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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.

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.

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.

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.

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 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 paper is to evaluate the optically stimulated luminescence (OSL) response of spodumene (LiAlSi2O6) silicate and its potential use for gamma radiation dosimetry. A natural Brazilian crystal of α-spodumene was used in this study. After the crystal grinding, pellets with the diameter of 6.0 mm were prepared using a mixture of α-spodumene and polytetrafluoroethylene (Teflon®) (1:2). To study the OSL response, the samples were irradiated with gamma radiation beam of Co-60 and the response was measured using an OSL Reader in two modes of operation: Continuous-wave and pulsed stimulation. The results of the integrated OSL curve of the pellets irradiated with the dose of 30 Gy showed that their response is reproducible within ±2%. The variation of the OSL response upon the dose exhibits a linear response in the range from 30 Gy to 10 kGy, with a correlation coefficient of 0.99. It is possible to conclude that the α-LiAlSi2O6/Teflon® has a great potential for OSL dosimetry of high gamma doses.

The purpose of this paper is to characterize the tiles placed on the walls of the Franciscan convent of "Santo Antônio" (Recife-PE) and to obtain information about the several expansions and structural reforms performed on the convent by dating the bricks. For this purpose, a portable energy dispersive x-ray fluorescence (EDXRF) was used to characterize the tiles. The dating of the bricks was performed using the Thermoluminescence (TL) technique. The results of the EDXRF analysis show that the dominant component of the white pigment is lead [2PbCO(3)·Pb(OH)(2)], used since the ancient times until the 20th century, while the dominant element of the blue pigment is cobalt (CoO·Al(2)O(3)), that has been used from 1807 until nowadays. The TL dating of bricks indicate that there were walls with different periods of construction, being one built around 1765, with a deviation of 28 years, whereas other was built later, around 1874, with a deviation of 15 years. These results provide new data towards understanding how and when the Recife Franciscan convent of "Santo Antônio" was designed and built, contributing to other research works presently underway on site.

A homemade cylindrical ionization chamber was studied for routine use in therapy beams of (60)Co and X-rays. Several characterization tests were performed: leakage current, saturation, ion collection efficiency, polarity effect, stability, stabilization time, chamber orientation and energy dependence. All results obtained were within international recommendations. Therefore the homemade ionization chamber presents usefulness for routine dosimetric procedures in radiotherapy beams.

Earlier, the sensitization of a thermoluminescence (TL) peak near 300 °C in Solonopole quartz was investigated taking into account the combined effect of heat-treatments and irradiation with high doses of γ rays. At that time, it was shown that the sequence: heat at 500 °C, irradiation at 25 kGy and annealing at 400 °C, was a suitable procedure to measure doses as low as 0.1 mGy using this quartz. However, sensitization with doses higher than 50 kGy and the kinetic analysis of the 300 °C peak were not considered. The aim of the present study is to measure the TL sensitivity and the main kinetic parameters of this peak as a function of various sensitization conditions. Five lots of samples were sensitized at different heating temperatures and incremental doses up to 200 kGy. The activation energy was calculated by the peak-shape and the repeated initial rise methods. As a result, the decay noticed in TL sensitivity above 100 kGy was less intense for the lots that were heated before irradiation. The geometrical factor analysis was important to clarify the kinetic-order and the probability of retrapping for each condition of sensitization. The activation energies measured by each method are in fair agreement with each other and were mainly affected by the heat-treatment performed at 1000 °C before irradiation. Activation energies averaging (1.51 ± 0.06) eV were calculated for untreated and heat-treated lots at 500 and 800 °C.

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.

The calibration procedure in radiotherapy treatments is very important and a sensitive task due to the high doses delivered to the patients. Generally, the air-kerma cavity standards for 60Co gamma rays are graphite cavity ionization chambers. In this work a new parallel-plate graphite ionization chamber was studied to analyze its potential use as a reference instrument. In order to evaluate its performance in 60Co beams, it was submitted to several characterization tests. Moreover, Monte Carlo simulations were undertaken using the EGSnrc code to study the influence of the chamber components on its response. The results obtained showed that this new ionization chamber presented a satisfactory performance in all evaluated tests.

The aim of this work was to study the performance of a pencil ionization chamber with a sensitive volume of only 1.06 cm3 and a length of 3.0 cm, developed at the Calibration Laboratory of the IPEN, in very low-energy radiotherapy X-ray beams. These beams are still used for certain skin cancer treatments due to their rapid attenuation in tissue. The dosimeter performance was evaluated in some tests proposed by the IEC 60731 standard: short- and long-term stability and linearity of response. For a complete analysis of the dosimeter response, the EGSnrc Monte Carlo simulation was utilized to investigate the influence of its different parts on the ionization chamber response. All results of the tests were in accordance with the recommended limits, and this work shows that it is possible to extend the application of this pencil-type ionization chamber developed at the LCI.

This paper investigates the relationship between Al- and OH-related point defects with the thermoluminescent (TL) response of natural quartz sensitized with high doses of γ radiation and heat-treatments. For this, specimens from a single crystal were progressively irradiated with doses of 60Co from 2 to 50 kGy. After each step of sensitization, the absorption bands related to [AlO4]0, [AlO4/H]0, [H4O4]0 and Li-dependent OH point defects were measured by optical absorption and infrared (IR) spectroscopy. The sensitization of the 280 °C TL peak increased up to 15 kGy and then its intensity remained constant. The absorption intensity at 470 nm increased with γ doses suggesting a progressive creation of [AlO4]0 acting as recombination centers for the sensitized peak. At the same time, the TL intensity of the 90 °C peak decreased with the accumulated dose. This effect was not related to the saturation in the number of recombination centers because both [H4O4]0 and [AlO4]0 bands were increasing after 50 kGy. Compared to the as-received condition, it was found that IR bands associated with [AlO4/H]0 and Li-dependent OH decreased with the effect of heat-treatments. The precursor for [AlO4]0 is [AlO4/Li]0 and the Li species dislodged from [AlO4/Li]0 and Li-dependent OH centers play an important role in the sensitization process.

The aim of this paper is to report the sensitization of the TL peak appearing at 270°C in the glow curve of natural quartz by using the combined effect of heat-treatments and irradiation with high γ doses. For this, thirty discs with 6 x 1 mm 2 were prepared from plates parallell to a rhombohedral crystal face. The specimens were separated into four lots according to its TL read out between 160 and 320 °C. One lot was submitted to y doses of 60 Co radiation starting at 2kGy and going up until a cumulative dose of 25kGy. The other three lots were initially heat-treated at 500, 800 and 1000°C and then irradiated with a single dose of 25kGy. The TL response of each lot was determined as a function of test-doses ranging from 0.1 to 30 mGy. As a result, it was observed that heat-treatments themselves did not produce the strong peak at 270 °C that was observed after the administration of high γ doses. This peak is associated with the optical absorption band appearing at 470 nm which is due to the formation of [AlO 4 ]○ acting as electron-hole recombination centers. The formation of the 270°C peak was preliminary analyzed in relation to aluminum- and oxygen-vacancy-related centers found in crystalline quartz.

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.

On October 26, 1991 a fatal radiological accident occurred in a 60Co irradiation facility in the town of Nesvizh in Belarus. Following a jam in the product transport system, the operator entered the facility to clear the fault. On entering the irradiation room the operator bypassed a number of safety features, which prevented him from perceiving that the source rack was in the irradiation position. After the accident average whole body absorbed doses between 8 and 16 Gy have been determined by TLD measurements, by isodose rate distributions, by biological dosimetry and by ESR measurements of clothes and teeth. In an earlier investigation the MAX/EGS4 exposure model had been used to calculate absorbed dose distributions for the radiological accident in Yanango/Peru, which actually represented the simulation of exposure from a point source on the surface of the body. After updating the phantom as well as the Monte Carlo code, the MAX/EGS4 exposure model was used to calculate the absorbed dose distribution for the worker involved in the radiological accident in Nesvizh/Belarus. For this purpose, the arms of the MAX phantom had to be raised above the head, and a rectangular 60Co source was designed to represent the source rack used in the irradiation facility. Average organ absorbed doses, depth-absorbed doses, maximum absorbed dose and average whole body absorbed dose have been calculated and compared with the corresponding data given in the IAEA report of the accident.

In this work, we present photoluminescence characterization of rare earth ion doped nanoporous aluminum oxide synthesized by anodization process in different aqueous electrolyte solutions. We found that the luminescence of doped aluminum oxide strongly depends on the synthesis medium. When synthesized in inorganic acid only rare earth ions fluorescence is present, whereas nanoporous aluminum oxide synthesized in organic solvent presents two strong unexpected luminescence emission lines, one at 429 nm and the other at 491 nm, with quite long decay time when excited with long wavelength ultraviolet light. Theses results suggest that light simulation of primary colors and chromaticity control of the emitted light can be achieved by carefully doping aluminum oxide nanoporous with a combination of different rare earth ions.

Al 2 O 3 :C is one of the most used radioluminescence materials for fiberoptic dosimetry due mainly to its high efficiency. However, this compound presents the drawback of emitting in the spectral region, where the spurious radioluminescence of fibers is also important. In this work, sintered samples of Al 2 O 3 :C doped with Tb, Sm, Ce and Tm have been prepared by combustion synthesis and their radioluminescence responses have been evaluated. The influence of the different activators on the radioluminescence spectra has been investigated.

In this work, an optical dosimeter for gamma radiation ( 60 Co) based on the color change of polyaniline nanofilms in the emeraldine oxidation state was developed by spin coating of the polymer films on glass substrates. After irradiation, the nanofilms were characterized by UV-visible (UV-Vis) absorption spectroscopy as a function of the 60 Co radiation dose. The deep blue color, characteristic of undoped polyaniline films before irradiation subsequently becomes green as the film is irradiated, and the film absorption coefficient exhibits a linear dependence with logarithm of the irradiation dose from 1 to 10 kGy. These results strongly suggest that polyaniline nanofilms can be used as a qualitative and quantitative dosimeter for gamma radiation in the analyzed dose range.

A high quality silicon–polyaniline heterojunction is produced by spin-coating of soluble polyaniline on silicon substrates. The devices have excellent reproducibility of their electrical characteristics and high rectification ratio. The rectification ratio is 60,000 at ±1.0 V at room temperature, and typical reverse current at −1.0 V is 3 nA. A G / I × G plot is used to analyze the current–voltage characteristics, yielding typical series resistance of 4 kΩ and ideality factor in a range from 1.0 to 2.0. The devices present great potential for use as radiation and/or gas sensors.

In this work we discuss the synthesis, characterization and the use of rare earth doped silica glass prepared by the sol–gel technique as a γ radiation detector. We obtain a glass material doped with rare earth ions in a high local symmetry, in contrast to the low symmetry found in glasses produced by conventional melting methods and technologies. The behavior of the luminescence spectra of the excited states of rare earth indicates a strong dependence with gamma radiation doses, where the magnetic dipole transition 5D0→7F1 of the Eu3+ ions presents an huge enhancement of 900% for irradiation doses up to 400 Gy.

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 work presents the preliminary results obtained with a high-resistivity magnetic Czochralski (MCz) silicon diode processed at the Helsinki Institute of Physics as a high-dose gamma dosimeter in radiation processing. The irradiation was performed using a 60 Co source (Gammacell 220, MDS Nordion) within total doses from 100 Gy up to 3 kGy at a dose rate of 3 kGy/h. In this interval, the dosimetric response of the diode is linear with a correlation coefficient ( r 2 ) higher than 0.993. However, without any irradiation procedure, the device showed a small sensitivity dependence on the accumulated dose. For total dose of 3 kGy, the observed decrease was about 2%. To clarify the origin of this possible radiation damage effect, some studies are under way.

Thermoluminescent (TL) α-Al 2 O 3 :C dosimeters, produced in the form of single crystals, show a high sensitivity to ionizing radiation (about 40–60 times higher than LiF:Mg,Ti). However, the crystal growth requires high temperatures (2050 °C) and highly reducing atmospheres. This paper presents the TL response of thin nanoporous Al 2 O 3 :C membranes obtained by electrochemical anodizing of aluminum in organic acid solutions at room temperature. The TL properties of the samples were analyzed as a function of the anodizing voltage in the interval 30–60 V and of the acid concentrations from 0.05 to 0.6 M. The dosimetric response of the samples for 60 Co gamma radiation is linear with dose, and the best response was found for samples anodized at 130 V with 0.10 M acid concentration.

In this paper, we describe the results obtained for the evaluation of a multi-guard ring (MGR) structure diode as diagnostic X-ray dosimeter. This device was developed in the framework of R&D programs for the future CMS experiment at the Large Hadron Collider (LHC) with high radiation hardness to fulfill the requirements from this accelerator environment. In order to use the MGR diode as a dosimeter, it was connected in the photovoltaic mode to the input of an integrating electrometer and positioned at the center of an X-ray beam, beside a previously calibrated ionization chamber. The dependence of the diode response on the X-ray beam doses was evaluated for 35–90 kV X-ray generator bias supply, with doses in the range of 50 μGy–5 mGy. The good linearity of the dose–response curve obtained showed the MGR diode dosimeter to be a reliable alternative method for diagnostic X-ray dosimetry.

Amorphous Brazilian bisphenol-A polycarbonate (Durolon) is used in medical supplies. Upon gamma-irradiation it undergoes main chain scissions. The major consequences are a decrease in the molecular weight and a yellowness of the polymer. The G (main chain scissions/100 eV)=1.49, calculated for the dose range of 10–200 kGy through the viscometry method, is not sufficient to promote significant changes in the mechanical properties. The FTIR spectra of irradiated samples show a decrease in carbonyl groups with increase of radiation dose, evidence of scissions in this groups. On the other hand, oxygenated products are not produced in the radiolysis of Durolon. The mechanical properties are not affected significantly up to a dose of 100 kGy, indicating that medical supplies made of Durolon can withstand four sterilization irradiations.

A commercial PIN silicon photodiode was tested as detector for soil water-content measurements by the γ-ray attenuation method. The results indicate that the portable photodiode is adequate for this application and can replace the more complicated and expensive method of NaI(TI) scintillation detection.

We discuss several aspects of the reliability physics of silicon–polyaniline heterojunctions, such as degradation effects induced by local heating, charge trapping and temperature changes. The results further confirm the quality of the devices electrical characteristics and their suitability for radiation and gas sensors applications.

Thin polyaniline films in the emeraldine oxidation state, deposited by spin coating on glass substrate when exposed to gamma-irradiation presents an interesting radiochromic effect, very similar to the protonic acid doping of polyaniline. The green color of the irradiated film and the two absorption bands developed at 420 and 832 nm is a strong evidence of the generation of polaron defect (radical cation) which is responsible for the high conductivity of the polymer. In this work we used the Atomic Force Microscopy (AFM) technique to investigate the morphology of polyaniline films irradiated with 60 Co gamma rays and compare with protonic acids doping effect.

In this work an optical dosimeter for gamma radiation ( 60 Co ) based on the color change of polyaniline nanofilms (thickness in the range 30– 50 nm ) in the emeraldine oxidation state was developed by spin coating of the polymer on glass substrates. The irradiated polyaniline nanofilms were characterized by UV-visible absorption spectroscopy as a function of the 60 Co radiation dose. The deep blue color, characteristic of undoped polyaniline film before irradiation, becomes subsequently green as the film is being irradiated in the dose range from 0 to 10 kGy .