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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.

This study examines the thermoluminescent emission of quartz whose existence can be registered with 1 mGy test-doses. Samples originated from three crystals were sensitized using the combined effect of gamma radiation and heat-treatments. The glow curves were registered under five optical setups to collect emissions from ultraviolet to yellow-orange bands. The emissions were scrutinized using a computerized deconvolution method. After sensitization, the activation energies of trapping states increased, and the violet/blue emissions exceeded the near-ultraviolet emission in the whole glow curve. The possibility to remove and restore the sensitization effect and the existence of strong emissions above 350 °C indicates that the rise in TL sensitivity occurs when competition between active and deep traps is annihilated. The narrow distribution of activation energies and the subtle changes in band emissions suggest that TL production in quartz consist of localized transitions involving different energetic levels of the same traps and recombination centers.

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.

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.

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.

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.

Measuring entrance exposures to diagnostic or therapeutic radiology patients is valuable to infer dose distributions within their bodies in order to minimize unnecessary exposures. For this purpose, we investigated the development of dosimeters consisting of waterproof, transparent, and flexible films containing OSL microcrystals. In our method, films are produced by casting solutions, followed by solvent evaporation. Non-aggressive chemicals are used, which allows the production of films containing large quantities of crystals without altering their structure. In this proof of principle study, we chose polyvinyl chloride (PVC) as a polymer matrix due to its high transparency and its waterproof nature and we produced films loaded with microcrystals of CaF 2 :Ce. A mixture of acetone:benzene (40:60 wt%) was selected as the best solvent for producing PVC films loaded with CaF 2 :Ce crystals. This solvent offers ease of handling, low toxicity, low cost, and does not affect the crystal structure nor its OSL emission. The PVC films can be loaded with any luminescent material. For proof of concept we chose to load them with CaF 2 :Ce micron sized particles because they emit an intense OSL signal for a low beta dose of 100 mGy, showing very good sensitivity for dosimetric applications. Our results indicate that films loaded with OSL crystals may be suitable for the production of a novel OSL dosimeter, which adheres closely to the body and could be used during a radiological procedure to estimate the entrance dose. As OSL materials are sensitive to light, somehow the films would have to be shielded from light for dosimetric purposes.

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.

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.

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.

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.

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.

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 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.

Objective: To estimate the entrance surface air kerma (Ka,e) and air kerma in the region of radiosensitive organs in radiographs of pediatric paranasal sinuses. Materials and Methods: Patient data and irradiation parameters were collected in examinations of the paranasal sinuses in children from 0 to 15 years of age at two children's hospitals in the city of Recife, PE, Brazil. We estimated the Ka,e using the X-ray tube outputs and selected parameters. To estimate the air kerma values in the regions of the eyes and thyroid, we used thermoluminescent dosimeters. Results: The Ka,e values ranged from 0.065 to 1.446 mGy in cavum radiographs, from 0.104 to 7.298 mGy in Caldwell views, and from 0.113 to 7.824 mGy in Waters views. Air kerma values in the region of the eyes ranged from 0.001 to 0.968 mGy in cavum radiographs and from 0.011 to 0.422 mGy in Caldwell and Waters views . In the thyroid region, air kerma values ranged from 0.005 to 0.932 mGy in cavum radiographs and from 0.002 to 0.972 mGy in Caldwell and Waters views. Conclusion: The radiation levels used at the institutions under study were higher than those recommended in international protocols. We recommend that interventions be initiated in order to reduce patient exposure to radiation and therefore the risks associated with radiological examination of the paranasal sinuses. Resumo Objetivo: Estimar o kerma no ar na superfície de entrada (Ka,e) e o kerma no ar na região de órgãos radiossensíveis em radiografias pediátricas dos seios paranasais. Materiais e Métodos: Foram coletados os dados dos pacientes e parâmetros de irradiação em exames de seios paranasais de crianças com 0 a 15 anos, em dois hospitais infantis na cidade do Recife, PE. O Ka,e foi estimado utilizando os rendimentos dos tubos de raios X e os parâmetros selecionados. Os valores de kerma no ar nas regiões dos olhos e tireoide foram estimados utilizando dosímetros termoluminescentes. Resultados: Os valores de Ka,e variaram de 0,065 a 1,446 mGy para radiografias cavum, 0,104 a 7,298 mGy para Caldwell e 0,113 a 7,824 mGy para Waters. Os valores de kerma no ar na região dos olhos variaram de 0,001 a 0,968 mGy para cavum e 0,011 a 0,422 mGy para Caldwell e Waters. Na região tireóidea, os valores de kerma no ar variaram de 0,005 a 0,932 mGy para cavum e 0,002 a 0,972 mGy para Caldwell e Waters. Conclusão: Os parâmetros de irradiação utilizados pelas instituições foram mais elevados do que os recomendados em protocolos britânicos. Ações de otimização são recomendadas de modo a contribuir para a redução da radiação nos pacientes e, portanto, os riscos.

Computed tomography (CT) examinations have increased significantly in recent years due to technological innovations. In some industrialised countries, CT contributes to the population dose as much as background radiation. In developing countries, the uses and risks of CT have not been well characterised. The purpose of this investigation was to assess potential stochastic and deterministic radiation effects from common CT exams performed in six hospitals of Recife, Pernambuco. Scanning parameters and patient gender and age were collected for a total of 285 patients undergoing CT examinations of the head (90), chest (75), abdomen (60) and abdomen?pelvis (60). The organ doses, which were calculated using the ImPACT dosimetry calculator, varied significantly among institutions. Organs such as the brain, the heart and the eye lenses, which exhibited doses as high as 85, 42 and 100?mGy, respectively, are of concern for the production of cerebrovascular and cardiovascular diseases and cataracts. Effective cancer risks were calculated using Brenner methodology and BEIR-VII risk factors. They range from 1.8 to 110.2 cases per 100?000 persons for cancer induction and from 1.5 to 63.0 cases per 100?000 for cancer mortality. To reduce doses, a quality assurance programme that includes procedural justification and radiation protection optimisation should be implemented.

MTS-N detectors are pellets of LiF:Mg,Ti produced at the Institute of Nuclear Physics (IFJ) in Krakow, Poland. The thermoluminescence (TL) response of these detectors to gamma radiation doses up to 10 kGy only has been studied earlier. The aim of this paper is to evaluate the TL and EPR response of MTS detectors irradiated with 60 Co gamma radiation at high doses up to 1200 kGy. The results indicate that the MTS-N glow curve presents a new peak at temperature near 420 °C for doses over 700 kGy. This peak is probably associated with the second EPR signal that appears for doses over 100 kGy. The defect center related to this signal is undergoing further studies.

This work shows results of type testing of a ring radiation dosimeter system under IEC 62387:2012. The personal dosimeter investigated in this work consists of a commercial one element plastic ring which contains an LiF:Mg,Ti thermoluminescent pellet. By applying requirements for statistical fluctuations and linearity, a minimum measurable dose in Hp(0.07) was established. Energy and angular dependence aided in determining energy correction factors and fading requirements were used to select the most appropriate preheat scheme. Type testing of passive radiation monitors was performed in the Radiation Metrology Laboratory (LMRI-DEN/UFPE) of the Federal University of Pernambuco and is a major step in Brazil for the independent evaluation of these dosimeters, currently not available in the country.

In this work we present an alternative route to synthesize rare-earth doped aluminum oxide materials for thermoluminescent (TL) dosimetry using the combustion synthesis (CS) technique. The samples were prepared by mixing aluminum nitrate ( Al ( NO 3 ) 3 · 9 H 2 O ) , urea ( CO ( NH 2 ) 2 ) , and europium nitrate ( Eu ( NO 3 ) 3 ) , terbium nitrate ( Tb ( NO 3 ) 3 ) and tetra-ethyl-ortho-silicate (TEOS, C 8 H 20 O 4 Si ) in appropriate amounts as dopants in an aqueous solution. The excess water was evaporated on a hot plate to form a gelatinous mixture, which was then transferred to a muffle furnace pre-heated to 500 ∘ C where it ignited spontaneously within a few seconds. The TL glow curve of the irradiated samples showed an isolated peak at around 200 ∘ C for the Eu doped sample which is suitable for radiation dosimetry. The europium concentration was varied from 0.005% to 7% in order to study the effect of the dopant concentration on the TL response and the optimum concentration was found to be 0.5%. The effect of different annealing temperatures of the sample on the TL response was also studied and the results showed a broad TL peak for 600 and 800 ∘ C and a well defined peak for a 1000 ∘ C annealing temperature. From these results it is possible to conclude that the CS method is a very suitable technique to prepare doped aluminum oxide materials. The technique is fast, low cost and produces well defined materials that can be used for dosimetric applications. Further work is still under way in order to optimize sensitivity for low dose measurements.

In this work thermoluminescent properties of α-Al 2 O 3 samples doped with Tb 3+ and Tm 3+ , prepared by the combustion synthesis route, were studied. Samples were prepared by mixing stoichiometric amounts of aluminum nitrate, urea and dopants with different amounts of terbium and thulium nitrates varying from 0 to 0.15 mol%. The mixture was ignited in a muffle furnace at low temperature (500 °C). After the combustion, the samples were sintered at 1400 °C for 4 h in order to obtain the pure α-phase crystalline structure. The TL response of these samples for Co-60 gamma radiation was evaluated. It was observed a TL glow peak around 220 °C and a linear response for doses in studied range of 0.1–1 Gy. It was observed that the 0.1 mol% concentrations of both dopants present the highest TL sensitivity. The sensitivity of the co-doped (0.10 mol%) samples is 5 times higher than the 0.1 mol% Tm-only doped Al 2 O 3 and 40 times higher than the sample doped only with 0.1 mol% of Tb. These results strongly suggest that the Al 2 O 3 :Tm–Tb, prepared through the combustion method, is a potential material for TL radiation dosimetry.

In this work, α-Al 2 O 3 doped either with Tb 3+ or Tm 3+ was prepared by combustion synthesis techniques for thermoluminescent (TL) ionizing radiation dosimetry applications. In this method, the reactants (aluminum nitrate, urea and therbium or thulium nitrate) are ignited in a muffle furnace at temperatures as low as 500 °C. This synthesis route is an alternative technique to the conventional fabrication methods of materials based on α-Al 2 O 3 (Czochralsky, Vernuil), where high melting temperatures and reducing atmospheres are required. After combustion, the samples were annealed at temperatures ranging from 1000 to 1400 °C for 4 h in order to obtain the pure α-phase structure and were then irradiated with a Co-60 gamma radiation source. The annealed samples present a well defined TL glow peak with a maximum at approximately 200 °C and linear TL response in the dose range 0.5–5 Gy. It was observed that a 0.1 mol% concentration of Tb 3+ or Tm 3+ and annealing at 1400 °C optimize the TL sensitivity. The highest sensitivity was found for Tm 3+ doped samples which were approximately 25 times more sensitive than Tb 3+ doped samples. These results strongly suggest that combustion synthesis is a suitable technique to prepare doped aluminum oxide material and that Tm 3+ doped aluminum oxide is a potential material for TL radiation dosimetry.

The aim of this paper is to evaluate the thermoluminescent (TL) response of a larimar, a variety of pectolite (NaCa 2 Si 3 O 8 [OH]). It is a blue pectolite only found on the terrestrial crust of the province of Barahona, in the south-western region of the Dominican Republic. The larimar rock used in this study, presented a light-blue color with brown areas. X-ray powder diffractometry (XRD), showed that the light-blue portion of the rock is composed essentially by pectolite and the brown portion is composed by a mixture of minerals. Aliquots of 5 mg of light-blue portions were irradiated with gamma rays with doses from 10 to 10 4 Gy and the TL glow curves were obtained from 50 to 400 °C. The glow curve showed a broad peak around 150 °C and a peak near 280 °C. Different pre-heat condition were used to remove the broad peak. The TL emission of the main peak appeared in the region of 580 nm. The TL response of the main peak showed a linear behavior up to 2500 Gy and a sub-linear behavior above this dose value. Studies of the 30 day fading effects in TL signal using a pre-heating temperature around 180 °C during 15 min were carried out and fading near 25% was observed.

This paper reports the results of an investigation carried out to determine the suitability of using a commercially available photodiode for dosimetry in mammography thereby providing a low cost dosemeter with a direct reading of the radiation dose. A mammographic X-ray generator (Siemens Mammomat 1000) with tube potential in the 23-30 kV range and a constant potential X-ray generator (Pantak) with a W/Mo anode/filter combination were used in this study. The results showed that the photodiode response is highly linear within mammographic dose ranges and that the energy dependence was

The aim of this study is to evaluate the incident air kerma (INAK) and the mean glandular dose (MGD) during mammography in Recife, North-east Brazil. The study was performed in three institutions: a private clinic (A), a public hospital (B) and a private hospital (C). The incident air kerma to mammography procedures were estimated using a standard breast phantom and the patient MGD, evaluated in the units B and C, was performed using the calibration of output method. This method involves the recording of the patient exposure parameters (kVp, mAs, filter) and the measurement of these parameters of the incident air kerma using a calibrated ionisation chamber. The results obtained showed that INAK for the standard breast phantom, in the institutions A, B and C, were 18.2, 9.4 and 8.5 mGy, respectively. The results of patient MGD values ranged from 0.23 to 7.46 mGy per film, and the MGD values per woman were between 8.23 and 40.6 mGy for the C institution and between 1.50 and 18.78 mGy for the B institution.

Purpose: This study determined image quality and organ doses for common CT exams in six hospitals of Recife, Pernambuco, in order to assess health risks.Method and Materials: Data were gathered from six helical CTscanners, one of them with 64 slices. Image quality was evaluated using the ACR accreditation phantom and protocol. Scan acquisition parameters (kV, mAs, scan time, slice thickness, table increment or pitch, scan length) and number of scans per patient were documented for 90 head, 75 chest, 60 abdomen and 60 abdomen/pelvis exams performed using these scanners. Patient age and gender were also recorded. Doses to relevant organs were calculated using the “ImPACT CT Patient Dosimetry Calculator”. Stochastic (and for the eye lenses, deterministic) risks were estimated using BEIR and ICRP data. Results: Only two scanners met all the ACR quality criteria. Two failed the spatial resolution test and two, the low contrast resolution one. The mean doses and [ranges] (in mGy) received by some relevant organs for each CT exam were as follows: Head — Eye lenses: 36±22 [7.9 ‐ 110]. Chest — Breast: 11.8±5.7 [1.7 ‐ 33]; thymus: 18.8±7.6 [9.9 ‐ 48]; heart: 15.2±7.2 [1.7 ‐ 42]; lung: 15.1±7.1 [4.6 ‐ 42]. Abdomen — Stomach: 19±13 [7.4 ‐ 55]; liver: 17±10 [6.7 ‐ 48]. Abdomen/pelvis (34 females, 26 males) — Ovaries: 21±11 [5.4 ‐ 39]; uterus: 23±12 [5.1 ‐ 42]; prostate: 16.0±8.6 [2.9 ‐ 39]; testes: 2.5±2.6 [0.2 ‐ 10]. Doses were unrelated to scanner type and/or image quality. The lowest doses were given by the scanner with the worse performance, suggesting a poor facility operation. Estimated risks and recommendations to optimize protection will be presented and discussed. Conclusion:Image quality is not adequate in all the hospitals. Dose ranges are wide and in several organs are high; some eye lens doses are near the cataract formation threshold.