Radiation-induced Electron Paramagnetic Resonance Signals Research Articles

Electron paramagnetic resonance and luminescence spectroscopy of transition metal ion impurities and X-ray-induced radicals in brushite

Calcium phosphates hold paramount importance as the constituents of hard tissue of living organisms. Among them, brushite (CaHPO4·2H2O), also known as dicalcium phosphate dihydrate (DCPD), is a common precursor in phosphate synthesis and is becoming increasingly appealing as a biomaterial for bone regeneration applications. This study presents a comparative analysis of structural, morphological, thermal, and spectroscopic properties of synthetic brushite prepared by the wet precipitation method with several brushite products available from commercial vendors. Electron paramagnetic resonance (EPR) spectroscopy revealed that Mn2+ and Fe3+ ions are common trace impurities in commercial products. Following exposure to X-rays, EPR signals of several phosphorous-related radicals emerge. The annealing of the irradiated samples gives rise to broad thermally stimulated luminescence (TSL) signals in the 40–120 °C range, which correlates with the annealing kinetics of the radicals. The stability of radiation-induced EPR and TSL signals is limited by the phase transformation temperature from brushite to monetite (CaHPO4). The results of this study provide novel insights into the formation and stability of phosphorous-related radicals and demonstrate how minuscule amounts of impurity ions can strongly influence the spectroscopic properties of brushite.

Исследование радиационно- индуцированного сигнала электронного парамагнитного резонанса зерен пшеницы, облученных низкоэнергетическим пучком электронов

The use of radiation processing of food and agricultural products entails the need to control the values of the applied doses. This work shows the possibility of using EPR spectrometry for dosimetry monitoring of wheat samples irradiated at the URT-0.5 (0.5 MeV) electron accelerator. The general view of the spectra of the radiation-induced EPR signal is presented, its time kinetics is studied. The dependences of the EPR signal intensity on the value of the absorbed dose are obtained.

Enhancement of radiation-induced EPR signal in bioapatites

Amplification of a dosimetric EPR signal in mineralized biological materials available in limited quantities has been demonstrated in this paper. Powders of irradiated enamel, dentin, and bone tissue were placed into silica ampoules with the outer diameter close to 1.4 mm. To amplify the signal, the dielectric insert in the form of cylinder with the outer radius 2.85 mm, the inner radius 0.75 mm, and the height 1.85 mm made of a high-κ and low-loss ceramic material BaTi4O9 + 8.5% ZnO has been used. It has been shown that maximum signal amplification (about an order of magnitude) has been achieved when the sample is completely inserted into this dielectric. It has been found that the line shape of the dosimetric signal is not distorted, if using the dielectric insert. Decomposition of the amplified EPR spectra allowed us to determine the relative contribution of two types of CO2– radicals to the dosimetric signal, which coincides with the literature data.

Investigation of radiation-induced electron paramagnetic resonance signal of an eggshell after electron beam irradiation

The development of radiation processing methods for food and agricultural products increases the demand for methods of control over the processing and circulation of products. ESR spectrometry is a promising method for monitoring and detecting, which is already being used to control products containing bones, cellulose and crystalline sugar. This research presents the results of a study of the radiation-induced ESR signal in eggshells and the kinetics of radicals over time. The samples were irradiated using the URT-0.5 (0.5 MeV) and UELR-10-10S2 (10 MeV) electron accelerators. The ESR signal spectra were obtained on an ELEXSYSE500 ESR spectrometer. The dependencies of the ESR signal intensity on the value of the absorbed dose were obtained, and a comparative analysis of the irradiation of chicken eggs with different energies was carried out.

Исследование радиационно- индуцированного сигнала электронного парамагнитного резонанса яичной скорлупы после облучения пучками электронов

Because of the development of radiation processing of food and agricultural products it requires new methods of control over the processing and turnover of products. A promising method for monitoring is EPR spectrometry. This research presents the results of a study of the radiation induced EPR signal in eggshells. The URT-0.5 (0.5 MeV) and UALR-10-10 S2 (10 MeV) accelerators were used for irradiation. It shows the kinetics of radicals over time. The dependences of the EPR signal intensity on the absorbed dose were obtained, and a comparative analysis of the irradiation of chicken eggs with different energies was performed. The kinetics of radicals over time and the dependence of the intensity of the EPR signal on the absorbed dose are shown. A comparative analysis of the irradiation of chicken eggs with different energies is carried out.

L-Band Electron Paramagnetic Resonance Tooth Dosimetry Applied to Affected Cattle Teeth in Fukushima

We applied a non-destructive tooth dosimetry technique using L-band electron paramagnetic resonance (EPR) to assess radiation doses in cattle due to the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, which occurred 10 years ago. The radiation exposure of cattle in the area affected by the FDNPS accident was estimated retrospectively with X-band and L-band EPR devices. Characteristic radiation-induced EPR signals were obtained from the teeth of the cattle in Fukushima, confirming their exposure. The estimated doses to the teeth were found to be consistent with the dose trends estimated for individual cows, while considerable uncertainties were seen in the doses of some tooth samples. This variation might be due to errors in the accuracy of the method but also might reflect the actual exposure because the cattle may have been exposed to higher areas of radioactivity in their quest for food and/or due to irradiation from absorption of the isotopes with localization in or near the teeth. However, at a minimum, these results confirm that L-band EPR can be used for non-destructive qualitative assessment of radiation exposure to animals using their teeth, which could be very valuable. Possible causes of the uncertainties should be investigated to enhance the value of the use of this technique.

Time evolution of radiation-induced EPR signals in different types of mobile phone screen glasses

In this study, samples of smart phone touch screen glass sheets and tempered glass screen protectors were examined with respect to their potential application in the dosimetry of ionizing radiation. The glass samples were obtained from various phones with different types of glass. Electron paramagnetic resonance (EPR) spectra of the radiation-induced signals (RIS) are presented and their dose dependence within a dose range of 0–20 Gy. Despite the observed fading with time of the dosimetric components of the signal, the remaining RIS turned out to be strong enough for a reliable dosimetry even 18 month after irradiation. The study also shows that crushing of the glass sheets and water treatment of the samples have no effect on the background and dosimetric EPR signals.

AN ADVANCE IN EPR DOSIMETRY WITH NAILS.

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%.

Otoliths as object of EPR dosimetric research.

Otoliths are the organs which fish use for hearing and keeping balance. Otoliths are the most calcified tissues in the fish body. In contrast to bones, otoliths are not affected by remodeling and, therefore, they are expected to accumulate any dose from ionizing radiation during lifetime. Therefore, EPR dosimetry with fish otoliths could be an important tool for dose reconstruction in radiobiology and radioecology. It could also provide useful information remediation actions to de-contaminate waterbodies. Consequently, in the present study, otoliths of three contaminated fish species (roach (Rutilus rutilus), pike (Esox lucius) and perch (Perca Fluviatilis)) were examined with Electron Paramagnetic Resonance (EPR) spectroscopy. The fish were caught at storage reservoirs of liquid radioactive waste from Mayak PA and from the upper reach of the Techa River, which have been contaminated with different levels of radionuclide activity concentrations. It is shown that the radiation-induced EPR signal of otolith is stable and characterized by a linear dose response. However, the slope of the calibration curve (corresponding to the radiation sensitivity of the material) is not the same for different species; this may be caused by differences in mineralization. The reconstructed doses were found to be in the range from undetectable (in fish from the upper stream of the Techa River) up to 265Gy (in roach from the most contaminated waterbody). In parallel, otoliths were measured with β-counter to detect 90Sr/90Y. Samples were also tested on the presence of alpha-emitters, but no alpha activity above background could be detected. However, a significant activity concentration of 90Sr was detected (from 1 × 101 to 2 × 104 Bq/g). The EPR doses measured correlated with the 90Sr activity concentration measured in the otolith samples.

EPR dosimetry in nail samples irradiated in vivo during total body irradiation procedures

Electron paramagnetic resonance (EPR) measurements of human's nails is a newly proposed method of retrospective biodosimetry based on quantitative ex vivo determination of EPR signals originating from free radicals induced in nails by ionizing radiation. In the presented study the nails were irradiated in vivo under controlled exposure conditions during total body irradiation (TBI) procedures with doses in nails about 15 Gy delivered through 3 days in 2 fractions per day. The authors applied two methods of reconstruction of the doses: one based on individualized calibration of the radiation-induced EPR signal (RIS) and the second one based on determination of the dose of maximum response (DMR) of so-called RIS5 EPR signal. The first method yielded doses from −3.5 Gy to 22.1 Gy for seven TBI patients. In all but one patient the reconstructed doses were considerably lower than the actual doses calculated by treatment plan, probably due to decay of the dosimetric EPR signal caused by contact of the nails with water during the patients' personal hygiene activities. The second method, based on the RIS5 signal, did not allow for reconstruction of the TBI doses mostly due to lack of the dose saturation features characteristic to RIS5. Further studies on the RIS5 method suggested, that its applicability can be related to the samples' geometry, i.e. the ratio of the total length (l) of cut edges to the mass (m) of the nail clippings: the dose saturation effect, characteristic for RIS5 radicals, was not observed for samples of relatively high l/m ratio. In addition, the study showed only limited resistance of the RIS5 radicals to water – water treatments longer than 10 min resulted in a decrease in the RIS intensity up to complete decay of the RIS for 60 min exposures of the irradiated clippings to water. Therefore it is concluded, that both methods are of limited reliability – only the method of direct calibration can provide, under conditions of minimized contact of nails with water before and after cutting, an indication of the radiation exposure in the examined dose range.

Camel molar tooth enamel response to gamma rays using EPR spectroscopy.

Tooth enamel samples from molar teeth of camel were prepared using a combined procedure of mechanical and chemical tooth treatment. Based on electron paramagnetic resonance (EPR) spectroscopy, the dose response of tooth enamel samples was examined and compared to that of human enamel. The EPR dose response of the tooth enamel samples was obtained through irradiation to gamma doses from 1Gy up to 100kGy. It was found that the radiation-induced EPR signal increased linearly with gamma dose for all studied tooth enamel samples, up to about 15kGy. At higher doses, the dose response curve leveled off. The results revealed that the location of the native signal of camel tooth enamel was similar to that of enamel from human molars at 2.00644, but different from that of enamel from cows and goats. In addition, the peak-to-peak width (ΔH pp) for human and camel molar teeth was similar. It was also found that the response of camel enamel to gamma radiation was 36% lower than that of human enamel. In conclusion, the results indicate the suitability of camel teeth for retrospective gamma dosimetry.

In Vivo Electron Paramagnetic Resonance Tooth Dosimetry: Dependence of Radiation-Induced Signal Amplitude on the Enamel Thickness and Surface Area of Ex Vivo Human Teeth.

In vivo L-band electron paramagnetic resonance tooth dosimetry is a newly developed and very promising method for retrospective biodosimetry in individuals who may have been exposed to significant levels of ionizing radiation. The present study aimed to determine the relationships among enamel thickness, enamel area, and measured electron paramagnetic resonance signal amplitude with a view to improve the quantitative accuracy of the dosimetry technique. Ten isolated incisors were irradiated using well-characterized doses, and their radiation-induced electron paramagnetic resonance signals were measured. Following the measurements, the enamel thickness and area of each tooth were measured using micro-focus computed tomography. Linear regression showed that the enamel area at each measurement position significantly affected the radiation-induced electron paramagnetic resonance signal amplitude (p < 0.001). Simulation data agreed well with this result. These results indicate that it is essential to properly consider enamel thickness and area when interpreting electron paramagnetic resonance tooth dosimetry measurements to optimize the accuracy of dose estimation.

IN-VIVO RADIATION DOSIMETRY USING PORTABLE L BAND EPR: ON-SITE MEASUREMENT OF VOLUNTEERS IN FUKUSHIMA PREFECTURE, JAPAN.

The aim of this study was to make direct measurements of the possible radiation-induced EPR signals in the teeth of volunteers who were residents in Fukushima within 80 km distance from the Fukushima Nuclear Power plant at the time of the disaster, and continued to live there for at least 3 month after the disaster. Thirty four volunteers were enrolled in this study. These measurements were made using a portable L-band EPR spectrometer, which was originally developed in the EPR Center at Dartmouth. All measurements were performed using surface loop resonators that have been specifically designed for the upper incisor teeth. Potentially these signals include not only radiation-induced signals induced by the incident but also background signals including those from prior radiation exposure from the environment and medical exposure. We demonstrated that it is feasible to transport the dosimeter to the measurement site and make valid measurements. The intensity of the signals that were obtained was not significantly above those seen in volunteers who had not had potential radiation exposures at Fukushima.

Identification of irradiated dried fruits using EPR spectroscopy

Abstract The dominating carbohydrates in fruits are monosaccharides like fructose, glucose, sorbose and mannose. In dehydrated fruits, concentration of monosaccharides is higher than in fresh fruits resulting in the formation of sugar crystallites. In most of dried fruits, crystalline fructose, and glucose dominate and appear in proportion near to 1:1. Irradiation of dried fruits stimulates radiation chemical processes resulting in the formation of new chemical products and free radicals giving rise to multicomponent EPR signal which can be detected for a long period of time. For that reason, it is used as a marker for the detection of radiation treatment of dried fruits. It has been found that EPR spectra recorded in dried banana, pineapple, papaya, and fig samples resemble the EPR spectrum obtained by computer addition of fructose and glucose spectra taken in proportion 1:1. The decay of radiation induced EPR signals proceeds in dried fruits fast during the first month of observation and becomes much slower and almost negligible after prolonged storage. However, it remains intense enough for EPR detection even one year after processing. The radiation induced EPR signal is easily detected in dried fruits exposed to 0.5 kGy of gamma rays. Thus, the EPR method of the detection of irradiated fruits can be used for the control of dried fruits undergoing quarantine treatment with 200-300 Gy of ionizing radiation.

Tooth Retrospective Dosimetry Using Electron Paramagnetic Resonance: Influence of Irradiated Dental Composites.

In the aftermath of a major radiological accident, the medical management of overexposed individuals will rely on the determination of the dose of ionizing radiations absorbed by the victims. Because people in the general population do not possess conventional dosimeters, after the fact dose reconstruction methods are needed. Free radicals are induced by radiations in the tooth enamel of victims, in direct proportion to dose, and can be quantified using Electron Paramagnetic Resonance (EPR) spectrometry, a technique that was demonstrated to be very appropriate for mass triage. The presence of dimethacrylate based restorations on teeth can interfere with the dosimetric signal from the enamel, as free radicals could also be induced in the various composites used. The aim of the present study was to screen irradiated composites for a possible radiation-induced EPR signal, to characterize it, and evaluate a possible interference with the dosimetric signal of the enamel. We investigated the most common commercial composites, and experimental compositions, for a possible class effect. The effect of the dose was studied between 10 Gy and 100 Gy using high sensitivity X-band spectrometer. The influence of this radiation-induced signal from the composite on the dosimetric signal of the enamel was also investigated using a clinical L-Band EPR spectrometer, specifically developed in the EPR center at Dartmouth College. In X-band, a radiation-induced signal was observed for high doses (25-100 Gy); it was rapidly decaying, and not detected after only 24h post irradiation. At 10 Gy, the signal was in most cases not measurable in the commercial composites tested, with the exception of 3 composites showing a significant intensity. In L-band study, only one irradiated commercial composite influenced significantly the dosimetric signal of the tooth, with an overestimation about 30%. In conclusion, the presence of the radiation-induced signal from dental composites should not significantly influence the dosimetry for early dose assessment.

New developed cylindrical TM010 mode EPR cavity for X-band in vivo tooth dosimetry.

EPR tooth in vivo dosimetry is an attractive approach for initial triage after unexpected nuclear events. An X-band cylindrical TM010 mode resonant cavity was developed for in vivo tooth dosimetry and used in EPR applications for the first time. The cavity had a trapezoidal measuring aperture at the exact position of the cavity’s cylindrical wall where strong microwave magnetic field H1 concentrated and weak microwave electric field E1 distributed. Theoretical calculations and simulations were used to design and optimize the cavity parameters. The cavity features were evaluated by measuring DPPH sample, intact incisor samples embed in a gum model and the rhesus monkey teeth. The results showed that the cavity worked at designed frequency and had the ability to make EPR spectroscopy in relative high sensitivity. Sufficient modulation amplitude and microwave power could be applied into the aperture. Radiation induced EPR signal could be observed remarkably from 1 Gy irradiated intact incisor within only 30 seconds, which was among the best in scan time and detection limit. The in vivo spectroscopy was also realized by acquiring the radiation induced EPR signal from teeth of rhesus monkey whose teeth was irradiated by dose of 2 Gy. The results suggested that the cavity was sensitive to meet the demand to assess doses of significant level in short time. This cavity provided a very potential option for the development of X-band in vivo dosimetry.

The effect of dose and water treatment on EPR signals in irradiated fingernails.

Fast and precise retrospective dosimetry is crucial in making decisions about medical procedures and safety measures in radiation accidents. Electron paramagnetic resonance (EPR) spectroscopy has a potential as one of available biodosimetry methods for use in victims of such incidents. In this study, authors present the findings on EPR dosimetry in fingernails. Authors describe changes of EPR signals in unirradiated and irradiated nails in time after cutting and the effect of water on the mechanically induced and radiation-induced EPR signals measured ex vivo in the fingernails. The effect of dose on amplitude of the EPR signal was measured in nails that were soaked for 10 min in water after their irradiation. The obtained dose-response curves, which reflect changes in concentration of the radiation-induced RIS5 radicals, reach their maximum for doses of 40-60 Gy.

Identification of gamma-irradiated fruit juices by EPR spectroscopy

The results of electron paramagnetic resonance (EPR) study on commercially available juices from various fruits and different fruit contents: 25%, 40%, 50%, and 100%, homemade juices, nectars and concentrated fruit syrups, before and after gamma-irradiation are reported. In order to remove water from non- and irradiated samples all juices and nectars were filtered; the solid residue was washed with alcohol and dried at room temperature. Only concentrated fruit syrups were dried for 60min at 40°C in a standard laboratory oven. All samples under study show a singlet EPR line with g=2.0025 before irradiation with exception of concentrated fruit syrups, which are EPR silent. Irradiation of juice samples gives rise to complex EPR spectra which gradually transferred to “cellulose-like” EPR spectrum from 25% to 100% fruit content. Concentrated fruit syrups show typical “sugar-like“ spectra due to added saccharides. All EPR spectra are characteristic and can prove radiation treatment. The fading kinetics of radiation-induced EPR signals were studied for a period of 60 days after irradiation.

In vivo EPR tooth dosimetry for triage after a radiation event involving large populations.

The management of radiation injuries following a catastrophic event where large numbers of people may have been exposed to life-threatening doses of ionizing radiation will rely critically on the availability and use of suitable biodosimetry methods. In vivo electron paramagnetic resonance (EPR) tooth dosimetry has a number of valuable and unique characteristics and capabilities that may help enable effective triage. We have produced a prototype of a deployable EPR tooth dosimeter and tested it in several in vitro and in vivo studies to characterize the performance and utility at the state of the art. This report focuses on recent advances in the technology, which strengthen the evidence that in vivo EPR tooth dosimetry can provide practical, accurate, and rapid measurements in the context of its intended use to help triage victims in the event of an improvised nuclear device. These advances provide evidence that the signal is stable, accurate to within 0.5 Gy, and can be successfully carried out in vivo. The stability over time of the radiation-induced EPR signal from whole teeth was measured to confirm its long-term stability and better characterize signal behavior in the hours following irradiation. Dosimetry measurements were taken for five pairs of natural human upper central incisors mounted within a simple anatomic mouth model that demonstrates the ability to achieve 0.5 Gy standard error of inverse dose prediction. An assessment of the use of intact upper incisors for dose estimation and screening was performed with volunteer subjects who have not been exposed to significant levels of ionizing radiation and patients who have undergone total body irradiation as part of bone marrow transplant procedures. Based on these and previous evaluations of the performance and use of the in vivo tooth dosimetry system, it is concluded that this system could be a very valuable resource to aid in the management of a massive radiological event.

EPR and OSL emergency dosimetry with teeth: A direct comparison of two techniques

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 CO3- radicals. OSL sensitivity can be enhanced if more teeth from the same individual will be used for the signal accumulation.