Gamma Dose Research Articles

On the response of the CR-39 NTD to low doses of gamma rays using optical and photoluminescence spectroscopy

In this work, the response of the CR-39 nuclear track detector (NTD) exposed to different low doses of gamma rays was investigated using UV–Vis and photoluminescence spectroscopy. Five NTDs of CR-39 were irradiated with low gamma-ray doses ranging from 10 to 120 kGy using a60Co source. The dose of gamma rays correlates with red shift in the absorption spectra of a gamma-irradiated CR-39 detector. As the gamma dose increases, the indirect and direct energy band gaps, as well as Urbach energy, decrease gradually. However, the decrease in the indirect optical band gap is greater than the decrease in the direct band gap. The observed spectra of the CR-39 detector after being irradiated with different doses of γ-rays showed an acceptable variation in photoluminescence (PL) emission spectra generated by a well-defined excitation wavelength of 290 nm. Starting at 45 kGy dose, the integrated area of the photoluminescence peak increases and tends to saturate, whereas the photoluminescence peak height is linearly correlated with the gamma dose with high sensitivity, which is 53.1 ± 6.3 CPS. kGy−1. According to the current findings, photoluminescence (PL) spectroscopy has a greater sensitivity than UV–Vis spectroscopy for measuring the response of the CR-39 detector to gamma rays in the dose range of 10–120 kGy. The results reflected a potential possibility of using the CR-39 detector in dosimetric applications of low gamma ray doses through the high resolution achieved by photoluminescence (PL) and UV–Vis spectroscopy.

Identification of gamma irradiated polycarbonate-polybutylene terephthalate stiff polymer blend products using HS-GC/MS, FTIR and UV/Vis spectroscopy

In this study, the fragmentation products of Makro-blend stiff polymer due to gamma exposure were identified using Head space (HS), Gas Chromatography, and Mass Spectrometry (HS-GC/MS) techniques and Fourier Transform Infra-Red (FTIR) spectroscopy. As well the electronic transitions due to gamma exposure were examined using UV/Vis spectroscopy. For the un-irradiated and 10 kGy irradiated samples, one product was detected by (HS-GC/MS) method with a clear peak of Dimethoxyethane (MW = 90), which has a peak area percentage of 98.58% and 97.13%, respectively. With increasing gamma doses the number of identified components was increased. At 1200 kGy, ten components were detected: Biethylene (MW = 54), Dimethoxyethane (MW = 90), 1,1-Dimethoxy-2-propanone (MW = 118), 1,1-Dimethoxy-2-propanol (MW = 120), 1,1-Dimethoxycyclopentane (MW = 130), 1,1-Dimethoxyheptane (MW = 160), 1,1-Dimethoxyoctane (MW = 174), Dimethyl terephthalate (MW = 194), 4-(Diethoxymethyl) benzaldehyde (MW = 208), and Terephthalate dihexyl (MW = 334), which have peaks area percentages of 4.22, 2.98, 25.84, 2.2, 10.65, 38.86, 1.57, 5.91, 1.22, and 6.48, respectively. The recorded mass spectrum of each component confirms the molecular ion peak. The FTIR measurements demonstrate the decrease in the detected band intensities following gamma radiation. Accordingly, a chain scission occurs, which causes the carbonate bond to scission, resulting in the creation of a hydroxyl group and the (–H) abstraction from the backbone of the irradiation blend samples. The absorbance edge of the gamma-exposed samples shifted towards a higher wavelength. This pattern shows that the band gap energy is declining. The use of FTIR and HS-GC/MS in mass spectrometry analysis will be useful tools for examining radiation-induced polymeric fragments and advancing our understanding of the process underlying the creation of these fragments in polymers.

Estimate of the Deterministic Neutron RBE for Radiation-induced Pseudo-Pelger Huët Cell Formation.

Using archival peripheral blood slides from radiation accident patients, we have recently described the pseudo-Pelger Huët anomaly (PPHA) in neutrophils as a new radiation-induced biomarker, useful for dosimetry not only immediately after a radiation incident but also potentially helpful as a tool in retrospective dosimetry. In conjunction with the Radiation Accident Registry at the Radiation Emergency Assistance Center/Training Site (REAC/TS), the frequency of PPHA cells has been compared from selected patients in the Y-12 criticality accident in Oak Ridge, TN, in 1958 and from the patient in the 1971 60Co accident at the USAEC Comparative Animal Research Laboratory (CARL), also in Oak Ridge. Patients A, C, and D in the Y-12 accident are described as having an average dose of 2.53 ± 0.14 Gy gamma + 0.90 ± 0.05 Gy neutron, while the patient in the CARL event had 2.6 Gy gamma dose from event reconstruction. Since the average gamma energies are almost identical in these two cohorts, it is possible to estimate the deterministic neutron relative biological effectiveness (RBEd) for PPHA formation in a criticality event. The neutron RBEd calculated in this way is an average value over the neutron fission energy spectrum and is found to be 3.4 ± 0.6, in good agreement with the currently recommended value of 3 for acute neutron dose to red marrow.

Structural and functional characterization of gamma-irradiation-enhanced nanocomposites for colorectal cancer therapy

The purpose of this research was to develop and evaluate a nanocomposite material for the treatment of colorectal cancer. The nanocomposite consisted of manganese-doped silver nanoparticles coated with silica (Si-Ag: Mn3O4). The nanocomposite was synthesized by co-precipitating silver and manganese oxide, followed by a silica coating using the Stöber method. Extensive characterization was conducted to assess the morphological, optical, and stability properties. The key findings of this study are the Si-Ag: Mn3O4 nanocomposite exhibited unexpected and potent cytotoxicity against colorectal cancer cells, exceeding the effects of the positive control, cisplatin. The silica coating increased the Ag: Mn ratio, further enhancing the efficacy of the nanocomposite in cancer treatment; the nanocomposite maintained cellular mobility without agglomeration or sedimentation, indicating its potential for targeted tumor destruction; and gamma irradiation of the nanocomposite further increased its cytotoxic effects on colorectal cancer cells. In conclusion, the unique combination of silver, manganese oxide, and silica in this nanocomposite framework shows great promise for advanced applications in selective cancer therapy. The nanocomposite demonstrated significant cytotoxicity against HT-29 colorectal cancer cells, particularly at a gamma dose of 5.256 kGy. The results of this study open new perspectives in biological research, cancer treatment, and nanomedicine.

Analyzing point defect polarization in tungsten and tungsten carbide under high gamma irradiation for radiation shielding applications

In this study, polycrystalline tungsten and tungsten carbide samples were irradiated with gamma rays at energies of 1.17 MeV and 1.33 MeV, respectively. The irradiation was performed using an “MRX-γ-25 M” radiation camera with an activity of approximately 6.54 Gy/s. Doppler positron spectroscopy (DPS) and positron lifetime spectroscopy (PALS) were utilized to investigate the mechanisms of defect formation in the polycrystalline structure of tungsten samples at different doses of gamma irradiation. In the initial tungsten sample, a significant number of free monovacancy (1 V) clusters were present. An increase in the positron lifetime component τ1 was observed with increasing gamma irradiation, accompanied by a decrease in its intensity. The τ2 value (218 ± 2 ps) suggests the presence of divacancies with a considerable intensity (∼20%). As the gamma dose accumulated, a dynamic evolution of structural defects was evident. The tungsten carbide (WC) samples displayed greater plasticity in response to increasing gamma irradiation doses. Changes in the void volume ratio within the samples were recorded as the gamma dose increased, and movement of these voids towards the surface was observed. Additionally, the operational limits of gamma-irradiated tungsten were assessed, determining a functional threshold of up to 3.378 MGy. This study provides valuable insights into the defect dynamics and structural changes in tungsten and tungsten carbide under gamma irradiation, contributing to the understanding of their behavior in radiation environments.

Synergistic effects of chitosan and gamma irradiation on enhanced fungal growth inhibition and biodegradability of natural rubber latex film

Developing novel formulations and processes to improve the fungal growth inhibition and biodegradability of NR products has become a major challenge for the scientific community, given the health risks associated with fungi in natural rubber (NR) products and the environmental concerns regarding NR waste. Consequently, this study comprehensively investigated the synergistic effects of chitosan and gamma irradiation on enhancing fungal growth inhibition and biodegradability in natural rubber latex (NRL) films. The research involved incorporating varying chitosan contents (0, 3, 6, or 9 phr) into NRL composites and exposing them to different gamma doses (0, 5, 10, or 15 kGy). The results showed that increasing the chitosan content and the gamma dose improved the ability of the NRL samples to inhibit fungal growth on their surfaces. This was evidenced by the absence of fungal colonies after 7 days of incubation on potato dextrose agar (PDA) plates for NRL samples irradiated at 5–15 kGy with 9 phr of chitosan. This determination was based on isolating fungi from the film surfaces, followed by serial dilution and a viable plate count. The biodegradability tests also revealed that the NRL films irradiated at 15 kGy with 9 phr of chitosan had the highest weight loss, reaching as high as 10.42 ± 0.62 % after soil burial for 8 weeks. However, the results indicated that gamma irradiation on the pristine NRL and chitosan/NRL films did not substantially alter the thermal stabilities, density, morphology, and functional groups of the samples. Lastly, by comparing the tensile properties of all the NRL films to the ASTM D3578-01a standard for examination gloves, the optimum conditions for the NRL films were 5 kGy of gamma irradiation with 9 phr of chitosan. This combination resulted in gloves with sufficient tensile strength and complete fungal growth inhibition.

Radiological assessment of radon in groundwater of the northernmost Kashmir Basin, northwestern Himalaya.

This study investigates the radon concentration in groundwater in Kupwara, the northernmost district of the Kashmir valley. It further assesses the annual effective dose experienced by the district's diverse population-infants, children, and adults-attributable to both inhalation of airborne radon released from drinking water and direct ingestion. In addition to this, the calculation of gamma dose rate is also carried out at each of the sampling site of radon. A portable radon-thoron monitor and a portable gamma radiation detector were respectively employed to estimate the activity concentration of radon in water samples and to measure the gamma dose rate. The radon concentration was found to exhibit variability from a minimum of 2.9BqL-1 to a maximum of 197.2BqL-1, with a mean of 26.3 BqL-1 and a standard deviation of 23.3BqL-1. From a total of 85 samples, 10.6% of the samples had radon activity concentrations exceeding the permissible limits of 40BqL-1 set by the United Nations Scientific Committee on Effects of Atomic Radiations as reported by UNSCEAR (Sources and effects of ionizing radiation, 2008) and only 1.2% of the samples have radon activity concentration exceeding the permissible limits of 100BqL-1 set by the World Health Organization as reported by WHO (WHO guidelines for drinking-water quality, World Health Organization, Geneva, 2008). The mean of the annual effective dose due to inhalation for all age groups as well as the annual ingestion dose for infants and children, surpasses the World Health Organization's limit of 100μSvy-1 as reported by WHO (WHO guidelines for drinking-water quality, World Health Organization, Geneva, 2008). The observed gamma radiation dose rate in the vicinity of groundwater radon sites ranged from a minimum of 138nSvh-1 to a maximum of 250nSvh-1. The data indicated no significant correlation between the dose rate of gamma radiation and the radon levels in the groundwater. Radon concentration of potable water in the study area presents a non-negligible exposure pathway for residents. Therefore, the judicious application of established radon mitigation techniques is pivotal to minimize public health vulnerabilities.

Effect of gamma irradiation on the linear and non-linear optical properties of magnetron Co-sputtered CdO–SnO2 thin films

In this work, CdO–SnO2 thin films were deposited using the magnetron Co-sputtering technique. The presence of single-phase Cadmium Stannate (Cd2SnO4) films was verified by X-ray diffraction (XRD) of the as-prepared and irradiated films. The obtained results reveal that crystallite size (D) increasing by gamma irradiation up to 50 kGY and then seem to be not affected by increasing the dose of gamma radiation for the different phases. The resulting dislocation density (δ) and number of crystallites per unit area (N) decreased irradiation of gamma till 50 kGY and seem to be not affected by increasing gamma irradiation. The microstrain εc did not show systematic variations with gamma dose. The refractive index of un-irradiated and irradiated films showed normal dispersion. Aurbach tail Eu, plasma frequency (ωp), and third order susceptibility χ(3) increased by irradiation and seem to be not affected by increasing gamma dose beyond 50 kGY. In contrast, the optical energy gap Eop found to be decrease by irradiation and seem to be not affected by increasing gamma dose beyond 50 kGY. Other optical parameters, including the absorption coefficient, and dispersion energies, are investigated before and after gamma irradiation.

Assessment of the Radioactivity, Metals Content and Mineralogy of Granodiorite from Calabria, Southern Italy: A Case Study.

In this paper, an assessment of the natural radioactivity level, radon exhalation, metal contamination, and mineralogy of a granodiorite rock sample from Stilo, in the Calabria region, Southern Italy is presented as a case study. This rock was employed as a building material in the area under study. The specific activity of 226Ra, 232Th and 40K natural radioisotopes was assessed through high-purity germanium (HPGe) gamma-ray spectrometry. Then, several indices such as the absorbed gamma dose rate (D), the annual effective dose equivalent (AEDE), the activity concentration index (ACI) and the alpha index (Iα), were quantified to determine any potential radiological health risk related to radiation exposure from the analyzed rock. Furthermore, E-PERM electret ion chambers and inductively coupled plasma mass spectrometry (ICP-MS) measurements were carried out to properly quantify the radon exhalation rate and any possible metal pollution, respectively. In particular, to further address metal pollution factors, the geo-accumulation index (Igeo) was calculated to properly address the toxicity levels of the ecosystem originating from the detected metals. Finally, with the aim of successfully discriminating the provenance of such naturally occurring radionuclides, a combined approach involving X-ray diffraction (XRD) and µ-Raman spectroscopy was employed for the identification of the main radioisotope-bearing minerals characterizing the investigated granodiorite. The results achieved in this case study can be taken as the basis for further inquiries into background levels of radioactivity and chemical contamination in natural stone employed as building materials.

Effects of Gamma-Synthesized Chitosan on Morphological, Thermal, Mechanical, and Heavy-Metal Removal Properties in Natural Rubber Foam as Sustainable and Eco-Friendly Heavy Metal Sorbents

The properties of natural rubber foam (NRF) containing gamma-synthesized chitosan (CS) powder were investigated to address the growing demand for efficient methods to treat industrial wastewater contaminated with heavy metals. The CS powder was prepared by irradiating chitin (CT) powder with varying doses of gamma rays (0–100 kGy), followed by deacetylation using 40% sodium hydroxide (NaOH) at 100 °C for 1 h. The resulting CS powders were then mixed with natural rubber latex (NRL) at different contents (0, 3, 6, and 9 parts per hundred parts of rubber by weight; phr) and processed using Dunlop techniques to prepare the foam samples. The experimental findings indicated that the degree of deacetylation (%DD) of the CS powder increased initially with gamma doses up to 60 kGy but then decreased at 80 and 100 kGy. In addition, when the CS powder was incorporated into the NRF samples, there were increases in total surface area, density, compression set, and hardness (shore OO), with increasing gamma doses and CS contents. Furthermore, the determination of heavy metal adsorption properties for Cu, Pb, Zn, and Cd showed that the developed NRF sample exhibited high adsorption capacities. For instance, their removal efficiencies reached 94.9%, 82.5%, 91.4%, and 97.0%, respectively, in NRF containing 9 phr of 60 kGy CS. Notably, all adsorption measurements were determined using 3 cm × 3 cm × 2.5 cm specimens submerged in respective metal solutions, with an initial concentration of 25 mg/L. However, the removal capacity per unit mass of the sample (mg/g) showed less dependencies on CS contents, probably due to the higher density of CS/NRF composites in comparison to pristine NRF, resulting in a smaller volume of the former being submerged in the solution, subsequently suppressing the effects from CS in the adsorption. Lastly, tests on the reusability of the developed NRF indicated that the samples could be reused for up to three cycles, with the Cu removal capacity remaining relatively high (83%) in the sample containing 9 phr of 60 kGy CS. The overall outcomes implied that the developed NRF with the addition of gamma-synthesized CS not only offered effective and eco-friendly heavy metal adsorption capacity to improve public health safety and the environment from industrial wastewater but also promoted greener and safer procedures for the synthesis/modification of similar substances through radiation technologies.

High-performance oxygen terminated synthetic single crystal diamond detector for high gamma dose rate measurement

A high-performance oxygen terminated synthetic single crystal diamond (SCD) detector (4.5 × 4.5 × 0.5 mm3) is presented. The SCD detector exhibits an extremely low leakage current value of 0.29 pA/mm2 with an electric field of 0.3 V/μm. The charge collection spectrum measured with a238Pu source (5.48 MeV α-particles) irradiation shows that the electron and hole charge collection efficiency (CCE) reach as high as 99.1% and 98.9%, with an energy resolution as low as 2.87% and 2.53%, respectively, compared to Si detector. The SCD detector shows excellent radiation hardness and stability under 60Co γ-ray irradiation with a dose rate of 12.737 kGy/h at 150 V bias and is able to withstand a cumulative dose of up to at least 9.3 kGy. The detector output in current mode is linearly related to the dynamic dose rate (0.409 Gy/h-12.737 kGy/h). Similarly, the counting rate of the detector in counting mode exhibits a strong linear variation within the range of 2.6 mGy/h-1269.36 Gy/h. Our results fully indicate that our fabricated SCD detector can be potentially applied to harsh γ irradiation scenarios, which is of guiding significance on real-time dose monitoring.

Monitoring of terrestrial gamma dose rate from the Kumaun Himalayan region of the Bageshwar district in Uttarakhand, India.

The present study is carried out in 42 sampling sites for the measurement of background gamma dose rate in six tehsils of the Bageshwar district that comes under the Kumaun Himalaya, Uttarakhand. The annual effective dose in the pre-monsoon and post-monsoon seasons was estimated from the measured values of the Gamma dose rate. It is found that the minimum and maximum values ranged between 0.01-0.39mSv per y (Arithmetic Mean=0.19mSv per y) in the pre-monsoon and 0.11-0.42mSv per y (Arithmetic Mean=0.20mSv per y) in the post-monsoon season of the year. The finding of the present study shows that the annual effective dose equivalent is higher than the worldwide average value recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation.

Technologies for retrospective radiation dosimetry.

Radiation dosimetry is an important task for assessing the biological damages created in human being due to ionising radiation exposure. Ionising radiation being invisible and beyond the perception of human natural sensors, the dosimetry equipments/systems are the utmost requirement for its measurement. Retrospective measurement of radiation doses is a challenging task as conventional radiation dosemeters are not available at the exposure site. The material/s in close proximity of exposed individual or individuals' biological samples may be used as retrospective radiation sensor for dosimetry purpose. Environment materials such as sand, bricks, ceramics, sand stones, quartz, feldspar, glasses and electronic chips have been utilised using TL (Thermoluminescence) techniques for retrospective gamma dose (min 10cGy) measurement. Electron Spin Resonance techniques have been employed to human biological samples such as tooth enamel, bones, nails, hair, etc. and reported for dosimetry for ~20cGymin dose measurement. Some commercial glasses have been found sensitive enough to measure the minimum gamma doses of the order of 100cGy using TL techniques. For internal retrospective dosimetry, the radioactivity contamination assessment in food items, water, other edible product and ambient air are the prerequisites. The radioactivity concentration vis-à-vis their consumption rate may help in controlling the internal contamination and estimation of dose absorption in human body. Defence Laboratory, Jodhpur has been working extensively on the dosimetry techniques for external dose measurement using environmental material and developed portable contamination monitoring systems for food and water radioactivity measurement in the range of 50Bq kg-1 to 1000kBq kg-1 in 60s measurement time. The recent research and development in the methodologies, equipments and systems undertaken towards capacity building and self-reliance in retrospective radiation dosimetry is reported in this paper.

Neutron spectrum measurements near KAMINI reactor south beam vault door using nested neutron spectrometer.

KAlpakkam MINI reactor (KAMINI) is a 233U fuelled research reactor has various neutron irradiation locations for experimental purposes. The pit at the south beam end of KAMINI reactor is being extensively utilised for neutron attenuation experiments in prospective shielding materials as well as for neutron radiography. During reactor operation, it will be closed by a movable shield. A vault door is located above the shield and the movable shield is used to attenuate streaming neutrons and gamma-rays during reactor operation. Even with the shield, there exists significant dose because of streaming neutrons and gamma rays. Its variation depends on the power of the reactor. The neutron and gamma dose rates close to the south beam vault door have recently been found to be 275-300μSv/h and 175-200μSv/h, respectively, when the reactor is operating at 10kW. In order to characterise the streaming neutron spectra of vault door place for the first time, measurements are done using the Nested Neutron Spectrometer. Along with the neutron flux, neutron mean energy and ambient dose-equivalent rate are also measured and compared with earlier measurements carried out inside the south beam pit. It is observed that the presence of paraffin shield reduces the neutron average energy from 370 to 178keV. Apart from energy reduction, 10kW normalised neutron flux of south beam pit is also attenuated by the shield by 25000 times and it is found that the neutron spectrum of the measured location is also more thermalized. Neutron reference data of the location are generated.

Radon levels in Bengaluru during monsoon season.

A study on the dynamics of Radon and meteorological parameters was conducted in Bengaluru (12056'44'' N, 77030'25″ E, 840m AMSL) during monsoon of 2014. All measured parameters exhibited a clear diurnal pattern, except for pressure, and are attributed to morning temperature inversion and afternoon enhanced vertical mixing. Concentration of Radon is higher during north eastern monsoon compared with south western monsoon and is due to the presence of continental air mass from north east of India. Monthly average Radon activity has exhibited a positive link with long wave radiation while displaying a negative correlation with ambient temperature, accumulated rainfall and soil temperature. During the study, ambient gamma dose rate of 190.8 nSv hour-1, shortwave radiation of 184.4 Wm-2, longwave radiation of -40.4 Wm-2, soil temperature (at 10cm) of 26.3°C, humidity of 62.9%, pressure of 918.1mbar and radon activity of 8.4±0.5Bq m-3 were recorded.

Ambient gamma radiation level around Kaveri river basin, Karnataka state, India.

Studies on ambient gamma radiation in indoor and outdoor environment and their effect on human health have created interest among the researchers across the world. The present study represents the results of indoor and outdoor ambient gamma dose rates around the Kaveri river basin from Talakaveri (Madikeri district) to Mekedatu (Ramanagara district) by using portable Environmental Radiation Dosemeter. The annual effective dose in the present study area varies between 0.14mSv.y-1 and 0.58mSv.y-1 with an average value of 0.30mSv.y-1 for indoor radiation. The outdoor annual effective dose ranged between 0.01mSv.y-1 and 0.14mSv.y-1 with an average value of 0.06mSv.y-1. The total annual effective dose varies from 0.17 to 0.72mSv.y-1 with an average value of 0.36mSv.y-1. The calculated values of indoor and outdoor annual effective dose in the study area (are found to be lower than the world average values (1mSv.y-1 and 0.48mSv.y-1).

Contribution of coupled ESR/U-series fossil dating to a Paleolithic-Neolithic transition site - Naminan, Southwest China

The coupled ESR and U-series (ESR/U-series) method has been increasingly utilized for dating fossil teeth from Early to Middle Pleistocene hominid sites. One significant advantage of this method is its ability to directly analyze fossil animal or human teeth. However, compared with other radiometric methods such as 14C charcoal dating, U-series carbonate dating, and OSL sediment dating, this dating method is rarely employed for Late Pleistocene or younger sites. In this study, we present an ESR/U-series dating investigation conducted at the Naminan site, a Paleolithic-Neolithic transition (P–N transition) site situated on the Sino-Myanmar border. The ESR/U-series analysis of eleven dental samples yields an age range of 18.1–13.2 ka for the fossils. These obtained ages are generally consistent with the 14C chronology of the site. When dealing with young fossil samples, it was observed that due to relatively low uranium concentration in dental tissues, internal dose rate plays a less significant role compared to external beta and gamma dose rates in the total dose rate of the fossil samples. Consequently, evaluating the dose rate of surrounding sediment becomes a primary source of uncertainty. Additionally, in this study we attempted to employ the standardized growth curve (SGC) and representative dose response curve method for determining Equivalent Dose (DE), which was then compared with values obtained using additive dose method (ADM). Although the precision of DE estimated by two methods are comparatively lower than that of ADM, it demonstrates the potential to efficiently determine a more rational Dmax for irradiation, identify samples with stratigraphic disturbances, and analyze small or valuable fossil specimens.

Impact of microwave power on equivalent dose (De) evaluation in ESR dating

ESR (electron spin resonance) spectra of quartz samples irradiated with varying gamma (γ) dose were measured at different microwave power levels (0–200 mW). The microwave power saturation characteristics of Al and E′ centers were systematically investigated, and the mechanisms by which the power saturation characteristics affected equivalent dose (De) fitting results in ESR dating were revealed. The experimental results demonstrated that irradiation reduces the spin-lattice relaxation time, resulting in the inability to intrinsically characterize the number of spins in a series of aliquots when the ESR intensity exhibits significant saturation. The simulation results indicated that changes in spin-lattice relaxation characteristics can cause distortion in the dose response curve (DRC) at high power levels, leading to deviations in De values. A method that uses the slope of the approximate linear regime of the power saturation curve (PSC) as an intrinsic metric of ESR intensity is proposed; this method has been preliminarily validated in both experiments and simulations.

Assessment of radiological hazards of soils from the city of Bitola (Macedonia) and its environs

ABSTRACT To establish the radioactivity level of soils and assess the associated radiological impact on residents, 58 samples from the town of Bitola and its environs were collected. After conducting gross alpha and gross beta measurements with a gas-flow proportional counter as a preliminary screening test, subsequent gamma-spectrometry measurements reveal the presence of 40K, 226Ra, 232Th, and 137Cs in the soil samples as radionuclides with the highest impact. The absorbed gamma dose rate, the annual effective dose, radium equivalent activity, external hazard index, gamma index, excess lifetime cancer risk, and annual gonadal dose were calculated using the obtained activity concentrations of the radionuclides. Upon comparison with similar studies conducted in the Balkan countries, the obtained results for radiation hazard indices were found to be the highest in the region. Coloured maps were generated to visually represent the spatial distribution of the absorbed gamma dose rate in air and annual effective dose, clearly indicating the combined influence of geology and human activities, including the nearby thermoelectric power plant operation.

Clinical application of a GPU-accelerated monte carlo dose verification for cyberknife M6 with Iris collimator

PurposeTo apply an independent GPU-accelerated Monte Carlo (MC) dose verification for CyberKnife M6 with Iris collimator and evaluate the dose calculation accuracy of RayTracing (TPS-RT) algorithm and Monte Carlo (TPS-MC) algorithm in the Precision treatment planning system (TPS).MethodsGPU-accelerated MC algorithm (ArcherQA-CK) was integrated into a commercial dose verification system, ArcherQA, to implement the patient-specific quality assurance in the CyberKnife M6 system. 30 clinical cases (10 cases in head, and 10 cases in chest, and 10 cases in abdomen) were collected in this study. For each case, three different dose calculation methods (TPS-MC, TPS-RT and ArcherQA-CK) were implemented based on the same treatment plan and compared with each other. For evaluation, the 3D global gamma analysis and dose parameters of the target volume and organs at risk (OARs) were analyzed comparatively.ResultsFor gamma pass rates at the criterion of 2%/2 mm, the results were over 98.0% for TPS-MC vs.TPS-RT, TPS-MC vs. ArcherQA-CK and TPS-RT vs. ArcherQA-CK in head cases, 84.9% for TPS-MC vs.TPS-RT, 98.0% for TPS-MC vs. ArcherQA-CK and 83.3% for TPS-RT vs. ArcherQA-CK in chest cases, 98.2% for TPS-MC vs.TPS-RT, 99.4% for TPS-MC vs. ArcherQA-CK and 94.5% for TPS-RT vs. ArcherQA-CK in abdomen cases. For dose parameters of planning target volume (PTV) in chest cases, the deviations of TPS-RT vs. TPS-MC and ArcherQA-CK vs. TPS-MC had significant difference (P < 0.01), and the deviations of TPS-RT vs. TPS-MC and TPS-RT vs. ArcherQA-CK were similar (P > 0.05). ArcherQA-CK had less calculation time compared with TPS-MC (1.66 min vs. 65.11 min).ConclusionsOur proposed MC dose engine (ArcherQA-CK) has a high degree of consistency with the Precision TPS-MC algorithm, which can quickly identify the calculation errors of TPS-RT algorithm for some chest cases. ArcherQA-CK can provide accurate patient-specific quality assurance in clinical practice.