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The main purpose of this study was to compare the parameters of computed tomography (CT) and the corresponding patient doses undergoing chest CT scan examinations in different regions of Brazil, providing the current scenario of how these procedures are being carried out in the country as well as the patient dose distribution. Thirty institutions, across 17 states and the Federal District participated in the survey. The evaluation included 30 multislice CTs of seven different models, manufactured by General Electric healthcare (GE). For each institution, data from 10 adult chest CT examinations, performed without contrast, were collected remotely. The analysis of the results showed a significant difference of the CTDIvol values, ranging from 1.1 mGy to 46.6 mGy. In 7 institutions. The mean value of CTDIvol was higher than values found in the literature and the UK Reference Levels. It was also observed that, regardless of the region of the country, for the same CT model, different scanning parameters were used, which resulted in CTDIvol up to five times higher among these institutions. Repetitions of CT acquisitions and scouts with radiation field dimensions larger than the region of interest were found in 25% of chest examinations, resulting in higher absorbed doses. The results of this work show a mapping of the chest CT procedures, which enable to establish strategic plans for the country. In addition, each institution will be able to implement an appropriate optimization program and establish institutional reference levels.

Purpose Optimization of CT scan practices can help achieve and maintain optimal radiation protection. The aim was to assess centering, scan length, and positioning of patients undergoing chest CT for suspected or known COVID-19 pneumonia and to investigate their effect on associated radiation doses. Methods With respective approvals from institutional review boards, we compiled CT imaging and radiation dose data from four hospitals belonging to four countries (Brazil, Iran, Italy, and USA) on 400 adult patients who underwent chest CT for suspected or known COVID-19 pneumonia between April 2020 and August 2020. We recorded patient demographics and volume CT dose index (CTDIvol) and dose length product (DLP). From thin-section CT images of each patient, we estimated the scan length and recorded the first and last vertebral bodies at the scan start and end locations. Patient mis-centering and arm position were recorded. Data were analyzed with analysis of variance (ANOVA). Results The extent and frequency of patient mis-centering did not differ across the four CT facilities (>0.09). The frequency of patients scanned with arms by their side (11–40% relative to those with arms up) had greater mis-centering and higher CTDIvol and DLP at 2/4 facilities (p = 0.027–0.05). Despite lack of variations in effective diameters (p = 0.14), there were significantly variations in scan lengths, CTDIvol and DLP across the four facilities (p Conclusions Mis-centering, over-scanning, and arms by the side are frequent issues with use of chest CT in COVID-19 pneumonia and are associated with higher radiation doses.

This work demonstrates the use of high-resolution 3D printing to fine-tune the low energy dependence of an eye lens dosimeter holder associated to a BeO OSL detector element (ezClip). Five geometries of the denominated iBe dosimeter were developed, three with a variation in the thickness of the wall in front of the sensitive element that tailor the response at low radiation energies; and three with variations of width and curvature in order to vary the angular response of the dosimeter badges. Additive manufacturing was accomplished using stereolithography which gave a high degree of accuracy and precision. The optimised dosimeter badges showed a low energy and angular dependence, within −20% to +20% in the energy range of 24 keV to 662 keV and from 0 to 60° incidence; and within −10% to +10% in the energy range of 24 keV to 164 keV and from 0 to 60° incidence. In contrast to other dosimeters with higher effective atomic numbers, the use of BeO as the sensitive element resulted in a flat energy and angular dependence response at low energies. A significant reduction in the measurement uncertainty in the diagnostic radiology energy range was achieved.

The aim of this multi-centre study was to evaluate the irradiation parameters and the radiation dose of abdomen CT exams without contrast, performed in adults In Brazil, in order to provide an overview of the CT installed base in the country and contribute for the establishment of optimization programs. Equipment of seven different models, with 16 and 64 channels, installed in 17 Brazilian states, plus the Federal District, were analyzed. The results show that the mean CTDIvol ranged from 6.60 mGy to 34.64 mGy. The results also showed that different irradiation parameters are used in equipment of the same model, resulting, in some cases, in three times higher CTDIvol values. These characteristics are not restricted to a given region of the country but distributed throughout the national territory. Repetitions of acquisitions and topograms with scan length larger than the region of interest were found in 13.5% of abdomen examinations, resulting in considerably higher absorbed doses than expected. This survey of the abdomen tomography exams, performed in about 74% of the Brazilian states, showed that in many clinics the procedures are not optimized. This study can be used for the planning of dose optimization programs and will contribute to the establishment of local diagnostic reference levels (DRL) for CT.

Computed tomography (CT) provides useful information in patients with known or suspected COVID-19 infection. However, there are substantial variations and challenges in scanner technologies and scan practices that have negative effect on the image quality and can increase radiation dose associated with CT. Objective: In this article, we present major issues and challenges with use of CT at five Brazilian CT facilities for imaging patients with known or suspected COVID-19 infection and offer specific mitigating strategies. Methods: Observational, retrospective and prospective study of five CT facilities from different states and regions of Brazil, with approval of research and ethics committees. Results: The most important issues include frequent use of CT, lack of up-to-date and efficient scanner technologies, over-scanning and patient off-centring. Mitigating strategies can include updating scanner technology and improving scan practices.

The aim of the present study was to evaluate the response of the MOSkin MOSFET dosimeter for X-ray diagnostic CT beams. Experiments were performed to investigate the sensitivity, energy dependence, reproducibility, fading and angular dependence of the dose response for the device. The dosimeter’s performance was evaluated for the standard radiation qualities RQT 8, RQT 9 and RQT 10 in a metrology laboratory. In a CT scanner, the MOSkin was used to assess the air kerma profile and the dose profile in a phantom. The integral of the dose profile was compared to the CPMMA,100 measured with a pencil ionization chamber. The results showed that the MOSkin response was linear and reproducible with doses in the CT range. Energy dependence varied up to a factor of 1.19 among the tested X-ray energies. Angular dependence of the response was not greater than 7.8% within the angle range from 0 to 90 degrees. Signal fading within 3 min was negligible. Additionally, the MOSkin was able to accurately assess the air kerma profile and the integral of the dose profile in a CT scanner. The integral of the dose profile in a phantom was in agreement with the CPMMA,100. The presented results demonstrated the potential of the MOSkin for application in CT dosimetry.

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

From Obsidian silicate, in its natural form, pellets were manufactured adding Teflon to the material in powder. These pellets were exposed to the gamma radiation beams of a 60Co source in a dose interval from 10 Gy to 10 kGy. The Obsidian in powder was investigated in relation to its physical and chemical characteristics, by means of the X-ray diffraction, scanning electronic microscopy and energy-dispersive X-ray spectroscopy techniques. After the irradiation procedure, the signal of the samples was evaluated by means of three techniques: thermoluminescence (TL), optically stimulated luminescence (OSL) and thermally stimulated exoelectron emission (TSEE). The objective of this work was to verify the TL, OSL and TSEE response of the Obsidian+Teflon pellets after exposure to high doses of gamma radiation. Different response characterization tests were performed, as TL and TSEE emission curves, OSL signal decay, reproducibility, dose-response curves, lower detection limits and fading. From these results, it can be observed that the Obsidian+Teflon pellets present good conditions to be used as high dose gamma radiation detectors; the results obtained with the OSL technique were the most adequate in terms of response in function of absorbed dose. The fading of the signals, varying from about 26% (TSEE) to 44% (OSL), in a time interval of 360 h post-irradiation, also showed favorable results for the use of this material as radiation detector, when the measurements are taken after a defined time interval.

Recent epidemiological studies suggested to lower the threshold dose for radiation induced cataract in the eye lens. Therefore, eye lens radiation protection became to play a more important role in personal dosimetry. The main objective of this work is to propose a new methodology for prototyping and benchmarking of an eye lens dosiemter based on the equivalent dose to the sensitive part of the eye lens, using CAD Software and Geant 4 Monte Carlo simulations with mesh modeling and 3D printing. A 3D printed dosimeter was type tested based on IEC 62387:2012, in terms of energy and angular dependence for the measurements of Hp(3). The results show that the methodology employed is suitable for the development of new eye lens dosimeters.

A comparison exercise of Latin American and Caribbean Secondary Standards Dosimetry Laboratories (SSDLs) was jointly organized by the International Atomic Energy Agency (IAEA) and the Ionizing Radiation Metrology Laboratory at the Federal University of Pernambuco (LMRI-DEN/UFPE). This exercise was organized during an IAEA regional meeting on the review and update of calibration capabilities in Latin America, held in Recife, during the period from 23 to 27 April 2018 under the technical cooperation project ME-RLA 9085-170572. Fifteen participating SSDLs were required to irradiate optically stimulated personal dosimeters in terms of the personal dose equivalent Hp(10) in 137Cs radiation quality. In addition, the IAEA Dosimetry Laboratory in Seibersdorf, Austria, and the National Physical Laboratory in Teddington, Middlesex, UK participated in this exercise as reference institutes. Each participant received 10 dosimeters that were hand-carried directly to the SSDL. Two nominal dose values of 2 mSv and 4 mSv were selected for this exercise. The participants irradiated the dosimeters using the setup and the procedures which are normally used in their standard laboratory for Hp(10) dosimeter irradiations. The dosimeters were evaluated as they were received by the coordinating laboratory, using a single BeOSL Reader. The results show that, except for one laboratory, the differences between the dosimeter reading and the assigned values were within 10%; this is consistent with the expanded uncertainty. The results indicate that most of the participant laboratories have a good capability to irradiate personal dosimeters in the quantity Hp(10).

This paper presents the results of X-ray fluorescence (XRF) analysis of bricks sampled from historical places in Pernambuco, a state in the northeastern region of Brazil. In this study, twenty bricks found in historical sites were analyzed. Two bricks made in the 17th century, presumably used as ballast in ships coming from Holland, five locally manufactured bricks: one from 18th century, three from 19th century, and one from 20th century, and thirteen bricks collected from a recent Archeological investigation of Alto da Se, in the town of Olinda. Qualitative determination of the chemical elements present in the samples was undertaken using a self-assembled portable XRF system based on a compact X-ray tube and a thermoelectrically cooled Si-PIN photodiode system, both commercially available. X-ray diffraction analysis was also carried out to assess the crystalline mineral phases present in the bricks. The results showed that quartz (SiO2) is the major mineral content in all bricks. Although less expressive in the XRD patterns, mineral phases of illite, kaolinite, anorthite, and rutile are also identified. The trace element distribution patterns of the bricks, determined by the XRF technique, is dominated by Fe and, in decreasing order, by K, Ti, Ca, Mn, Zr, Rb, Sr, Cr, and Y with slight differences among them. Analyses of the chemical compositional features of the bricks, evaluated by principal component analysis of the XRF datasets, allowed the samples to be grouped into five clusters with similar chemical composition. These cluster groups were able to identify both age and manufacturing sites. Dutch bricks prepared with different geological clays compositions were defined.

Excavations in the Lagoa Uri de Cima Archaeological Site (Salgueiro, Pernambuco, Brazil) revealed considerable Pleistocene mammalian fossils and lithics in multiple sedimentary layers of the ancient lake, currently dry. The site was found in 2010 during the construction of an open-air system of canals to connect water sheds of the semi-arid regions with the Sao Francisco River. The coexistence of a variety of extinct mammals and archaeological remains suggested the possibility of further light on the question of overlapping occupation of Northeastern Brazil by megafauna and humans in the Late Pleistocene. Electron spin resonance (ESR) dating of tooth enamel of mammal fossils can provide valuable information on the chronology of this site. This work presents the ESR dating of four teeth of two mammal species: Toxodon platensis (2) and Haplomastodon waringi (2). Dose-response curves were constructed using T1-B1 and T1-B2 amplitudes of the ESR signal of the hydroxyapatite CO2−radical, measured with a Bruker EMX-10+ X-band spectrometer. To verify the experimental protocol and the reliability of the exponential fittings for additive-doses and ESR signal intensities, the dose-response curve of one Toxodon platensis sample was independently obtained with a Jeol FA-200 X-band spectrometer. Equivalent dose to age conversions were carried out with the ROSY ESR dating program, with the external dose rate given by the environment and cosmic radiation and the internal dose rate given by probable uranium uptake models. The results show ages varying from 12,000 to 19,000 years for the four samples. The stratigraphical consistency is sub-optimal, but can be explained by the overall geomorphology of the site. These results place the creation of the lowest sedimentary levels of Lagoa Uri de Cima within the Late Pleistocene.

Optically Stimulated Luminescence (OSL) is the luminescence emitted from a previously irradiated with ionizing radiation material by exposure to light. The aim of this paper is to evaluate the Blue Stimulation Luminescence (BSL) and Infra-Red Stimulation Luminescence (IRSL) for CaF2:Ce produced by the Solution Combustion Synthesis (SCS) method. The results showed that the OSL response of CaF2:Ce is strongly influenced by post-combustion thermal sintering temperature and dopant concentration. OSL response to dose are of the same order of magnitude of Al2O3:C, indicating the possibility of use of this material for radiation dosimetry.

Significant changes of the glow curve shape of LiF:Mg,Cu,P have been observed when it is exposed to doses above 50 kGy. In order to clarify one of these changes, i.e., the appearance of a thermoluminescent (TL) peak (the so-called “B” peak) centered above 400 °C, this work investigated the changes induced by γ radiation in the electron paramagnetic resonance (EPR) spectra of LiF:Mg,Cu,P powder used for the production of the MCP-N dosimeters. To achieve this, aliquots were irradiated with 1, 100, 227 and 500 kGy of γ rays (60Co) and preheated at different temperatures up to 500 °C. EPR signals were measured at room and liquid nitrogen temperatures with an X-band spectrometer. Glow curves and TL emission spectra were measured for the same aliquots. EPR spectra were shown to originate mainly from unpaired electrons of Cu2+ ions, occurring in deformed octahedral sites, showing axially symmetric spectroscopic g-factors (g┴ = 2.1937; g║ = 2.0765). Two less intense signals with g-factors equal to 2.008 and 1.989, probably associated with different types of F centers, were observed after irradiation with doses ≥ 100 kGy. The analysis of EPR and TL intensities as a function of radiation doses and preheat temperatures suggested that the creation of the B peak is basically dependent on the electronic trapping states formed by Cu2+ and/or Cu+ ions and the F-related center responsible for the signal with g-factor equal to 1.989. The wavelength of the emitted light (peaked at ~ 360 nm) confirmed that recombination occurs along the same path for both the B peak and the dosimetric peak centered at 220 °C. In contrast to standard TL models, the position of the B peak shifted towards higher temperatures when the dose was increased. These results support the assumption that the origin of the B peak can be explained by localized transitions within spatially correlated defect clusters assembling Cu2+ and Mg2+ ions together with F-related centers.

Skin cancer affects a lot of people being a malignant cutaneous melanoma one of the most aggressive neoplasms. Nowadays, the FDA-approved drugs to treat them are not as efficient as needed. Thus, the development of new agents or treatments is quite urgent. In that sense, the use of radioactive materials could represent a good alternative and especially Radium-223 is already been explored with promising results. Here, a Carbopol gel-like formulation was designed and irradiated with different doses in order to prove that it is suitable to include Radium-223 for its combined application by topic route. A formulation was obtained by the addition of triethanolamine to the Carbopol solution until pH 5.0. Physical and rheological tests showed that the formulation is a weak gel with a proper consistence to be administered by both routes. The formulation kept its appearance of transparent gel without change in color, presence of grits or syneresis after all tratments. The microstructure of gels was only slightly modified when the irradiation was made with 1000 Gy while the spreadability and viscosity were more deeply affected. Since the properties of this Carbopol gel-like formulation were maintained under irradiation doses until 100 Gy it is possible to consider that the formulation is suitable to include Radium-223 in order to evaluate its performance as localized drug delivery system for topical administration.

Nanocrystalline powder samples of barium sulfate doped with Europium (BaSO4:Eu2+) were prepared, at a dopant concentration of 0.02 mol%, by the combustion solid-state technique in air atmospheres. Thermoluminescence (TL) response and dosimetric studies have been carried out for this phosphor in order to characterize it as a radiation dosimeter. The results showed that the TL glow curve of BaSO4:Eu2+present an intense TL peak at 200 °C accompanied by a small shoulder peak at 270 °C. The TL low detection limit for BaSO4:Eu (0.02 mol%) was found to be 17.8 μ G y for the gamma radiation emitted by 137Cs . The comparative study with the LiF:Mg, Ti (TLD-100) and calcium fluoride doped with thulium CaF2:Tm dosimeters showed that the TL response of the BaSO4:Eu(0.02 mol%) synthesized by the combustion solid-state technique is highly sensitive: it is 5.8 times higher than the response of the CaF2:Tm pellets and 9.4 times higher than the response of TLD-100. The high sensitivity of BaSO4:Eu and its linear dose response indicate that it can be used as sensor for gamma ionizing radiations.

This study investigates the origin of point defects involved with a strong sensitization of the thermoluminescence (TL) signal of natural quartz between 220 and 400 °C. The sensitization was produced by the combined effect of high-dose of γ radiation and heat-treatments at moderate temperatures. The point defects related to silicon and oxygen vacancies and also with Al, Ge, Li, and OH impurities were assessed by infrared (IR) and electron paramagnetic resonance (EPR) spectroscopy in samples prepared from two single crystals with different sensitivities. The signal intensities of the point defects were measured in as-received, zeroed, γ-irradiated, sensitized and also after heat-treatments carried out up to 600 °C. The deconvolution of the TL curves showed that the major peaks appeared around 240 and 325 °C. The spectroscopic analysis showed the presence of several point defects identified as E’1, [E’1-GeO4]0, [O23-/Li+]0, [GeO4/Li]0, [AlO4]0, [AlO4/H]0, [BO4/H]0 and Li-dependent OH centers. The sensitization process was efficient to increase the number of electron traps by means of a stable coupling (up to 400 °C) between E’1, [GeO4]0 and Li+ ions dislodged from [AlO4/Li]0 centers. It was concluded that the active electron traps responsible for the TL emission above 220 °C were [GeO4/Li]0 and E’1 centers whereas [AlO4]0 was the main recombination center. The thermal behaviour observed for [E’1-GeO4]0 and [O23-/Li+]0 signals showed that the creation of these centers are connected each other. A sequence of reactions involving Li+ motion plus electron-hole recombination at localized transitions within ([GeO4/Li]0, [AlO4]0), (E’1, [AlO4/Li]-) and ([E’1-GeO4]0, [O23-/Li+]0) defect pairs were proposed to explain the TL process in sensitized samples after the impartment of a given test-dose. The precursors for [E’1-GeO4]0 and [O23-/Li+]0 centers were assumed to compete with the active traps responsible for TL peaks found at 240 and 325 °C peaks.

Ainda que o vidro seja um dos materiais mais antigos preparados pelo homem, ele apareceu apenas no século XX como um material que possui propriedades excelentes em áreas distintas. É um sólido amorfo com ausência de ordem a longo alcance e periodicidade, que possui transição vítrea. Pode ser obtido por várias formas, porém em grande parte é obtido pelo processo de fusão seguido do resfriamento rápido do fundido. Neste processo, a viscosidade determina as condições de fusão dos óxidos formadores do vidro, taxa de desvitrificação, etc. Este trabalho tem como objetivo avaliar a variação na viscosidade do vidro LKB (Li2CO3 – K2CO3 – H3BO3) quando adicionado óxido de alumínio (Al2O3) em diferentes proporções. A análise será efetuada utilizando o software SciGlass 7.0. Para tanto, quatro composições de vidros boratos foram desenvolvidas e estudadas. O cálculo da viscosidade em função da temperatura foi obtido para cada tipo de vidro a partir da composição dos óxidos em % mol. Resultados preliminares mostraram que a adição do óxido de alumínio aumenta a viscosidade na matriz LKB. Além disso, foi possível preparar amostras vítreas com alta transparência e homogeneidade em todos os casos a partir da correlação entre a viscosidade e a temperatura.

Cell or tissue renewal and regeneration are the two main developmental requirements of adult organisms.

The results obtained with a standard float zone (FZ) silicon diode, processed at the Helsinki Institute of Physics, used as on-line diagnostic X-ray dosimeter are described in this work. The device was connected in the short-circuit current mode to the input of an integrating electrometer. The response repeatability and the current sensitivity coefficient of the diode were measured with diagnostic X-ray beams in the range of 40-80 kV. The dose-response of the device, evaluated from 10 mGy up to 500 mGy, was linear with high charge sensitivity. Nevertheless, significant energy dependence was observed in the charge sensitivity of FZ device for energies below 70 kV. The dosimetric characteristics of this FZ diode were compared to those of an XRA-50 commercial Si diode, specially designed to X-ray dosimetry. The results obtained with the FZ diode evidenced that it can be an alternative choice for diagnostic X-ray dosimetry, although it needs to be calibrated for individual X-ray beam energies. The studies of long-term stability and the radiation hardness of these diodes are under way.

In the clinical context, assessment involves a complex process including a variety of measurement techniques, with primary reliance on observation of performance, and integration of diverse information in a summary judgment.

Tomography image analysis is one of the most important steps in clinical diagnosis for many different pathologies, as they provide a great amount of visual information of virtually inaccessible areas of the body, such as the brain.

Prostatic artery embolisation (PAE) is used to treat patients with benign prostatic hyperplasia and with lower urinary obstructive tract symptoms. It is an interventional procedure which uses fluoroscopy equipment and can result in exposure to high doses of radiation in patients and staff. We aimed to demonstrate the reduction of radiation doses received by staff during PAE by implementing an optimised protocol called Radiation Exposure Curtailment for Embolisation (RECiFE). This protocol was implemented in cooperation with the medical team and technical team using Siemens Combined Applications to Reduce Exposure (CARE) protocol. The results showed approximately 83% reduction in the radiation doses received by the main physician during PAE. Thus, by adjusting the acquisition parameters of the angiographic equipment and implementing the RECiFE protocol, it is possible to optimise the PAE procedure and reduce the staff radiation dose.

The response of thin diodes (SFH206k) as dosimeters has been investigated employing the beam of an electron accelerator within the dose rate range of 2–8 kGy/s and accumulated doses up to 100 kGy. These devices, operating in the short-circuit mode and under industrial irradiation conditions, deliver current signals nonlinearly dependent on the dose rate, whichever the dose history of the diodes, due to the high density of the generated electron-hole pairs herein achieved. Despite this nonlinearity, the dose rate response is stable and characterized by current signals with repeatability better than 2.0%, regardless of the accumulated dose. It is also found that the dose responses are quite linear with sensitivities slightly dependent on the accumulated dose at a constant dose rate. The decrease in the charge sensitivity, taking as reference that obtained before any radiation damage, reaches only 9% (k = 2) at 100 kGy, which is much smaller than the values reported in the literature. From this low aging and the repeatability of both dose rate and dose responses, it seems that the photodiode under investigation is a low budget alternative, good enough for routine dosimetry, provided it has been previously calibrated in the same processing facility.

This work reports the results obtained from the comparison involving 7 laboratories in Brazil. This exercise is about the calibration service of surface contamination monitors. The monitor has been calibrated to BS ISO 7503-3, the calibration factor in terms of surface emission rate. The comparison was conducted by the Brazilian National Laboratory of Ionizing Radiation Metrology (LNMRI / IRD) from October 2018 to July 2019. The extensive sources used were 14C, 137Cs, 60Co, 90Sr/90Y, 36Cl and 241Am. The result of this proficiency test was excellent and proved the calibration capacity of the Brazilian network in the calibration service for surface contamination monitors.

The thermoluminescence (TL) and infrared stimulated luminescence (IRSL) responses of in-house produced CaF2:Tm dosimeters are investigated in this work, envisaging their application in electron beam (EB) radiation processing. The irradiations were performed at an industrial EB accelerator (1.5 MeV) covering a dose rate range of 2–8 kGy/s and dose up to 10 kGy. In general, the TL glow curves display four peaks, termed as peaks 2, 3, 4, and 5, corresponding to temperatures at ~150, 200, 240, and 300 °C, respectively. The intensity of the low-temperature peaks (2 and 3) grows with the dose, while the others remain constant (saturated). Nevertheless, an evident dose effect on the glow curves manifests in decreased peak3/peak2 ratio with increasing doses. The CW-IRSL curves exhibit similar patterns with an initial signal increase, followed by an exponential decay. Instead of the normal monotonic decays, these peak-shaped curves might be due to the charge capture competition between empty shallow traps and recombination centers. Both TL and IRSL intensities increase linearly with doses up to 6 kGy, and for higher doses, they become sub-linear with a saturation trend around 10 kGy. Another common feature of TL/IRSL response is its dose rate dependence, being more sensitive at higher dose rates. Despite being dose-rate dependent, the CaF2:Tm dosimeters might be suitable for EB processing dosimetry. However, for their use as routine dosimeters, relevant dosimetric characteristics, such as fading and response reproducibility, have to be investigated. Work in this direction is underway.

The aim of this paper is to characterize the IRSL response of rare earth doped CaF2 and co-doped with Al or Li, produced by the solution combustion synthesis (SCS). The results showed a high intensity of the infrared optically stimulated luminescence (IRSL) response for the samples of CaF2 doped with Tb and co-doped with Li. For the samples of CaF2 doped with Ce and co-doped with Li present better IRSL response than the samples co-doped with Al. It was also observed that the samples of CaF2:Ce,Li present a high fading with 50% reduction of the IRSL signal in a period of 60 min. In case of the CaF2:Tb,Li there is no significant fading during this period. For clinical dosimetry the fast fading of the dosimeter is not adequate. However, this feature can be exploited for other applications such as tamper-proof passive systems that detect and timestamp the movement of undeclared nuclear materials, by the estimation of the OSL response of materials with different fading rates.

In this work, the response of the natural material Opal was studied in relation to its thermoluminescence (TL) and optically stimulated luminescence (OSL), after exposure to the gamma radiation of a 60 Co source. The structure of the powdered Opal was verified using the X-ray diffraction, scanning electronic microscopy and energy-dispersive X-ray spectroscopy techniques. The material, in its stone form, was turned into powder and mixed to Teflon (also in powder) in three different concentrations, and then pellets were manufactured. The aim of this work was to evaluate the response of these pellets in high-doses of gamma radiation beams, and to observe their possible application as dosimeters, using the TL and OSL techniques. The dosimetric properties of the samples were analyzed by means of different tests, as: TL emission curves and OSL signal decay curves, reproducibility of TL and OSL response, minimum detectable dose, TL and OSL dose–response curves (5 Gy–10 kGy), and fading. The results obtained in this work, for the TL and OSL phenomena, demonstrated that the pellets of Opal + Teflon present an adequate performance e possibility of use as dosimeters in beams of high-dose gamma radiation.

The Spectrolite, from the silicate family, a variety of Labradorite, was already studied in relation to its thermoluminescence (TL) and optically stimulated luminescence (OSL) responses, in high-dose gamma radiation fields; the results indicated their good application as gamma radiation detectors. In the present work, the analyses performed to investigate powdered Spectrolite are presented, by means of the XRD, SEM and EDX techniques. The luminescent behavior of Spectrolite + Teflon samples, in the concentration of 1:1, was studied in beta radiation beams (90Sr + 90Y), using the luminescent phenomena of TL and OSL. The results showed adequate TL and OSL reproducibility of the samples; the dose–response curves for both techniques presented a linear behavior in a range from 0.5 Gy to 1 kGy, and the fading showed that after 150 h there were 46.7% and 31.6% of the remaining signal of samples for TL and OSL responses, respectively. Therefore, the Spectrolite + Teflon pellets may be used in beta radiation dosimetry.

Calcium Fluoride is one of the oldest known thermoluminescent materials and is considered to be one of the most sensitive. This work presents the dosimetric properties results of CaF2:Tm produced by combustion synthesis. The X-ray diffraction confirmed that CaF2 was successfully produced. TL emission spectra, obtained using a Hammamatsu optical spectrometer, have the same lines of commercial CaF2:Tm, although transitions 3P0→3F4 (455 nm) and 1G4→3H6 (482 nm) are shown to be proportionally more intense. The deconvolution technique was employed and seven glow peaks were found similar to the commercial CaF2:Tm. A linear dose response curve was obtained for the range 0.1 mGy to 100 Gy, with the onset of a supralinear behavior at 50 Gy up to 100 Gy. The minimum measurable dose for gamma was around 100 μGy for a 6.0 mm diameter by 1.0 mm in thickness pellet. No significant fading was observed in 60 days of storage, within experimental uncertainties, showing that the main dosimetric peak is stable.

This work presents the results on the Blue Stimulation Luminescence (BSL) and Infra-Red Stimulation Luminescence (IRSL) of CaF2:Tm produced by the Solution Combustion Synthesis (SCS) method. XRD confirmed the formation of calcium fluoride. BSL showed a dose independent signal due to excitation-emission of Tm bands which was not observed for IRSL. A linear dose response curves was obtained for both Blue-OSL and IR-OSL. IRSL was found approximately three times higher sensitivity than Blue-OSL. The minimum measurable dose (MMD) for BSL was found to be around 1.0 mGy. For IRSL a MMD of around 100 μGy was obtained. The results demonstrated that CaF2:Tm produced by SCS has a strong potential for OSL dosimetry.

This study investigates patient and staff dose measurements in pediatric barium meal series fluoroscopic procedures. It aims to analyze radiographic techniques, measure the air kerma-area product (PKA), and estimate the staff's eye lens, thyroid and hands equivalent doses. The procedures of 41 patients were studied, and PKA values were calculated using LiF:Mg,Ti thermoluminescent dosimeters (TLDs) positioned at the center of the patient’s upper chest. Furthermore, LiF:Mg,Cu,P TLDs were used to estimate the equivalent doses. The results showed a discrepancy in the radiographic techniques when compared to the European Commission recommendations. Half of the results of the analyzed literature presented lower PKA and dose reference level values than the present study. The staff‘s equivalent doses strongly depends on the distance from the beam. A 55-cm distance can be considered satisfactory. However, a distance decrease of ~20% leads to, at least, two times higher equivalent doses. For eye lenses this dose is significantly greater than the annual limit set by the International Commission on Radiological Protection. In addition, the occupational doses were found to be much higher than in the literature. Changing the used radiographic techniques to the ones recommended by the European Communities, it is expected to achieve lower PKA values ​​and occupational doses.

The purpose of this paper is to evaluate the use of alanine-EPR as a transfer standard dosimetry system for low energy X radiation, such as that in RS-2400, which operates in the range from 25 to 150 kV and 2 to 45 mA. Two types of alanine dosimeters were investigated. One is a commercial alanine pellets from Aerial-Centre de Ressources Technologiques, France and one was prepared in our laboratory (LMRI-DEN/UFPE). The EPR spectra of the irradiated dosimeters were recorded in the Nuclear Energy Department of UFPE, using a Bruker EMX10 EPR spectrometer operating in the X-band. The alanine-EPR dosimetry system was calibrated in the range of 20–220 Gy in this X-ray field, against an ionization chamber calibrated at the relevant X-ray energy with traceability to PTB. The results showed that both alanine dosimeters presented a linear dose response the same sensitivity, when the EPR signal was normalized to alanine mass. The total uncertainty in the measured dose was estimated to be about 3%. The results indicate that it is possible to use the alanine-EPR dosimetry system for validation of a low-energy X ray irradiator, such as RS-2400.

The objective of this study was to assess the radiation doses received by anaesthetists from prostatic artery embolization (PAE) procedures. Ten PAE procedures conducted in a reference hospital in the city of Recife, Brazil were investigated. Occupational dosimetry was performed using thermoluminescent dosemeters which were located next to the eyes, close to the thyroid (over the shielding), on the thorax (under the apron), on the wrist and on the feet of the physician’s body. The results showed that the anaesthetist’s feet received the highest doses followed by the eyes and the hands. In some complex PAE procedures the doses received by anaesthetists on the lens of the eyes and the effective dose were higher than those received by the main operator due to the anaesthetist’s close position to the patient’s table and the use of oblique projections. The personal dose equivalent Hp(3) per procedure for the anaesthetist’s right eyebrow ranged from 20.2 μSv to 568.3 μSv. This result shows that anaesthetists assisting PAE procedures can exceeds the annual eye lens dose limit of 20 mSv recommended by the ICRP with only one procedure per week if radiation protection measures are not implemented during procedures.

The objective of this work was to evaluate the air kerma-area product (PKA) and the skin absorbed dose in the region of the eyes, salivary glands and thyroid of the patient from mandible examinations performed with three cone-beam computed tomography (CBCT) scanners, i.e. i-CAT classic, Gendex CB-500 and PreXion 3D. For the dosimetric evaluation, an anthropomorphic head phantom (model RS-250) was used to simulate an adult patient. The CBCT examinations were performed using standard and high-resolution protocols for mandible acquisitions for adult patients. During the phantom's exposure, the PKA was measured using an ionising chamber and the absorbed doses to the skin in the region of the eyes, thyroid and salivary glands were estimated using thermoluminescence dosemeters (TLDs) positioned on the phantom's surface. The PKA values estimated with the CBCT scanners varied from 26 to 138 µGy m(2). Skin absorbed doses in the region of the eyes varied from 0.07 to 0.34 mGy; at the parotid glands, from 1.31 to 5.93 mGy; at the submandibular glands, from 1.41 to 6.86 mGy; and at the thyroid, from 0.18 to 2.45 mGy. PKA and absorbed doses showed the highest values for the PreXion 3D scanner due to the use of the continuous exposure mode and a high current-time product.

The 110 °C TL glow peak of quartz has been used in dating and retrospective dosimetry due to the pre-dose effect and the sensitivity changes caused by heating. One of the main difficulties related to TL dating is the sureness that the geological signal was completely zeroed by firing. In this study, the sensitivity change of the 110 °C peak and the EPR signal intensity of the E 1 ′ center were combined to account for the burning status of archaeological pebbles. For this, a quartz pebble was sawn into many pieces and each piece was heat-treated at different temperatures from 200 to 800 °C. Powdered aliquots were γ-irradiated and stored into an ice-bath before the TL readout. Peak-maximum temperature, TL intensity and activation energy of the 110 °C peak were determined by glow curve deconvolution methods. The thermal activation characteristic obtained in this study showed a peak maximum at 500 °C and a sensitization ratio higher than 200. The heating temperature also affected the intensity of the E 1 ′ center. The usefulness of the burning pattern was tested by measuring the TL and EPR signals of several archaeological pebbles, initially classified as “burnt”, “unburnt” or “unidentified”, and also from two specimens burnt in a campfire. The main achievement of this study was the possibility to infer the temperature in which a pebble was heated in the past independent of visual signs.

This study investigates the optically stimulated luminescence (OSL) and the photo-transferred thermoluminescence (PTTL) signals in quartz single crystals showing a strong TL peak near 300 °C after being sensitized by irradiation with 25 kGy of gamma rays and heating at 400 °C. Natural and sensitized samples were prepared from two crystals with different sensitivity levels in the 300 °C TL region. Continuous-wave (CW) and linearly-modulated (LM) OSL signals were stimulated with blue light-emitting diodes during 40 and 1000 s, respectively. Two components were isolated from the CW-OSL signals of sensitized samples. These components were clearly seen in LM-OSL measurements together with two long-term components. LM-OSL showed that the sensitization process considered in this study sensitized an ultrafast OSL component of these crystals. The similar behavior found for the thermal stabilities of OSL and TL signals and the dependence of these signals with sample origins suggested that the trapping site related to the ultrafast component is also related to the TL process of the sensitized peak. The PTTL signal induced by blue LEDs increased the intensity of the sensitized glow peak. On the other hand, a remarkable reduction in the intensity of this peak as a result of the accumulated effect of blue light exposure was clearly seen in both kinds of crystals. These results were explained by a mechanism of competition between optically unstable deep traps and trap levels responsible to the sensitized TL peak.

Doped Calcium fluoride (CaF2) is a well known dosimetric material used for measurement of ionizing radiation. In the literature we can find several synthetic routes to prepare this materials, however the majority of the methods present disadvantages such as long time for preparation, use of hazardous materials or crystal growth infrastructure. In order to overcome these problems, in this paper we present a simple wet chemical process by which calcium fluoride doped with thulium was fabricated. The crystal structure and particle size of the synthesized material was characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The thermoluminesce response for samples irradiated with 60Co gamma radiation showed a linear response up to 10 kGy. Additionally, the TL emission spectra shows spectroscopic emission lines characteristic of Tm3+, where the relative intensity of each line depend on the fabrication parameters.

The objective of this study was to evaluate the entrance surface air kerma in pediatric chest radiography. An evaluation of 301 radiographical examinations in anterior–posterior (AP) and posterior–anterior (PA) (166 examinations) and lateral (LAT) (135 examinations) projections was performed. The analyses were performed on patients grouped by age; the groups included ages 0–1 y, 1–5 y, 5–10 y, and 10–15 y. The entrance surface air kerma was determined with DoseCal software (Radiological Protection Center of Saint George׳s Hospital, London) and thermoluminescent dosimeters. Two different exposure techniques were compared. The doses received by patients who had undergone LAT examinations were 40% higher, on average, those in AP/PA examinations because of the difference in tube voltage. A large high-dose “tail” was observed for children up to 5 y old. An increase in tube potential and corresponding decrease in current lead to a significant dose reduction. The difference between the average dose values for different age ranges was not practically observed, implying that the exposure techniques are still not optimal. Exposure doses received using the higher tube voltage and lower current-time product correspond to the international diagnostic reference levels.

The aim of this article was to verify the performance of the Mirion InstadoseTM dosemeter under clinical conditions and to compare its response in typical X-ray fields used during interventional and cardiology procedures with the TLD-100, usually used for radiation dosimetry. It was also objective of this study to verify the feasibility of using the InstadoseTM dosemeter response at the chest level for estimation of occupational eye lens dose in cardiology and interventional radiology. Initially the response of the dosemeter was tested using continuous X-ray beams and the results showed that the Instadose dosemeter present a satisfactory behavior of the most important dosimetric properties based on the tests as described in the IEC 62387 standard. The measurements performed in clinical conditions showed that the InstadoseTM dosemeter response was comparable to that of TL dosemeters used in interventional radiology and cardiology procedures and there is a correlation between the eye lens doses and the chest doses measured with the InstadoseTM. Based on the results obtained, we recommend the use of the InstadoseTM dosemeter for purposes of occupational whole-body monitoring of medical staff in interventional radiology and cardiology procedures.

The dosimetric response of a multi guard ring structure (MGR) diode has been studied with clinical electron beam energies from 5 MeV to 15 MeV. The results showed that the MGR dose response is linear in the range of 5–320 cGy and presents reproducibility with variation coefficients less than 0.4%. The field output factors measured with the MGR agreed within 2% with those measured with an ionization chamber. This study evidences that this diode can be used for clinical electron beam dosimetry.

Introduction Digital mammography present many advantages in comparison to conventional mammography, such as high dynamic range and the post-processing of acquired images. One problem is that protocols may not be optimized, resulting in higher absorbed doses to patients. The objective of this work is to evaluate image quality and to estimate mean glandular doses (MGD) in patients submitted to mammography examinations with three digital systems and one screen-film system in Recife, Brazil. Methods To estimate the MGD, the parameters used to acquire images of 5475 patients, with ages between 40 and 64 years and compressed breasts between 2 and 9 cm, were registered. The MGD was calculated by multiplying the incident air kerma with conversion coefficients depending on the anode/filter, breast glandularity and half-value layer. The image quality evaluation of the digital systems was made using objective and subjective European criteria. Results The results showed MGDs in the range of 0.4-10.3 mGy and the higher values were observed with digital systems. It was also observed that in the digital systems the use of compression force is not adequate and the irradiation parameters are not optimized. The images failed to reproduce the pectoral muscle and the contrast-to-noise ratio was not adequate for one system, indicating the need to improve the patient’s positioning and the exposure parameters. Conclusion It can be concluded that the use of non-optimized irradiation parameters is causing the higher doses with digital systems, highlighting the insufficient compression force.

The purpose of bowtie filters in CT scanners is to homogenize the x-ray intensity measured by the detectors in order to improve the image quality and at the same time to reduce the dose to the patient because of the preferential filtering near the periphery of the fan beam. For CT dosimetry, especially for Monte Carlo calculations of organ and tissue absorbed doses to patients, it is important to take the effect of bowtie filters into account. However, material composition and dimensions of these filters are proprietary. Consequently, a method for bowtie filter simulation independent of access to proprietary data and/or to a specific scanner would be of interest to many researchers involved in CT dosimetry. This study presents such a method based on the weighted computer tomography dose index, CTDIw, defined in two cylindrical PMMA phantoms of 16 cm and 32 cm diameter. With an EGSnrc-based Monte Carlo (MC) code, ratios CTDIw/CTDI100,a were calculated for a specific CT scanner using PMMA bowtie filter models based on sigmoid Boltzmann functions combined with a scanner filter factor (SFF) which is modified during calculations until the calculated MC CTDIw/CTDI100,a matches ratios CTDIw/CTDI100,a, determined by measurements or found in publications for that specific scanner. Once the scanner-specific value for an SFF has been found, the bowtie filter algorithm can be used in any MC code to perform CT dosimetry for that specific scanner. The bowtie filter model proposed here was validated for CTDIw/CTDI100,a considering 11 different CT scanners and for CTDI100,c, CTDI100,p and their ratio considering 4 different CT scanners. Additionally, comparisons were made for lateral dose profiles free in air and using computational anthropomorphic phantoms. CTDIw/CTDI100,a determined with this new method agreed on average within 0.89% (max. 3.4%) and 1.64% (max. 4.5%) with corresponding data published by CTDosimetry (www.impactscan.org) for the CTDI HEAD and BODY phantoms, respectively. Comparison with results calculated using proprietary data for the PHILIPS Brilliance 64 scanner showed agreement on average within 2.5% (max. 5.8%) and with data measured for that scanner within 2.1% (max. 3.7%). Ratios of CTDI100,c/CTDI100, p for this study and corresponding data published by CTDosimetry (www.impactscan.org) agree on average within about 11% (max. 28.6%). Lateral dose profiles calculated with the proposed bowtie filter and with proprietary data agreed within 2% (max. 5.9%), and both calculated data agreed within 5.4% (max. 11.2%) with measured results. Application of the proposed bowtie filter and of the exactly modelled filter to human phantom Monte Carlo calculations show agreement on the average within less than 5% (max. 7.9%) for organ and tissue absorbed doses.