ObjectiveDerive filtered tungsten X-ray spectra used in digital mammography systems by means of Monte Carlo simulations.Materials and MethodsFiltered spectra for rhodium filter were obtained for tube potentials between 26 and 32 kV. The half-value layer (HVL) of simulated filtered spectra were compared with those obtained experimentally with a solid state detector Unfors model 8202031-H Xi R/F & MAM Detector Platinum and 8201023-C Xi Base unit Platinum Plus w mAs in a Hologic Selenia Dimensions system using a direct radiography mode.ResultsCalculated HVL values showed good agreement as compared with those obtained experimentally. The greatest relative difference between the Monte Carlo calculated HVL values and experimental HVL values was 4%.ConclusionThe results show that the filtered tungsten anode X-ray spectra and the EGSnrc Monte Carlo code can be used for mean glandular dose determination in mammography.

ObjectiveTo evaluate the mean glandular dose with a solid state detector and the image quality in a direct radiography system, utilizing phantoms.Materials and MethodsIrradiations were performed with automatic exposure control and polymethyl methacrylate slabs with different thicknesses to calculate glandular dose values. The image quality was evaluated by means of the structures visualized on the images of the phantoms.ResultsConsidering the uncertainty of the measurements, the mean glandular dose results are in agreement with the values provided by the equipment and with internationally adopted reference levels. Results obtained from images of the phantoms were in agreement with the reference values.ConclusionThe present study contributes to verify the equipment conformity as regards dose values and image quality.

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The dosimetry of intraoral radiography procedures is of great interest since dental examinations are among the most numerous radiological procedures. Usually, the surveys are performed using measurements free in air. The entrance surface air kerma (K e ) can be estimated from measurements of incident air kerma and the use of backscatter factors (BSF). The purpose of this work is to calculate BSF values suitable for intraoral radiography. In addition to specific intraoral radiography, a comprehensive reassessment of internationally recommended BSF values was performed through Monte Carlo simulations. Moreover, the K e was estimated using the calculated BSF values for a sample of 44 intraoral radiography systems. The interpolation of intraoral radiography BSF values from reference data can lead to an overestimation of up to 10% and 6% in comparison with the values calculated in this work for monoenergetic photons and x-ray spectra, respectively. Such discrepancy may be relevant when defining diagnostic reference levels (DRLs) or performing quality control tests. The calculations for a sample of 44 intraoral radiography systems showed that the majority of the equipment operates with an entrance surface air kerma higher than 3.5 mGy. In the case of adopting a single value to estimate K e , the use of BSF equal to 1.2 results in less dispersion compared to calculated values in this work and the use of 1.1 can underestimate K e values up to 12%.

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Objective: To evaluate the feasibility of using radiochromic films as an alternative dosimeter to estimate the multiple scan average dose on the basis on kerma profiles. Materials and Methods: The radiochromic films were distributed in cylinders positioned in the center and in four peripheral bores of a standard abdominal phantom utilized for computed tomography dosimetry. Results: Values for multiple scan average dose values corresponded to 13.6 ± 0.7, 13.5 ± 0.7 and 18.7 ± 1.0 mGy for pitch of 0.75, 1.00 and 1.50, respectively. Conclusion: In spite of results showing lower values than the reference level for radiodiagnosis (25 mGy) established by the Brazilian regulations for abdominal studies, it is suggested that there is room to optimize procedures and review the reference level for radiodiagnosis in Brazil. Keywords: Kerma profiles; Computed tomography; Radiochromic films; MSAD.Objetivo: Verificar a viabilidade de filmes radiocrômicos como um dosímetro alternativo para estimativa da dose média em cortes múltiplos a partir dos perfis de kerma. Materiais e Métodos: Os filmes foram distribuídos em cilindros posicionados no centro e nas regiões periféricas de um objeto simulador padrão de abdome utilizado para dosimetria em tomografia computadorizada. Resultados: Os valores de dose média em cortes múltiplos calculados foram 13,6 ± 0,7, 13,5 ± 0,7 e 18,7 ± 1,0 mGy para os valores de passo (pitch) de 0,75, 1,00 e 1,50, respectivamente. Conclusão: Apesar de os resultados mostrarem valores menores que o nível de referência de radiodiagnóstico de 25 mGy estabelecido pela legislação brasileira para exames de abdome, eles sugerem que há espaço para otimização dos procedimentos e uma revisão do valor para o nível de referência de radiodiagnóstico brasileiro. Unitermos: Perfis de kerma; Tomografia computadorizada; Filmes radiocrômicos; MSAD. AbstractResumo