Dosimetry Purposes Research Articles

Effect of phase change, particle size and annealing in reducing and oxidizing atmospheres on UV-dosimetry characteristics of SrAl2O4:Eu using mechanoluminescence technique

SrAl2O4:Eu is a known ML phosphor. The material was successfully synthesized using combustion method, downsized to different particle-size ranges (from microcrystalline to nanocrystalline sizes) through ball milling. It was further annealed at different high temperatures (200–800oC) and characterized by XRD and FESEM. Reorganization of the material from SrAl2O4 (monoclinic, space group P21/c) to Sr2Al6O11 (orthorhombic, space group Pnnm) plus SrO (cubic, space group Fm3̅m) phases on annealing above 800oC was observed. ML studies show that the electron traps lost during mechanical/thermal stimulation could be regenerated by UV-irradiation. This property of the material was explored here to estimate the doses of UV radiations (UV-A, B and C). Also, dose responses of the materials having different particle size ranges from microcrystalline to nanocrystalline sizes were studied and found that the dose ranges get widened with the particle size decreasing with little sacrifice of the sensitivity. Thus, very high doses of the UV-radiation could also be estimated using ML nanophosphors. Fading at room temperature was little high but remaining ML is good enough for the dosimetry purpose. To the best of our knowledge such kind of detailed study on dosimetry of UV-radiations using ML technique is not found in the literature. It was also found that this material did not yield any ML after annealing the material above 800oC and even after UV-irradiation. It was further explored by annealing the material in reducing and oxidizing atmospheres that whether it is due to the phase transitions or redox reactions.

GAFchromic EBT film lateral resolution and contrast reproduction in the UV-blue range

The sensitivity of radiochromic films to UV-blue light is increasingly considered for light dosimetry purposes, owing to their bidimensional detection capabilities and ease of use. While film response to radiation intensity has been widely investigated by commercial scanners, spatial resolution studies remain scarce, especially for small field-of-view applications. These are of growing interest due to the antimicrobial or photo-bio-stimulating effects of UV-blue light sources in in vitro, ex vivo and in vivo models, where precise knowledge of irradiation conditions with adequate spatial resolution is crucial. In this study, we report the spatial lateral resolution and contrast reproduction of GAFchromic EBT2 and EBT3 models. Upon film irradiation by a 405 nm laser source or 365 nm LED, a confocal microscope setup was employed to read the film response at 405, 470, 488, 532 and 570 nm wavelengths, with radiant exposure of 10–70 J/cm2. The measured lateral resolution ranged from 8 to 33 μm. The film capability to reproduce contrast across various spatial frequencies (4–14 lines/mm) was evaluated using modulation transfer function analysis with irradiation performed at 365 nm and 405 nm, revealing a pronounced dependency on both radiant exposure and reading wavelength. These results confirm the film capacity to detect and resolve light intensity variability with a ~ 10 μm resolution, with notable applications in micro-beam profiling and light dosimetry.

Dosimetric saturation effect study and correction calculation method of ionization chamber at ultra-high dose rate (FLASH)

Backgroundand Purpose: FLASH radiotherapy has aroused strong interest among researchers, but how to monitor dose in real time and lack of generally accepted ion correction model are one of the challenges. This study is based on previous research work, the dosimetric verification of FLASH ionization chamber was performed using a 200 keV electron beam irradiation platform at an ultra-high dose rate. At the same time, the finite element program is written to analyze and calculate the ion correction factor. In addition, the results are compared with the calculation results of Boag model. MethodsIn this study, the pressure of the sensitive volume in the detector was adjusted to 16 mbar for the purpose of dosimetry of dose rates in excess of 100 Gy/s. In order to monitor the response of the detector, the beam frequency and pulse width were adjusted accordingly. However, due to the saturation effect of the ionization chamber, the processes of electron ion pair drift, attachment, recombination and diffusion in the sensitive volume were modelled on the basis of the relevant physical principles. Finally, the correction factor was calculated by the finite element analysis. ResultsThe experimental results demonstrate that the FLASH ionization chamber is capable of meeting the requirements of dose measurement and beam monitoring of the electron beam at ultra-high dose rates. Furthermore, the analytical model is able to more accurately describe the saturation effect and calculate the correction factor. ConclusionIn this paper, the method of reducing air pressure is employed for the purpose of monitoring the dose of ultra-high dose rate. Simultaneously, the finite element method was employed to analyze the physical process of electron–ion pairs within the chamber and to calculate the ion correction factor analytically. A comparison with the Boag model indicates that the proposed approach is effective. However, the results exhibit a certain degree of divergence from experimental outcomes. This discrepancy may be attributed to the influence of the input parameters, which require further calibration to enhance the accuracy and the robustness of the model.

Biological effectiveness of combined exposure to neutrons and gamma radiation applied in two orders of sequence: Relevance for biological dosimetry after nuclear emergencies

ObjectiveAfter a nuclear detonation, people will be exposed to varying mixtures of neutrons and gamma radiation and the biological effectiveness of mixed beams is not well known. Additionally, it is not known how far both radiation types interact, a question that is relevant for generating calibration curves for the purpose of biological dosimetry. The objective of this study was to investigate the potential impact of two different combinations of neutron and gamma radiation on gene expression and dicentric chromosomes in peripheral blood mononuclear cells (PBMC). MethodsWhole blood from 3 human donors was exposed to neutrons with an energy spectrum similar to that of the Hiroshima uranium bomb, to gamma radiation from a 60Co source and to a 50:50 combination of both radiations, given in two orders of sequence. In all cases the total doses were 0.5, 0.75 and 1.0 Gy. Dicentric chromosomes were analyzed by light microscopy and the expression of six known radiation-responsive genes BBC3, CDKN1A, FDXR, GADD45A, MDM2, and XPC were analyzed by RT-qPCR. ResultsPer unit dose, exposure to neutrons lead to a higher level of dicentrics and gene expression as compared to gamma radiation. Dose-response relationships for both endpoints were linear, allowing calculating the expected outcome of combined exposure by arithmetic. For dicentric chromosomes, the RBE values for 60Co→neutrons, neutrons→60Co and neutrons were 4.05, 3.62 and 7.30 respectively. For gene expression the RBE values were gene-specific, but showed values in the range of 1.14–3.01 for 60Co→neutrons, 1.33–2.68 for neutrons→60Co and 1.39–3.91 for neutrons. ConclusionsThe results demonstrate that combined exposure to neutrons and gamma radiation, regardless of the order of sequence, leads to an additive response at both endpoints. This indicates that calibration curves for mixed beams can be constructed from dose response relationships of the single beam components.

A review of criticality dosimetry at the Y-12 National Security Complex and practical importance of dose accuracy in emergency response

A nuclear criticality results in the emission of both neutron and gamma radiation and can produce doses to personnel near the event that exceed 0.1 Gy (10 rad). The primary purpose of nuclear accident dosimetry is to rapidly identify affected personnel in need of prompt medical treatment and to reassure personnel who have been only minimally exposed. While accurate dosimetry is desired, it must be recognized that dose determinations made from whole-body dosimeters or simple triage methods are very rough estimates and contain significant uncertainties. Even when accounting for factors like varying neutron energy spectra, mean photon energies, body orientation within the radiation field, and transient effects on dosimeter response, etc., the end value is a dosimetric quantity defined for very specific radiological conditions and determined within a simple phantom usually at a single depth. Of more importance is the biological response to the radiation, which will vary by person and can be affected by the individual's radiation sensitivity, age, gender, mass, and underlying health conditions. The overall biological, person-specific response to a given dose cannot be precisely determined except by patient symptom observation and individual biological dosimetry (e.g. chromosome analysis, lymphocyte ratios, etc.). This work describes and discusses the criticality accident dosimetry program at the Y-12 National Security Complex, a United States Department of Energy National Nuclear Security Administration facility. The primary goals of the Y-12 accident dosimetry program are, among others, the rapid identification of significantly exposed persons, prompt routing of exposed workers for medical evaluation and treatment, and the ultimate processing of dosimeters to assign doses to personnel.

Technologies for retrospective radiation dosimetry.

Radiation dosimetry is an important task for assessing the biological damages created in human being due to ionising radiation exposure. Ionising radiation being invisible and beyond the perception of human natural sensors, the dosimetry equipments/systems are the utmost requirement for its measurement. Retrospective measurement of radiation doses is a challenging task as conventional radiation dosemeters are not available at the exposure site. The material/s in close proximity of exposed individual or individuals' biological samples may be used as retrospective radiation sensor for dosimetry purpose. Environment materials such as sand, bricks, ceramics, sand stones, quartz, feldspar, glasses and electronic chips have been utilised using TL (Thermoluminescence) techniques for retrospective gamma dose (min 10cGy) measurement. Electron Spin Resonance techniques have been employed to human biological samples such as tooth enamel, bones, nails, hair, etc. and reported for dosimetry for ~20cGymin dose measurement. Some commercial glasses have been found sensitive enough to measure the minimum gamma doses of the order of 100cGy using TL techniques. For internal retrospective dosimetry, the radioactivity contamination assessment in food items, water, other edible product and ambient air are the prerequisites. The radioactivity concentration vis-à-vis their consumption rate may help in controlling the internal contamination and estimation of dose absorption in human body. Defence Laboratory, Jodhpur has been working extensively on the dosimetry techniques for external dose measurement using environmental material and developed portable contamination monitoring systems for food and water radioactivity measurement in the range of 50Bq kg-1 to 1000kBq kg-1 in 60s measurement time. The recent research and development in the methodologies, equipments and systems undertaken towards capacity building and self-reliance in retrospective radiation dosimetry is reported in this paper.

Comparison of a 3D CZT and conventional SPECT/CT system for quantitative Lu-177 SPECT imaging

PurposeNext-generation SPECT/CT systems with CdZnTe (CZT) digital detectors in a ring-like setup are emerging to perform quantitative Lu-177 SPECT imaging in clinical routine. It is essential to assess how the shorter acquisition time might affect the image quality and uncertainty on the mean absorbed dose of the tumors and organs at risk compared to a conventional system.Methods A NEMA Image Quality phantom was scanned with a 3D CZT SPECT/CT system (Veriton, by Spectrum Dynamics) using 6 min per bed position and with a conventional SPECT/CT system (Symbia T16, by Siemens) using 16 min per bed position. The sphere-to-background ratio was 12:1 and the background activity concentration ranged from 0.52 to 0.06 MBq/mL. A clinical reconstruction protocol for dosimetry purposes was determined for both systems by maximizing the sphere-to-background ratio while keeping the coefficient of variation of the background as low as possible. The corresponding image resolution was determined by the matching filter method and used for a dose uncertainty assessment of both systems following an established uncertainty model..ResultsThe optimized iterative reconstruction protocol included scatter and attenuation correction for both systems and detector response modeling for the Siemens system. For the 3D CZT system, 6 iterations and 8 subsets were combined with a Gaussian post-filter of 3 mm Full Width Half Maximum (FWHM) for post-smoothing. For the conventional system, 16 iterations and 16 subsets were applied with a Gaussian post-smoothing filter of 1 mm FWHM. For these protocols, the sphere-to-background ratio was 18.5% closer to the true ratio for the conventional system compared to the 3D CZT system when considering the four largest spheres. Meanwhile, the background coefficient of variation was very similar for both systems. These protocols resulted in SPECT image resolution of 14.8 mm and 13.6 mm for the 3D CZT and conventional system respectively. Based on these resolution estimates, a 50% dose uncertainty corresponded to a lesion volume of 28 mL for the conventional system and a lesion volume of 33 mL for the 3D CZT system. ConclusionsAn optimized reconstruction protocol for a Veriton system with 6 min of acquisition time per bed position resulted in slightly higher dose uncertainties than a conventional Symbia system using 16 min of acquisition time per bed position. Therefore, a 3D CZT SPECT/CT allows to significantly reduce the acquisition times with only a very limited impact on dose uncertainties such that quantitative Lu-177 SPECT/CT imaging becomes much more accessible for treatment concurrent dosimetry. Nevertheless, the uncertainty of SPECT-based dose estimates remains high.

Segmentation of liver and liver lesions using deep learning.

Segmentation of organs and lesions could be employed for the express purpose of dosimetry in nuclear medicine, assisted image interpretations, and mass image processing studies. Deep leaning created liver and liver lesion segmentation on clinical 3D MRI data has not been fully addressed in previous experiments. To this end, the required data were collected from 128 patients, including their T1w and T2w MRI images, and ground truth labels of the liver and liver lesions were generated. The collection of 110 T1w-T2w MRI image sets was divided, with 94 designated for training and 16 for validation. Furthermore, 18 more datasets were separately allocated for use as hold-out test datasets. The T1w and T2w MRI images were preprocessed into a two-channel format so that they were used as inputs to the deep learning model based on the Isensee 2017 network. To calculate the final Dice coefficient of the network performance on test datasets, the binary average of T1w and T2w predicted images was used. The deep learning model could segment all 18 test cases, with an average Dice coefficient of 88% for the liver and 53% for the liver tumor. Liver segmentation was carried out with rather a high accuracy; this could be achieved for liver dosimetry during systemic or selective radiation therapies as well as for attenuation correction in PET/MRI scanners. Nevertheless, the delineation of liver lesions was not optimal; therefore, tumor detection was not practical by the proposed method on clinical data.

Regression fitting megavoltage depth dose curves to determine material relative electron density in radiotherapy.

The relative electron density (RED) parameter is ubiquitous throughout radiotherapy for clinical dosimetry and treatment planning purposes as it provides a more accurate description of the relevant radiological properties over mass density alone. RED is in practice determined indirectly from calibrated CT Hounsfield Units (HU). While CT images provide useful 3D information, the spectral differences between CT and clinical LINAC beams may impact the validity of the CT-ED calibration, especially in the context of novel tissue-mimicking materials where deviations from biologically typical atomic number to atomic weight ratios 〈Z/A〉 occur and/or high-Z materials are present. A theoretical basis for determining material properties directly in a clinical beam spectrum via an electron-density equivalent pathlength (eEPL) method has been previously established. An experimental implementation of this approach is introduced whereby material-specific measured percentage depth dose curves (PDDs) are regressed to a PDD measured in a reference material (water), providing an inference of 〈Z/A〉, which when combined with the physical density provides a determination of RED. This method is validated over a range of tissue-mimicking materials and compared against the standard CT output, as well as compositional information obtained from the manufacturer's specifications. The measured PDD regression method shows consistent results against both manufacturer-provided and CT-derived values between 0.9 and 1.15 RED. Outside of this soft-tissue range a trend was observed whereby the 〈Z/A〉 determined becomes unrealistic indicating the method is no longer reporting RED alone and the assumptions around the eEPL model are constrained. Within the soft-tissue RED range of validity, the regression method provides a practical and robust characterisation for unknown materials in the clinical setting and may be used to improve on the CT derived RED where high Z material components are suspected.

The effects of heat treatment on the OSL signal in sodium chloride crystals

Luminescence studies focusing on sodium chloride crystals have been conducted in various parts of the world, including Brazil, India, Greece, Türkiye, Australia, Spain, and Poland. This material shows great promise in the field of dosimetry, as it has demonstrated high sensitivity, excellent reproducibility, a linear response, and a low minimum detectable dose. Moreover, it holds significant potential for applications in accidental dosimetry, providing valuable results for dating and retrospective dosimetry purposes. Natural sodium chloride encompasses different types of salts, such as Himalayan black salt, pink salt, and sea salt. The presence of these salt variations is attributed to their composition, which includes not only pure sodium chloride but also other elements like magnesium, potassium, sulfur, and calcium. These additional elements contribute to the unique characteristics and properties exhibited by these types of salts. A comprehensive study was conducted to investigate the effects of thermal treatments on pink salt crystals, aiming to enhance their luminescent intensity and thereby improve their sensibility to detect ionizing radiation. By subjecting the crystals to various thermal treatments, we observed significant changes in their luminescent signals. Firstly, we observed a change in the shape of the Thermoluminescence (TL) curve, indicating modifications in the properties of the luminescent F-centers present in the crystals. Additionally, we noticed a significant increase in the Optically Stimulated Luminescence (OSL) signal, indicating a greater ability of the crystals to store and release energy under optical stimulation. A particularly interesting discovery was the reduction in intensity of the third component of the OSL signal in darker-toned crystals. Also the spontaneous regeneration reported by other researchers was almost eliminated. Furthermore, our results demonstrated only a 2.5% fluctuation in experimental repeatability, indicating high consistency and reliability of the obtained data.

Methodology for computed tomography characterization of commercially available 3D printing materials for use in radiology/radiation oncology.

3D printing in medical physics provides opportunities for creating patient-specific treatment devices and in-house fabrication of imaging/dosimetry phantoms. This study characterizes several commercial fused deposition 3D printing materials with some containing nonstandard compositions. It is important to explore their similarities to human tissues and other materials encountered in patients. Uniform cylinders with infill from 50 to 100% at six evenly distributed intervals were printed using 13 different filaments. A novel approach rotating infill angle 10o between each layer avoids unwanted patterns. Five materials contained high-Z/metallic components. A clinical CT scanner with a range of tube potentials (70, 80, 100, 120, 140 kVp) was used. Density and average Hounsfield unit (HU) were measured. A commercial GAMMEX phantom mimicking various human tissues provides a comparison. Utility of the lookup tables produced is demonstrated. A methodology for calibrating print materials/parameters for a desired HU is presented. Density and HU were determined for all materials as a function of tube voltage (kVp) and infill percentage. The range of HU (-732.0-10047.4 HU) and physical densities (0.36-3.52g/cm3 ) encompassed most tissues/materials encountered in radiology/radiotherapy applications with many overlapping those of human tissues. Printing filaments doped with high-Z materials demonstrated increased attenuation due to the photoelectric effect with decreased kVp, as found in certain endogenous materials (e.g., bone). HU was faithfully reproduced (within one standard deviation) in a 3D-printed mimic of a commercial anthropomorphic phantom section. Characterization of commercially available 3D print materials facilitates custom object fabrication for use in radiology and radiation oncology, including human tissue and common exogenous implant mimics. This allows for cost reduction and increased flexibility to fabricate novel phantoms or patient-specific devices imaging and dosimetry purposes. A formalism for calibrating to specific CT scanner, printer, and filament type/batch is presented. Utility is demonstrated by printing a commercial anthropomorphic phantom copy.

A voxel-by-voxel method for mixing two filaments during a 3D printing process for soft-tissue replication in an anthropomorphic breast phantom

Objective. In this study, a novel voxel-by-voxel mixing method is presented, according to which two filaments of different material are combined during the three dimensional (3D) printing process. Approach. In our approach, two types of filaments were used for the replication of soft-tissues, a polylactic acid (PLA) filament and a polypropylene (PP) filament. A custom-made software was used, while a series of breast patient CT scan images were directly associated to the 3D printing process. Each phantom´s layer was printed twice, once with the PLA filament and a second time with the PP filament. For each material, the filament extrusion rate was controlled voxel-by-voxel and was based on the Hounsfield units (HU) of the imported CT images. The phantom was scanned at clinical CT, breast tomosynthesis and micro CT facilities, as the major processing was performed on data from the CT. A side by side comparison between patient´s and phantom´s CT slices by means of profile and histogram comparison was accomplished. Further, in case of profile comparison, the Pearson´s coefficients were calculated. Main results. The visual assessment of the distribution of the glandular tissue in the CT slices of the printed breast anatomy showed high degree of radiological similarity to the corresponding patient´s glandular distribution. The profile plots´ comparison showed that the HU of the replicated and original patient soft tissues match adequately. In overall, the Pearson´s coefficients were above 0.91, suggesting a close match of the CT images of the phantom with those of the patient. The overall HU were close in terms of HU ranges. The HU mean, median and standard deviation of the original and the phantom CT slices were −149, −167, ±65 and −121, −130, ±91, respectively. Significance. The results suggest that the proposed methodology is appropriate for manufacturing of anthropomorphic soft tissue phantoms for x-ray imaging and dosimetry purposes, since it may offer an accurate replication of these tissues.

Anti-CENP-C Antibody-Based Immunofluorescence Dicentric Assay: Radiation Dose-Response, Validation Studies, and Radiation Dose-Dependency on Sister Centromere Fluorescence.

Dicentric chromosome assay (DCA) is the most accepted cytological technique for the purpose of biological dosimetry in radiological and nuclear accidents, however, it is not always easy to evaluate dicentric chromosomes because of the technical difficulty in identifying dicentric chromosomes on Giemsa-stained metaphase chromosome samples. Here, we applied an antibody recognizing centromere protein (CENP) C, CENP-C, whose antigenicity is resistant to the fixation with Carnoy's solution. Normal human diploid cells were irradiated with various doses of 137Cs γ rays at 1 Gy/ min, treated with hypotonic solution, fixed with Carnoy's fixative, and metaphase chromosome spreads were stained with anti-CENP-C antibody. Dose-dependent induction of dicentric chromosomes was confirmed between 1 and 10 Gy of γ rays, and the results were compatible with those obtained by the conventional Giemsa-stained chromosome samples. The CENP-C assay also uncovered the difference in the fluorescence from the sister centromeres on the same chromosome, which was more pronounced after radiation exposure. Although the underlying mechanism is still to be determined, the result suggests a novel effect of radiation on centromeres. The innovative protocol for CENP-C-based DCA, which enables ideal visualization of centromeres, is simple, effective and reliable. It does not require skilled examiners, so that it may be an alternative method, avoiding uneasiness of the current DCA using Giemsa-stained metaphase chromosome samples.

Comparison of PSMA-TO-1 and PSMA-617 labeled with gallium-68, lutetium-177 and actinium-225

BackgroundPSMA-TO-1 (“Tumor-Optimized-1”) is a novel PSMA ligand with longer circulation time than PSMA-617. We compared the biodistribution in subcutaneous tumor-bearing mice of PSMA-TO-1, PSMA-617 and PSMA-11 when labeled with 68Ga and 177Lu, and the survival after treatment with 225Ac-PSMA-TO-1/-617 in a murine model of disseminated prostate cancer. We also report dosimetry data of 177Lu-PSMA-TO1/-617 in prostate cancer patients.MethodsFirst, PET images of 68Ga-PSMA-TO-1/-617/-11 were acquired on consecutive days in three mice bearing subcutaneous C4-2 xenografts. Second, 50 subcutaneous tumor-bearing mice received either 30 MBq of 177Lu-PSMA-617 or 177Lu-PSMA-TO-1 and were sacrificed at 1, 4, 24, 48 and 168 h for ex vivo gamma counting and biodistribution. Third, mice bearing disseminated lesions via intracardiac inoculation were treated with either 40 kBq of 225Ac-PSMA-617, 225Ac-PSMA-TO-1, or remained untreated and followed for survival. Additionally, 3 metastatic castration-resistant prostate cancer patients received 500 MBq of 177Lu-PSMA-TO-1 under compassionate use for dosimetry purposes. Planar images with an additional SPECT/CT acquisition were acquired for dosimetry calculations.ResultsTumor uptake measured by PET imaging of 68Ga-labeled agents in mice was highest using PSMA-617, followed by PSMA-TO-1 and PSMA-11. 177Lu-PSMA tumor uptake measured by ex vivo gamma counting at subsequent time points tended to be greater for PSMA-TO-1 up to 1 week following treatment (p > 0.13 at all time points). This was, however, accompanied by increased kidney uptake and a 26-fold higher kidney dose of PSMA-TO-1 compared with PSMA-617 in mice. Mice treated with a single-cycle 225Ac-PSMA-TO-1 survived longer than those treated with 225Ac-PSMA-617 and untreated mice, respectively (17.8, 14.5 and 7.7 weeks, respectively; p < 0.0001). Kidney, salivary gland, bone marrow and mean ± SD tumor dose coefficients (Gy/GBq) for 177Lu-PSMA-TO-1 in patients #01/#02/#03 were 2.5/2.4/3.0, 1.0/2.5/2.3, 0.14/0.11/0.10 and 0.42 ± 0.03/4.45 ± 0.07/1.8 ± 0.57, respectively.ConclusionsPSMA-TO-1 tumor uptake tended to be greater than that of PSMA-617 in both preclinical and clinical settings. Mice treated with 225Ac-PSMA-TO-1 conferred a significant survival benefit compared to 225Ac-PSMA-617 despite the accompanying increased kidney uptake. In humans, PSMA-TO-1 dosimetry estimates suggest increased tumor absorbed doses; however, the kidneys, salivary glands and bone marrow are also exposed to higher radiation doses. Thus, additional preclinical studies are needed before further clinical use.

Three-dimensional conformal radiotherapy breast cancer planning: An evaluation study comparing two techniques using homemade phantom

Anthropomorphic phantoms, which can provide equivalent human tissue densities, are one of the best solutions for verifying the quality of radiotherapy treatment plans produced by treatment planning systems. The goal of this work was to develop and fabricate a breast phantom to estimate radiation doses to the breast, lung, and surface using radiochromic films (EBT3) for basically two techniques of three-dimensional conformal radiotherapy (3D-CRT) treatment planning. Thirty-two acrylic slices were used to construct the phantom. Cork and Teflon were used to mimic the lung and bone, respectively. Four slots were drilled for dosimetry purposes to allow access to the areas of ionization chamber installation. Both wedged and open of two tangential beams techniques were applied. With a mean deviation of 1.02 ± 1.1, the variation between estimated point doses and measurements using the three ionization chambers ranged from 2.9 to 1.4%. Using 0, 5 and 10 mm boluses, the mean percentage doses on the target surface were 54.7, 88.6 and 91.7% of the prescribed dose (PD), respectively. The homemade phantom was appropriate for conducting quality control (QC) tests for 3D-CRT planning techniques for breast radiotherapy.

Raman spectroscopy of electron irradiated Multi-Walled Carbon Nanotube for dosimetry purposes

In this experimental work, dosimetry characteristics of Multi-Walled Carbon Nanotube (MWCNT), including linearity, repeatability, and long-term stability, were carried out using a 10 MeV electron-beam at various absorbed doses of 0, 10, 20, 30, 50, 80, 150, and 200 kGy at room temperature by Raman spectroscopy. HRTEM, FESEM, and FTIR tests were performed to investigate changes in the atomic and molecular structures in the material at various doses. Results of the HRTEM, and FESEM tests were in good accordance with the experimental data in justifying the dosimeter behavior. FTIR analysis confirmed the presence of C–C, C–O, CC, CO, CH, CH2, and OH functional groups in the samples. The samples were analyzed by Raman spectroscopy to identify defects created in the carbon atoms of the MWCNT. Results showed that the amount of ID/IG quantity, as the dosimeter response, versus absorbed dose was linear up to 50 kGy with a standard deviation of 9.8%. Finally, fading analysis was carried out after 4 months, where a significant change in the dosimeter response was observed. Our findings show the benefits of Raman spectroscopy to measure the response of the dosimeter as quickly as possible. Also, it is recommended to study on the fading effect at various time intervals.

TL response evaluation for UVA and UVC of LaAlO3:Pr3+ powder

Thermoluminescence properties of lanthanum aluminum oxide (LaAlO3) doped with optically active rare earth ions have been investigated for ultraviolet dosimetry purposes. LaAlO3:Pr3+ powder samples were doped with 2% of Pr3+, for the first research they show two thermoluminescent (TL) peaks at 215±5 °C and 340±4 °C which can be sensitized after 1 min to 12 min of UVA exposure. The material shows TL output and linear response for UVA lamp in 365 nm wavelength light. On the other hand, the powder samples that were irradiated with a UVC lamp at 254 nm, it also shows one peak and a shoulder, the maximum peak in a range that goes from 195 °C to 220 °C, in which the exposure time was varied from 5 to 30 seconds and the shoulder remains stable at 345± 8 ° C. The experiments demonstrates that LaAlO3: Pr3+ powders are very attractive to be investigated as UVA and UVC dosimeters.

TL and OSL characteristics of the fluoroperovskite KMgF3:Eu,Yb, Li for dosimetry applications

The purpose of this work was to investigate the dosimetric and luminescence properties of the novel KMgF3:Eu0.5%,Yb0.1%,Li15% fluoroperovskite synthesized using the sol-gel method. The luminescence signals were characterized using Optically Stimulated Luminescence (OSL) spectra, Linearly-Modulated OSL (LM-OSL), Continuous-Wave OSL (CW-OSL), and Thermoluminescence (TL) techniques. The blue light (470 nm) stimulated OSL associated with Eu2+, and Eu3+ emissions was correlated with the TL peaks up to 300 °C. The photoionization cross-section of each OSL component was evaluated using deconvolution analysis following two different optical stimulation modes, namely LM-OSL and CW-OSL. The activation energy values were evaluated using the Tm-Tstop and CGCD methods. OSL signal fading of 5% and 13% was observed at the end of 24 h and over the next three months, respectively. The results indicate that the OSL from KMgF3:Eu0.5%,Yb0.1%,Li15% fluoroperovskite has suitable properties for dosimetry, including high sensitivity to ionizing radiation and a wide linear dose range (0.1–500 Gy). These results enhance the understanding of the origin of the luminescence properties in this material and this work paves the way toward its utility for dosimetry purposes.

A phantom-based experimental and Monte Carlo study of the suitability of in-vivo diodes and TLD for entrance in-vivo dosimetry in small-to-medium sized 6 MV photon fields

In-vivo dosimetry is recommended for radiotherapy treatment verification. The main purpose of the study is to investigate the suitability of various dosimeters for performing in-vivo measurements in small 6 MV photon fields by measurement as well as Monte Carlo simulation. Two types of diode dosimeters designed for placement on skin for the purpose of in-vivo dosimetry (EDD-5 and EDP-10), 3.1 × 3.1 × 0.89 mm3 LiF TLDs, and an electron field diode (EFD) were used for dosimetric measurements in a custom-made PMMA phantom. An Elekta accelerator’s treatment head was Monte Carlo modeled in detail, which was used together with validated Monte Carlo models of the diodes. Dose perturbation effects of the dosimeters and their suitability for in-vivo measurements were investigated. In fields ≥2 × 2 cm2, differences in the measured response of EDD-5, EDP-10 and TLD from the Monte Carlo gold-standard were <2%. For the 1 × 1 cm2 field, however, the differences from the Monte Carlo gold-standard were all greater than 2% due to the influence of dosimeter size as well as any misalignment and set-up uncertainties. In fields ≥1 × 1 cm2, EDD-5, EDP-10, and TLD produced 2.2%–3.2%, 5.3%–6.6% and 0.8–1.1% dose perturbation (≤10 cm depths), respectively. A better than 2% dosimetric accuracy was not achieved by these diodes for field sizes smaller than 2 × 2 cm2. Routine patient in-vivo dosimetry is feasible with the EDD-5 diode and TLD for field sizes down to 2 × 2 cm2 without exceeding the 5% tolerance level for overall uncertainty. But the EDP-10 diode produces a higher perturbation making it much less suitable for this purpose.

Retrospective OSL Dosimetry With Common Pharmaceuticals and Food Supplements.

Several common pharmaceuticals such as ibuprofen, paracetamol, aspirin, oral contraceptives, drugs for the prevention of motion sickness and food supplements such as table vitamins and minerals have been studied for the purposes of retrospective dosimetry using optically stimulated luminescence (OSL). The essence is that the tablets with these drug substances contain additive crystalline materials which, after irradiation and stimulation, may exhibit luminescence. For most of the pharmaceuticals and food supplements, a radiation-induced dose-dependent OSL signal was detected. Subsequently, basic dosimetric characteristics of the materials were studied, specifically sensitivity changes during repeated OSL readings, dose response, zero-dose, minimum detectable dose (MDD) and fading. The most radiation sensitive materials were food supplements with Mg providing zero-dose and MDD values at the level of several mGy. For Mg supplements, considerable sensitivity changes in OSL signal were observed. Despite this, they could be corrected using a Single-Aliquot Regenerative-dose (SAR) protocol. The OSL signals of the other materials were relatively weak but they were well reproducible and exhibited linear dose response. The MDD values were variable among the materials and ranged from 0.1 to several Gy. However, for some of the pharmaceuticals, a very high and variable zero-dose of more than 3 Gy was observed that would rule out the possibility of dose reconstruction for triage purposes. The OSL signal exhibited a significant fading rate for most of the materials. The measurements for dose reconstruction should be performed as soon as possible after irradiation, i.e. within a maximum of a few days.