X-ray Dose Measurements Research Articles

Thermoluminescence dosimetry and microstructural characteristics of gamma-irradiated natural flake graphite

Thermoluminescence (TL) and microstructural analysis were conducted on natural flake graphite (NFG) to assess its suitability for radiotherapeutic x-ray dose measurements. The investigations encompassed the examination of TL glow curves, linearity, sensitivity, signal decay, and repeatability. NFG samples were exposed to 60Co gamma radiation doses ranging from 2 Gy to 20 Gy. The microstructure of the irradiated NFG was probed using a 532 nm laser Raman spectrometer. Promisingly, the NFG exhibited remarkable characteristics, including a moderately higher response to dose (R2 of about 96%), increased sensitivity at lower doses, and good repeatability (∼4%). Nevertheless, its fading rate reached about 80% after 14 days of irradiation. Additionally, the NFG intensity ratios of defect (D) to graphite (G), denoted as ID/IG, closely mirrored the oscillatory pattern observed in 50 μm thick graphite sheets and were approximately 1.6 times lower than those of similar graphite sheets with comparable carbon content (about 98% carbon). These findings suggest that NFG holds potential for the development of an affordable, non-hygroscopic, and tissue-equivalent TL dosimeter, with possible applications in the medical field.

Radiophotoluminescence properties of Bi-doped NaCaBO3

Bi-doped NaCaBO3 exhibits radiophotoluminescence (RPL) properties, where the Bi2+ centre is formed through X-ray irradiation. As a result of RPL, a broad emission band appears around 800 nm in the photoluminescence (PL) spectrum, attributed to X-ray irradiation. The intensity of the PL signal is proportional to the irradiation dose, making it useful for measuring accumulated radiation dose. The sensitivity depends on the doping concentration of Bi, and the optimal concentration to maximize sensitivity is approximately 0.005%. With a laboratory-constructed reader system, the optimal sample enables measurement of X-ray dose as low as 25 mGy. Following irradiation, the Bi2+ signal slightly increases by about 13%, but it is significantly reduced to around 7% of the initial value after heat treatment at 500°C for 100 s. The formation and annihilation of the Bi2+ centre can be reproduced multiple times. Therefore, RPL of Bi-doped NaCaBO3 is attractive for radiation dosimetry applications.

Analysis of the Geiger Muller Ability on the Effect of Collimation Area and Irradiation Distance on the Dose of X-Ray Machine Measurements

Radiation cannot be felt directly by the five human senses. For the occupational safety and security, a radiation worker or radiographer is endeavored to receive radiation dose as minimum as possible, which is by monitoring the radiation using a radiation measuring device. The purpose of this study was to analyze the effect of collimation area and irradiation distance on x-ray dose measurement using Geiger Muller. In this case, the author tried to make a dosimeter by using the Muller Geiger module and displayed it on a personal computer. This research employed Muller Geiger sensor to detect X-ray dose and velocity, Arduino for data programming, Bluetooth HC-05 for digital communication tool between hardware and personal computer, and personal computer to display the reading. Current research was conducted using Pre-Experimental research design. Based on the results of data collection and comparison with the standard tool, it can be concluded that the greater the tube current setting (mA), the greater the dose and rate of radiation exposure at a distance of 100cm with 50KV and 70KV settings, and a distance of 150cm with 50KV settings. However, it is inversely proportional to the measurement results at a distance of 150cm with a 70KV setting. The results of this study are further expected to determine the ability of Geiger Muller to measure the dose to the irradiation distance or collimation area and can be used as a reference for further research in this field.

Influence of electrode geometry on X-ray emission, plasma inductance, voltage, and current derivative signals obtained from a plasma focus device

Plasma focus devices have been investigated as a pulsed radiation source. Different studies have shown that the shape of the anode affects strongly the plasma dynamic and X-ray emission that takes place in plasma focus devices. In the present work, a hybrid-type plasma focus device (6 μF, 16 ± 1 kV), named PF-2kJ, is operated at various pressures of hydrogen gas with five cylindrical anodes of the same lengths but different in shapes, without cathode bars. The effect of cathode bars on various electric parameters is studied for the anode that has the maximum X-ray emission. The electrical signals of Rogowski coil (current derivative), voltage divider (voltage at the anode), and photomultiplier tubes (X-rays) were analyzed for all the anodes. Inductance and the voltage at the time of the pinch were derived from the measured voltage and current derivative signals. The X-ray dose measurements were performed using thermoluminescent dosimeters (TLD-100). The PF-2kJ performance is not the best while using the cathode bars. Our results show that by changing the anode shape just over the insulator sleeve the plasma focus devices can be switched between close energies stored in the capacitor bank.

XDose: toward online cross-validation of experimental and computational X-ray dose estimation

PurposeAs the spectrum of X-ray procedures has increased both for diagnostic and for interventional cases, more attention is paid to X-ray dose management. While the medical benefit to the patient outweighs the risk of radiation injuries in almost all cases, reproducible studies on organ dose values help to plan preventive measures helping both patient as well as staff. Dose studies are either carried out retrospectively, experimentally using anthropomorphic phantoms, or computationally. When performed experimentally, it is helpful to combine them with simulations validating the measurements. In this paper, we show how such a dose simulation method, carried out together with actual X-ray experiments, can be realized to obtain reliable organ dose values efficiently.MethodsA Monte Carlo simulation technique was developed combining down-sampling and super-resolution techniques for accelerated processing accompanying X-ray dose measurements. The target volume is down-sampled using the statistical mode first. The estimated dose distribution is then up-sampled using guided filtering and the high-resolution target volume as guidance image. Second, we present a comparison of dose estimates calculated with our Monte Carlo code experimentally obtained values for an anthropomorphic phantom using metal oxide semiconductor field effect transistor dosimeters.ResultsWe reconstructed high-resolution dose distributions from coarse ones (down-sampling factor 2 to 16) with error rates ranging from 1.62 % to 4.91 %. Using down-sampled target volumes further reduced the computation time by 30 % to 60 %. Comparison of measured results to simulated dose values demonstrated high agreement with an average percentage error of under 10 % for all measurement points.ConclusionsOur results indicate that Monte Carlo methods can be accelerated hardware-independently and still yield reliable results. This facilitates empirical dose studies that make use of online Monte Carlo simulations to easily cross-validate dose estimates on-site.

BITEWING DOSIMETRY OF 3-DIMENSIONAL INTRAORAL TOMOSYNTHESIS DENTAL X-RAY IMAGING SYSTEM

<h3>Background</h3> There is substantial evidence for a cumulative dose-related response to ionizing radiation in the form of cancer development years after initial exposure. Therefore, this study focused on effective dose, a quantity with direct correlations to biologic risk from dental x-ray exposures. <h3>Objective</h3> The purpose of this study was to measure doses and to calculate the effective doses (E) resulting from exposure parameters that are used for stationary intraoral tomosynthesis (s-IOT) and conventional imaging for adult posterior bitewing examinations of the dentition. Additionally, this study sought to evaluate the effect of sensor attenuation on patient dose. <h3>Materials and Methods</h3> To meet these aims, a human tissue equivalent adult phantom and optically stimulated luminescent (Landauer, Inc., Glenwood, IL) dosimeters were used to measure dose produced during simulated posterior bitewing examinations (n = 4). Optically stimulated luminescent dosimeters were used to measure x-ray dose at 24 head and neck tissue/organ sites of interest. Dosimetry was acquired by using a tissue equivalent phantom simulating the anatomy of an average adult male (AtomMax Model 711 HN,CIRS Inc., Norfolk, VA). Exposure parameters used were 70 kV/7 mA (0.7 mAs) and 0.12 mAs for s-IOT and conventional (KaVo FOCUS, Charlotte, NC), respectively. Analysis of variance (ANOVA) and Tukey's HSD ("honest significant difference") statistics on dose were utilized to demonstrate significant data relationships. <h3>Results</h3> Effective dose by modality (μSv)ModalityDose (μSv)Rectangular Conventional with Sensor1.1Rectangular Conventional without sensor4.6s-IOT with sensor5.9s-IOT without sensor11.9Circular Conventional with sensor8.2Circular Conventional without sensor15.7 Sensor-present doses were significantly lower than sensor-absent for all modalities (<i>P</i> = .0001). Significant differences in E were found for all modality combinations with the exception of s-IOT sensor-present modalities vs conventional rectangular sensor-absent modalities (<i>P</i> = .0482). <h3>Discussion</h3> Unadjusted s-IOT dose was 26% less than conventional-circular exposures and 61% greater than conventional-rectangular for sensor-absent exposures. Unadjusted sensor-present s-IOT dose was 28% less than conventional-circular exposures and 81% greater than conventional-rectangular exposures. Despite a 4-fold increase in mAs for s-IOT imaging compared with conventional imaging, E from s-IOT imaging was at least 26% less than the current most commonly implemented bitewing technique, conventional-circular, while providing substantially greater diagnostic yield in the form of 3-dimensional (3-D) information.

Compliance with Radiation Protection Principles in Radiotherapy Units

Background: One of the most harmful agents in hospital settings is ionizing radiation such as X-rays that physicians and other staff expose in surgeries and diagnostic tests. Therefore, the aim of this study was to measure X-ray dose in the diagnostic radiology units of hospitals affiliated to North Khorasan University of Medical Sciences. Methods: This is a descriptive-analytical, cross-sectional study, in which all of the hospitals' diagnostic radiology units including CT scan, mammography, fluoroscopy and radiography were studied. X-ray dose was measured by a dosimeter-radiometer device (MKS-05 Terra-P). The International Radiation Protection Association (IAEA) checklist was used to check the observance of the Radiation Protection Principles. Results: The results of this study showed that the X-ray doses in the CT scan, mammography, and fluoroscopy units of Bojnord Imam Ali Hospital were 0.16, 0.08 and 0.01 μSv/h, respectively. The doses of X-ray in the radiology units of Imam Ali (PBUH), Imam Reza (PBUH), Esfarayen and Shirvan Hospitals were 0.12, 0.12, 0.11, and 0.11 μSv/h, respectively. Conclusion: According to the results, the X-ray doses in the diagnostic radiology units of hospitals were lower than the standard limit proposed by the International Radiation Protection Association. However, it is proposed to use appropriate protective lead aprons to further protect the exposed staff in the units in question.

Vertical Au/ZnO Schottky Barrier Diode Based on High-Resistivity ZnO Film for X-Ray Dose Measurement

Vertical Au/ZnO Schottky barrier diodes (SBDs) were fabricated on an n+ Si substrate and tested as X-ray detectors in this paper. The high-resistivity ZnO film-based SBDs had a large effective area about 0.78 cm2 and showed a notable sensitivity about 0.78 uC/Gy for X-ray illumination. The detector with linear outputs achieved an X-ray dose measurement across four orders of magnitude of the dose rate from 3.83 mGy/s to 19.00 Gy/s. The response current to switched X-ray illumination exhibited a repeatable and stable characteristic, and the response current mechanism was given and discussed. The results imply the potential of junction devices based on ZnO material for X-ray dose measurement.

EBT3 Films in Low Solar Ultraviolet and X-Ray Dose Measurement: A Comparative Analysis.

The purpose of this study is to investigate the potentiality of Gafchromic external beam therapy 3 (EBT3) film to measure low dosage of solar ultraviolet (SUV; 0-10 600 mJ/cm2) and x-ray (0–750 mGy) radiation. In this experiment, 2 groups of EBT3 films were prepared with size 2 cm × 1 cm. The first group of films was exposed by incremental SUV dose in the middle of the day. The other group was irradiated by x-ray at 100 kVp, 100 mA, and 2 S of tube voltage, tube current, and exposure time, respectively. The measured SUV consists of 90% ultraviolet A (UVA) and 10% ultraviolet B. The film discoloration was represented by visible absorbance spectroscopy technique using Jaz spectrometer from Ocean Optics Inc. Simple linear regression produced high accuracy with coefficients of determination, r 2 of 0.9804 and root mean square error (RMSE) of 434.88 mJ/cm2 for the measurement of SUV dose. On the other hand, r 2 of 0.98 and RMSE of 31 mGy was produced for the measurement of x-ray dose. The application of multiple linear regression enhanced the measurement accuracy with R 2 of 99% and 99.7% and RMSE of 327.06 mJ/cm2 and 15.045 mGy for SUV and x-ray dose, respectively. The spectral analysis shows a promising measurement at selected wavelengths for SUV and x-ray dose.

Energy and air kerma dependence of response of a photodiode-based dosimetric system for radioprotection

Low-level X-ray dose measurements are carried out to characterize a portable photodiode-based dosimetric system. In this paper, the energy and air kerma dependence of response is evaluated. The developed system is capable of real-time direct-reading radiation-dose measurement for radioprotection (occupational monitoring) or radiodiagnostic (patient dosimetry). The system can be configured to use various remote portable dosimeters and a computer server for data processing and display. The communication between the portable dosimeter and the server can be carried out in two modes: wireless or USB. The wireless connection is the standard usage mode, and the USB connection is for configuration or testing. The communication protocol is custom-made. For occupational monitoring, ISO 4037–1 was applied, and the following radioprotection qualities were tested: N40, N60, N80, N100, and N120. It was also tested in the following radiodiagnostic qualities: RQR3, RQR5, RQR8, and RQR10, as defined by IEC 61267. Besides X-rays, the developed dosimeter was evaluated for gamma ray energies of Cs-137 and Co-60. It is observed that the dosimeter sensitivity response displays a standard deviation less than 10% within a coefficient of variation of 1% in the reproducibility tests. The system is considered closely linear for air kerma dependence in the radiation qualities investigated. Goodness of fit was evaluated with the reduced chi-squared test.

Dose Measurements in a 20-J Repetitive Plasma Focus

In this article, the results of X-ray dose measurements executed using thermoluminescent dosimeters in experiments with a very small (20 J) repetitive plasma focus device named SORENA-1 are presented and analyzed. The working gas in these experiments was Argon. Also, pinch formation in experiments with this device has been observed. This device has been designed and constructed in Plasma and Nuclear Fusion Research School of Nuclear Science and Technology Research Institute of Iran. From these results, it is concluded that we can do experiments with this device using Ar as working gas all over the working days of year, and a good symmetry for measured dose around the device has been seen.

DEVELOPMENT OF ISOTOPICALLY ENRICHED BORON-DOPED ALUMINA DOSIMETER FOR THERMAL NEUTRONS.

A novel optically stimulated luminescence (OSL) detector containing isotopically enriched boron was developed for thermal neutron dosimetry. Alumina containing isotopically enriched boron (Al2O3:B) was synthesised by the sol-gel method. The Al2O3:B was annealed up to ~1800 K. For X-ray diffractometer (XRD) analysis, the diffraction pattern of the Al2O3:B had reflex peaks corresponding to α-Al2O3. The sensitivity of Al2O3:B to photons was slightly 2% of that of a commercial Al2O3:C. The Al2O3:B detector had satisfactory linearity in X-ray dose measurement. A thermal neutron field was constructed using a 241Am-Be neutron source and graphite blocks. A pair of Al2O3:10B and Al2O3:11B detectors were set in the thermal neutron field. The response of Al2O3:10B was larger than that of Al2O3:11B owing to the 10B(n,α)7Li reactions. The sensitivity of Al2O3:10B to thermal neutrons was estimated to be two orders less than the photon sensitivity. Therefore, the pair of Al2O3:10B and Al2O3:11B detectors were useful for thermal neutron dosimetry.

Optimum wavelength of ultraviolet rays in gafchromic EBT2

Introduction Gafchromic films have been used for the measurement of X-ray dose in diagnostic radiology. UV-A ray can be used as a substitute for X-rays in the double exposure technique to compensate for nonuniformity error of Gafchromic EBT2. Purpose When using a UV-A light emitting diode (UV-A LED), it is necessary to determine the optimal UV-A wavelength to react with the active layer of Gafchromic EBT2. Therefore, changes in the optical density of Gafchromic EBT2 induced by UV-A were investigated by irradiating it at various wavelengths with UV-A LED. Materials and methods At first, Gafchromic EBT2 was pre-irradiated using a uniform UV-A by using fluorescent lamp for 60 min from a distance of 72 cm to reduce nonuniformity error. Second, Gafchromic EBT2 was irradiated for 60 min from a distance of 5.3 cm using a UV-A LED at a wavelength of 353–410 nm. The maximum, minimum, and mean ± standard deviation of pixel values of the subtraction images were evaluated using 0.5 inch of circular region of interest (ROI). The most sensitive wavelength of UV ray was decided. In addition, UV strength was measured in each UV-A LED. Results When a UV-A LED wavelength of 375 nm was used, the mean ± SD of pixel value of Gafchromic EBT2 was indicated highly pixel value. It was 8915.25 ± 608.86. A 375 nm wavelength UV-A was most effective and sensitive for Gafchromic EBT2. Conclusion The 375 nm wavelength of UV-A is available as a substitute for X-rays in the double exposure technique. Disclosure Research supported by JSPS KAKENHI Grant Number 26460740 .

Ultraviolet ray wavelength in Gafchromic XR-RV3 and XR-SP2 films

Introduction Gafchromic films have been used for the measurement of X-ray dose in diagnostic radiology. Correlation between color density change and ultraviolet (UV) wavelength of Gafchromic XR-RV3 and XR-SP2 were studied. UV irradiation is considered as an X-ray substitute in the double exposure technique. It is one of the correction methods for the nonuniformity error of Gafchromic XR-RV3 and XR-SP2. Purpose It is to determine the UV suitable wavelength of a UV light emitting diode (UV LED) that is used as a substitute for X-rays in the double exposure technique for the Gafchromic XR-RV3 and XR-SP2. Materials and methods UV LED that UV rays at a wavelength of 353 nm and 5-nm increments from 360 to 400 nm were used. Gafchromic XR-RV3 or XR-SP2 was irradiated with UV of different wavelengths through the 30 mm diameter of irradiation hole for 2 and 4 h, at a distance of 53 mm, respectively. Gafchromic XR-RV3 or XR-SP2 was fixed onto an acrylic plate of 3 mm thickness for assistance with scan. A circular region of interest (ROI) of 0.5 inch for measurements of pixel value was set in the center of the UV irradiation region. The mean pixel values ± standard deviation (SD) was obtained. Results Indicated high pixel value of Gafchromic XR-RV3 and XR-SP2 were 1276.81 ± 254.30 (395 nm) and 576.46 ± 219.75 (400 nm), respectively. Conclusions The irradiation of Gafchromic XR-RV3 and XR-SP2 with homogeneous UV rays by the UV-LED wavelengths of 395 or 400 nm can correct the nonuniformity error of the active layer efficiently. Disclosure Research supported by JSPS KAKENHI Grant Number 26460740 .

Correction of nonuniformity error of Gafchromic EBT2 and EBT3.

This study investigates an X‐ray dose measurement method for computed tomography using Gafchromic films. Nonuniformity of the active layer is a major problem in Gafchromic films. In radiotherapy, nonuniformity error is reduced by applying the double‐exposure technique, but this is impractical in diagnostic radiology because of the heel effect. Therefore, we propose replacing the X‐rays in the double‐exposure technique with ultraviolet (UV)‐A irradiation of Gafchromic EBT2 and EBT3. To improve the reproducibility of the scan position, Gafchromic EBT2 and EBT3 films were attached to a 3‐mm‐thick acrylic plate. The samples were then irradiated with a 10 W UV‐A fluorescent lamp placed at a distance of 72 cm for 30, 60, and 90 minutes. The profile curves were evaluated along the long and short axes of the film center, and the standard deviations of the pixel values were calculated over large areas of the films. Paired t‐test was performed. UV‐A irradiation exerted a significant effect on Gafchromic EBT2 (paired t‐test; p=0.0275) but not on EBT3 (paired t‐test; p=0.2785). Similarly, the homogeneity was improved in Gafchromic EBT2 but not in EBT3. Therefore, the double‐exposure technique under UV‐A irradiation is suitable only for EBT2 films.PACS number(s): 87.53 Bn

Radiation dose measurements of an on-board imager X-ray unit using optically-stimulated luminescence dosimeters.

Cone beam computed tomography (CBCT) is now widely used to image radiotherapy patients prior to treatment for the purpose of accurate patient setup. However each CBCT image delivered to a patient increases the total radiation dose that they receive. The measurement of the dose delivered from the CBCT images is not readily performed in the clinic. In this study, we have used commercially available optically stimulated luminescence (OSLD) dosimeters to measure the dose delivered by the Varian OBI on a radiotherapy linear accelerator. Calibration of the OSLDs was achieved by using a therapeutic X-ray unit. The dose delivered by a head CBCT scan was found to be 3.2 ± 0.3 mGy which is similar in magnitude to the dose of a head computed tomography (CT) scan. The results of this study suggest that the radiation hazard associated with CBCT is of a similar nature to that of conventional CT scans. We have also demonstrated that the OSLDs are suitable for these low X-ray dose measurements.

The use of semiconducting single-walled carbon nanotube films to measure X-ray dose

The conduction responses of semiconducting single-walled carbon nanotube (SWCNT) films irradiated by 6 and 15MV X-rays were evaluated. Results indicate that the average resistance–dose rate relations of the SWCNT network are quasi-linear and can be used for dosimetry measurements in medical radiation applications. The dynamic responses exhibit fluctuations which reveal an intrinsic feature of SWCNT networks due to the large number of interconnections between individual SWCNTs.

Studies on x-ray and UV emissions in electron cyclotron resonance x-ray source

A novel electron cyclotron resonance x-ray source is constructed based on the ECR technique. In this paper, the possibility of using the ECR x-ray source for producing UV rays by optimizing the plasma parameters is explored. X-ray and UV emissions from the ECR x-ray source are carried out for argon, nitrogen, and CO(2) plasma. The x-ray spectral and dose measurements are carried with NaI(Tl) based spectrometer and dosimeter, respectively. For UV measurement, a quartz window arrangement is made at the exit port and the UV intensity is measured at 5 cm from the quartz plate using UV meter. The x-ray and UV emissions are carried out for different microwave power levels and gas pressures. The x-ray emission is observed in the pressure range < or =10(-5) Torr, whereas the UV emission is found to be negligible for the gas pressures <10(-5) Torr and it starts increasing in the pressure range between 10(-5) and 10(-3) Torr. At high-pressure range, collision frequency of electron-atom is large which leads to the higher UV flux. At low pressure, the electron-atom collision frequency is low and hence the electrons reach high energy and by hitting the cavity wall produces higher x-ray flux. By choosing proper experimental conditions and plasma gas species, the same source can be used as either an x-ray source or an UV source.

Measurement of radiotherapy superficial X-ray dose under eye shields with radiochromic film

Accurate measurement and knowledge of dose delivered under eye shield during superficial X-ray radiotherapy is required for patient peripheral dose assessment. Critical structures can include the cornea, lens and retina. Measurement of dose under eye shields has been historically performed with Thermoluminescent Dosimeters (TLD's) due to their small size and design. Restrictions include the energy dependence and the fact that they only provide a point dose assessment. This note investigates the use of a low energy dependence radiochromic thin film for measurement of dose under eye shields in a phantom and compares results to theoretical calculation of dose. Results have shown a good match between predicted and experimentally measured results at the centre of an eye shield irradiated with 50 kVp and 150 kVp beams. The added advantage of radiochromic film compared to TLD measurements is the two dimensional dose map which is recorded for the assessment of dose providing not only an assessment at the site of the cornea, lens and retina in a phantom but in other areas as well. Radiochromic film has been found to accurately measure dose under eye shield in phantom treatments.

Ion emission at the target of the radiographic devices PIVAIR and AIRIX

On an AIRIX facility, a high-intensity electron beam is used to generate an x-ray pulse for radiographic purposes. The measured electron beam spot size is found to be much larger than its computed value. It is shown that this discrepancy is removed considering ion emission at the target, under electron beam interaction. A model has been developed to simulate the plasma produced during the interaction of the electron beam with the target. The predictions have been compared with ion identification results developed on the PIVAIR prototype accelerator as well as with the x-ray spot size and dose measurements obtained on AIRIX. The simulations show that the ion effect can be reduced by placing a thin foil (100 µm thickness) at an appropriate distance from the target to catch the ions emitted and to stabilize the electron beam spot size. The X-spot size is then reduced, as found experimentally on AIRIX. Moreover, for a smaller thickness barrier foil (5 µm), the ion effect can even be suppressed, producing an X-spot size close to that obtained without ion emission.