Search Results (74)

Accurately estimating the radiation dose received by an individual is essential for evaluating potential damage caused by exposure to ionizing radiation. Most retrospective dosimetry methods require the time since exposure to be known and rely on calibration curves specific to that time point. In this work, we introduce a novel method tailored to the γ-H2AX assay, which is a protein-based biomarker for radiation exposure, that enables the estimation of both the radiation dose and the time of exposure within a plausible post-exposure interval. Specifically, we extend calibration curves available at two distinct time points by incorporating the biological decay of foci, resulting in a model that captures the joint dependence of foci count on both dose and time. We demonstrate the applicability of this approach using both real-world and simulated data. Full article

Background: We present the implementation of an in vivo dosimetry program that enhances treatment setups, ensuring high accuracy that is needed globally. This approach proves valuable in smaller departments by helping to detect and prevent errors. Evaluation studies have shown that in vivo dosimetry is a reliable method for assessing the overall accuracy of treatment delivery. Methods: Comprehensive development and validation of an in vivo dosimetry program using silicon diodes, ionization chambers, and calibrated electrometers for accurate radiation in dose measurements for treatments involving Co-60 or 6 MV X-ray beams. Results: The outcomes demonstrated that all diodes were dependable, with deviations of less than 1% (0.89 ± 0.10 cGy). Calibration curves were generated, showing dose variations of only 0.13% in the diode readings. The overall analysis revealed a mean deviation of up to 1%. Conclusions: These results provide a thorough assessment for patients’ treatment and facilitate timely interventions when needed, helping to ensure that dose variations stay within acceptable limits. Full article

This work introduces an original approach to the manufacturing of ionizing radiation-sensitive systems for radiotherapy applications—dosimetry. They are based on the Fricke dosimetric solution and the formation of macro-gels and capsules, and nano- and micro-gels. The reaction of ionic polymers, such as sodium alginate, with Fe and Ca metal ions is employed. Critical polymer concentration (c*) is taken as the criterion. Reaction of ionic polymers with metal ions leads to products related to c*. Well below c*, nano- and micro-gels may form. Above c*, macro-gels and capsules can be prepared. Nano- and micro-gels containing Fe in the composition can be used for infusion of a physical gel matrix to prepare 2D or 3D dosimeters. In turn, macro-gels can be formed with Fe ions crosslinking polymer chains to obtain radiation-sensitive hydrogels, so-called from wall-to-wall, serving as 3D dosimeters. The encapsulation process can lead to capsules with Fe ions serving as 1D dosimeters. This work presents the concept of manufacturing various gel structures, their main features and manufacturing challenges. It proposes new directions of research towards novel dosimeters. Full article

This work presents a Fricke radiochromic gel dosimeter with xylenol orange (XO) and a gelatin matrix modified with sorbitol. The dosimeter, combined with 2D scanning using a flatbed scanner and data processing using dedicated software packages, creates a radiotherapy dosimetry measurement system. The dosimeter reacts to ionizing radiation by changing color as a result of the formation of complexes of Fe³⁺ and XO molecules. It was characterized in terms of thermal and chemical stability and mechanical properties. The presence of sorbitol improved the mechanical and thermal properties of the dosimeter. The dosimeter maintains chemical stability, enabling its use in dosimetric applications, for at least six weeks. The dose–response characteristics of the dosimeter are discussed and indicate a dynamic dose–response of the dosimeter (up to saturation) of about 20 Gy and a linear dose–response of about 12.5 Gy. The following applications of the dosimeter are discussed: (i) as a 2D dosimeter in a plastic container for performing a coincidence test of radiation and mechanical isocenters of a medical accelerator, and (ii) for in vivo dosimetry as a 2D dosimeter alone and simultaneously as a bolus and a 2D dosimeter. Research has shown that the dosimeter has promise in many applications. Full article

Interventional radiology offers minimally invasive procedures guided by real-time imaging, reducing surgical risks and enhancing patient recovery. While beneficial to patients, these advancements increase occupational hazards for physicians due to chronic exposure to ionizing radiation. This exposure raises health risks like radiation-induced cataracts, cardiovascular disease, and cancer. Despite regulations like the European Council Directive 2013/59/EURATOM, which sets limits on whole-body and eye lens doses, no dose limits exist for the brain and meninges, since the brain has traditionally been considered a radioresistant organ. Recent studies, however, have highlighted radiation-induced brain damage, suggesting that meningeal exposure in interventional radiology may be underestimated. This study evaluates the entrance air Cumulative mean annual entrance air kerma to the skullull during interventional radiology procedures, using thermoluminescent dosimeters and controlled exposure simulations. Data were collected by varying the exposure time and analyzing the contribution to the entrance air kerma on each side of the head. The results indicate that, considering the attenuation of the cranial bone, the absorbed dose to the brain, obtained by averaging the head entrance air kerma for the right, front, and left sides of the operator’s head, could represent 0.81% to 2.18% of the annual regulatory limit in Italy of 20 mSv for the average annual effective dose of exposed workers (LD 101/2020). These results provide an assessment of brain exposure, highlighting the relatively low but non-negligible contribution of brain irradiation to the overall occupational dose constraint. Additionally, a correlation between entrance air kerma and the Kerma-Area Product was observed, providing a potential method for improved dose estimation and enhanced radiation safety for interventional radiologists. Full article

The two-dimensional (2D) measurement of radiation dose distribution on non-planar surfaces requires the use of a flexible dosimeter. This work concerns the use of a unique cotton textile-based dosimeter to characterize the dose distribution of a ⁶⁰Co source used in the research and sterilization of products. Alternatively, for high-dose-rate experiments, an electron beam accelerator has been used. The dosimeter was prepared by the padding-squeezing-drying of a cotton textile made of cellulose, where a 10% solution of nitrotetrazolium blue chloride (NBT) was used for the padding process. NBT served as a radiation-sensitive compound, which transformed into a purple-brown NBT formazan upon exposure to ionizing radiation. The NBT dosimeter is scanned after irradiation using a flatbed scanner, and the data is processed using dedicated software packages, which together constitute a 2D dose distribution measurement system. The green channel of the RGB color model contributes the most to the color change of the dosimeter. The calibration relation obtained for the green channel showed that the dosimeter responds to doses of 0.8–45 kGy. Conversions of the green channel signal were performed using the calibration relation to analyze the 2D dose at a large distance and close to a ⁶⁰Co source shielded by a solid metal and a cylindrical metal structure with holes. Additionally, the dose distribution was assessed using a dosimeter placed on metal implant models undergoing radiation serialization. This work demonstrates the potential of such a dosimeter for characterizing high-dose-rate ⁶⁰Co sources and measuring the dose distribution on non-planar surfaces. Full article

This study presents a comprehensive dosimetric characterization and commissioning of a grid-type collimator manufactured via 3D printing using PLA-W composite filament, following an international protocol for small-field dosimetry. PLA doped with high concentrations of tungsten (>90% w/w) enables the fabrication of miniaturized collimators (<1 cm) with complex geometries, suitable for non-conventional radiotherapy applications. However, accurate assessment of spatial dose modulation is challenged by penumbra overlap between closely spaced beamlets, limiting the application of conventional instrumentation and protocols. To address this, absolute and relative dose distributions were evaluated for various radiation field configurations (number of beamlets) in both lateral and depth directions. Measurements were performed according to the IAEA TRS-483 protocol, using micro-ionization chambers and diode detectors. Additionally, long-term stability assessments were carried out to evaluate both the structural integrity and modulation performance of the printed grid over time. Point dose measurements using the same detectors were repeated after one year, and 2D surface dose distributions measured with EBT3 films were compared to SRS MapCHECK measurements two years later. The generated radiation field size of the central beamlet (FWHM) differed by less than 0.2% (15.8 mm) from the physical projection size (15.6 mm) and the lateral transmission due simultaneous beamlets resulted in FWHM variations of less than 3.8%, confirming manufacturing precision and collimator capability. Output factor measurements increased with the number of beamlets, from 0.75 for a single beamlet to 0.82 for the full beamlets configuration. No significant changes were observed in the depth of maximum dose across the different beamlets configurations (1.20 ± 0.20 cm). On the other hand, the long-term evaluations show no relevant changes in the FWHM or VPR, confirming the performance and reliability of the system. These results support the clinical feasibility and lasting performance stability of in-house manufactured grid collimators using PLA-W filaments and accessible 3D printing technology. Full article

The thermoluminescence (TL) method is one of the most widely used techniques in various studies, including dosimetric applications, dating of archaeological and geological materials, luminescence spectroscopy of certain insulating or semiconducting phosphors, and the detection of ionizing radiation damage. This study examines the TL properties of plagioclase, a feldspar group mineral, focusing on its dose–response behavior, kinetic parameters, and glow curve characteristics. TL measurements of plagioclase samples were carried out with different ionizing radiation doses ranging from 0.1 to 550 Gy. The results show a strong linear dose–response relationship in the 0.3–550 Gy range, with no evidence of saturation or supralinearity. A computerized glow curve deconvolution (CGCD) analysis revealed that the TL glow curve of the mineral consists of five distinct TL peaks with activation energies ranging from 0.842 eV to 0.890 eV and obeying general order kinetics. In addition, an artificial neural network (ANN) model was developed to predict TL glow curves using three optimization algorithms, including Levenberg–Marquardt (LM), Bayesian Regularization (BR), and Scaled Conjugate Gradient (SCG). Among these, the BR algorithm demonstrated the best performance with an accuracy value of 0.99915, a Mean Absolute Error (MAE) of 2.34 × 10⁻³, and a Mean Squared Error (MSE) of 3.82 × 10⁻⁵, outperforming LM and SCG in in terms of generalization and accuracy. The findings of this study demonstrate the effectiveness of combining TL analysis with ANN-based modelling for accurate dose–response predictions and the improved luminescence characterization of plagioclase, supporting the applications of luminescence studies in radiation dosimetry and geochronology. Full article

This study aims to determine the density of two hydrogel-based media, medium with agar-agar and medium with agar-agar and glucose, which are suitable for both irradiation and bacterial growth, considering the presence or absence of Staphylococcus aureus and Escherichia coli strains. The viability of Escherichia coli cell-inoculated systems was also evaluated to explore potential applications in radiation dosimetry within the 0–10 Gy range, using spectrophotometric and bacterial culture methods. Mass density measurements were performed at varying temperatures using two approaches: the first one, based on direct measurements of mass and volume, yielded densities comparable to liquid water, with uncertainties ranging from 9 to 16%, while the second approach, employing Archimedes’ principle (mass in air vs. mass in a liquid of known density), produced more accurate results, with uncertainties between 0.04 and 0.08%, thus proving more reliable for density determinations. Furthermore, the feasibility study of Escherichia coli-inoculated systems for ionizing radiation dosimetry demonstrated a linear spectrophotometric response to radiation doses across the investigated range, particularly for samples stored at 25 °C. The studied systems were characterized in terms of the corresponding growth curve and post-irradiation bacterial survival, supporting their potentiality as reliable ionizing radiation dosimeters. Full article

Background: Digital tomosynthesis (DTS) is an advanced imaging modality that enhances diagnostic accuracy by offering three-dimensional visualization from two-dimensional projections, which is particularly beneficial in breast and lung imaging. However, this increased imaging capability raises concerns about patient exposure to ionizing radiation. Methods: This study explores the energy and angular dependence of thermoluminescent dosimeters (TLDs), specifically TLD100H, to improve the accuracy of organ dose assessment during DTS. Using a comprehensive experimental approach, organ doses were measured in both DTS and traditional RX modes. Results: The results showed lung doses of approximately 3.21 mGy for the left lung and 3.32 mGy for the right lung during DTS, aligning with the existing literature. In contrast, the RX mode yielded significantly lower lung doses of 0.33 mGy. The heart dose during DTS was measured at 2.81 mGy, corroborating findings from similar studies. Conclusions: These results reinforce the reliability of TLD100H dosimetry in assessing radiation exposure and highlight the need for optimizing imaging protocols to minimize doses. Overall, this study contributes to the ongoing dialogue on enhancing patient safety in diagnostic imaging and advocates for collaboration among medical physicists, radiologists, and technologists to establish best practices. Full article

Stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) require precise small-field dosimetry, verified through patient-specific quality assurance (PSQA). This study evaluated the feasibility of using a single-crystal cadmium–zinc–telluride (Cd_0.9Zn_0.1Te, CZT) detector for PSQA in SRS and SBRT. We fabricated a CZT detector with Au electrodes and examined its fundamental characteristics, including dose linearity, dose rate dependence, energy dependence, angular dependence, source-to-surface distance (SSD) dependence, field size dependence, depth dependence, and reproducibility, under 6 and 10 MV LINAC beam irradiation and compared the results with those from a standard ionization chamber. The results revealed that the CZT detector demonstrated excellent linearity across 0–1000 cGy with minimal deviation in the low-dose region, negligible dose rate dependence, and minimal energy dependence, exhibiting a 2.2% drop at 15 MV relative to 6 MV. Its angular and SSD dependencies deviated slightly from the ionization chamber, consistent with the expected physical behaviors and correctable in clinical practice. The detector also revealed consistent performance over time with excellent reproducibility, and its depth dependence results were consistent with those of the ionization chamber. Thus, the CZT detector provides consistent performance in small-field measurements under varying conditions, satisfying the requirements for SRS and SBRT. Full article

This study evaluated the occupational exposure of radiopharmacists, nurses, radiological technologists, and radiological technologist assistants involved in ^99mTc-MDP bone scintigraphy procedures. Actual occupational effective doses for individual staff needed ascertaining. An environmental radiation exposure audit revealed all nuclear medicine areas were compliant with ICRP and IAEA guidelines. To ascertain individual doses, they were recorded by OSL badges. The highest exposure was to the radiopharmacists, Hp(0.07) 2.19 µSv during radiolabeling. The nurse administering ^99mTc-MDP recorded a dose of 0.27 µSv at Hp(0.07), 26.01% of the total occupational effective dose. The radiological technologist and assistant receive 73.05% of the total effective dose. However, the highest effective dose was received by the technologist assistant positioning patients for SPECT/CT scans, with an effective dose of 32.03 µSv. Single and double dosimetry effective dose estimate algorithms were evaluated, resulting in the double dosimetry being more accurate. The Padovani et al. algorithm was found to most closely align with ^99mTc-MDP actual effective dose values (p > 0.05), thereby validating the measurement methods used in this study. The research offers benchmark environmental exposure and effective doses applicable in audits and the continuous effort to enhance radiation safety for personnel during ^99mTc-MDP bone scintigraphy. Full article

Radiotherapy (RT) has been shown to be a cornerstone of both palliative and curative tumor care. RT has generally been reported to be sharply limited by ionizing radiation (IR)-induced toxicity, thereby constraining the control effect of RT on tumor growth. FLASH-RT is the delivery of ultra-high dose rate (UHDR) several orders of magnitude higher than what is presently used in conventional RT (CONV-RT). The FLASH-RT clinical trials have been designed to examine the UHDR deliverability, the effectiveness of tumor control, the dose tolerance of normal tissue, and the reproducibility of treatment effects across several institutions. Although it is still in its infancy, FLASH-RT has been shown to have potential to rival current RT in terms of safety. Several studies have suggested that the adoption of FLASH-RT is very limited, and the incorporation of this new technique into routine clinical RT will require the use of accurate dosimetry methods and reproducible equipment that enable the reliable and robust measurements of doses and dose rates. The purpose of this review is to highlight the advantages of this technology, the potential mechanisms underpinning the FLASH-RT effect, and the major challenges that need to be tackled in the clinical transfer of FLASH-RT. Full article

The Dicentric Chromosome Assay (DCA) is widely used in biological dosimetry, where the number of dicentric chromosomes induced by ionizing radiation (IR) exposure is quantified to estimate the absorbed radiation dose an individual has received. Dicentric chromosome scoring is a laborious and time-consuming process which is performed manually in most cytogenetic biodosimetry laboratories. Further, dicentric chromosome scoring constitutes a bottleneck when several hundreds of samples need to be analyzed for dose estimation in the aftermath of large-scale radiological/nuclear incident(s). Recently, much interest has focused on automating dicentric chromosome scoring using Artificial Intelligence (AI) tools to reduce analysis time and improve the accuracy of dicentric chromosome detection. Our study aims to detect dicentric chromosomes in metaphase plate images using an ensemble of artificial neural network detectors suitable for datasets that present a low number of samples (in this work, only 50 images). In our approach, the input image is first processed by several operators, each producing a transformed image. Then, each transformed image is transferred to a specific detector trained with a training set processed by the same operator that transformed the image. Following this, the detectors provide their predictions about the detected chromosomes. Finally, all predictions are combined using a consensus function. Regarding the operators used, images were binarized separately applying Otsu and Spline techniques, while morphological opening and closing filters with different sizes were used to eliminate noise, isolate specific components, and enhance the structures of interest (chromosomes) within the image. Consensus-based decisions are typically more precise than those made by individual networks, as the consensus method can rectify certain misclassifications, assuming that individual network results are correct. The results indicate that our methodology worked satisfactorily in detecting a majority of chromosomes, with remarkable classification performance even with the low number of training samples utilized. AI-based dicentric chromosome detection will be beneficial for a rapid triage by improving the detection of dicentric chromosomes and thereby the dose prediction accuracy. Full article

This research reviews a novel artificial intelligence (AI)-based application called TLDetect, which filters and classifies anomalous glow curves (GCs) of thermoluminescent dosimeters (TLDs). Until recently, GC review and correction in the lab were performed using an old in-house software, which uses the Microsoft Access database and allows the laboratory technician to manually review and correct almost all GCs without any filtering. The newly developed application TLDetect uses a modern SQL database and filters out only the necessary GCs for technician review. TLDetect first uses an artificial neural network (ANN) model to filter out all regular GCs. Afterwards, it automatically classifies the rest of the GCs into five different anomaly classes. These five classes are defined by the typical patterns of GCs, i.e., high noise at either low or high temperature channels, untypical GC width (either wide or narrow), shifted GCs whether to the low or to the high temperatures, spikes, and a last class that contains all other unclassified anomalies. By this automatic filtering and classification, the algorithm substantially reduces the amount of the technician’s time spent reviewing the GCs and makes the external dosimetry laboratory dose assessment process more repeatable, more accurate, and faster. Moreover, a database of the class anomalies distribution over time of GCs is saved along with all their relevant statistics, which can later assist with preliminary diagnosis of TLD reader hardware issues. Full article