Optically Stimulated Luminescence Dosimeters Research Articles

Luminescence properties of SrB6O10:Ce,Gd phosphor for applications in OSL dosimetry and lighting

Strontium hexaborate (SrB6O10) doped with different metals and/or lanthanides has been studied widely as the thermoluminescence (TL) dosimeter. However, there is almost no dosimetry study concerning the utility of Optically Stimulated Luminescence (OSL) on SrB6O10. This preliminary study aims to examine the luminescence properties of SrB6O10 phosphor for their application in the areas of dosimetry and lighting technologies. Undoped and doped material to get an OSL dosimeter were synthesized by incorporating the dopants Ce3+, in the range of 0.1–0.7 % wt, and Gd3+, in the range of 0.1–1 % wt into the SrB6O10 structure using the solution combustion (SCS) method. The structural and morphological characterizations were performed using X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) methods, respectively. Two TL peaks of SrB6O10:Ce0.1%,Gd0.5% occurred at 70 °C and 182 °C after 1 Gy exposure to beta rays with a heating rate of 2 °C/s. The step annealing measurements were carried out to determine the traps responsible for the OSL signal. Various properties of the luminophore including dose-response and reusability were investigated using blue light stimulation. The phosphor showed a little variation of response up to 20 cycles within 2 % deviation (STD) from the first OSL readout. The OSL output within the range of 2–20 Gy was determined as linear. Radioluminescence (RL) measurement was investigated by emission in the range λem = 200–1000 nm. The parent compound displayed UV emission subdivided into UVA (315–400 nm), and UVB (280–315 nm) emissions at room temperature. The Chromaticity Coordinates (CIE) of SrB6O10:Ce0.1%,Gd0.5% were calculated as x = 0.2165, y = 0.1767. These remarkable characteristics show that, if developed, SrB6O10 could be used as an OSL dosimeter.

Surface Dose measurement and Comparison between TLD and OSLD during Modified re constructive Mastectomy Irradiation.

The surface dose response of luminescent detectors (LD), in particular thermoluminescent dosimeter (TLD) and optically stimulated luminescent dosimeter (OSLD), during modified re constructive mastectomy (MRM) irradiation has been compared. The study utilized 100 MRM patients with LDs (n=500) for the irradiation of TLD (n=250) and OSLD (n=250) during irradiation from an Elekta Versa HD Linear accelerator.A more pronounced dose-response relationship was evident for both TLD and OSLD. These findings indicate a close adherence to the vendor-specified tolerance limits, affirming the suitability of these dosimeters, as substantiated by individual investigations on each type. While a minor difference in dose measurement was noted between TLD and OSLD, the study's outcomes support the applicability of both TLD and OSLD as effective dosimeters during MRM breast irradiation for surface dose evaluation.&#xD.

The development of a cylindrical phantom for nanoDotTM calibration with multiple beam angles

Background: The nanoDotTM dosimeter, an optically stimulated luminescent dosimeter (OSLD), is compact and precise, ideal for various applications like radiation dosimetry. The nanoDotTM requires calibration before use with the detector alignment perpendicular to the central beam axis. It exhibits angular dependence that may impact the calibration factor, requiring the fabrication of a specific cylindrical phantom for the calibration procedure. Objective: This study aimed to develop a cylindrical phantom for nanoDotTM calibration to facilitate dose measurements in composite fields with various beam angles and to evaluate the nanoDotTM calibration factors for different plans. Materials and methods: The cylindrical phantom was constructed using cast nylon material to accommodate the nanoDotTM or a cylindrical ionization chamber (IC). The novel phantom underwent validation for physical characteristics, including dimensions, density, and uniformity. Validation for the calibration factor, using cylindrical phantom (CF cylin) under standard conditions with a 10x10 cm² field size at 10 cm depth was conducted with 6 MV X-rays, comparing it with calibration factor using slab solid water phantoms (CFsolid). The CFcylin for different numbers of beams were determined and validated against a reference IC in various planning conditions. Furthermore, angular correction factors were determined for their application in the single-beam calibration factor. Results: The cylindrical phantom had dimensions of 20 cm in diameter and 30 cm in length, a density of 1.145 g/cm³ and good uniformity. As a result of single beam, the CF cylin, agreed well with CFsolid, showing a difference of -0.069%. The CFcylin increased with the number of beams, ranging between 1.179 and 1.242. Additionally, the angular correction factor increased as the number of beams increased, peaking at 1.058 with 9 beams. When comparing the results to the IC, it was observed that with an increase in the number of beams to 4 beams, the single-beam calibration factor exhibited a variation of more than 2%. However, when applying the CF cylin specific to the number of beams or correcting for the angular correction factor, the dose differences between nanoDotTM and IC measurements were within 2%. Conclusion: The developed cylindrical phantom is suitable for nanoDotTM calibration under single beam angle and in composite fields with various beam angles. The new calibration factors for specific numbers of beams allow for accurate dose measurements using nanoDotTM, thus reducing the dose difference from the IC to acceptable levels. Further studies should investigate its application in clinical situations.

Beam quality conversion factor of BeO-OSLD for high-energy photon beams

Optically stimulated luminescence (OSL) dosimeters are used in radiotherapy. The beam quality conversion factor () of dosimeters is essential for correcting energy dependence. However, the of an OSL dosimeter using BeO (BeO-OSLD) has not yet been reported for high-energy photon beams. In this study, the of BeO-OSLD was investigated for high-energy photon beams using experiments and Monte Carlo calculations. In the experiments, was evaluated as the ratio of calibration coefficients determined using high-energy photon beams and 60Co γ-rays. Ten OSL dosimeters were used to reduce the statistical uncertainty of the determined values, and the same dosimeters were repeatedly used to obtain the data set of high-energy photon beams and 60Co γ-rays. Pre-irradiation with 10 Gy and bleaching were performed on fresh dosimeters before dosimetry to reduce the dependence of the detector response on the accumulated dose. In Monte Carlo calculations, both the absorbed dose to water and that of the BeO dosimeter for high-energy photon beams and 60Co γ-rays were calculated, and then was determined using the ratio of these values. The determined values in high-energy photon beam were 0.998 ± 0.011 and 1.021 ± 0.005 for the experiment and the calculation, respectively. These results showed that the variation in for 6 to 25 MV was negligible in practical dosimetry. This result indicates that BeO can be used to evaluate doses for different beam qualities without correcting for energy dependence.

Basic characteristics of Vision badge and its performance as an eye lens dosimeter for endoscopists

Vision badge is an eye lens dosimeter to measure H p(3). This study aimed to evaluate the basic characteristics of the Vision badge and its performance as an eye lens dosimeter for endoscopists by phantom study. Energy dependence was evaluated by changing the tube voltage to 50 kV (effective energy of 27.9 keV), 80 kV (32.2 keV), and 120 kV (38.7 keV). Dose linearity was evaluated by changing the number of irradiation to 1, 5, and 40 times, which corresponded to 0.53, 5.32, and 21.4 mGy. Batch uniformity was evaluated by calculating the coefficient of variation of H p(3) obtained from 10 Vision badges. Angular dependence was evaluated at 0° (perpendicular to the incident direction of x-rays), 30°, 60°, 75°, and 90°. The Vision badge and optically stimulated luminescence (OSL) dosimeter were attached to the inside of the radioprotective glasses, worn on the endoscopist phantom, and the H p(3) obtained from both dosimeters were compared. The H p(3) obtained from the Vision badge with 38.7 keV was 3.8% higher than that with 27.9 keV. The Vision badge showed excellent linearity (R 2 = 1.00) with the air kerma up to 21.4 mGy. The coefficient of variation of the H p(3) for 10 Vision badges was 3.47%. The relative dose of the Vision badge decreased as the angle increased up to 75°, but increased at 90°. The H p(3) obtained by the OSL dosimeter and the Vision badge were decreased as the endoscopist phantom was turned away from the patient phantom. The H p(3) that was obtained by the Vision badge was 35.5%–55.0% less than that obtained by the nanoDot. In conclusion, the Vision badge showed specific angular dependence due to its shape, but satisfactory basic properties were exhibited for all characteristics. In phantom study, the Vision badge showed generally similar trends with the OSL dosimeter.

Addressing challenges in diagnostic X-ray dosimetry: uncertainties and corrections for Al2O3:C-based optically stimulated luminescent dosimeters.

The use of Al2O3:C-based optically stimulated luminescent dosimeters (OSLDs) in diagnostic X-ray is a challenge because of their energy dependence (ED) and variability of element sensitivity factors (ESFs). This study aims to develop a method to determine ED and ESFs of Landauer nanoDot™ OSLDs for clinical X-ray and investigate the uncertainties associated with ESFand ED correction factors. An area of 2 × 2 cm2 at the central axis of the X-ray field was used to establish the ESFs. A total of 80 OSLDs were categorized into "controlled" (n = 40) and "less-controlled" groups (n = 40). The ESFs of the OSLDs were determined using an 80 kVp X-raybeam quality in free-air geometry. The OSLDs were cross-calibrated with an ion chamber to establish the average calibration coefficient and ESFs. The OSLDs were then irradiated at tube potentials ranging from 50 to 150 kVp to determine their ED. The uniformity of the X-ray field was ± 1.5% at 100cm source-to-surface distance. The batch homogeneities of user-defined ESFs were 2.4% and 8.7% for controlled and less-controlled OSLDs, respectively. The ED of OSLDs ranged from 1.125 to 0.812 as tube potential increased from 50 kVp to 150 kVp. The total uncertainty of OSLDs, without ED correction, could be as high as 16%. After applying ESF and ED correction, the total uncertainties were reduced to 6.3% in controlled OLSDs and 11.6% in less-controlled ones. OSLDs corrected with user-defined ESF and ED can reduce the uncertainty of dose measurements in diagnostic X-rays, particularly in managing less-controlled OSLDs.

Effects of low-dose ionizing radiation on the molecular pathways linking neurogenesis and autism spectrum disorders in zebrafish embryos

Prenatal exposure to environmental factors may play an important role in the aetiopathogenesis of autism spectrum disorder (ASD). We aim to investigate the potential effects of low-dose x-rays from dental diagnostic x-rays on neurodevelopment and molecular mechanisms associated with ASD in developing zebrafish embryos. Zebrafish embryos were divided into four groups and exposed using a dental x-ray unit: control, 0.08, 0.15 and 0.30 seconds, which are exemplary exposure settings for periapical imaging. These exposure times were measured as 7.17, 23.17 and 63.83 mSv using optical stimulated luminescence dosimeters. At the end of 72 hours post-fertilization, locomotor activity, oxidant-antioxidant status, and acetylcholine esterase (AChE) activity were analyzed. Expression of genes related to apoptosis (bax, bcl2a, p53), neurogenesis (α1-tubulin, syn2a, neurog1, elavl3) and ASD (eif4eb, adsl2a, shank3) was determined by RT-PCR. Even at reduced doses, developmental toxicity was observed in three groups as evidenced by pericardial edema, yolk sac edema and scoliosis. Deleterious effects of dental x-rays on neurogenesis through impaired locomotor activity, oxidative stress, apoptosis and alterations in genes associated with neurogenesis and ASD progression were more pronounced in the 0.30s exposure group. Based on these results we suggest that the associations between ASD and low-dose ionizing radiation need a closer look.

Not All Flat-Panel C-Arms Are Created Equal: A Comparison of Three Major Manufacturers.

Introduction: Flat-panel detector C-arms (FCs) are reported to reduce radiation exposure and improve image quality compared with conventional image intensifier C-arms (CCs). The purpose of this study was to compare radiation exposure and image quality between three commonly used FCs. Materials and Methods: A cadaver model was placed in the prone position to simulate percutaneous nephrolithotomy. We compared the following three FCs: OEC Elite CFD from GE HealthCare, Zenition 70 from Philips, and Ziehm Vision RFD from Ziehm Imaging. To measure the radiation dose, optically stimulated luminescence dosimeters (OSLDs) were utilized during five 300-second trials, conducted under three settings: automatic exposure control (AEC), AEC with low dose (LD), and LD with the lowest pulse rate (LDLP). Ten blinded urologists evaluated the image quality. Data were statistically analyzed using the analysis of variance (ANOVA) and Tukey's B post hoc tests. Results: In the AEC setting, the Philips C-arm demonstrated lower ventral OSLD exposure (42,446 mrad) compared with both the GE (51,076 mrad) and Ziehm (83,178 mrad; p < 0.001) C-arms. Similarly, in the LD setting, the Philips C-arm resulted in less ventral OSLD exposure (25,926 mrad) than both the Ziehm (30,956 mrad) and GE (38,209 mrad; p < 0.001) C-arms. Meanwhile, in the LDLP setting, the Ziehm C-arm showed less ventral OSLD exposure (4019 mrad) than both the GE (7418 mrad) and Philips (8229 mrad; p < 0.001) C-arms. All three manufacturers received adequate image quality ratings at the AEC and LD settings. However, at LDLP, the Ziehm C-arm received inadequate ratings in 8% of images, whereas both the GE and Philips C-arms received 100% adequate ratings (p = 0.016). Conclusions: Radiation produced by flat-panel C-arms varies dramatically, with the highest exposure (Ziehm) being almost double the lowest (Philips) in AEC. Improved picture quality at the lowest settings may come at the cost of increased radiation dose. Surgeons should carefully select the machine and settings to minimize radiation exposure while still preserving the image quality.

Impact of beam collimation of z-overscanning on dose to the lens and thyroid gland in paediatric thoracic computed tomography imaging.

Adaptive collimation reduces the dose deposited outside the imaged volume along the z-axis. An increase in the dose deposited outside the imaged volume (to the lens and thyroid) in the z-axis direction is a concern in paediatric computed tomography (CT). To compare the dose deposited outside the imaged volume(tothe lens and thyroid) between 40-mm and 80-mm collimation during thoracic paediatric helical CT. We used anthropomorphic phantoms of newborns and 5-year-olds with 40-mm and 80-mm collimation during helical CT. We compared the measured dose deposited outside the imaged volume using optically stimulated luminescence dosimeters (OSLD) at the surfaces of the lens and thyroid and the image noise between the 40-mm and 80-mm collimations. There were significant differences in the dose deposited outside the imaged volume (to the lens and thyroid) between the 40-mm and 80-mm collimations for both phantoms (P < 0.01). Compared with that observed for 80-mm collimation in helical CTscans of the paediatric thorax, the dose deposited outside the imaged volume (tothe lens and thyroid) was significantly lower in newborns and 5-year-olds with 40-mm collimation.

A Comparative Analysis between SR-Pb Shield and TCM in Eye Dose of Head CT Examination

This study aims to compare the effectivity of silicone rubber-lead (SR-Pb) eye shields and TCM technique during head CT examinations. In this study, a 95-5 wt% SR-Pb eye shield was developed with dimensions of 17 cm ×17 cm ×0.6 cm. This study was carried out at three tube voltages, namely 80, 100, and 120 kV. The measurements were conducted using Optically Stimulated Luminescence Dosimeter (OSLD) as the point dosimeter. Image noise and CT number were measured within specified region of interests (ROIs). These ROIs were positioned in three regions: the right eye, the left eye, and the central area of the head. Comparison of dose and noise was carried out in three conditions: without using SR-Pb and TCM (initial conditions), only using SR-Pb, and only using the TCM technique. From this study, it was found that the use of SR-Pb reduced eye dose as the use of TCM. It was found that a greater dose reduction was obtained when using SR-Pb compared to using TCM. Meanwhile, the use of SR-Pb led to slightly increasing noise and changing the CT number. In conclusion, the use of SR-Pb eye shield can serve as an alternative for eye dose reduction in CT machines that do not support TCM mode.

Assessment of Radiation Dose and Phantom Skin Dose in Transarterial Chemoembolization in a Single Center with 2 Digital Subtraction Angiography Units

Objectives: This study aimed to assess and compare the radiation dose and phantom skin dose in transarterial chemoembolization (TACE) of two digital subtraction angiography (DSA) units (unit A: Philips Allura Xper FD20, unit B: Artis zee biplane)Material and Methods: The dose area product (DAP), reference air kerma (RAK), number of images (NI) and fluoroscopy time (FT) of 240 cases (120 cases/DSA unit) were retrospectively reviewed and collected. To assess skin dose, 28 nanoDot optically stimulated luminescence dosimeters (OSLDs) were placed on the phantom’s back and the TACE procedure was performed with 2 DSA units.Results: The median DAP, RAK, NI, and FT of unit A were 200.49 Gy·cm2, 379.84 mGy, 115 images, and 9.04 minutes, while for unit B were 109.74 Gy·cm2, 276.55 mGy, 121 images, and 10.19 minutes, respectively. Significant differences were observed in DAP, RAK, and FT. The RAK of all patients was less than 2 Gy. The phantom skin dose obtained from unit B was significantly lower than that of unit A in all positions. The peak skin doses of the phantom studies from both units were 973.15 and 658.66 mGy, respectively.Conclusion: The median DAP of the unit A DSA was higher than the national diagnostic reference levels (DRLs). The TACE procedure from both units is safe from skin reaction. To benefit patients, the planning of a dose optimization process of unit A DSA and management of TACE cases using the existing DSA machine must be considered.

Initial Experience with the Commercial Electron FLASH Research Extension

The purpose of this study was to introduce a new commercial electron FLASH system that has the potential to become widely available for FLASH researchers globally. In this study, we first present the initial acceptance and commissioning tests for the FLASH system, and second, we highlight preliminary FLASH effect results from our cell studies. A linear accelerator was converted into a commercial research platform with the FLASH Research Extension, enabling the generation of a powerful 16 MeV electron FLASH beam. The dosimetric and stability tests were conducted using various dosimeters (i.e., radiochromic film, optically stimulated luminescent dosimeters (OSLDs), and a plane-parallel ionization chamber). To evaluate the FLASH effect, normal and cancer cell lines were FLASH irradiated using different pulse repetition frequencies (PRF) of 18 pulses/s and 180 pulses/s. The electron FLASH mode was able to generate over 1 Gy per pulse at the isocenter and a dose rate of up to 690 Gy/s near the accessory mount of the Linac gantry head. The charge collected by the plane-parallel ionization chamber at the highest PRF (i.e., 180 pulses/s) showed a linear relationship with the delivered number of pulses (i.e., 1 to 99 pulses) with a coefficient of determination (R2) of 0.9996. The absorbed dose measured using radiochromic film and OSLDs agreed within 3%, on average, and followed an inverse square law as the source-to-axis distance (SAD) varied for which the R2 values were 0.9972 and 0.9955 for radiochromic film and OSLDs, respectively. The profile of the FLASH beam was symmetrical but was not as flat as the conventional 16 MeV electron beam due to the use of a thinner custom scattering foil to reduce the degradation of the ultra-high dose rate. The depth-dose curve beyond the build-up region for the FLASH beam was similar to the conventional 16 MeV electron beam for which the range at 50% the maximum dose (R50) agreed within 0.5 mm. The FLASH beam output remained consistent over a 4-month period with a variation of 2.5%, on average. The FLASH sparing effect was observed in vitro for healthy human pancreatic cells. Furthermore, we observed that the highest PRF beam (180 pulses/s) was more effective at destroying pancreatic cancerous cells while minimizing damage to healthy cells compared to the lowest PRF beam (18 pulses/s). The novel commercial FLASH Research Extension system was dosimetrically characterized for pre-clinical FLASH research, and preliminary in vitro results demonstrated the FLASH effect. Given the prevalence of linear accelerators, this new commercial system has the potential to greatly increase the access to FLASH research.

Shaping success: clinical implementation of a 3D-printed electron cutout program in external beam radiation therapy.

The integration of 3D-printing technology into radiation therapy (RT) has allowed for a novel method to develop personalized electron field-shaping blocks with improved accuracy. By obviating the need for handling highly toxic Cerrobend molds, the clinical workflow is significantly streamlined. This study aims to expound upon the clinical workflow of 3D-printed electron cutouts in RT and furnish one year of in-vivo dosimetry data. 3D-printed electron cutouts for 6x6 cm, 10x10 cm, and 15x15 cm electron applicators were designed and implemented into the clinical workflow after dosimetric commissioning to ensure congruence with the Cerrobend cutouts. The clinical workflow consisted of four parts: i) the cutout aperture was extracted from the treatment planning system (TPS). A 3D printable cutout was then generated automatically through custom scripts; ii) the cutout was 3D-printed with PLA filament, filled with tungsten ball bearings, and underwent quality assurance (QA) to verify density and dosimetry; iii) in-vivo dosimetry was performed with optically stimulated luminescence dosimeters (OSLDs) for a patient's first treatment and compared to the calculated dose in the TPS; iv) after treatment completion, the 3D-printed cutout was recycled. QA and in-vivo OSLD measurements were conducted (n=40). The electron cutouts produced were 6x6 cm (n=3), 10x10 cm (n=30), and 15x15 cm (n=7). The expected weight of the cutouts differed from the measured weight by 0.4 + 1.1%. The skin dose measured with the OSLDs was compared to the skin dose in the TPS on the central axis. The difference between the measured and TPS doses was 4.0 + 5.2%. The successful clinical implementation of 3D-printed cutouts reduced labor, costs, and removed the use of toxic materials in the workplace while meeting clinical dosimetric standards.

Development of a novel flexible thin PWO(Er)/ZnO(Ag) nanocomposite for ionizing radiation sensing

Radiation dosimetry is an essential aspect of modern radiotherapy. Optically stimulated luminescence (OSL) dosimetry is a promising technique that uses materials to measure radiation doses. However, current OSL dosimeters are limited in their ability to provide comprehensive validation of spatial dose distributions, particularly in flexibility radiation sensitivity. In this regard, a novel flexible PWO(Er)/ZnO(Ag) nanocomposite sensor has been developed by a solvothermal procedure and its ionization radiation responses were investigated under UV, proton, laser 980 nm, and 241Am sources. The calculated alpha detection efficiency showed that the prepared PWO(Er)/ZnO(Ag) sensor is highly sensitive to alpha radiation (99.6 %) with good stability/repeatability and linear response. According to the Photo/Ionoluminescence study, the doped dual nanocomposite sample showed the strongest blue, green, and yellow emissions at room temperature compared with pure and single doped samples with an exciton lifetime of τ = 143.30 ±0.07 μs. The XRD, FTIR, Raman, and EDX results indicated that the prepared pure and doped nanocomposites have two-phase compositions of PWO and ZnO and related chemical compounds/elements in the nanocomposite structure. The morphologies of the PWO and PWO(Er) nanoparticles (NPs) were mostly cubic and heterogeneous with average particle sizes of 125 and 82 nm. ZnO and ZnO(Ag) had hexagonal, spherical, and rod-shaped particles with typical particle diameters of 130 and 90 nm, respectively. Our results indicate the prepared luminescent nanocomposites are transparent, flexible, highly stable, highly sensitive to ionizing radiation, and have the potential for practical use in optoelectronics and medical imaging in the future.

Dosimetric impact of hollow intraoral stents for head and neck cancer radiotherapy: A phantom study.

To investigate the dosimetric impact of the calculation boundaries and dose calculation algorithms of radiotherapy in head and neck cancer patients with an opened oral cavity connected to the exterior by a hollow intraoral positioning stent. A homemade silicone phantom with an opened oral cavity was placed in a CIRS head phantom to model head and neck cancer patients with a hollow intraoral positioning stent. 3D-CRT plans were designed on CT images of the phantom in Monaco and Pinnacle3 treatment planning systems (TPSs) with the same beam parameters. The default boundary and manually extrapolated boundary were both adopted in these two TPSs to explore the dosimetric impact on treatment plans. The nanoDot™ optically stimulated luminescence dosimeters (OSLDs) were chosen to measure the planned dose surrounding the oral cavity of the head phantom after calibration. The doses in the air cavity and two measuring points at the joint area were dramatically changed from 0.0, 92.4 and 148.8 cGy to 177.8, 244.2 and 244.1 cGy in Monaco after adopting the extrapolated boundary. While the calculated doses at the same place were changed from 61.2, 143.7 and 198.3 cGy to 175.4, 234.7 and 233.2 cGy in Pinnacle3 with a similar calculation boundary. For the Monaco TPS, the relative errors compared to the OSLD measured doses were 2.94±1.93%, 0.53±8.64%, 2.65±1.87% and 3.93±1.69% at 4 measuring positions. In contrast, the relative errors 4.03±1.93%, 4.85±8.64%, 7.61±1.87% and 5.61±1.69% were observed in Pinnacle3 . The boundary setting of an opened oral cavity in TPSs has a significant dosimetric impact on head and neck cancer radiotherapy. An extrapolated boundary should be manually set up to include the whole oral cavity in the dose calculation domain to avoid major dose deviations.

Studies of OSL properties of alkali- and rare earth-doped BeO based novel dosimeters for applications in external beam radiotherapy

This study aims to assess the feasibility of a novel Beryllium Oxide (BeO) based ceramics to be used as optically stimulated luminescence (OSL) dosimeters for monitoring of high-energy beams used in radiotherapy. The BeO ceramic dosimeters doped with alkali and rare earth metals (BeO:Na5%,Ce0.005%,Tb0.05%, BeO:Na5%,Ce0.01%,Er0.01%, and BeO:Na5%,Ce0.01%,Dy0.01%) were fabricated in pellet forms, and their luminescence responses were measured at the virtual water phantom interfaces for various field sizes of a 6 MV flattening filter-free photon beam of Varian LINAC. The OSL dosimeter's performance has been confirmed their practical usefulness as in vivo dosimeters in radiotherapy clinics. The provided dose estimates were validated using varying X-ray energies and doses, typically employed for actual medical radiotherapy systems. Our results indicated that the studied dosimeters rendered an almost linear response in the dose range of 0.05 Gy–20 Gy delivered from the 6 MV X-ray beam. Fading of the stored OSL was found to be less than 5% after a short storage period. The dependencies of OSL responses concerning beam energy, dose rate, irradiation angle, depth, and field size are all found to be supportive of the successful utilization of the BeO OSLDs in clinical environments.

Whole body and extremity doses of nuclear medicine personnel involved in manual and semi-automated methods of dispensing liquid iodine-131

This study aimed to evaluate the whole body dose Hp (10) and extremity dose Hp (0.07) of nuclear medicine personnel who administered liquid I-131 by using manual and fabricated semi-automated dispenser system. The semi-automated dispenser system comprises of peristaltic pumps and a motor controller was developed for dispensing liquid I-131. Optically stimulated luminescent dosimeters (OSLD) were used on two radiopharmacists to evaluate the whole body dose HP (10). NanoDot dosimeters were placed on personnel fingers to measure extremity dose HP (0.07). The mean doses were calculated for both manual and automated dispensing techniques. The findings revealed a significant 87.65%–92.31% reduction in both whole body and extremity doses when utilising semi-automated dispenser system compared to manual dispensing. Additionally, the semi-automated dispenser system demonstrated high accuracy with ≤5% error in dispensing the prescribed amount of liquid I-131. The use of the semi-automated system resulted in a significant reduction in whole body and extremity doses due to less contact between personnel and the source, and high accuracy of the prescribed amount of I-131.

Comparing brass mesh to tissue equivalent bolus materials for volumetric modulated arc therapy chest wall irradiation.

To compare the superficial dose when using brass mesh bolus (BMB), no bolus, or 3mm tissue-equivalent bolus with a pseudo-flash volumetric modulated arc therapy (VMAT) breast treatment planning technique. Two different beam arrangements for right-sided irradiation and one beam arrangement for bilateral irradiation were planned on an inhomogeneous thorax phantom in accordance with our clinical practice for VMAT postmastectomy radiotherapy (PMRT). Plans were optimized using pseudo-flash and representative critical organ optimization structures were used to shape the dose. Plans were delivered without bolus, with 3mm tissue-equivalent bolus (TEB), or with one-layer BMB. Optically stimulated luminescence dosimeter (OSLD) and radiochromic film measurements were taken and analyzed to determine the superficial dose in each case and the relative enhancement from the no bolus delivery. Superficial dose measured with OSLDs was found to be 76.4±4.5%, 103.0±6.1%, and 98.1±5.8% of prescription for no physical bolus (NB), TEB, and BMB, respectively. Superficial dose was observed to increase from lateral to medial points when measured with film. However, the relative increase in superficial dose from NB was consistent across the profile with an increase of 43±2.1% and 34±3.3% of prescription for TEB and BMB, respectively. The results are in good agreement with expectations from the literature and the experience with tangential radiotherapy. Three millimeter TEB and one-layer BMB were shown to provide similar enhancement to the superficial dose compared to delivery without bolus. BMB, which does not significantly affect dose at depth and is more conformal to the patient surface, is an acceptable alternative to 3mm TEB for chest wall PMRT patients treated with pseudo-flash PMRT.

Application of OSL strips in CT dosimetry according to the AAPM methodology

Computed tomography (CT) images contribute to high-quality medical diagnosis, but radiation dose can be quite high, requiring accurate assessment. CT dose index (CTDI) was developed for dosimetric purposes, but for scanners operated exclusively in axial mode. Nowadays, CTDI underestimate patient dose in helical CT exams. AAPM report TG111 (2010) suggested a new metric in which the patient's radiation dose is obtained from dose profiles constructed from several measurements made with a small ionization chamber. It is also possible to obtain dose profiles using properly calibrated OSL (optically stimulated luminescence) strips. The main objective of the present work is to contribute to optimizing CT dosimetry, comparing dose profiles obtained with OSL strips with measurements obtained by other authors. In this work, a “pencil” ionization chamber and 20 cm x 0.3 cm OSL strips were X-ray-irradiated, in air and in the holes of two cylindrical CT phantoms, using 100, 120, 140 kV peak voltages, both in lab and in a clinical CT scanner. Irradiated strips were read using an OSL reader built in the GDRFM. OSL profiles were calibrated against ionization chamber. From them, CTDIw and CTDIvol values were determined, differing approximately 3.9% from those of the CT scanner. From the profiles, also the planar equilibrium dose Deq,p (TG111) was evaluated in some CT protocols; Deq,p exceeded the CTDI values from the CT scanner in every case. E.g.: The percentage difference between Deq,p and CTDIvol for the head phantom ranged between 33-25%. Thus, in some cases, it could be advantageous to use calibrated OSL dosimeters instead of ionization chambers to obtain the profiles, saving time, because it is possible to obtain five OSL profiles from a single phantom irradiation.

Radiosurgery dosimetry using CaSO4:Eu OSLD film-a feasibility study.

Recent studies demonstrated that optically stimulated luminescence (OSL) systems allow the evaluation of doses for 2D mapping in a relatively fast and simple way and results show submillimeter resolution. This work presents, for the first time, an optically stimulated luminescence dosemeter (OSLD) in the form of film made with CaSO4:Eu particles embedded in a silicone elastomer matrix. The OSLD film was produced using a low-cost and relatively simple methodology. This film is reusable and the signal can be satisfactorily bleached using blue LEDs. The main dosimetric properties were evaluated using TL/OSL Risø reader with blue stimulation and Hoya U-340 filter. Investigation shows repeatability within 3% when measuring with the same film sample. Regarding the OSLD film homogeneity, nearly 12% sensitivity change was observed within the 5×5cm2 produced film. Additionally, the dose response curve shows linearity from 5 to 25Gy. Fading of the OSL signal is relatively high, about 50% in the first week and then is stable. Nevertheless, a 3×3cm2 OSLD film was successfully used to map dose distribution in radiosurgery (6MV photon beam). This work demonstrates the feasibility of 2D dosimetry using reusable OSLD films based on CaSO4:Eu.