quantity of cumulative dose determined in the sampled medium to a dose quantity that can be applied in the reconstruction of dose to individuals and/or populations; these take into account the source terms, release patterns and the movements of people in the affected areas. One role for retrospective luminescence dosimetry has been to provide benchmark dose determinations for testing the models employed in dose reconstruction for exposed populations, notably at Hiroshima and Nagasaki. The discussion is framed within the context of the well-known radiation incidents mentioned above.

Human teeth were studied for potential use as emergency Optically Stimulated Luminescence (OSL) dosimeters. By using multiple-teeth samples in combination with a custom-built sensitive OSL reader, (60)Co-equivalent doses below 0.64 Gy were measured immediately after exposure with the lowest value being 27 mGy for the most sensitive sample. The variability of OSL sensitivity, from individual to individual using multiple-teeth samples, was determined to be 53%. X-ray and beta exposure were found to produce OSL curves with the same shape that differed from those due to ultraviolet (UV) exposure; as a result, correlation was observed between OSL signals after X-ray and beta exposure and was absent if compared to OSL signals after UV exposure. Fading of the OSL signal was "typical" for most teeth with just a few of incisors showing atypical behavior. Typical fading dependences were described by a bi-exponential decay function with "fast" (decay time around of 12 min) and "slow" (decay time about 14 h) components. OSL detection limits, based on the techniques developed to-date, were found to be satisfactory from the point-of-view of medical triage requirements if conducted within 24 hours of the exposure.

This paper presents the results of the 4th International Comparison of in vitro electron paramagnetic resonance dosimetry with tooth enamel, where the performance parameters of tooth enamel dosimetry methods were compared among sixteen laboratories from all over the world. The participating laboratories were asked to determine a calibration curve with a set of tooth enamel powder samples provided by the organizers. Nine molar teeth extracted following medical indication from German donors and collected between 1997 and 2007 were prepared and irradiated at the Helmholtz Zentrum Munchen. Five out of six samples were irradiated at 0.1, 0.2, 0.5, 1.0 and 1.5 Gy air kerma; and one unirradiated sample was kept as control. The doses delivered to the individual samples were unknown to the participants, who were asked to measure each sample nine times, and to report the EPR signal response, the mass of aliquots measured, and the parameters of EPR signal acquisition and signal evaluation. Critical dose and detection limit were calculated by the organizers on the basis of the calibration-curve parameters obtained at every laboratory. For calibration curves obtained by measuring every calibration sample three times, the mean value of the detection limit was 205 mGy, ranging from 56 to 649 mGy. The participants were also invited to provide the signal response and the nominal dose of their current dose calibration curve (wherever available), the critical dose and detection limit of which were also calculated by the organizers.

Radiation-induced electron paramagnetic resonance (EPR) signals were studied in samples of plastic materials of various origin: buttons, details of underwear, elements of mobile phones, etc. The following parameters were investigated: dose response curve in the range 0-25 Gy; stability of potential dosimetric signals at different temperatures of storage after exposure; and influence of solar radiation on the dosimetric properties of materials. Plastics from personal goods were found to be a potentially acceptable material for use as individual EPR dosimeters with sensitivity threshold below 5 Gy. Radiation-induced EPR signals in plastic demonstrated clear saturation for doses above 10 Gy. Fading of dosimetric signals was best described by the two-exponential decay function with fast and slow decay components. Values of slow decay constant were approximately 2 and 15 d, while the corresponding values for the fast decay component were approximately 2 and 15 h for temperatures of +25 degrees C and -18 degrees C, respectively. Strong influence of solar light radiation on EPR spectra was observed for unexposed and gamma-irradiated plastic samples, which may affect drastically the results of dose reconstruction.

The influence of age on tooth enamel as an EPR dosimeter has been investigated using a big collection of teeth extracted from several tens of persons living in different regions of Ukraine. The study was focused on two groups of teeth. The first one represented the urban population while the second corresponded to residents of rural settlements. Age dependences of two above groups were quite different: for example, doses for the 65–75 year age group were approximately 200 mGy higher for urban population compared to habitants of rural settlements. This effect was explained by contribution of medical X-ray exposure: the comparison of corresponding lingual and buccal doses revealed the more frequent presence of X-ray dose for urban population. Another observed effect was the difference between average intensities of native signals for two studied groups. At present time, no correlation with age was seen for this effect.

Dose profiles in teeth have been experimentally and theoretically studied for different energies and geometries of incident X- and gamma-rays. The experiments were conducted with teeth inside of an Alderson phantom using monodirectional radiation beams at selected energies; they revealed two effects: an apparent lack of dose attenuation between the buccal and the lingual sides of the teeth for energies higher than 120 keV and an attenuation between first and last tooth layers for low-energy beams in the range from 0.28 to 0.57. Monte Carlo simulations confirmed the experimental data and provided dose profiles for other energies and geometries. In particular, exposure in the rotational radiation field produces pronounced dose profiles only for energies lower than 60 keV. The usefulness of these data to estimate the average energy of accidental radiation field is discussed.

For intercomparison of methods of dose determination using electron paramagnetic resonance (EPR) spectroscopy of tooth enamel, the same sets of enamel samples were analyzed in different laboratories using similar recording parameters. The sets of samples included calibration samples irradiated in known doses, test samples irradiated to doses unknown to the participants and accidental dose samples prepared from teeth of humans affected by radioactive fallout from nuclear tests in the Semipalatinsk Nuclear Test Site in Kazakhstan. The test samples were analyzed to determine the differences in the resulting doses using different spectrometers and different spectra processing methods. The accidental dose samples were analyzed in order to test the precision of doses determined by EPR spectroscopy and to obtain more accurate values by averaging the results from different laboratories.

In order to investigate the effects of spectrum processing procedures on the results of dose determination using EPR spectroscopy of human tooth enamel, spectra of the same samples measured in different laboratories in the course of the intercomparison were processed by some of the participants using their own unique procedures. Spectra of samples irradiated to known doses (calibration samples) and of samples irradiated to doses unknown to the participants (test samples) were analyzed. By comparison of the results obtained using different spectrum processing methods, it is shown that the precision of calibration and the accuracy of dose determination may be improved by appropriate choice of spectrum processing procedure.

The determination of external dose to teeth of inhabitants of settlements near the Semipalatinsk Nuclear Test Site (SNTS) was conducted using the EPR dosimetry technique to assess radiation doses associated with exposure to radioactive fallout from the test site. In this study, tooth doses have been reconstructed for 103 persons with all studied teeth having been formed before the first nuclear test in 1949. Doses above those received from natural background radiation, termed “accident doses”, were found to lie in the range from zero to approximately 2 Gy, with one exception, a dose for one person from Semipalatinsk city was approximately 9 Gy. The variability of reconstructed doses within each of the settlements demonstrated heterogeneity of the deposited fallout as well as variations in lifestyle. The village mean external gamma doses for residents of nine settlements were in the range from a few tens of mGy to approximately 100 mGy.

Despite the considerable improvement in accuracy in comparison with previous intercomparison programmes, the outcome of the recent 3rd International Intercomparison on EPR Tooth Dosimetry has demonstrated that performance of various protocols practised in different laboratories significantly varies. SCRM and MUG took part in this intercomparison with their own versions of EPR dosimetry protocols, demonstrating the good correlation between reconstructed and nominal doses (best result for SCRM and fourth best for MUG) and the lowest both absolute and relative mean deviations from the nominal doses. Although the general results of the 3rd Intercomparison are being discussed elsewhere in this issue by Wieser et al., this presentation is focused on the discussion of the common features of the two techniques, which may have an effect on good performance in dose reconstruction. In addition to the mthods of analysis of the intercomparison results, as used in Wieser et al., SCRM and MUG studied the influence of an additional factor--the selection of the standard of the native signal--on the quality of the dose reconstruction.

The transferability of a measurement protocol from one laboratory to another is an important feature of any mature, standardised protocol. The electron paramagnetic resonance (EPR)-tooth dosimetry technique that was developed in Scientific Center for Radiation Medicine, AMS, Ukraine (SCRM) for routine dosimetry of Chernobyl liquidators has demonstrated consistent results in several inter-laboratory measurement comparisons. Transferability to the EPR dosimetry laboratory at the National Institute of Standards and Technology (NIST) was examined. Several approaches were used to test the technique, including dose reconstruction of SCRM-NIST inter-comparison samples. The study has demonstrated full transferability of the technique and the possibility to reproduce results in a different laboratory environment.

Variability of EPR signal parameters in retrospective dosimetry with teeth has been studied among five different oblasts (regions) of Ukraine. It was found that the native signal in enamel is region-invariant and has peak-to-peak width of 0.85±0.01 mT and intensity of 1.0±0.20 normalized units. Low-frequency background signals in the spectra of enamel, 1 expressed in terms of dose were estimated to represent 15–20 mGy. Variability of radiation sensitivity among different teeth (inter-sample variability measured using 100 mg aliquots) was ±4% while among different parts of one tooth (intra-sample variability measured using 5–10 mg aliquots)—±7%.

We present here a particular application area for EPR dosimetry with teeth—use as a source of reference dose values for validation/verification of other retrospective dosimetry techniques and existing dose records. The conditions of application of EPR dosimetry in this role as well as practical design of such studies are shown. Particular attention is given to the requirements to the techniques in terms of precision and throughput, as well as to the issue of availability of samples for analysis and practical solution of this problem. Practical application of this approach is illustrated by several examples of completed validation sub-studies, which were performed in the framework of large-scale post-Chernobyl epidemiological studies.

The matrix method of EPR spectra decomposition is developed and adapted for routine application in retrospective EPR dosimetry with teeth. According to this method, the initial EPR spectra are decomposed (using methods of matrix algebra) into several reference components (reference matrices) that are specific for each material. Proposed procedure has been tested on the example of tooth enamel. Reference spectra were a spectrum of an empty sample tube and three standard signals of enamel (two at g =2.0045, both for the native signal and one at g ⊥ =2.0018, g || =1.9973 for the dosimetric signal). Values of dosimetric signals obtained using the given method have been compared with data obtained by manual manipulation of spectra, and good coincidence was observed. This allows considering the proposed method as potent for application in routine EPR dosimetry.

A method for evaluating the overall uncertainty of alanine EPR transfer dosimetry in the therapeutic dose range is described. The method uses experimental data on EPR signal reproducibility from replicate dosimeters irradiated to low doses (1–5 Gy), estimates of Type B uncertainties, and Monte Carlo simulations of heteroscedastic orthogonal linear regression. A Bruker ECS106 spectrometer and Bruker alanine dosimeters have been used for this evaluation. The results demonstrate that alanine dosimetry can be used for transfer dosimetry in that range with the overall uncertainty 1.5–4% (1σ) depending on the dose, the number of replicate dosimeters, and the duration of the calibration session (the session should not exceed one working day).