Dosimeters Research Articles

ESR spectroscopic analysis of fructose as a dosimeter for gamma radiation

In this research, fructose was used as a dosimeter, and ESR examined the influence of radiation dose on the dosimeter’s properties. Microwave power, g-value, and decay of response tests were carried out at doses of 1, 5, and 10 kGy. The results show that fructose possesses linearity at doses of 5 × 10−2–30 kGy. The radiation detection sensitivity of fructose is better than sucrose’s but less than alanine’s over the entire dose range. The irradiation dose influences microwave saturation on ESR intensity, occurring at 5 and 10 kGy. The microwave power for irradiated fructose ranges from 1.00 to 2.46 mW. The ESR signal intensity increases with higher radiation doses, primarily due to the formation of more free radicals. Additionally, higher radiation doses lead to faster decay of the fructose dosimeter’s response. The fructose ESR intensity stability compared to alanine and sucrose at 1, 5, and 10 kGy are alanine > sucrose > fructose, alanine > fructose > sucrose, and alanine > fructose ≈ sucrose, respectively.

New opportunities for molecular photoswitches as wearable ultraviolet radiation dosimeters

Australians have the highest incidence of melanoma globally, despite increasing awareness of the risks of excessive sun exposure. Although excess ultraviolet radiation (UVR) can cause irreparable cell damage and lead to cancer, some exposure is vital to maintain bodily processes such as vitamin D production. For an individual, finding the balance between healthy exposure and skin damage is largely guesswork. The ability to provide a simple, individualised indicator of cumulative UVR dosage could be transformative in preventing skin cancer. This review will provide a brief overview of the variety of UVR sensor technologies and explain the important role of colourimetric dosimeters. The chemistry behind some recent examples of colourimetric dosimeters will be discussed, identifying that molecular photoswitches are ideal candidates to enable this technology. We discuss the chemical mechanisms of photoswitches and how to modify their chemical structure to optimise their properties for use as dosimeters. Through this lens, diarylethenes have been identified as prime dosimeter candidates, owing to their sensitivity, stability, adaptability and the variety of visually striking colours possible. Finally, some specific challenges are identified in the design and fabrication of personalised colourimetric dosimeters that can equitably meet the requirements of all users in our community.

Polyvinyl alcohol dyed with methyl red as a radiochromic film dosimeter for gamma radiation

Abstract A Radiochromic film dosimeter for gamma radiation was prepared from polyvinyl alcohol (PVA) and methyl red (MR) by condensation polymerization. To confirm the reaction, the obtained PVA-MR film was characterized by Fourier-transform infrared spectroscopy (FTIR) and compared to PVA film. The result shows the appearance of new vibrational stretching at ~1700 cm−1, related to carbonyl groups, indicating that the reaction between PVA and MR has been successfully done. The effect of radiation on the color change characteristic of PVA-MR film and its possibility to be used as a radiochromic film dosimeter were investigated using ultraviolet (UV)-Vis spectrophotometry. The absorption spectrum of PVA-MR can be seen in the visible region at ~420 nm, which is characteristic of red, and the film undergoes decolorization gradually from red to transparent when exposed to gamma radiation up to 100 kGy. Moreover, the response of these dosimeters at different times after irradiation was tested and the energy band gap, Eg, was also calculated.

Optical characteristics and surface dendritic growth of Nd,Y:CaF2 crystals irradiated by high-energy He ions

This study aims to investigate the various responses of the optical characteristics to He-ion irradiation at different fluences and energies in Nd,Y:CaF2 crystals. Through optical absorption and photoluminescence spectra, we observe that electrons excited by He-ion irradiation are trapped by anionic vacancies, He ions and Nd3+ to form F-centers, He atoms and Nd2+, respectively. At an energy of 5 MeV, F-centers decrease with increasing fluence, whereas at a fluence of 1 × 1013 ions/cm2, increasing the energy promotes Nd2+ formation, and a further increase in the fluence based on an energy of 16 MeV can significantly promote the production of Nd2+. After the irradiation, the electrons from F-centers are also captured by Nd3+, leading to the decay of F-centers and an increase in Nd2+ with time. In addition, the growth of CaF2 dendrites with multiple morphologies on the surface by high-energy irradiation is observed. It is explained by the surface recrystallization between the escape of F and surface metallization due to high-energy irradiation. This research provides significant insights into the irradiation conditions modulating defect generation and evolution, as well as laying the groundwork for future applications of radiation-exposed crystals as radiation dosimeters and lasers.

Structural Properties of Al-Li-Zn Borate Glass Activated with Dysprosium (Dy3+) for Radiation Dosimeter

This study explores the properties of Al-Li-Zn glass doped with dysprosium ions as a potential radiation dosimeter. The glass was prepared using the novel quenching technique, and various characterisations were performed to evaluate its properties. X-ray diffraction (XRD) analysis confirmed the amorphous phases in the glass. UV-vis spectroscopy revealed a noticeable absorption peak in the visible region, characteristic of the dysprosium ions. PL spectra luminous peaks at 348 nm (yellow), 529 nm (green), and 625 nm (orange hue), which corresponded to the 4H15/2 → 6P7/2, 4F9/2 → 6H15/2, 4F9/2 → 6H15/2, and 4F9/2 → 6H13/2 transitions in 1.5 and 2.5 dysprosium ions respectively. Significant decrease in Tg from 257°C in the undoped sample to 101°C in the doped sample, Tm of the doped sample dropped from 862°C to 815°C and Tc of the doped sample dropped from 756°C to 444°C, suggesting a reduced crystallisation threshold. FTIR analysis demonstrated that OH groups displayed peaks within the 2200 to 4000 cm range. Stretching vibrations of BO3 units occurred between 1200 and 1600. Stretching vibrations of BO4 units were observed between 800 and 1200; these show that the presence of Dy3+ and zinc oxide altered the arrangement of the glass structure, causing a transformation from B03 groups to B04 groups. This transformation leads to defects in a stable trap environment suitable for thermoluminescence phenomena. Considering its properties and optical characteristics, the samples with 1.5 and 2.5 mol % of Dy3+ showed remarkable thermoluminescence properties, suggesting its suitable use as a dosimeter to gauge radiation exposure. The glass demonstrates stability and absorption capability, making it worth considering for radiation detection applications.

Initial Results of Low Earth Orbit Space Radiation Dosimeter on Board the Next Generation Small Satellite-2

As human exploration goals shift from missions in low Earth orbit (LEO) to long-duration interplanetary missions, radiation protection remains one of the key technological issues that must be resolved. The low Earth orbit space radiation dosimeter (LEO-DOS) instrument to measure radiation levels and create a global dose map in the LEO on board the the next generation small satellite-2 (NEXTSat-2) was launched successfully on May 25, 2023 using the Nuri KSLV-III in Korea. The NEXTSat-2 orbits the Earth every 100 minutes, in an orbit with an inclination of 97.8° and an altitude of about 550 km above sea level. The LEO-DOS is equipped with a particle dosimeter (PD) and a neutron spectrometer (NS), which enable the measurement of dosimetric quantities such as absorbed dose (D), dose equivalent (H) for charged particles and neutrons. To verify the observations of LEO-DOS, we conducted a radiation dose estimation study based on the initial results of LEO-DOS, measured from June 2023 to September 2023. The study considered four source categories: (i) galactic cosmic ray particles; (ii) the South Atlantic Anomaly region of the inner radiation belt (IRB); (iii) relativistic electrons and/or bremsstrahlung in the outer radiation belt (ORB); and (iv) solar energetic particle (SEP) events.

Characterization of Neutron Irradiator as a Source of Reference Radiation Field for Calibrating Dosemeters and Doserate Meters at PSI Laboratory

A new neutron calibration laboratory has been installed at the Paul Scherrer Institute in Switzerland. The calibration laboratory has been equipped with a newly developed neutron irradiator with two calibration benches, remote control instruments and related ancillary equipment for calibrating dosemeters and doserate meters. The actual dimensions of the calibration laboratory are 2.0 m (H) X 6.8 m (W) X 12.6 m (L). On the steel grid at a height of 2 m from the basement floor, two calibration benches are installed. A transport channel is installed in the middle of the benches for the transfer of the radiation sources. The radiation sources are moved from the safe position of the irradiator to the reference irradiation position using an air pressure unit. The reference position is at a height of 1.2 m from the grid floor. The neutron irradiator is equipped with two Am-Be sources. Characterization of neutron radiation field has been calculated in detail by the MCNPX neutron transport code as well as energy distribution of neutrons and contribution of scattered neutrons. Experimentally, it was measured with a neutron/gamma digital spectrometric system equipped with a stilbene detector. The quality of the neutron radiation field has been characterized by ambient dose equivalent rate and the shape of the Am-Be spectra has been verified with the ISO-8529 standard.

Real time eye dose reduction in fluoroscopy with auditory and visual feedback dosimeter through swine model experiments

This paper proposes measurement and reduction of eye dose in real time for the physician and the assistant performing fluoroscopy guided arterial puncture. Eye dose rates were measured for 30 fluoroscopy-guided punctures of bilateral femoral arteries in pigs. Fifteen fluoroscopy-guided punctures were performed using real time radiation dosimeter without auditory and visual feedback and other fifteen punctures were done using real time radiation dosimeter with visual and auditory feedback worn on forehead by an interventional cardiologist having experience of more than 10 years. The mean radiation dose rate for eyes of physician during arterial puncturing with real time radiation dosimeter with auditory feedback was 0.07 mSv/h (n = 15) whereas it was 0.18 mSv/h (n = 15) without visual and auditory feedback. The percentage of reduction with the device was 61% for eyes. In case of assistant the reduction was 33% for eyes (n = 15). The real time visual and auditory feedback dosimeter has reduced the eye dose rate of the physician and assistant and also helped him staying away from the X-ray source. Real time radiation dosimeters can be an effective tool to measure and reduce the dose to the eyes. The radiation eye dose rate for physician and assistant was significantly reduced by using real time radiation dosimeter with visual and auditory feedback. The real time radiation dosimeter not only helps in measuring but also help in minimizing the radiation dose rate for the physician and assistant in real time.

Evaluation of cutout factors with small and narrow fields using various dosimetry detectors in electron beam keloid radiotherapy.

The inherent problems in the existence of electron equilibrium and steep dose fall-off pose difficulties for small- and narrow-field dosimetry. To investigate the cutout factors for keloid electron radiotherapy using various dosimetry detectors for small and narrow fields. The measurements were performed in a solid water phantom with nine different cutout shapes. Five dosimetry detectors were used in the study: pinpoint 3D ionization chamber, Farmer chamber, semiflex chamber, Classic Markus parallel plate chamber, and EBT3 film. The results demonstrated good agreement between the semiflex and pinpoint chambers. Furthermore, there was no difference between the Farmer and pinpoint chambers for large cutouts. For the EBT3 film, half of the cases had differences greater than 1%, and the maximum discrepancy compared with the reference chamber was greater than 2% for the narrow field. The parallel plate, semiflex chamber and EBT3 film are suitable dosimeters that are comparable with pinpoint 3D chambers in small and narrow electron fields. Notably, a semiflex chamber could be an alternative option to a pinpoint 3D chamber for cutout widths≥3 cm. It is very important to perform patient-specific cutout factor calibration with an appropriate dosimeter for keloid radiotherapy.

Evaluation of a novel physically cross-linked fricke-xylenol orange-polyvinyl alcohol radio-chromic gel dosimeter for radiotherapy

In this work, a novel sensitive composition of Fricke radio-chromic gel dosimeter based on polyvinyl alcohol (PVA), xylenol orange (XO), and physical cross-linking agent gellan gum (GG) is presented and evaluated with two optically detection methods. The Fricke dosimeter was irradiated up to 30Gy using medical linear accelerator and analyzed optically using ultraviolet visible (UV–Vis) spectrophotometry technique at wavelengths of 585 nm (i.e., within the visible range) and two-dimensional optical imaging system of charge-coupled-device (CCD) camera with a uniform red light-emitting-diode (LED) array source. The Fricke dosimeter demonstrated important properties including independence of beam energy and dose rate over the range studied. In addition, these dosimeters have high sensitivity in the range of 0–10Gy, and significant low diffusion coefficient of 0.070 mm2 h−1. In addition, the composition shows a lower diffusion coefficient with respect to those reported so far for a Fricke dosimeter. The total uncertainty of the estimated doses for the Fricke dosimeter was 3.96% at 95% confidence level.

INNOVATIVE RADIATION SHIELDING: PERFORMANCE OF LOCALLY MADE BaSO4 -COATED BUILDING BLOCKS FROM FCT, ABUJA AS LOW COST EFFECTIVE RADIATION BARRIERS

This study explores the innovative use of locally made blocks from four area councils (Abuja Municipal, Gwagwalada, Kuje, and Kwali) within the Federal Capital Territory of Abuja, coated with Barium Sulfate paint, as an effective shielding material against radiation. Soil samples were collected from each area, and blocks measuring 10 cm x 10 cm with varying thicknesses of 1-4 cm were molded. These coated blocks were exposed to low-energy X-rays at 100 kV and 10 mAs, and radiation doses passing through them were measured using a Raysafe Thin-X dose meter, including the free air exposure without any block. One uncoated block from Abuja Municipal area was also exposed to compare the effectiveness of barium sulfate. The Linear Attenuation Coefficients and Half-Value Layers for the blocks from each council area were determined. The block sample derived from soil collected in the Abuja Municipal Area and coated with Barium Sulfate exhibited the highest linear attenuation coefficient of 1.114 cm⁻¹ and the lowest half-value layer of 6.22 mm. In contrast, an uncoated block from the same soil showed 0.702 cm-1 and 9.87 mm as the linear attenuation coefficient and the half-value layer respectively. Blocks from the Gwagwalada, Kuje, and Kwali Area Councils showed linear attenuation coefficients of 1.027, 0.900, and 0.968 cm⁻¹ and half-value layers of 6.75, 7.70, and 7.16 mm, respectively. These values were compared with the half-value layers of concrete and lead. From the findings, Barium Sulfate coated blocks were found to be the most effective and cost-efficient alternative for radiation shielding.

Development and characterization of Staphylococcus aureus-hydrogel-based radiation dosimeter

In the search of innovative methods within radiation dosimetry to provide solutions to the high demanding modern ionizing radiation applications, this work proposes an original approach to combine microorganisms and gel dosimetry characteristics by adapting biotechnology and molecular biology procedures. The design of bacterial culture media and the evaluation of viability as systems for radiation dosimetry are reported. In preliminary assessments, a highly promising dose-response has been observed for samples stored at 4 °C, displaying a linear trend within the investigated dose range. This underscores a promising performance, indicating the potential utility of the system as a radiation dosimeter.

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.

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).

Radiation-tolerant dose sensor based on undoped amorphous silicon

Single-crystal silicon diodes are replacing gas-filled dose-rate meters because they are batch-processable, mechanically robust, compact, and operable at low voltages. However, they are prone to radiation damage in high dose fields. Hydrogenated amorphous silicon (a-Si:H) provides the manufacturing and operational benefits of silicon while adding inherent radiation hardness because of its wider bandgap and disordered microstructure. Previously, sensors with tens of micrometers thick a-Si have been investigated for direct dose sensing in x-ray imaging applications. However, the limited charge carrier lifetimes of the medium can reduce the charge collection efficiency and thereby the sensitivity. If a higher density, higher Z active media is coupled to thin amorphous silicon active layers, then an additional indirect component can be added to this direct signal to exhibit ∼15 μGy/s dose-rate sensitivities at zero and low-bias (<0.5 V) operation. Here we show that thin (150, 300, 450 nm) a-Si:H optical sensors can produce external quantum efficiencies above 40% and internal quantum efficiencies that exceed 70 % over a broad band from 380 nm to 650 nm, resulting in dose-rate sensitivity even at 0 V. When the charge-collecting electrodes abutting the a-Si:H serve the dual purpose as reflective layers in a lossy Fabry-Perot cavity, then internal quantum efficiencies greater than 83 % can be realized in a 30 nm thick layer at 410 nm. Cobalt-60 gamma-ray irradiation to 100 kGy (air) shows no radiation-induced degradation for even the thicker 300 nm sample; rather, a radiation hardening effect is observed as evinced in reduced dark current.

Thermoluminescence characteristics of gamma-irradiated Gd:Mg doped silica glass

This study explores the characteristics of thermoluminescence (TL) yield of silica glass doped with Gd2O3 and MgO for dosimetry via sol-gel route, with varying concentrations of rare earth metal oxides, ranging from 0.1 to 0.8 mol%. Gamma irradiation was delivered using 1.25 MeV 60Co, with entrance doses of 2–10 Gy. The characterization of Gd:Mg-doped SiO2 included assessing TL dose response, sensitivity, linearity index, glow curve, and fading. It has been found that 0.2 mol% Gd:Mg-doped SiO2 shows promising TL dosimetric properties due to its high linearity, high sensitivity, and low thermal fading. In addition, it demonstrated exceptional dosimetric response across the entire dose range studied, with a coefficient of determination R2 exceeding 91%. A computerized glow curve deconvolution method was conducted to determine the kinetic parameters by using Glowfit software. The glow curves include five peaks associated with activation energies and frequency factors with values 0.88–2.42 eV and 5.58 × 106–7.22 × 1026 s−1, respectively. The 0.2 mol% Gd:Mg-doped SiO2 demonstrates minimal fading effects, retaining a significant portion of the TL signal with ∼33% of the initial signal lost over 28 days post-irradiation. The results indicate that the Gd:Mg-doped SiO2 offers a promising performance as a low-cost passive radiation dosimeters.

A method to improve sensitivity of Ferrous ammonium sulfate - Benzoic acid - Xylenol orange (FBX) aqueous radiation dosimeter

Ferrous ammonium sulfate - Benzoic acid - Xylenol orange (FBX) solution is known for its dosimetry properties in the dose range applicable in radiation oncology. Several attempts at improving its dose sensitivity have been reported in literature. The current work explores a novel method to improve the dose response of the system in the range 0–10 Gy with the original standard composition of the solution. Value of the sensitivity of the dosimeter was found to be 7.471/Gy with excellent linearity using the developed method. This is 115 times higher than the sensitivity obtained using the conventional methods.

The possibility of using the DKS-AT1123 dosimeter for radiation monitoring of medical electron accelerators with the energy of more than 10 MeV

In the Russian Federation, there is a constant increase in the number of radiation medical installations with electron accelerators. Over the past 4 years, their number has increased 2.5 times. These installations contain pulsed electron accelerators that generate pulsed bremsstrahlung radiation with a maximum energy from 6 to 21 MeV. Currently, there are no devices designed for dosimetry of the pulsed photon radiation with energy of more than 10 MeV in the state register of measuring instruments of the Russian Federation. The most widely used radiation monitoring device for pulsed electron accelerators is the DKS-AT1123 X-ray and gamma radiation dosimeter designed for dosimetry of pulsed bremsstrahlung radiation with an energy of up to 10 MeV. The purpose of this work is to evaluate the possibility of using this device for dosimetry of pulsed bremsstrahlung radiation with a maximum energy of up to 20 MeV. The authors calculated the energy spectra of bremsstrahlung radiation for a point source with a maximum energy of 20 MeV behind flat concrete screens with a thickness of 1 m, 2 m and 3 m by the Monte Carlo method using the GEANT4 calculation program. The energy dependence of the registration efficiency of the DKS-AT1123 dosimeter was extrapolated to the energy range of 10–50 MeV in the kerma-approximation without taking into account the energy transfer by secondary electrons. It was assumed that it corresponds to the energy dependence of the total mass attenuation coefficient for the absorbed energy of gamma quanta in water. Using conversion coefficients for converting the fluence of monoenergetic photons into the effective dose rate at an anterior-posterior radiation incidence on the human body, real dose rates were calculated, and using the energy dependence of the dosimeter readings, the predicted results of measuring the unit dose rate with the DKS-AT1123 dosimeter behind a concrete protection with a thickness of 1, 2 and 3 m were obtained. It is shown that the maximum expected underestimation of the measurement results will not exceed 40% and practically does not depend on the thickness of the concrete shield in the thickness range from 1 to 3 m. To account for this underestimation, it is necessary to use the value of additional measurement error due to the energy dependence of the sensitivity of this device for the photon radiation energy of more than 10 MeV, equal to 70%. This makes it possible to use the measurement results obtained using this dosimeter to adequately characterize the state of radiation safety during operation of pulsed electron accelerators with a maximum energy of up to 20 MeV. It is possible to use a correction factor to the measurement results equal to 1.63 ±0.04 to compensate for this underestimation. The proposed approach can be used to create a methodology for using this dosimeter for radiation monitoring of medical electron accelerators with the energy of up to 20 MeV, if there are correction factors for radiation protection configurations and radiation energies encountered in practice.

Balancing Performance and Portability: A Study on CsI(Tl) Crystal Sizes for Real-Time Gamma-Ray Spectrum and Dose Monitoring

Current radiation dosimeters sometimes face accuracy limitations or provide only cumulative doses over long periods. To contribute to this area, we developed a portable monitor that measures the energy spectrum and dose of gamma rays in real time. To achieve this, we used an improved sequential Bayesian estimation algorithm. The dose rate was then derived from the energy spectrum by applying a flux-to-dose conversion coefficient. The monitor consists mainly of a CsI(Tl) scintillator and a multi-pixel photon counter (MPPC). In developing this device, we focused on striking a balance between measurement accuracy, ease of use, and portability. As an essential aspect of the research, we investigated the influence of the CsI(Tl) crystal size on the performance of the monitor to determine an optimal size. This was accomplished by calculating the detection efficiency and energy resolution through experimental measurements using standard gamma-ray sources and simulations using MCNP5. Within the scope of the research, detector response functions were created for each crystal size for an energy range of 10 keV to 3 MeV. Considering an optimal balance of detection efficiency and energy resolution alongside a compact size suitable for portable applications, the crystal measuring 2.6 × 2.6 × 1.3 cm3 was deemed preferable.

Preliminary study on a bifunctional, elastic NBT–PVA radiochromic gel acting as a bolus and dosimeter in radiotherapy

Preliminary study on a bifunctional, elastic NBT–PVA radiochromic gel acting as a bolus and dosimeter in radiotherapy