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The objective of the present study was to evaluate the intensity and spatial distribution of the scattered radiation caused by the use of hand-held x-ray equipment in the zone occupied by the operator, using the Monte Carlo simulation for radiographic views of the upper and lower incisor teeth, and the consequent evaluation of the equivalent dose in the lens. In order to carry out this evaluation, the geometry of a typical dental facility with plaster walls containing the scattering object was used for the computational scenario implemented for the Monte Carlo method simulation. The PENELOPE code for Monte Carlo simulation of electron and photon transport was used with the radiation beam represented by a 60 kV spectrum, 1.5 mm Al and tungsten target. The simulations were carried out with typical parameters for workload and the number of radiographs/week. The results showed that the exposure levels varied significantly according to the angle of the x-ray beam and with the distance to the scattering object. It is concluded that the incorporation of hand-held equipment in dental radiology must be accompanied by the surveillance of occupational exposure levels and a review of the training structure of professionals in dental radiology regarding aspects of radiological protection and the particularities of using this type of equipment.

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Introdução: os equipamentos de radiodiagnóstico evoluíram desde unidades muito simples à incorporação de sistemas digitais. Concomitante, a qualidade da imagem gerada por esses equipamentos tem alcançado elevado padrão diagnóstico. Todas as modalidades do radiodiagnostico médico e odontológico têm, nas últimas décadas, incorporado novos recurso de aquisição e processamento da imagem inclusive com a utilização da tecnologia digital. No entanto, normalmente, as regulamentações destinadas à avaliação da segurança e qualidade da imagem, apresentam algum nível de desatualização. Objetivo: o objetivo do presente estudo foi avaliar criticamente a regulamentação brasileira aplicável ao controle de qualidade em radiologia diagnóstica geral, exceto mamografia. Metodologia: foi realizado um estudo comparativo entre quatro documentos: a normativa vigente no Brasil, Portaria SVS/MS 453/98 e três protocolos internacionais: EC Report 162; ARCAL XLIX; Protocolo Español. A verificação; a periodicidade e a tolerância dos testes selecionados foram usadas como critérios da análise. Para melhor compreensão os parâmetros foram analisados em dois conjuntos: (1) gerador e (2) receptor de imagem. Resultados: verifica-se que para sistemas analógicos a regulamentação nacional não contempla todos os parâmetros essenciais. Discussão: para os sistemas digitais a regulamentação federal brasileira deixa uma lacuna de 100% dos testes específicos para avaliação do receptor de imagem digital. Igualmente para novas modalidades, tais como CBCT. As lacunas e as deficiências ocorrem por: definições físicas equivocadas; valores limites e/ou periodicidade aquém do esperado. Conclusão: conclui-se que apesar do Brasil ser signatário de alguns destes documentos internacionais, a desatualização ou omissão de alguns itens fundamentais para avaliação da qualidade da imagem, produzem resultados insatisfatórios na obtenção de imagens diagnósticas

Introduction: the radiology equipment has evolved from very simple units to the incorporation of digital systems. Concomitantly, the image quality generated by such equipment has reached a high diagnostic standard as a result of modernization. All the modalities of medical and dental radiology have, in the last decades, incorporated new features of image acquisition and processing, including digital technology. However, normally, the regulations designed to assess the safety and quality of the image, have some level of outdatedness. Objectives: in this context, the objective of the present study was to critically evaluate the Brazilian regulations applicable to quality control in general diagnostic radiology, except mammography. Methodology: a comparative study was carried out between four documents: the Brazilian Federal legislation, and three international protocols that were adopted as a reference in this approach: EC Report 162; ARCAL XLIX; Spanish Protocol. The verification; the periodicity and tolerance of the selected tests were used as analysis criteria. For a better understanding, the parameters were analyzed in two sets: (1) generator and (2) image-receptor. Results: as result have been verified that for analogical systems the national regulation does not contemplate all the essential parameters. Discussion: for digital systems the Brazilian regulation leaves a gap of 100% of the specific tests for evaluation of the digital image-receptor. The same is true for new modalities, such as CBCT. The gaps and deficiencies occur by: physical definitions that do not apply to the purpose of the test; limit values and/or periodicity less than currently expected for the parameter. Conclusion: it is concluded that although Brazil is a signatory of some of these international documents, the outdated or omission of some fundamental items for the evaluation of image quality, produce unsatisfactory results in obtaining diagnostic images.

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This study aimed at the development and validation of the models of phantom: CQ-02-IFBA and CQ-01-IFBA, the first filled with water and the second fully with a solid structure in polymethylmethacrylate (PMMA). Both models allow its use in various models of cone beam computed tomography (CBCT), independent of the size of the field of view. The two phantoms are used to evaluate seven parameters of quality control: intensity or average value of pixels of five different plastics, signal to noise ratio, resolution, low contrast, spatial resolution, the accuracy of distances on the z axis, the geometric distortion and image uniformity. Spatial resolution is a critical parameter that differs significantly in the various imaging modalities in dental radiology, and in these two phantoms, it can be evaluated by two different methods: MTF obtained by Fourier transformation of the function LSF (line spread function) and/or by analysis visual image to a pattern of bars up to 16 lp/cm. Validation was performed in three models CBCT: CareStream CS 9000 3D, i-CAT Classical and Sirona Orthophos XG 3D. The two phantom models were viable and also complied with the specifications and data available in the literature. It is concluded that the two phantom models are viable for use in CBCT with different characteristics.

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ABSTRACT The aim of this study was to evaluate the kerma at the surface of the lens in TMJ CBCT and to derive the equivalent dose. An anthropomorphic phantom of the head and neck manufactured by Radiation Support Devices (model RS-230) was used. The dosimetric measurements were obtained by using fourteen thermoluminescent dosimetry (TLD) dosimeters (LiF: Mg, Ti), divided in two pairs (one pair for each eye) and positioned on the surface of the phantom, per scanner evaluated. The tomographic images were acquired in three types of CBCT equipment (CS 9000, Gendex GXCB 500 and i-CAT). Values of equivalent dose obtained were: 5.82 mSv (CS 9000); 5.38 mSv (Gendex GXCB 500) and 7.98 mSv (i-CAT), which varied in accordance with the scanner and the exposure factors used in the image acquisition. The Gendex GXCB 500 used larger FOV and higher kV, resulting in levels close to those obtained on the CS 9000, while larger doses were associated with the i-CAT. The dose values associated with TMJ radiological procedures should be performed with awareness and appropriateness due to sensitivity of the lens.

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This study has the purpose of assessing the radiation absorbed dose in organs/tissues and estimating the effective dose using five different models of Cone Beam Computed Tomography equipment using protocols with similar purpose. For this purpose, 26 thermoluminescent dosimeters were inserted in the position of the organs/tissues of a female anthropomorphic phantom. From the measurements the contribution of wT×HT in the organs and tissues the effective dose were calculated. The measurements have shown the effective dose values within the range 9.3-111.5µSv. The effective dose values by field of view (FOV) size are within the following ranges: 9.3-51.2µSv, 17.6-52.0µSv, and 43.1-111.5µSv for small/located, medium and large FOV respectively. Protocols with same purpose, carried out with different models of equipment, presented significant differences in the values of the equivalent and effective doses. From the point of view of radiological protection, it is not enough to have knowledge about the dimensions of the FOV and the purpose of the examination. It is necessary to assess the dose using the different models of the equipment and protocols available. In this context, this study provides useful information for this assessment.

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This study aims to evaluate and compare protocols with similar purposes in a cone beam CT scanner using thermoluminescent dosimeter (TLD) and the air kerma-area product (PKA) as the kerma index. The measurements were performed on two protocols used to obtain an image of the maxilla-mandible using the equipment GENDEX GXCB 500: Protocol [GX1] extended diameter and asymmetric beam (14cm×8.5cm-maxilla/mandible) and protocol [GX2] symmetrical beam (8.5cm×8.5cm-maxillary/mandible). LiF dosimeters inserted into a female anthropomorphic phantom were used. For both protocols, the value of PKA was evaluated using a PTW Diamentor E2 meter and the multimeter Radcal Rapidose system. The results obtained for the effective dose/PKA were separated by protocol image. [GX1]: 44.5µSv/478mGycm(2); [GX2]: 54.8µSv/507mGycm(2). Although the ratio of the diameters (14cm/8.5cm)=1.65, the ratio of effective dose values (44.5µSv/54.8µSv)=0.81, that is, the effective dose of the protocol with extended diameter is 19% smaller. The PKA values reveal very similar results between the two protocols. For the cases where the scanner uses an asymmetric beam to obtain images with large diameters that cover the entire face, there are advantages from the point of view of reducing the exposure of patients when compared to the use of symmetrical beam and/or to FOV images with a smaller diameter.

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OBJECTIVE: This study aimed to explore whether cone beam computed tomography (CBCT) and multislice computed tomography (MSCT) can be used to quantify tissue density and to determine if the Hounsfield unit scale is applicable. STUDY DESIGN: A clinical MSCT scanner and effective energy adjusted photon beam attenuation references were used to compare the gray scale of CBCT images of the mandible region. A phantom was scanned using axial cadaver slices and 4 different homogeneous reference objects. The consistency of the references' gray values and 12 linear profile lines from both scanner data sets were compared. RESULTS: The gray values of the 2 scans showed strong correlation with quantified position-dependent differences as an outcome of the validation process. CONCLUSIONS: The introduced internal, in-scan validation is able to estimate and has a potential to compensate for the differences between MSCT and CBCT protocols. This validation serves as a guide in situations where the users can expect deviations.

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Discutimos aqui aspectos vinculados ao enquadramento legal, a recomendações internacionais e a programas de formação em proteção radiológica; ao angiógrafo e à qualidade da imagem; aos efeitos biológicos e aos riscos das radiações ionizantes; às lesões em operadores e pacientes; aos níveis de referência do paciente; ao limite de dose ocupacional e a suas medidas de prevenção. O uso das radiações ionizantes acarreta riscos, que, contudo, justificam-se em procedimentos diagnósticos e terapêuticos. A consciência e o conhecimento desses riscos minimizam o dano, otimizando a qualidade da imagens e o uso seguro das radiações ionizantes. Tem-se demonstrado a ocorrência de cataratas radioinduzidas em trabalhadores de laboratórios de cateterismo. Diversos estudos sugerem que pode haver um risco significativo de opacidade do cristalino, caso não se utilizem adequadamente os dispositivos de proteção radiológica. Adicionalmente, esses tipos de procedimentos intervencionistas são realizados na América Latina, geralmente por médicos especialistas, com a colaboração de enfermeiros, tecnólogos e técnicos, que, muitas vezes, não têm formação adequada em proteção radiológica.

We discuss some aspects related to the legal framework, international recommendations and training programs on radiological protection; image quality and equipment; the biological effects and risks of ionizing radiation; lesions in patients and operators; patient's reference levels; occupational dose limit and preventive actions. The use of ionizing radiation involves risks that are justified in diagnostic and therapeutic procedures. The awareness and knowledge of these risks minimizes the damage, optimizing the quality of images and safe use of ionizing radiation. There is evidence of radiation-induced cataracts in individuals who work in catheterization laboratories. Several studies suggest there may be a significant risk of lens opacity, if radiological protection devices are not properly used. Additionally, these interventional procedures are performed in Latin America, usually by medical specialists in collaboration with nurses, technologists and technicians, who often do not have adequate training in radiological protection.

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