Electron Paramagnetic Resonance Dosimetry Research Articles

Retrospective EPR dosimetry in glass and tooth enamel – The methodology and results of MUG group in RENEB 2021 inter-laboratory comparison

Electron Paramagnetic Resonance (EPR) is recognized method in retrospective dosimetry, based on detection of stable paramagnetic centres induced by radiation in biological materials, like enamel, bones, nails, or artificial materials, like glasses and other. EPR dosimetry in glass and enamel were included, in addition to several biological dosimetry tests, in the recent intercomparison project RENEB ILC 2021 as one of the physical dosimetry methods potentially applicable for dose assessment in radiation accidents. EPR group from Medical University of Gdansk (MUG) was one of participants in this intercomparison. The participants reconstructed doses in three blinded samples of watch glass, Gorilla Glass from phone screens and in enamel irradiated with 0 Gy, 1.2 Gy and 3.5 Gy (these doses were revealed after reporting the final results by all participants). For reconstruction of doses in the glass samples the respective calibration samples were provided by organizers of the ILC project. For dosimetry in enamel the participants used their own calibration data. The doses reconstructed by us in the blinded samples (in terms of kerma in air) were: in watch glass: −0.05 Gy, 1.03 Gy, 3.16 Gy, in Gorilla Glass: −0.03 Gy, 1.20 Gy, 3.44 Gy, in enamel: 0.1 Gy, 1.3 Gy, 3.1 Gy. The differences between the reconstructed and the nominal doses were small and the accuracy was sufficient for triage of irradiated people at the level of 1–2 Gy. The small sample mass of the enamel, suitable rather to Q-band EPR dosimetry and potentially available without whole tooth extraction, allowed to obtain satisfactory accuracy of EPR dosimetry also in the X-band measurements.

Towards liquid EPR dosimetry using nitroxides in aqueous solution.

Objective. Water-equivalent dosimeters are desirable for dosimetry in radiotherapy. The present work investigates basic characteristics of novel aqueous detector materials and presents a signal loss approach for electron paramagnetic resonance (EPR) dosimetry.Approach. The proposed principle is based on the radiation dose dependent annihilation of EPR active nitroxides (NO·) in aqueous solutions. Stable nitroxide radicals (3-Maleimido-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (MmP), 3-Carbamoyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (CmP)) in aqueous solutions containing dimethyl sulfoxide (DMSO) as an additive were filled in glass capillaries for irradiation and EPR readout. Radiation doses ranging from 1 to 64 Gy were applied with a clinical 6 MV flattening filter free photon beam. EPR readout was then performed with a X-band benchtop spectrometer. The dose response, temporal stability and reproducibility of the samples' EPR signal amplitudes as well as the influence of the nitroxide concentration between 10 and 160μM on the absolute signal loss were investigated using MmP. CmP was used to examine the dependence of the dose response on DMSO concentration between 0 and 10 vol%. An indirect effect model was fitted to the experimental data assuming irradiation induced radical reactions as the underlying mechanism.Main results. For an initial MmP concentration of 20μM, absolute EPR signal loss is linear up to a dose of 16 Gy with a yield G(-NO·) of approximately 0.4μmol J-1. Within five weeks upon sample irradiation to doses between 0 and 32 Gy relative EPR signal fluctuations were on average (126 readouts) below 1% (1σ). For c(MmP) ≥ 20μM, absolute signal loss is only weakly dependent on c(MmP), whereas it increases strongly with increasing c(DMSO) in the range 0-5 vol%. An indirect effect model is applicable to describe the reaction mechanism resulting in the observed dose response curve.Significance. Liquids consisting of nitroxides in aqueous solution and small amounts of DMSO (2 vol%) show promising basic characteristics for application as water-equivalent EPR dosimeter materials in radiotherapy. The EPR signal loss is based on an indirect effect mediated by diffusing radicals originating from the radiolysis of the water/DMSO mixture.

Adapting a practical EPR dosimetry protocol to measure output factors in small fields with alanine.

Modern radiotherapy techniques often deliver small radiation fields. In this work, a practical Electron Paramagnetic Resonance (EPR) dosimetry protocol is adapted and applied to measure output factors (OF) in small fields of a 6 MV radiotherapy system. Correction factors and uncertainties are presented and OFs are compared to the values obtained by following TRS-483 using an ionization chamber (IC). Irradiations were performed at 10cm depth inside a water phantom positioned at 90cm source to surface distance with a 6 MV flattening filter free photon beam of a Halcyon radiotherapy system. OFs for different nominal field sizes (1×1, 2×2, 3×3, 4×4, normalized to 10×10 cm2 ) were determined with a PinPoint 3D (PTW 31022) IC following TRS-483 as well as with alanine pellets with a diameter of 4mm and a height of 2.4mm. EPR readout was performed with a benchtop X-band spectrometer. Correction factors due to volume averaging and due to positional uncertainties were derived from 2D film measurements. OFs obtained from both dosimeter types agreed within 0.7% after applying corrections for the volume averaging effect. For the used alanine pellets, volume averaging correction factors of 1.030(2) for the 1×1 cm2 field and <1.002 for the larger field sizes were determined. The correction factor for positional uncertainties of 1mm was in the order of 1.018 for the 1×1 cm2 field. Combined relative standard uncertainties uc for the OFs resulting from alanine measurements were estimated to be below 1.5% for all field sizes. For IC measurements, uc was estimated to be below 1.0%. A practical EPR dosimetry protocol is adaptable for precisely measuring OFs in small fields down to 1×1cm2 . It is recommended to consider the effect of positional uncertainties for field sizes <2×2cm2 .

Electron paramagnetic resonance spectroscopy for the detection of radiation exposure in dreissenid mussels.

Electron paramagnetic resonance (EPR) spectroscopy, established for radiation measurements in calcified tissues, was identified as a methodology that merits investigation for the purpose of environmental radiation measurements using dreissenid mussels from the Great Lakes. With the refinement of sample preparation and measurement protocols, a linear relationship of dose with the peak-to-peak height of the radiation-induced signal at g = 2.0034 was established. A dedicated analysis algorithm was developed to process batches of samples, eliminating the need for manual peak-to-peak height measurement. Varying background EPR signals were identified in different sampling groups, with samples gathered in winter having a markedly lower background signal. Through optimisation of spectrum acquisition normalisation methods, it was possible to resolve doses as low as 0.2 Gy. This work provides further validation that EPR dosimetry of shelled species has the potential to contribute to better characterisation of absorbed doses in aquatic environments.

Second intercomparison on electron paramagnetic resonance (EPR) retrospective dosimetry in Korea using hydroxyapatite

The Korea retrospective dosimetry (KREDOS)–electron paramagnetic resonance (EPR) group undertook an intercomparison investigation utilizing hydroxyapatite. This analysis involved four institutions: the Korea Institute of Radiological and Medical Sciences, Dongnam Institute of Radiological and Medical Sciences, Korean Association for Radiation Application, and Radiation Health Institute of Korea Hydro & Nuclear Power. Following the irradiation of the hydroxyapatite sample, the recorded build-up was analyzed. To validate the reliability of the EPR dosimetry findings and enhance its operational performance, a hydroxyapatite dose–response curve was plotted and dosimetry was performed for a blind sample. The proficiency of each laboratory was assessed by employing an interlaboratory comparison methodology. This involved a comparative analysis of the measurement results by calculating the relative bias, z-score, and En value. The results submitted by the participating laboratories demonstrated satisfactory ratings for doses of 1.006, 3.999, and 6.993 Gy. Following the second intercomparison, efforts to optimize their hydroxyapatite-EPR dosimetry systems are underway in the participating laboratories. The current assessment of hydroxyapatite dose yielded the foundational data required to establish the parameters of dental dosimetry. In future, the third intercomparison experiment will be conducted for exploring other materials.

Electron Paramagnetic Resonance Measurements of Lifetime Doses in Teeth of Durham Region Residents, Ontario.

The Canadian Nuclear Safety Commission (CNSC) and Ontario Power Generation (OPG) determined the total dose contribution of nuclear power plants in Durham Region populations by analyzing environmental samples from the surrounding areas of both nuclear generating stations (Pickering and Darlington). However, the total doses from the various sources were unknown in Durham Region populations, Ontario. Electron paramagnetic resonance (EPR) dosimetry with tooth enamel has been successfully established as an effective tool for gamma dose assessment for chronic and acute exposures in individuals, groups, or populations to reconstruct the absorbed dose down to 30 mGy. This study collected the extracted teeth from people of different ages in Durham Region, Ontario, and analyzed them using the x-band continuous wave (CW) EPR spectrometer. The total dose rate from the natural and anthropogenic sources was 1.9721 mSv y-1. The anthropogenic dose rate from the various sources was 0.6341 mSv y-1, about 47.39% of the natural background dose (1.338 mSv y-1) in Durham Region, Ontario. The combined anthropogenic doses from these sources were lower than the local background dose in Durham Region and lower than the regulatory annual effective dose limit of 1 mSv y-1 in Canada. Based on these data, this study concluded that the anthropogenic dose contribution was lower than the regulatory limit to the local populations.

Fish otoliths as biological dosimeter: internal dose calculation.

Otoliths are organs used by fish for hearing and keeping balance. They consist of biogenic crystals of hydroxyapatite and do not contain any living cells. Upon exposure to ionizing radiation, otolith hydroxyapatite accumulates radiation-induced stable CO2- radicals whose amount is proportional to absorbed dose. In electron paramagnetic resonance (EPR) dosimetry, carbonate ions are registered and, hence, the total accumulated dose in the fish otolith can be quantified. Therefore, otoliths can be used as individual fish dosimeters to support radiobiological and radioecological studies. An important aspect of otolith-based EPR dosimetry on fish from contaminated water bodies is the potential presence of bone-seeking 90Sr. Consequently, cumulative absorbed doses measured with EPR in otoliths may reflect the superposition of internal exposure to 90Sr/90Y and external exposure due to radionuclides circulating in soft tissue of the fish as well as due to environmental contamination. The objective of the present study was to develop a method that allows for an assessment of the contribution of 90Sr to the total dose in otolith. The method has been tested using otoliths from seven fish taken from reservoirs located in the Southern Urals contaminated with radionuclides including 90Sr. It has been shown that dose to otoliths is largely determined by 90Sr in the hydroxyapatite. The internal dose component can be calculated using activity concentration-to-dose conversion factors, which vary slightly in the range of 2.0-2.8 × 10-3Gyyear-1 perBqg-1 depending on fish species and age. Internal doses to fish from water bodies with different levels of 90Sr contamination were calculated in the range from 2mGy to ~ 200Gy. External dose contribution was derived for two fish only to be about 100 and 40Gy. It is concluded that EPR dosimetry on fish otoliths is a promising tool when external exposure prevails or is comparable to internal exposure due to 90Sr.

Electron Spin Resonance Dosimetry Studies of Irradiated Sulfite Salts.

The study of new materials for radiation dosimetry is important to improve the present state of the art and to help in cases of accidents for retrospective dosimetry. Sulfites are compounds that contain a sulfur ion, widely used in the food industry. Due to the significant application of these compounds, sulfites are interesting candidates for accidental dosimetry, as fortuitous radiation detectors. The presence of the SO3− anion enables its detection by electron spin resonance (ESR) spectroscopy. The Dose–Response behavior, signal stability and other spectral features were investigated for sodium sulfite, sodium bisulfite, sodium metabisulfite and potassium metabisulfite, all in crystalline forms. The ESR spectrum of salts presented stability and proportional response with dose, presenting potential for dosimetry applications.

Methodology and Instrumentation for Electron Paramagnetic Resonance Dosimetry With Tooth Enamel

Abstract When tooth enamel is exposed to ionizing radiation, it generates a dose-dependent concentration of free radical centers (i.e., unpaired electrons). The concentration of these free radical centers is identified and quantified using electron paramagnetic resonance (EPR) spectroscopy in the form of an EPR spectrum. The intensity of the spectrum is proportional to the absorbed dose. Four international intercomparisons have already demonstrated that the EPR tooth enamel dosimetric technique is reliable for retrospective dose assessment in acute and chronic exposure scenarios. Additionally, EPR dosimetry is regarded same as a gold standard for reconstructing the total lifetime dose of individuals using tooth enamel. The accuracy and reproducibility of EPR dose reconstruction depend on the sample preparation, spectrum acquisition, and EPR spectra analysis techniques. So, this paper reviews some of the widely applied and accepted laboratory protocols or methodologies for the EPR dosimetric methods. The minimum detection limit in tooth enamel using this technique was 30 mGy. So, this review aims to share these protocols so that it would be easy to reconstruct the accident doses or chronic exposures with reliable accuracy and precision. Different bands (e.g., L, X, Q, etc.) continuous wave (CW) EPR spectrometers have been used in many historical and accident dose reconstructions; however, due to the availability, moderate price, and not being much influenced by the small amount of moisture in a sample, the X-band has been widely used. A well-developed methodology, a highly sensitive EPR spectrometer, and a well-trained operator are vital for the reliable measurements of absorbed low doses in EPR dosimetry with tooth enamel.

Applicability of the Dose Spiking Electron Paramagnetic Resonance Method for the Quantitative Measurements of Low Doses in Alanine Dosimetry

Abstract Ionizing radiation generates unpaired electrons or free radical centers in alanine. The electron paramagnetic resonance (EPR) detects, identifies, and quantifies these free radicals, proportional to the absorbed dose. The accurate measurements of low doses using EPR dosimetry with alanine are highly challenging due to (1) the weak EPR dosimetric signal from low dose alanine and measurement errors, (2) the sample anisotropy in crystalline alanine, and (3) the background signals from sample impurities. This study explores the feasibility of using the dose spiking EPR technique to overcome these challenges and decreases the detection limit up to 20 milligray (mGy) in a low dose measurement using EPR. The measurement errors from the sample anisotropy were reduced by rotating the samples relative to the constant magnetic field direction using a goniometer and averaging the resulting EPR spectra. This technique decreased the measurement errors at high doses; however, it was insufficient to decrease the detection limit and increase the measurement accuracy at low doses (&amp;lt;0.5 Gy). As a result, the high measurement accuracy at the high doses (&amp;gt;4 Gy) was exploited to increase the accuracy at the low doses using the dose spiking EPR technique. To this end, the low-dose alanine sample, undetectable and not reliably measurable in the X-band continuous wave (CW) EPR spectrometer, spikes with a high dose (4 Gy). Then, the total dose was measured and subtracted from a spike dose to get the initial low dose. This technique detected and measured the low doses with reliable accuracy (±10%). As a result, we concluded that this method has great potential to solve the low dose measurement problems in alanine dosimetry.

Electron spin resonance (ESR) study on gamma irradiated some modern paper samples

In this work, we use paramagnetic defects induced by gamma radiation in some modern paper samples to determine their main dosimetric properties in the decontamination dose range (0.5–10 kGy) of ancient papers. Electron spin resonance (ESR) spectra of photo paper, cigarette paper, white paper napkin (napkin), cash register receipt, straw paper and white photocopy paper recorded before and after irradiation with gamma rays were reported. Photo paper, cigarette paper and napkin samples displayed the radiation-induced cellulose-like ESR signals well known from the literature on cellulose-containing foods. Cash register receipt, straw paper, and white photocopy paper are another set of samples where different ESR spectra were recorded. The ESR signals of these three paper samples were shown to originate from carbonate mineral filler grains. Inorganic mineral fillers are commonly used in paper manufacturing. The dose-response curves associated with the radiation-induced sharp ESR signals originating from the CaCO3 filler of the cash register receipt (g = 2.0027), the straw paper (g = 1.9995), and the white photocopy paper (g = 1.9996) were found to follow a single exponential saturation function. Despite the observed decreases with time in the signal intensities of cash register receipt and white photocopy paper, detectable ESR signals were obtained even 100 days after irradiation for them and straw paper. The radiation-induced free radicals responsible for the ESR spectrum of straw paper were more stable than those of cash register receipt and white photocopy paper. The results indicate that free radicals induced in mineral CaCO3 filler grains incorporated within papers have the potential to be used for application to retrospective ESR dosimetry in the range of 0.5–10 kGy.

Dose Variations Using an X-Ray Cabinet to Establish in vitro Dose-Response Curves for Biological Dosimetry Assays.

In biological dosimetry, dose-response curves are essential for reliable retrospective dose estimation of individual exposure in case of a radiation accident. Therefore, blood samples are irradiated in vitro and evaluated based on the applied assay. Accurate physical dosimetry of the irradiation performance is a critical part of the experimental procedure and is influenced by the experimental setup, especially when X-ray cabinets are used. The aim of this study was to investigate variations and pitfalls associated with the experimental setups used to establish calibration curves in biological dosimetry with X-ray cabinets. In this study, irradiation was performed with an X-ray source (195 kV, 10 mA, 0.5 mm Cu filter, dose rate 0.52 Gy/min, 1st and 2nd half-value layer = 1.01 and 1.76 mm Cu, respectively, average energy 86.9 keV). Blood collection tubes were irradiated with a dose of 1 Gy in vertical or horizontal orientation in the center of the beam area with or without usage of an additional fan heater. To evaluate the influence of the setups, physical dose measurements using thermoluminescence dosimeters, electron paramagnetic resonance dosimetry and ionization chamber as well as biological effects, quantified by dicentric chromosomes and micronuclei, were compared. This study revealed that the orientation of the sample tubes (vertical vs. horizontal) had a significant effect on the radiation dose with a variation of −41% up to +49% and contributed to a dose gradient of up to 870 mGy inside the vertical tubes due to the size of the sample tubes and the associated differences in the distance to the focal point of the tube. The number of dicentric chromosomes and micronuclei differed by ~30% between both orientations. An additional fan heater had no consistent impact. Therefore, dosimetric monitoring of experimental irradiation setups is mandatory prior to the establishment of calibration curves in biological dosimetry. Careful consideration of the experimental setup in collaboration with physicists is required to ensure traceability and reproducibility of irradiation conditions, to correlate the radiation dose and the number of aberrations correctly and to avoid systematical bias influencing the dose estimation in the frame of biological dosimetry.

STUDY OF DOSIMETRY POSSIBILITIES USING ELECTRON PARAMAGNETIC RESONANCE ON ALANINE FOR ILU-10 ACCELERATOR INP RK

Experimental studying possibilities of the electron paramagnetic resonance (EPR) method application for the dose control using alanine deteectors in the process of technological irradiations with brake radiation at the accelerator ILU-10 INP RK has been carried out. The EPR signal stability and sensitivity of original alanine detectors have been studied, serviceability in standard modes was shown in the range of small doses of brake irradiation (0,005–1 kGy); for dose estimation the calibration on gamma-irrdiation was used. The obtained data confirmed the promise of alanine EPR dosimetry at the ILU-10 accelerator INP RK.

EPR dosimetry in glass: a review.

Electron Paramagnetic Resonance (EPR) spectroscopy enables detection of paramagnetic centers generated in solids by ionising radiation. In the last years, the ubiquity of glass in personal utility items increased significance of fortuities retrospective dosimetry based on EPR in glass parts of mobile phones and watches. Despite of fading of the signals and their susceptibility to light, it enables dosimetry at medical triage level of 1-2Gy. In this article information relevant for assessment of applicability and planning of the EPR dosimetry is presented-particularly at dose levels typical for radiation accidents. Reported data on fading of the radiation-induced spectral components are presented and compared. Effects of light on background spectra and on the dosimetric signals are also presented. It is concluded that when properly accounting for the fading and for the obscuring effects of light, the EPR dosimetry in glasses from mobile phones and watches can be used in dose assessment after radiation accidents.

The Dose Spiking Technique for Measuring Low Doses in Deciduous Teeth Enamel Using EPR Spectroscopy for Retrospective and Accident Dosimetry.

Dose estimation by electron paramagnetic resonance (EPR) has been accomplished using the standard EPR dosimetry technique (ISO protocol 13304-1 for EPR retrospective dosimetry). However, different studies showed that these techniques have high measurement errors in measuring the low doses (10-100 mGy) in enamel. This work proposes a new method to make a dosimetric signal visible and measurable at low doses. The sample was purified using both chemical and mechanical processes. The pure sample mass and position and the EPR acquisition parameters were optimized to enhance the spectrometer's sensitivity for the quantitative low dose measurements. At the same time to reduce errors from the sample and spectrum anisotropy, the total doses (low plus spike) and the spike dose (4 Gy) were measured by rotating 0 to 360 degrees (i.e., 40 degrees at a time) relative to constant magnetic field direction using a goniometer. Subsequently, the spectra were averaged after their g-factor normalization. However, at low doses (<30 mGy), the radiation induced signal (RIS) was obscured by the background signal (BGS). So, the dose spiking technique was used as an alternative method. Ten low-dose deciduous molar tooth enamel (10-100 mGy) samples were spiked to the higher doses by delivering 4 Gy and measured using the X-band continuous wave (CW) EPR (Bruker EMXmicro) spectrometer. The total dose EPR signal was distinctly visible, and the peak-to-peak (P2P) amplitude height was measured. Then, the total dose was subtracted with the spike, often called a reference sample, to determine the initial low doses. The measurement errors using this method were lower than the previous methods. These results demonstrated that this method could be promising for solving low dose measurement problems in EPR dosimetry with deciduous and permanent tooth enamel.

Dose enhancement factor caused by gold nanoparticles: influence of the dosimetric sensitivity and radiation dose assessed by electron spin resonance dosimetry

Gold nanoparticles have been extensively used to increase the sensitivity of radiation dosimeters. In this work, nanocomposites of alanine (Ala), 2-methylalanine (2MA), asparagine (Asn) and monosodium glutamate (MSG) containing gold nanoparticles were prepared. The influence of the mass percentage of gold (0.1% up to 3%), absorbed dose (2 Gy–10 kGy) and the intrinsic sensitivity of these materials on the dose enhancement factor (DEF) were investigated. The prepared nanocomposites were characterized by UV–vis absorption spectroscopy and dynamic light scattering technique. Electron spin resonance spectroscopy was employed to assess the dosimetric response. The results revealed that the gold nanoparticles aggregated in the nanocomposites of MSG and Asn but not in the Ala and 2MA samples. Higher DEFs were observed for materials with lower intrinsic sensitivities (Asn and MSG) and for lower doses of radiation, suggesting that the dosimetric response of the nanocomposite dosimeters is governed by the probability of radical recombination. The higher the radiation dose, gold mass percentage and/or intrinsic sensitivity of the dosimetric material, the higher the production of radiation-induced free-radicals, enhancing the probability of radical recombination and resulting in lower DEFs. These results bring new insights about the use of gold nanoparticles to the construction of more sensitive radiation dosimeters.

Detailed tooth models for ICRP mesh-type reference computational phantoms

For use in electron paramagnetic resonance dosimetry with tooth enamel, in the present study, very detailed mesh-type tooth models composed of 198 individual tooth models (i.e. newborn: 20; 1 year: 28; 5 years: 48; 10 years: 38; 15 years: 32; and adult: 32) were developed for each sex. The developed tooth models were then implanted in the International Commission on Radiological Protection pediatric and adult mesh-type reference computational phantoms and used to calculate tooth enamel doses, by Monte Carlo simulations with Geant4, for external photon exposures in several idealized irradiation geometries. The calculated dose values were then compared to investigate the dependency of the enamel dose on the age and sex of the phantom and the sites of the teeth. The results of the present study generally show that, if the photon energy is low (i.e. <0.1 MeV), the enamel dose is significantly affected by the age and sex of the phantom and also the sites of the teeth used for dose calculation; the differences are frequently greater than a few times or even orders of magnitude. However, with a few exceptions, the enamel dose was hardly affected by these parameters for energies between 0.1 and 3 MeV. For energies >3 MeV, moderate differences were observed (i.e., up to a factor of two), due to the existence of dose build-up in the head of the phantom for high-energy photons. The calculated dose values were also compared with those of the previous studies where voxel and mathematical models were used to calculate the enamel doses. The results again show significant differences at low energies, e.g., up to ∼3500 times at 0.015 MeV, which are mainly due to the differences in the level of tooth-modeling detailedness.

Suitability of superficial electron paramagnetic resonance dosimetry for in vivo measurement and verification of cumulative total doses during IMRT: A proof of principle

PurposeThe present study investigates superficial in vivo dosimetry (IVD) by means of a previously proposed electron paramagnetic resonance (EPR) dosimetry system aiming at measuring and verifying total doses delivered by complex radiotherapy treatments. In view of novel regulatory requirements in Germany, differences between measured and planned total doses to the EPR dosimeters are analyzed and compared to reporting thresholds for significant occurrences. MethodsEPR dosimeters, each consisting of one lithium formate monohydrate (LFM) and one polycrystalline l-alanine (ALA) pellet, were attached to the surface of an anthropomorphic head phantom. Three head and neck treatments with total target doses ranging from 30 to 64Gy were fully delivered to the phantom by helical tomotherapy. During each treatment, eight EPR dosimeters were placed at distinct spots: (i) within or next to the planning target volume (PTV), (ii) near to organs at risk including the parotids and the lenses, (iii) at the thyroid lying out-of-field. EPR read out was always performed after all fractions were delivered. EPR results were compared to thermoluminescence dosimeter (TLD) measurements and to the planned total doses derived from the treatment planning system (TPS). Planned total doses to the EPR dosimeters ranged from about 2 to 64Gy. ResultsBy taking uncertainties into account, the measured and planned doses were in good agreement. Exceptions occurred mainly at the thyroid (out-of-field) and lenses (extreme sparing). The maximum total dose difference between EPR results and corresponding planned doses was 1.3Gy occurring at the lenses. Remarkably, each LFM and ALA pellet placed within or next to the PTV provided dose values that were within ±4% of the planned dose. Dose deviations from planned dose values were comparable for EPR and TLD measurements. ConclusionThe results of this proof of principle study suggests that superficial EPR-IVD is applicable in a wide dose range and in various irradiation conditions – being a valuable tool for monitoring cumulative total doses delivered by complex IMRT treatments. EPR-IVD in combination with helical tomotherapy is suitable to reliably detect local dose deviations at superficial dosimeter spots in the order of current national reporting thresholds for significant occurrences (i.e. 10%/4Gy).

Эмаль зубов человека как тест для оценки последствий радиационного загрязнения среды обитания

Technogenic radioactive contamination of the external environment has a radiation effect on flora and fauna, including humans. Radionuclides entering the biosphere become a source of external, contact and internal radiation in a variety of combinations. The electron paramagnetic resonance dosimetry is a technique that allows a retrospective assessment of an individual dose to be made. Purpose of the study. Assessment of the long-term consequences of the impact of radiation contamination of the territories adjacent to the landfill on the health of the population using biotesting methods. Material and methods. A reconnaissance and radioecological survey of environmental objects was carried out using analytical methods, which made it possible to determine the quantitative content of toxic components, priority pollutants and radioactive isotopes. The objects of study are the Bokeyordinsky and Zhanibeksky districts of the West Kazakhstan region (WKR), adjacent to the Kapustin Yar test site. The values of the volumetric activity of natural and technogenic radionuclides in soil samples, drinking water and biosubstrates (teeth, samples of human peripheral blood) from settlements of the surveyed areas were studied. Results and discussion. Measurements of gamma radiation showed that along the perimeter of the polygon and in nearby settlements, the radiation level is in the range of 0.06–0.14 µSv/h. An insignificant excess of the level of radioactivity persists near the fall of missiles in the Bokeyordin region. The indicators of the general morbidity of the adult population of maternal and child mortality in the indicated regions were also studied. It was found in the inhabitants of the Bokeyordinsky district with a reliability of p = 95% in the studied teeth, betta and gamma activity is less than the natural level and indicates that the content of radionuclides in the studied teeth is not higher than their natural level. A noticeable excess of the activity of radionuclides K40 and Ra226 is noted among residents of Zhanibeksky district. Conclusions. In the surveyed districts of the region, there is an unsatisfactory state of health of children and women, especially of fertile age, a high level of primary morbidity, maternal mortality; there is a tendency for the growth of eco-dependent human diseases (previously unrecorded forms of oncological diseases, congenital malformations, diseases of the hematopoietic and nervous systems). The conclusions can be used to implement measures to improve the ecological state of the region and the health of the population. Keywords: radionuclides, radioactivity, biosubstrate, polygon, ecology, eco-dependent diseases.

A practical EPR dosimetry system for routine use in radiotherapy: uncertainty analysis of lithium formate dosimeters at the therapeutic dose level

In electron paramagnetic resonance (EPR) dosimetry, solid dosimeter materials such as alanine (AL) or, more recently, lithium formate monohydrate (LFM) are typically used. These materials offer high potential for applications in radiotherapy based on their favorable dosimetric properties. Nevertheless, EPR dosimetry is not widespread in the clinics. This work presents an uncertainty analysis of EPR dosimetry in the dose range from 1 to 70 Gy using a compact spectrometer and applying a practical procedure being suitable for routine use in radiotherapy. The performances of self-pressed LFM pellets and commercial AL pellets are compared side by side.All pellets had a diameter of 4 mm and a height of 2 mm (AL) or 4 mm (LFM). The mean pellet mass was 35.81 mg and 73.81 mg for AL and LFM, respectively. Before irradiation, the pellets were stored for at least 8 weeks at 34 ± 2% relative humidity. For irradiation, the pellets were put inside an airtight capsule. In total, 25 pellets per material were examined. The pellets were irradiated at a temperature of 25 ± 2.5 (2σ) °C to doses of either 1, 5, 20, 50 or 70 Gy (five pellets per dose value and material) by a clinical 6 MV photon beam. Measurement uncertainties were obtained from five independent readouts per pellet within five weeks following irradiation using a benchtop EPR spectrometer. The measurement time of a single readout was restricted to 10 min per pellet. Dose values were derived from EPR signal amplitudes using a specifically developed spectral fitting procedure. Signal fading characteristics were analyzed and taken into account during evaluation.The relative dose uncertainties (1σ) for a single readout at doses ≥ 5 Gy are below 2.8% (AL) and 1.1% (LFM) but increase to 12.3% (AL) and 2.6% (LFM) at 1 Gy. By averaging five independent readouts, the uncertainties at 1 Gy decrease to 2.6% (AL) and 0.8% (LFM).In terms of dose uncertainty, the LFM pellets are superior to the commercial AL pellets owing to their narrower EPR spectrum and approximately doubled mass resulting in higher EPR signal intensities. In case of the LFM pellets, the EPR dosimetry system shows a high level of precision (< 3%) down to 1 Gy being preferable for applications in radiotherapy. The uncertainties can be further decreased by averaging multiple dose values from independent readouts.