[Analysis of the results of personal monitoring to ionizing radiation at workplaces]. / Analiza wyników rutynowego monitoringu narazenia personelu na promieniowanie jonizujace w miejscach pracy.

BACKGROUND: The paper presents the results of dosimetric measurements routinely performed by the Radiation Protection Department of the Nofer Institute of Occupational Medicine (NIOM) in Lódz in 2022 for people occupationally exposed to X and γ radiation. MATERIAL AND METHODS: The evaluation of the effective dose as part of individual dosimetry was provided using the film or thermoluminescent dosimetry (TLD). Additionally, based exclusively on the TLD method, measurements of the ambient dose equivalent H*(10) and personal dose equivalents Hp(0.07) and Hp(3) were performed. In 2022, the dosimetric service of the Radiological Protection Department of the NIOM covered >30 000 workers employed in >4500 laboratories (mainly health care departments). All measurements were performed in accordance with accredited research procedures (number AB 327). RESULTS: In 2022, the average annual dose of Hp(10) was equal to 0.26 mSv, whereas Hp(0.07) measured using ring and wrist dosimetry was equal to 0.63 mSv and 0.78 mSv, respectively. In turn, the average Hp(3) value was 0.21 mSv. In 2022, there was not a single case of exceeding the annual dose limit among people measured by the NIOM. CONCLUSIONS: The data collected in the "Dosimetry" database of the NIOM and a detailed analysis of annual doses received by people occupationally exposed to ionizing radiation indicate a well-functioning radiological protection system in Poland. Med Pr Work Health Saf. 2024;75(5).

Do we need dosimetry for optimization of theranostics in CNS tumors?

Radiopharmaceutical theranostic treatments have grown exponentially worldwide, and internal dosimetry has attracted attention and resources. Despite some similarities with chemotherapy, radiopharmaceuticals treatments are essentially radiotherapy treatments, as the release of radiation into tissues is the determinant of the observed clinical effects. Therefore, absorbed dose calculations are key to explain dose-effect correlations and to individualize radiopharmaceutical treatments. The present article introduces the basic principles of internal dosimetry and provides an overview of available locoregional and systemic radiopharmaceutical treatments for CNS tumors. The specific characteristics of dosimetry as applied to these treatments are highlighted, along with their limitations and most relevant results. Dosimetry is performed with higher precision and better reproducibility than in the past, and dosimetric data should be systematically collected, as treatment planning and verification may help exploit the full potential of theranostic of CNS tumors.

Novel EBT3 film calibration using an integrated HSV color space analysis.

PURPOSE: Radiochromic EBT3 films are commonly used as dosimeter for clinical practice and research on radiotherapy. In principle, they are associated with a flatbed scanner to determine the optical density change, which can be correlated to the absorbed dose after calibration. Several approaches have been proposed to reduce the uncertainties during acquisition and to compensate the lighting inhomogeneities, thus improving the dose measurement. Those works have shown that good accuracy can be achieved for absorbed dose using EBT3 films, at the expense of complex data processing and time-consuming acquisition protocols. METHOD: We introduce the new method to determine the calibration curve based on the HSV color space analysis, which provides robustness and invariance to illumination changes. RESULTS: With this new approach, it allows to compute the calibration curve by performing only a single scan of film pieces regardless either the lateral positions or control points on the scanner bed. Using the hue channel in HSV color space, we prove that the dose can be accurately reconstructed with a much simpler protocol than when using RGB channels with blank scans rectification. Our HSV approach includes comparative gamma index for conventional film analysis. It achieves a gamma index (3%/3mm) over 99% when comparing measurement and AAA computation for a modulated beam. CONCLUSION: Compared to most existing approaches, our approach does not rely on complex mathematical reconstructions or additional scans. Instead, it uses another color model representation to rectify the scanner response, coping the dose measurement homogeneity problem over the scanner window. It facilitates the overall scan calibration to be much simpler, save time, and less manipulations, which also decreases the risk of human error.

In vivo dosimetry of total body irradiation patients: A 10 year retrospective analysis.

Myeloablative Total Body Irradiation (TBI) used in our Institution, as part of the conditioning scheme for haematopoietic stem cell transplantation, is an extended-distance supine technique that has been implemented using a 15 MV LINAC beam, lead lung compensators, PMMA, and water bolus to improve homogeneity. This study reviews in-vivo dosimetry (IVD) over 10 years of treatments, assessing the technique's robustness, accuracy, and efficiency. A 2-lateral opposite fields plan was calculated from planning CT with validated Oncentra TPS (Elekta AB, Sweden). Monitor units (MUs), lung compensators shape and thickness were calculated to deliver the prescription dose (12 Gy in 6 bi-daily fractions or 9.9 Gy in 3 daily fractions) to the patient's abdomen midline at the umbilical level, maintaining lung dose within ±5 % range of prescription. Data from 103 patients, of which more than 87 % were pediatric, were retrieved and analyzed for a total of 537 treatment fractions. The impact of IVD omission was evaluated, supposing doing it only once or in the first two fractions, if necessary. Median ΔMU from planned was -1.2 %. Median percentage dose deviation from prescription in 6 anatomical regions was below 2 %. IVD omission could have resulted in an increase of 7 patients registering at least one anatomical region outside the ±5 % dose range at the end of treatment. It is possible to confirm the implemented technique's robustness and accuracy in delivering the prescribed dose under IVD monitoring. Nevertheless, this technique and associated IVD are time-consuming and IVD omission could be assessed with limited drawbacks.

Seasonal variation of particle number concentration in a busy urban street with exposure assessment and deposition in human respiratory tract.

Ultrafine particles (UFP) associated with air quality and health impacts are a major concern in growing urban regions. Concentrations of UFP (particles of size between 10 and 100 nm) and accumulation mode (Nacc) (particles of size >100 and up to 1000 nm), are analyzed over a highly polluted megacity, Delhi, in conjunction with vehicular flow density, during peak (morning, and evening) and non-peak hours. UFP contributes ≥60% to total particle concentration during autumn and monsoon. UFP concentrations are about 50,000 particles per cm3 in winter which reduces to about 25,000 particles during monsoon. Nacc are about 20,000 (winter) and 10,000 (monsoon) particles per cm3. UFP concentration and Nacc during peak hours are at least twice higher than those obtained in non-peak hours, confirming the dominant influence of emissions from vehicular exhaust in the study region. Seasonal analysis of UFP size distribution reveals that direct emissions dominate the particle concentrations during winter and autumn, whereas new particle formation mechanism contributes the highest in spring and summer. Assessment of inhalable particle number concentration and particle deposition in the human respiratory tract using Multiple Path Particle Dosimetry (MPPD) model, performed for the first time, shows that the order in which these particles deposit in the human respiratory tract is alveoli > bronchiole > bronchus. The deposition ranges between 10 and 18 million nanoparticles during different hours of the day, whereas the estimated inhalable particle concentration (IPN) varies between 0.5 and 1 billion. Results on the IPN during activities classified from light (walking), medium, heavy, very heavy to severe (long-distance running) provide insights into health effects on vulnerable populations. These quantitative results obtained over a megacity on hourly and seasonal variations of nanoparticles along with IPN and deposition rates for different activities are important, and are invaluable inputs for developing mitigation policies aimed to improve air quality and public health, both of which are major concerns in South Asia.

A Four-dimensional Computed Tomography Generated Internal Target Volume Approach to Paediatric High Risk Neuroblastoma to Reduce Organ at Risk and Normal Tissue Irradiation.

AIMS: The magnitude of upper abdominal organ motion in children may be overestimated by current planning target volumes (PTV). A four-dimensional computed tomography (4DCT) - derived internal target volume (ITV) is frequently used in adult radiotherapy to take respiratory-related organ motion into account. In this study, the dosimetric consequences for target coverage and organs at risk from the use of an ITV approach compared to standard PTV margins in children with high-risk neuroblastoma were investigated. MATERIALS AND METHODS: 14 patients, median age 4.1 years, range 1.5 - 18.9 years, (9 midline targets, 5 lateralised) each had two dual arc volumetric modulated arc therapy (VMAT) plans (14 ×1.5 Gy) generated. One used an ITV-approach; motion information derived from 4DCT (PTV_itv) with a 5mm ITV to PTV expansion, and the other a PTV margin of 10mm from CTV to PTV (PTV_standard). Differences in absolute PTV volume and organ at risk doses are described. RESULTS: The ITV approach resulted in a highly significant reduction in PTV size of 38% (p<0.0001). For midline targets, an ITV approach resulted in a small but statistically significant reduction in combined mean kidney dose of 0.8Gy, p 0.01. Mean heart and lung dose were reduced by an average of 1 Gy with an ITV approach. Non-PTV integral dose from 30.4 Gy L to 27.8 Gy L using an ITV approach. CONCLUSION: An ITV-approach to respiratory related organ motion management in children can significantly reduce absolute PTV volumes, maintain target coverage and reduce dose delivered to normal tissue in proximity to the target. This is an essential step to maximising the benefits of highly conformal radiotherapy techniques including VMAT for this patient group, and in the future with Proton Therapy.

Whole-blood RNA biomarkers for predicting survival in non-human primates following thoracic radiation.

Radiation injury, either from radiotherapy or a mass-casualty event requires a health care system that can efficiently allocate resources to patients. We conducted a comprehensive transcriptome analysis of whole blood from a nonhuman primate model that received upper thoracic radiation (9.8-10.7 Gy). Blood samples were collected at multiple time points, extending up to 270 days post-irradiation with a minimum n = 6 for initial time points (Day 3-Day 40) and a total number of n = 28 primates. No males receiving the higher dose survived to Day 270. Using the Elastic Net model in R we found that pooling biomarkers from Day 3-21 increased our accuracy in discerning survival time, pleural effusion or dose compared to using biomarkers specific to a single day. For survival data, in predicting short term (less than 90 day), medium term (Day 91-269) or long-term survival (Day 270), prediction accuracy using only Day 3 data was 0.14 (95% Confidence Interval (CI) 0.1, 0.19) while pooled data for Male and Female was 0.76 (CI 0.69, 0.82). When pooled data was divided by biological sex, accuracy was 0.7 (CI 0.58, 0.8) for pooled data from Males and 0.84 (CI 0.76, 0.91) for Females. The development of RNA biomarkers as a tool to aid in clinical decision-making could significantly improve patient care in cases of radiation injury, whether from radiotherapy or mass-casualty events. Further validation and clinical translation of these findings could lead to improved patient care and management strategies in cases of radiation exposure.

E-Brachy: New dosimetry package for electronic brachytherapy sources.

BACKGROUND: Large reported variability in the material composition and geometrical components of the Xoft electronic high-dose-rate brachytherapy Causes inter-source discrepancy in the source output. This variability is due to the manual manufacturing and assembly of the sources. PURPOSE: This study aimed to develop a dosimetry software tool called E-Brachy to characterize the Xoft source and quantify the discrepancies in its photon spectrum and dosimetric properties. METHODS: E-Brachy is based on the Geant4 Monte Carlo toolkit and consists of two parts. In part one, the geometry and material composition for the source received in the computer-aided design format from the vendor were converted to the geometry description markup language format using the GUIMesh Python tool and integrated into the E-Brachy software. There was a large variation in material composition and thickness for some of the tube components. The simulation started from electrons and resulted in x-ray generations in the anode region. Multithreading, a track length estimation, and the uniform bremsstrahlung splitting variance reduction techniques were used to decrease the simulation time and increase the x-ray production. The photon energy, position, and momentum were saved into a phase space file as the photon exited the source, but before interacting with the external environment. The obtained x-ray energy spectrum was compared with measurements from the National Institute of Standards and Technology (NIST). In part two, by sampling from the generated photons, the dose rates and dosimetric parameters according to the TG-43 protocol were calculated for model S7500 and compared to the ones previously calculated for model S700 source, which were deemed identical by the manufacturer. RESULTS: The material composition that resulted in the most similar spectrum as the measured NIST spectrum with Pearson's correlation coefficient of 0.99 and a calculated Euclidean difference of 0.061 ± 0.001 $0.061\,\pm \,0.001$  keV was chosen for further dosimetric analysis of the model S7500 source. Characteristic peaks showed the presence of tungsten, yttrium, and silver in the source components. Differences in dose rates between the two source models surpassed 20% for polar angles θ ≥ 150 ∘ $\theta \,\ge \,150^\circ$ , reaching a peak at r = 3 $r\,=\,3$  cm and θ = 175 ∘ $\theta \,=\,175^\circ$ . The differences in the radial dose function values were within 5%. The relative difference in percentage between the anisotropy function values of the two models was closer to 0 for smaller θ $\theta$ values, but at higher polar angles, they increased to 300%. CONCLUSIONS: A software package called E-Brachy was successfully developed for the characterization and dosimetry of Xoft electronic brachytherapy sources. E-Brachy can be combined with spectral measurements to investigate the inter- and intra-source variability. The software package was tested by comparing the simulated spectra from the S7500 Xoft source model with NIST measurements and its TG-43 parameters with the S700 model. The TG-43 parameters between the two sources significantly exceed the recommendations of TG-56.

Air Quality Geospatial Analysis in Vulnerable Areas. Case Study of Valencia (Spain).

The escalating concern over poor air quality, particularly nitrogen dioxide (NO2), poses a critical public health challenge, especially for vulnerable populations, such as children, older adults, and those with chronic diseases. This study aimed to analyze air quality in areas with vulnerable populations through a geospatial analysis of NO2 concentration measured by the passive dosimetry method in 2022. The results reveal high vulnerability caused by areas with over-centralized facilities and high concentrations of nitrogen dioxide, often coinciding with busy avenues. The study emphasizes the urgent need to address air quality disparities, providing crucial insights for public decision-makers to allocate resources effectively and reduce environmental inequalities in the city, ultimately safeguarding the health of at-risk communities.

In silicodosimetry for a prostate cancer treatment using198Au nanoparticles.

OBJECTIVE: To estimate dose rates delivered by using radioactive198Au nanoparticles for prostate cancer nanobrachytherapy, identifying contribution by photons and electrons emmited from the source. Approach: Utilizingin silicomodels, two different anatomical representations were compared: a mathematical model and a unstructured mesh model based on the International Commission on Radiological Protection (ICRP) Publication 145 phantom. Dose rates by activity were calculated to the tumor, and nearby healthy tissues, including healthy prostate tissue, urinary bladder wall and rectum, using Monte Carlo code MCNP6.2. Main results: Results indicate that both models provide dose rate estimates within the same order of magnitude, with the mathematical model overestimating doses to the prostate and bladder by approximately 20% compared to the unstructured mesh model. The discrepancies for the tumor and rectum were below 4%. Photons emmited from the source were defined as the primary contributors to dose to other organs, while 97.9% of the dose to the tumor was due to electrons emmited from the source. Significance: Our findings emphasize the importance of model selection in dosimetry, particularly the advantages of using realistic anatomical phantoms for accurate dose calculations. The study demonstrates the feasibility and effectiveness of198Au nanoparticles in achieving high dose concentrations in tumor regions while minimizing exposure to surrounding healthy tissues. Beta emissions were found to be predominantly responsible for tumor dose delivery, reinforcing the potential of198Au nanoparticles in localized radiation therapy. We advocate for using realistic body phantoms in further research to enhance reliability in dosimetry for nanobrachytherapy, as the field still lacks dedicated protocols. .

MIRD Pamphlet No. 31: MIRDcell V4-Artificial Intelligence Tools to Formulate Optimized Radiopharmaceutical Cocktails for Therapy.

Radiopharmaceutical cocktails have been developed over the years to treat cancer. Cocktails of agents are attractive because 1 radiopharmaceutical is unlikely to have the desired therapeutic effect because of nonuniform uptake by the targeted cells. Therefore, multiple radiopharmaceuticals targeting different receptors on a cell is warranted. However, past implementations in vivo have not met with convincing results because of the absence of optimization strategies. Here we present artificial intelligence (AI) tools housed in a new version of our software platform, MIRDcell V4, that optimize a cocktail of radiopharmaceuticals by minimizing the total disintegrations needed to achieve a given surviving fraction (SF) of tumor cells. Methods: AI tools are developed within MIRDcell V4 using an optimizer based on the sequential least-squares programming algorithm. The algorithm determines the molar activities for each drug in the cocktail that minimize the total disintegrations required to achieve a specified SF. Tools are provided for populations of cells that do not cross-irradiate (e.g., circulating or disseminated tumor cells) and for multicellular clusters (e.g., micrometastases). The tools were tested using model data, flow cytometry data for suspensions of single cells labeled with fluorochrome-labeled antibodies, and 3-dimensional spatiotemporal kinetics in spheroids for fluorochrome-loaded liposomes. Results: Experimental binding distributions of 4 211At-antibodies were considered for treating suspensions of MDA-MB-231 human breast cancer cells. A 2-drug combination reduced the number of 211At decays required by a factor of 1.6 relative to the best single antibody. In another study, 2 radiopharmaceuticals radiolabeled with 195mPt were each distributed lognormally in a hypothetical multicellular cluster. Here, the 2-drug combination required 1.7-fold fewer decays than did either drug alone. Finally, 2 225Ac-labeled drugs that provide different radial distributions within a spheroid require about one half of the disintegrations required by the best single agent. Conclusion: The MIRDcell AI tools determine optimized drug combinations and corresponding molar activities needed to achieve a given SF. This approach could be used to analyze a sample of cells obtained from cell culture, animal, or patient to predict the best combination of drugs for maximum therapeutic effect with the least total disintegrations.

Cell-nanoparticle stickiness and dose delivery in a multi-model in silico platform: DosiGUI.

BACKGROUND: It is well-known that nanoparticles sediment, diffuse and aggregate when dispersed in a fluid. Once they approach a cell monolayer, depending on the affinity or "stickiness" between cells and nanoparticles, they may adsorb instantaneously, settle slowly - in a time- and concentration-dependent manner - or even encounter steric hindrance and rebound. Therefore, the dose perceived by cells in culture may not necessarily be that initially administered. Methods for quantifying delivered dose are difficult to implement, as they require precise characterization of nanoparticles and exposure scenarios, as well as complex mathematical operations to handle the equations governing the system dynamics. Here we present a pipeline and a graphical user interface, DosiGUI, for application to the accurate nano-dosimetry of engineered nanoparticles on cell monolayers, which also includes methods for determining the parameters characterising nanoparticle-cell stickiness. RESULTS: We evaluated the stickiness for 3 industrial nanoparticles (TiO2 - NM-105, CeO2 - NM-212 and BaSO4 - NM-220) administered to 3 cell lines (HepG2, A549 and Caco-2) and subsequently estimated corresponding delivered doses. Our results confirm that stickiness is a function of both nanoparticle and cell type, with the stickiest combination being BaSO4 and Caco-2 cells. The results also underline that accurate estimations of the delivered dose cannot prescind from a rigorous evaluation of the affinity between the cell type and nanoparticle under investigation. CONCLUSION: Accurate nanoparticle dose estimation in vitro is crucial for in vivo extrapolation, allowing for their safe use in medical and other applications. This study provides a computational platform - DosiGUI - for more reliable dose-response characterization. It also highlights the importance of cell-nanoparticle stickiness for better risk assessment of engineered nanomaterials.

Characterization of brass mesh bolus for electron beam therapy.

Purpose. Bolus is often required for targets close to or on skin surface, however, standard bolus on complex surfaces can result in air gaps that compromise dosimetry. Brass mesh boluses (RPD, Inc., Albertville, MN) are designed to conform to the patient's surface and reduce air gaps. While they have been well characterized for their use with photons, minimal characterization exists in literature for their use with electrons.Methods and materials.Dosimetric characteristics of brass mesh bolus was investigated for use with 6, 9 and 12 MeV electrons using a 10 × 10 cm2applicator on standard multi-energy LINAC. Measurements for bolus equivalence and percentage depth doses (PDDs) under brass mesh, as well as surface dose measurements were performed on solid water and a 3D printed resin breast phantom (Anycubic Photon MonoX, Shenzhen, China) using Markus®parallel-plate ionization chamber (Model 34045, PTW Freiburg, Germany), thermoluminescent detectors (TLD) and EBRT film. After obtaining surface dose measurements, these were compared to dose calculated on the Pinnacle3 treatment planning system (TPS, 16.2, Koninklijke Philips N.V.).Results. Measurements of surface dose under brass mesh showed consistently higher dose than without bolus, confirming that brass mesh can increase the PDD at surface up to ∼ 94% of dose at dmax, depending on incident electron energy. This increase is equivalent to using ∼ 7.2 mm water equivalent bolus for 6 MeV, ∼ 3.6 mm for 9 MeV and ∼ 2.2 mm bolus for 12 MeV electrons. TPS results showed close agreement within-vivomeasurements, confirming the potential for brass mesh as bolus for electron irradiation, provided blousing effect is correctly modelled.Conclusions. To increase electron surface dose, a brass mesh can be used with equivalent effect of water-density bolus varying with electron energy. Proper implementation could allow for ease of treatment, as well as increase bolus conformality in electron-only plans.

New approach methodologies (NAMs) for the in vitro assessment of cleaning products for respiratory irritation: workshop report.

The use of in vitro new approach methodologies (NAMs) to assess respiratory irritation depends on several factors, including the specifics of exposure methods and cell/tissue-based test systems. This topic was examined in the context of human health risk assessment for cleaning products at a 1-day public workshop held on 2 March 2023, organized by the American Cleaning Institute® (ACI). The goals of this workshop were to (1) review in vitro NAMs for evaluation of respiratory irritation, (2) examine different perspectives on current challenges and suggested solutions, and (3) publish a manuscript of the proceedings. Targeted sessions focused on exposure methods, in vitro cell/tissue test systems, and application to human health risk assessment. The importance of characterization of assays and development of reporting standards was noted throughout the workshop. The exposure methods session emphasized that the appropriate exposure system design depends on the purpose of the assessment. This is particularly important given the many dosimetry and technical considerations affecting relevance and translation of results to human exposure scenarios. Discussion in the in vitro cell/tissue test systems session focused on the wide variety of cell systems with varying suitability for evaluating key mechanistic steps, such as molecular initiating events (MIEs) and key events (KEs) likely present in any putative respiratory irritation adverse outcome pathway (AOP). This suggests the opportunity to further develop guidance around in vitro cell/tissue test system endpoint selection, assay design, characterization and validation, and analytics that provide information about a given assay's utility. The session on applications for human health protection emphasized using mechanistic understanding to inform the choice of test systems and integration of NAMs-derived data with other data sources (e.g., physicochemical properties, exposure information, and existing in vivo data) as the basis for in vitro to in vivo extrapolation. In addition, this group noted a need to develop procedures to align NAMs-based points of departure (PODs) and uncertainty factor selection with current human health risk assessment methods, together with consideration of elements unique to in vitro data. Current approaches are described and priorities for future characterization of in vitro NAMs to assess respiratory irritation are noted.

TL response of Sm-doped MgO to 60Co gamma radiation.

The thermoluminescent (TL) response of MgO doped with different rare earths was investigated. The TL material was synthesized by the solution combustion method and sintered at 1173 K; the obtained powders were prepared in pellet form. Before irradiation, the dosimeters were annealed at 623 K for 30 min to eliminate any TL signal generated during their manufacture. Independent tests were performed doping the MgO with Tm, Dy, Ce and Sm. The highest TL response was found for Sm-doped MgO (MgO:Sm) reaching the highest sensitivity for 0.4 mol% of Sm. For this sample, the TL response showed linearity from 0.001 to 500 Gy of 60Co gamma radiation. The lower detection limit was found to be equal to 1.17 µGy. The sensitivity of the MgO:Sm prepared dosimeter was approximately 10% the sensitivity of the commercial TLD-100. The TL signal fading was found to be 6% after one month. The deconvolution of the glow curve showed a symmetric peak with a general order kinetics, b, centered at 474 K. These results suggest that this new TL material could be a promising detector to use in diverse dosimetry applications.

Size-Sorted Superheated Nanodroplets for Dosimetry and Range Verification of Carbon-Ion Radiotherapy.

Nanodroplets have demonstrated potential for the range detection of hadron radiotherapies. Our formulation uses superheated perfluorobutane (C4F10) stabilized by a poly(vinyl-alcohol) shell. High-LET (linear energy transfer) particles vaporize the nanodroplets into echogenic microbubbles. Tailored ultrasound imaging translates the generated echo-contrast into a dose distribution map, enabling beam range retrieval. This work evaluates the response of size-sorted nanodroplets to carbon-ion radiation. We studied how thesize of nanodroplets affects their sensitivity at various beam-doses and energies, as a function of concentration and shell cross-linking. First, we show the physicochemical characterization of size-isolated nanodroplets by differential centrifugation. Then, we report on the irradiations of the nanodroplet samples in tissue-mimicking phantoms. We compared the response of large (≈900 nm) and small (≈400 nm) nanodroplets to different carbon-ions energies and evaluated their dose linearity and concentration detection thresholds by ultrasound imaging. Additionally, we verified the beam range detection accuracy for the nanodroplets samples. All nanodroplets exhibited sensitivity to carbon-ions with high range verification precision. However, smaller nanodroplets required a higher concentration sensitivity threshold. The vaporization yield depends on the carbon-ions energy and dose, which are both related to particle count/spot. These findings confirm the potential of nanodroplets for range detection, with performance depending on nanodroplets' properties and beam parameters.

Influence of X-ray spectrum and bowtie filter characterisation on the accuracy of Monte Carlo simulated organ doses: Validation in a whole-body CT scanning mode.

PURPOSE: For patient-specific CT dosimetry, Monte Carlo dose simulations require an accurate description of the CT scanner. However, quantitative spectral information and information on the bowtie filter material and shape from the manufacturer is often not available. In this study, the influence of different X-ray spectra and bowtie filter characterisation methods on simulated CT organ doses is studied. METHODS: Using ImpactMC, organ doses of whole-body CTs were simulated in twenty adult whole-body voxel models, generated from PET/CT examinations previously conducted in these patients. Simulated CT organ doses based on the manufacturer X-ray spectra and bowtie filter data were compared with those obtained using alternative characterisation models, including spectrum generators and experimentally measured dose data. A total of four different X-ray spectra and one bowtie filter model were defined based on these data. RESULTS: For all X-ray spectra and bowtie filter combinations, estimated CT organ doses are within 6% from those resulting from simulations with the CT characterisation models provided by the manufacturer. While varying the bowtie filter model results in CT organ dose differences smaller than 1%, dose differences up to 6% are observed when X-ray spectra are not based on the quantitative data from the manufacturer. CONCLUSIONS: Estimated organ doses slightly depend on the applied CT characterisation model. When manufacturer's data are not available, half-value layer and dose measurements provide sufficient input to obtain equivalent X-ray spectra and bowtie filter profiles, respectively.

On the optical response of novel coumarin-fused NIR BODIPY dyes to X-rays.

This paper reports synthesis and characterization of three new coumarin-fused NIR BODIPY dyes 16-18, as well as the detailed study of their optical response to exposure with X-rays (up to 1000 Gy) in solvents of various nature. A strong reaction to irradiation (both in terms of absorption and fluorescence changing) is found in chlorinated solvents (CCl4 and CHCl3) and acetonitrile, while no significant respond of the dyes is observed in toluene and propanol-1. Herewith, their responses turned out to be very versatile: a complex change in fluorescence (quenching of the main band accompanied by the flare-up in a new spectral region) is observed together with colorimetric reaction (e.g., the color of 17 changes from green to blue at 50-80 Gy, and then becomes pink closer to ≈350 Gy). In general, the dyes show good linearity in their response to irradiation up to ≈70-100 Gy and are quite sensitive. For example, the limit of detection (LOD) values for 18 are from 0.29 to 6.73. At the same time, the ratiometric fluorescent response of the compound 16 turns out to be linear over the entire range up to 1000 Gy (to date, this is the first BODIPY-based X-ray probe with optical response over such a wide dose range). Thus, the synthesized dyes seem to be promising for dosimetric support of radiation processing/sterilization procedures.

Internal radiation dose estimates in organs of Wistar rats exposed to sprayed neutron-activated 31SiO2 microparticles: first results of international multicenter study.

Neutron-activated 31Si is an almost pure beta emitter and is one of the short-lived radionuclides, including beta-gamma emitter 56Mn, which were created in a form of residual radioactivity in the early period after the atomic bombing of Hiroshima and Nagasaki. The features of the biological effects of internal irradiation by these radionuclides are a subject of scientific discussions and research. The publication presents data on internal radiation doses in experimental Wistar rats that were exposed to sprayed neutron-activated microparticles of 31SiO2. Doses of internal radiation could be conditionally divided into three groups according to their values. It has been found that elevated values of internal radiation doses in rats' organs/tissues as a result of exposure to sprayed 31SiO2 microparticles with initial activity of 3.2 × 107 Bq varied from 10 to 120 mGy (eyes, lungs, skin, stomach, jejunum, large intestine). The moderate dose values were in the range from 1.9 to 3.7 mGy (trachea, esophagus, ileum). The smallest doses were received by the kidney, testis, blood, cerebellum, heart, liver, cerebrum, bladder, spleen and thymus (from 0.11 to 0.94 mGy). The obtained data are important for interpreting the results of ongoing and planned biological experiments with 31SiO2 microparticles-in comparison with the previously published data on features of biological effects caused by beta-gamma emitting 56MnO2 neutron-activated microparticles.

Dosimetric commissioning of a high-resolution CMOS 2D detector array for patient-specific QA of single-isocenter multi-target VMAT stereotactic radiosurgery.

Stereotactic radiosurgery (SRS) using the single-isocenter-multiple-target (SIMT) technique by volumetric modulated arc therapy is increasingly popular for treating multiple brain metastases. However, the complex nature of SIMT SRS necessitates rigorous patient-specific quality assurance (PSQA). This study presents a multi-institutional dosimetric commissioning of a high-resolution complementary metal oxide semiconductor (CMOS) 2D detector array, the myQA SRS device for SIMT SRS PSQA. Basic dosimetric properties such as dose-rate, field-size, energy and angular dependencies were characterized for the CMOS detectors. Additionally, gamma index analyses were performed between the measured dose and the films for nine simulated and clinical plans. The results showed that the CMOS detector was dose-rate, field-size, energy and beam-angle dependent. Specific to SIMT SRS, angular dependence on gantry rotations was invariant to couch rotations but was sensitive to off-isocenter distances. With appropriate dose calibration and angular corrections, myQA SRS showed a high dosimetric correlation with films. The average gamma index pass rates were 99.9 ± 0.03% and 99.2 ± 1.1% at 3%/2 mm/10%thr(global) and 1 mm/1%/10%thr(local) criteria, respectively. The average dose difference between myQA SRS and films was 0.4 ± 1.3%. In conclusion, the CMOS 2D detector array has demonstrated its potential as a reliable tool for PSQA for SIMT SRS. The excellent dosimetric agreement with the films was consistent in multiple institutions, further validating the dosimetric accuracy and reproducibility. It provides a timely alternative to film dosimetry for commissioning and quality assurance.