Ionizing Radiation Dosimeters Research Articles

Flexible Cotton Fabric-Based Ionizing Radiation Dosimeter for 2D Dose Distribution Measurements over a Wide Dose Range at High Dose Rates.

This work presents an ecological, flexible 2D radiochromic dosimeter for measuring ionizing radiation in the kilogray dose range. Cotton woven fabric made of cellulose was volume-modified with nitrotetrazolium blue chloride as a radiation-sensitive compound. Its features include a color change during exposure from yellowish to purple-brown and flexibility that allows it to adapt to various shapes. It was found that (i) the dose response is up to ~80 kGy, (ii) it is independent of the dose rate for 1.1-73.1 kGy/min, (iii) it can be measured in 2D using a flatbed scanner, (iv) the acquired images can be filtered using a mean filter, which improves its dose resolution, (v) the dose resolution is -0.07 to -0.4 kGy for ~0.6 to ~75.7 kGy for filtered images, and (vi) two linear dose subranges can be distinguished: ~0.6 to ~7.6 kGy and ~9.9 to ~62.0 kGy. The dosimeter combined with flatbed scanner reading and data processing using dedicated software packages constitutes a comprehensive system for measuring dose distributions for objects with complex shapes.

Thermoluminescence study of indium doped phosphate glass

The phosphate glass doped with indium oxide was synthesized and studied for the influence of the dopant on thermoluminescence behavior. During studies, high doses of radiation were used (up to 35 kGy, β−). TL studies were investigated using various methods, such as direct measurements of TL response vs. radiation dose, TMax-Tstop method, and Computing Glow Curve Deconvolution (CGCD) method. It has been established, that doping phosphate glass with indium oxide with an amount of 0.5% (w/w) leads to a decrease of total thermoluminescence signals in comparison to native glass (sensitivity decrease ca. 5 times). On the other hand, using indium oxide leads to increasing the linearity range from 6.5 kGy (for native glass) up to 23.0 kGy. Data from signal loss in time and CGCD analysis indicates a reduction in signal loss over time and the formation of 7 defects with multiple kinetics. The collected data indicate the potential use of indium oxide as a dopant in ionizing radiation dosimeters based on phosphate glasses. Indium can potentially be an alternative to rare earth metals - the most commonly used dopants in phosphors.

Enhanced thermoluminescence, radioluminescence, and optically stimulated luminescence from lithium fluoride and silver nanoparticles composites

Plasmonic properties of metals can increase the sensitivity of ionizing radiation dosimeters. In this work, we study the plasmon resonance of silver nanoparticles (AgNp) to increase the optically stimulated luminescence (OSL) intensity of lithium fluoride (LiF) polycrystals. We produced LiF/Ag nanocomposites with different volumes of a silver nanoparticle dispersion and investigated their OSL response. We also investigated their thermoluminescence (TL) and radioluminescence/scintillation (RL) responses. X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopy characterized the synthesized materials. XRD results clearly show the characteristic peaks of LiF and AgNps. TEM images revealed silver nanoparticles with diameters between 80 and 120 nm and LiF crystals with sizes between 1 and 5 μm. Reflectance spectroscopy showed a band around 420 nm, attributed to the plasmon resonance of silver nanoparticles. The responses of the OSL curves to X-ray irradiation were analyzed, showing higher OSL sensitivity with 14 mL AgNp, attributed to the AgNp plasmon resonance. A significant increase in TL and RL intensity could be observed for the LiF/Ag nanocomposites. TL, RL, and OSL results support that addition of AgNps do not lead to the creation of more and new traps or luminescent centers. The increase of TL and RL intensities is therefore related to the coupling of the luminescent centers with the AgNPs plasmons, in an energy-transfer mechanism (plasmon-coupled emission), whereas the enhanced OSL intensity directly correlates with the increased photoionization cross-section of the electronic traps under plasmon resonance conditions (plasmon-coupled excitation). Therefore, these results indicate that AgNp are potential candidates to increase the OSL, TL, and RL intensity from LiF dosimeters.

Preliminary comparison of organic electret-style devices on silicon and flexible plastic substrates as real-time ionizing radiation dosimeters

Preliminary comparison of organic electret-style devices on silicon and flexible plastic substrates as real-time ionizing radiation dosimeters

Testing of a new ionizing radiation detector based on multimode optical fibers

"This paper presents our results investigation to evaluation effects of the electron beams radiation generated in multimode optical fibers at high irradiation doses in order to develop an ionizing radiation dosimeter. The radiation induced attenuation has been shown to exhibit a linear dependence as a function on the applied dose on a certain doses range and after the irradiation the optical fibers go through a “recovery process” during which the optical properties improve again. The surface morphological changes due to electron beam irradiation were investigated by Scanning Electron Microscopy and Atomic Force Microscopy."

Experimental method for determining the supply current of a PMOS power transistor for use as a RADFET dosimeter

Radiation Sensitive MOSFETs (RADFETs) have been commonly used as ionizing radiation dosimeters. The threshold voltage variation is the main transistor parameter used for radiation dosimetry, as this voltage variation is directly related to total dose and it can be easily determined by using simple measurement and biasing circuits. In this work it is presented a novel experimental method to determine the optimal drain-source current value to be supplied to a p-type MOSFET used in a traditional RADFET configuration (diode connected transistor) for monitoring of the accumulated X- and gamma-radiation dose. Experimental results from irradiations with 60Co gamma-rays and comparison measurements with semiconductor analyzer indicate that lower supply current values result in more precise dose measurement results.

Enhanced X-ray Dose Response of Radio-fluorescent Hydrogels Enabled by Persulfate Salts.

Coumarin 3-carboxylic acid (CCA)-loaded radio-fluorescent hydrogels have attracted interest for ionizing radiation dosimeters, but their sensitivity needs to be improved. In this study, we added ammonium persulfate (APS) to a polyacrylamide (PAAm)-CCA hydrogel. The introduction of APS improved the hydrogel dose sensitivity to 336.02Gy- 1, which is 1.8 times that of the counterpart without APS. Our hydrogel can measure the X-ray dose in a range of 0 - 15Gy with a lower limit of detection (LOD) of 0.1Gy. Additionally, the hydrogel can sense X-ray doses within a wide range of the dose rate and temperature, and the dose‒response can be well retained 7 days postirradiation. Therefore, we think this study provides a simple and robust method to improve the sensitivity of CCA hydrogel dosimeters, presenting great potential in clinical radiotherapy.

First Combined, Double‐Density LCV‐Pluronic F‐127 Radiochromic Dosimeter Mimicking Lungs and Muscles

AbstractThis work reports on a new type of combined radiochromic ionizing radiation dosimeter for radiotherapy. The LCV‐Pluronic F‐127 serves for this purpose, which is a leuco crystal violet embedded in a physical hydrogel matrix of poly(ethylene oxide)‐block‐poly(propylene oxide)‐block‐poly(ethylene oxide) (Pluronic F‐127) with additives. This dosimeter responds to ionizing radiation by developing a blue color with an intensity related to the radiation dose. The LCV‐Pluronic F‐127 dosimeter is improved for lower temperature stability by adding sodium chloride (NaCl). Subsequently, a method for manufacturing the LCV‐Pluronic F‐127 lung mimicking dosimeter is proposed. Next, the LCV‐Pluronic F‐127 3D composite dosimeter is elaborated, which contains in one container two dosimetric zones of different densities mimicking soft tissues: muscles and lungs. The following are investigated: i) LCV‐Pluronic F‐127 phase transition with and without NaCl, ii) dose response characteristics, iii) stability during storage, iv) foams characteristics – lung mimicking dosimeter, v) tissue equivalence, and vi) dose response of LCV‐Pluronic F‐127 combined dosimeter to a medical accelerator X‐ray irradiation. In summary, this work proves the possibility of formation complex dosimeters and opens a new area of research toward the development and application of such dosimeters containing dosimetric zones corresponding to many tissues in one vial.

Extension of the RADTriage Colorimetric Dosimeter to Low-Dose Gamma-Ray Exposure Using Scanning Densitometry.

There is a need for an instantly indicating, easy-to-read, and inexpensive ionizing radiation dosimeter for first responders and members of the general public. One commercially available option is the RADTriage50 TM colorimetric dosimeter. However, existing literature has not adequately addressed the accuracy of RADTriage50 dosimeters at low doses of ionizing radiation (<50 mSv) or the need for methods to quantitatively read the RADTriage50 dosimeters after they are exposed. In this paper, we use digital scanning methods to read the RADTriage50 dosimeters. The performance of the dosimeters was evaluated by irradiation with a gamma irradiator traceable to national standards. Experiments covered a range of deep dose equivalents (50 mSv to 2,000 mSv) within the manufacturer's specified range (50 mSv to 4,000 mSv) and also below 50 mSv to determine if the digital scanning densitometry method allowed for a quantitative readout with a greater dynamic range. We also conducted tests using different gamma energies, 137 Cs (662 keV) and 60 Co (1.17 and 1.33 MeV), and different dose rates to evaluate the dependency of the RADTriage50 dosimeters on these parameters. Modeling of our measurements suggests that the dose-response of the RADTriage50 dosimeter is linear at low doses with strong non-linearity beginning at ~750 mSv and the dosimeter response appearing to plateau at ~2,000 mSv, although additional measurements at doses beyond 2,000 mSv are needed to confirm this finding. We also found that the RadTriage50 dosimeter response varied with gamma energy, but not with dose rate.

Impact of Salt on Thermal Stability and Dose Response of the Fricke-XO-Pluronic F-127 3D Radiotherapy Dosimeter.

Fricke-XO-Pluronic F-127 has recently been proposed as a 3D dosimeter for radiotherapy. It contains the typical ingredients of the Fricke ionizing radiation dosimeter, which are embedded in a physical gel of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F-127). The main reactions upon irradiation are the conversion of Fe+2 to Fe+3 and the formation of a colored complex with XO ([XO-Fe]+3). The study attempts to optimize the dosimeter in terms of its solution-to-gel transition temperature. In order to lower this temperature, the use of NaCl salt has been proposed. The new composition was characterized in order to obtain information on its thermal performance, storage stability, dose response to irradiation with a medical accelerator emitting different types of radiation, and tissue equivalence. The results obtained show an improvement in the sol-gel transition temperature and dose sensitivity compared to the composition without NaCl and broaden the knowledge of the Fricke-XO-Pluronic F-127.

Fully Textile X‐Ray Detectors Based on Fabric‐Embedded Perovskite Crystals

AbstractThe interest and thrust for wearable ionizing radiation dosimeters are rapidly growing, stimulated by a large number of different applications impacting on humankind, spanning from medicine to civil security and space missions. Lead halide perovskites are considered one of the most promising classes of novel materials for X‐ray detectors due to their superior electronic and detection performance coupled with compatibility with solution‐based printing processes, allowing fabrication onto flexible substrates. It is reported on fully textile perovskite‐based direct X‐ray detectors, where the photoactive layer is constituted by a silk‐satin fabric functionalized with methylammonium lead bromide perovskite crystals embedded in the textile. The reliability of the proposed fabrication process, based on simple and low‐tech deposition techniques adaptable to industrial printing technologies for textiles, is assessed by realizing different detector's architectures that exhibit comparable detection performances. Sensitivity values up to (12.2 ± 0.6) µC Gy−1 cm−2 and a limit of detection down to 3 μGy s−1 are achieved, and low bias operation (down to 1 V) is demonstrated, validating wearable applications. Further, fully textile pixelated matrix X‐ray sensors are implemented and tested, providing the proof of principle for large‐area scalability.

Statistical analysis of the periodic intermediate checks results on the standards used for calibrations of ionizing radiation dosimeters in a 60Co gamma ray beam

Periodic intermediate checks on the equipment used for calibration activity accredited for the conformity with the international norm ISO/IEC 17025 are an essential issue for monitoring the validity of calibration laboratory's results. These checks should be carried out according to a procedure defined by each accredited laboratory. The results of these checks should not exceed the acceptance criteria established in the laboratory and statistical techniques shall be applied to the reviewing of the results. In this work, a simple method of carrying out intermediate checks on working standards used for calibrations of ionizing radiation dosimeters in a 60Co gamma ray beam was presented. Moreover, the statistical analysis of obtained results was presented. This analysis allowed for a reliable inference regarding the operation of the working standards used to calibrate the customer's devices. The presented methods can be used as a guidance in order to conform to the ISO/IEC 17025 requirements for carrying out and reviewing of periodic intermediate checks results in the area of calibrations of ionizing radiation dosimeters for external beam radiotherapy.

Preliminary Evaluation of Pentacene Field Effect Transistors with Polymer Gate Electret as Ionizing Radiation Dosimeters

Interest in the use of organic electronic devices in radiation sensing applications has grown in recent years. The numerous device configurations (e.g., diodes, thin film transistors) and potential for improved tissue equivalence compared to their silicon-based analogues make them attractive candidates for various radiation dosimetry measurements. In this work, a variation of the organic thin film transistor (OTFT) is studied, in which a polymer electret is added. An OTFT electret design can be used in either a wired or wireless configuration for in vivo dosimetry with the possibility of real-time detection. The linearity, reproducibility, and dependence on energy of these devices were measured through exposure to 100 kVp photons from an orthovoltage treatment unit (Xstrahl 300) and 6 MV photons from a Varian TrueBeam medical linear accelerator. Prior to irradiation, all transistors were programmed with a −80 V bias applied to the Gate electrode (Vg) for 3 s. In the wireless configuration, after each delivered dose, the transfer characteristic was scanned to readout the amount of erased charges by monitoring the drain current change. When the programmed charge was sufficiently depleted by radiation, transistors were reprogrammed for repeated use. The real-time readout in a wired configuration was performed by measuring the drain current with Vg = −15 V; Vd = −15 V. The 6 MV photon beam was turned on and off at different dose rates of 600, 400, 300, 200, and 60 cGy/min to quantify the sensitivity of the device to changes in dose rate. The wireless transistors showed a linear increase in current with increasing dose. The sensitivities for different energies were 60 ± 5 nA/Gy at 6 MV at a dose rate of 600 cGy/min and 80 ± 10 nA/Gy at 100 kVp at a dose rate of 200 cGy/min. The sensitivity of detectors tested in a wired configuration at Vd = −15 V; Vg = −15 V was 8.1 nA/s at a dose rate of 600 cGy/min. The principle of pentacene OTFTs with polymer electret as radiation detectors was demonstrated. Devices had excellent linearity, reproducibility, and were able to be reprogrammed for multiple uses as wireless detectors. The wired transistors demonstrated an effective response as real-time detectors.

Four-Year Operation of Tanpopo: Astrobiology Exposure and Micrometeoroid Capture Experiments on the JEM Exposed Facility of the International Space Station.

The Tanpopo experiment was the first Japanese astrobiology mission on board the International Space Station. It included exposure experiments of microbes and organic compounds as well as a capture experiment of hypervelocity impacting microparticles. We deployed three Exposure Panels, each consisting of 20 Exposure Units that contained microbes, organic compounds, an alanine UV dosimeter or an ionizing radiation dosimeter. The three Exposure Panels were situated on the zenith face of the Exposed Experiment Handrail Attachment Mechanism (ExHAM) that was pointing in zenith direction toward space, which was attached on a handrail of the Japanese Experiment Module (Kibo) Exposed Facility (JEM-EF) outside the International Space Station. The three Exposure Panels were one by one retrieved and returned to the ground after approximately 1, 2, and 3 years of exposure to the space environment. Capture Panels, each of which contained one or two blocks of amorphous silica aerogel, were exposed to collect hypervelocity impact microparticles. Possible captured particles may include micrometeoroids, human-made orbital debris, and natural terrestrial particles. Each year, Capture Panels containing from 11 to 12 aerogel blocks were attached to the three faces of the ExHAM (pointing to zenith, ram, and port); they remained in place for about 1 year and were then returned to the laboratory. This process was repeated three times, in total, during 2015-2018. Additional exposure of a Capture Panel facing ram was conducted between 2018 and 2019. Once the aerogel blocks were returned to the laboratory, they were encapsulated in dedicated transparent plastic cases and optically inspected by a specially designed microscopic system. Once located and recorded, hypervelocity impact signatures were excavated one by one and distributed for further detailed analyses. The apparatus, operation, and environmental factors of all the Tanpopo experiments are summarized in this article.

The Essence and Application of the Optical Absorption Method for Quantitative and Qualitative Analysis of Radiation Defects in Optical Crystals

Today ionic crystals are widely used in devices for various purposes. In X-ray spectral optics they are widely used as crystal monochromators; ionic crystals are used in optical devices where lenses and transparent optical media (light filters) are made of optically pure materials - ionic crystals. In general, the main positive feature of these materials is transparency regarding the transmission of radiation in the visible region of the spectrum (transmittance of about 0.9) and neutrality - that is, approximately the same reaction of the medium to different spectral ranges of radiation. Ionic crystals are also widely used in detectors (scintillators, ionizing radiation dosimeters) and lasers. They are also widely used in acousto-optics and electrical engineering (lines of electrical signals delay, which gain efficiency due to the relatively small absorption of ultrasonic waves, and, therefore, it is possible to work with a wide sequence of signals probing the crystal). It is known that when ionizing radiation passes through ionic crystals, color centers appear in them, which can change the spectral composition of radiation both in the UV region and in the visible range. For example, the simplest configurations of color centers (F-centers) lead to the appearance in optical materials of additional absorption bands localized on the wavelength axis with a maximum at the wavelength lmax = 248 нм , but more complex configurations of radiation damage in solids already lead to the appearance of absorption bands at wavelengths in the visible range. This already presents some difficulties for developers and designers of relevant equipment, as changes in the spectral composition of radiation passing through the optical system of the device can lead, for example, to loss of efficiency of the selected radiation receiver, the main characteristic of which is primarily spectral sensitivity. Taking into account possible changes in the spectral composition of radiation is an important and urgent task of modern optical instrumentation. The purpose of this work is the analysis and justification of a method that takes into account structural changes in externally irradiated ionic crystals.

Investigations on graphene oxide for ion beam dosimetry applications

The oxygen content in graphene oxide (GO) can be reduced by the ion beam irradiation in high vacuum conditions. The reduction changes the C/O atomic ratio that increases with the absorbed ion dose. Moreover, as the level of reduction increases, the surface flattens and the material becomes denser. At high absorbed doses, greater than about 100 MGy, the material is affected by the high energy deposited with damage radiation effects which make the C/O ratio not proportional to the dose. At low doses, less than about 100 MGy, the C/O atomic ratio shows an optimal linearity with the ion dose and is independent of the ion stopping power, thus assuming the characteristics of a good biocompatible water-tissue equivalent dosimeter.The aim of the work was that to explore the possibility to use GO as ionizing radiation dosimeter for energetic ion beams by the measure of the compositional C/O atomic ratio.

Linearity response characterization of Polystyrene/ Graphene oxide nanocomposite as real-time dosimeter for therapeutic purposes

Introduction: In recent years, one of the emerging two dimensional (2D) carbon based nano- materials namely Graphene Oxide has been incorporated into polymeric matrices to enhance the electrical properties of the composites. The electrical conductivity of Graphene Oxide is excellently used in fabricating polymer-based sensors, energy-related systems, biotechnology, anti-statics, microwave absorbers, conductive coatings, and ionizing radiation dosimeters. The objective of this experimental work is to evaluate the linearity response of Polystyrene/Graphene oxide (0.1 wt%) nanocomposite as real-time dosimeter for therapeutic purposes. Materials and Methods: PS 1540 was supplied by Tabriz Petrochemical Company. Graphene oxide (GO) naopowder was prepared from US Nano Inc, and finally high purity toluene and DCM as the solvents were purchased from Merck Company. Solution processing has been used to prepare 0.1 wt% PS/GO nanocomposite for dosimetry purposes. A Picker-V9 60Co gamma-cell installed in the Secondary Standard Dosimetry Laboratory (SSDL) of Iran was used to irradiate the nanocomposite at various dose rates in the range of 98-159 mGy/min. Results: From the SEM images of fractured surfaces of PS/GO nanocomposite, the nano size scale of GOs nanoparticles can be observed as 140 nm. The plot of photocurrent versus dose rate for 0.1 wt% PS/GO was investigated. Results showed that the linearity was obtained in the range of 98-159 mGy/min with R2=1. The I-V measurements of the nanocomposite in a constant dose rate of 75 mGy/min at the SSD=80 cm were exhibited, in which the response was linear within the ±1000 V with R2=0.99, and also repeatability was examined for each measurement with the standard deviation less than 1%. Conclusion: In this experimental research, the linearity of Polystyrene/Graphene oxide nanocomposite as real-time dosimeter was carried out. Results showed that this nanocomposite exhibited a linear response in different dose rates ranging from 98-159 mGy/min that can be used as a real-time dosimeter utilized in therapeutic level.

Thermoluminescence Characteristics of Aluminium Oxide Doped Carbon Exposed to Cobalt-60 Gamma Radiation

This study concerns on the thermoluminescence (TL) characteristics of carbon doped aluminum oxide (Al2O3:C) as ionizing radiation dosimeter. The thermoluminescence response, linearity and sensitivity subjected to Co-60 gamma irradiation were investigated. Carbon doped (0.2 mol %) aluminum oxide samples in form of powder were irradiated to 1.25 MeV Co-60 gamma ray with doses ranging from 1 Gy to 50 Gy. Irradiations were performed by using Co-60 gamma ray model 220 Excel with the source activity, A = 2.310925534 kGy h1 at Universiti Kebangsaan Malaysia. The glow curves were analysed to determine various characterizations of the TLDs. It is shown that the glow curve of the sample contains a single peak at about 180°C with broad peak appears at the right of the spectrum. It is also shown that the TL intensity has linear relationship with delivered dose and the average TL sensitivity was calculated as 3.30 nC mg-1 Gy-1.

Collapsed-Hole Ge-Doped Photonic Crystal Fiber as a Diagnostic Radiation Dosimeter

A new type of microstructured optical fiber, fabricated by collapsing down the entire array of holes formed by a Photonic Crystal Fiber (referred to herein as PCF-collapsed), is used in this study as an ionizing radiation dosimeter. The performance of the optical fiber is evaluated for diagnostic applications, covering doses from a fraction of 1 mGy up to 10 Gy. The effect of different x-ray beam accelerating potentials from 40 up to 125 kVp photon beam, 6 MeV electrons, and 6 MV photons are demonstrated. The performance of the PCF-collapsed is compared with the uncollapsed PCF (PCF-structured) and a conventional 20-μm-core-diameter optical fiber, all three types of fiber being fabricated from the same Ge-doped-preforms. It is shown that while a PCF-structured has relatively low sensitivity, by collapsing all of the holes in the PCF, the TL response of the fiber is increased by more than 16 times, being also more than four times greater than that of the conventional form optical fiber. The PCF-collapsed can detect a minimum dose as low as 0.6 mGy measured and 5.75 ± 0.11 mGy calculated. The TL analysis suggests that a collapsed-hole-PCF enhances structural defects in an uncollapsed-hole-PCF, highly desirable for dosimeter applications.

Thermoluminescence Response of Copper-Doped Potassium Borate Glass Subjected to 6 Megavolt X-Ray Irradiation

This study addresses the characteristics of Cu-doped and undoped potassium borate glass for use as ionizing radiation dosimeters by investigating and comparing the thermoluminescence responses, linearity, sensitivity and dose response s of the two types of glasses. A number of samples based on xK2CO3+ (100 – x)H3BO3, where 10 = x = 30 mol.%, have been prepared using a melt quenching technique. The amorphous phases were identified using X-ray diffraction (XRD). The undoped potassium borate samples 20K2CO3+ 80H3BO3(mol.%) and Cu-doped (0.5 mol.%) samples were placed in a solid phantom apparatus and irradiated with in X-ray tube under 6 MV accelerating voltage with doses ranging from 0.5 to 4.0 Gy. This beam was produced by the Primus MLC 3339 linear accelerator (LINAC) available at Hospital Sultan Ismail, Johor Bahru, Malaysia. The results clearly show the superiority of Cu-doped glass in terms of response and sensitivity to producing luminescence over undoped potassium borate glass. The sensitivity of Cu-doped glass is 6.75 times greater than that of undoped glass.