Fermin Garcia Velasco

Optimization of Image Quality and Dose in Digital Mammography

Nowadays, the optimization in digital mammography is one of the most important challenges in diagnostic radiology. The new digital technology has introduced additional elements to be considered in this scenario. A major goal of mammography is related to the detection of structures on the order of micrometers (μm) and the need to distinguish the different types of tissues, with very close density values. The diagnosis in mammography faces the difficulty that the breast tissues and pathological findings have very close linear attenuation coefficients within the energy range used in mammography. The aim of this study was to develop a methodology for optimizing exposure parameters of digital mammography based on a new Figure of Merit: FOM ≡ (IQFinv)2/AGD, considering the image quality and dose. The study was conducted using the digital mammography Senographe DS/GE, and CDMAM and TORMAM phantoms. The characterization of clinical practice, carried out in the mammography system under study, was performed considering different breast thicknesses, the technical parameters of exposure, and processing options of images used by the equipment’s automatic exposure system. The results showed a difference between the values of the optimized parameters and those ones chosen by the automatic system of the mammography unit, specifically for small breast. The optimized exposure parameters showed better results than those obtained by the automatic system of the mammography, for the image quality parameters and its impact on detection of breast structures when analyzed by radiologists.

Optimization of the exposure parameters in digital mammography using contrast-detail metrics

PURPOSE Optimization studies in digital mammography aid to assure the image quality and radiological protection of the patient. The aim of this work is to test effectiveness and applicability of a method based on a Figure of Merit (FOM=(IQFinv)2/AGD) to improve all the exposure parameters (Target/Filter combination, kVp and mAs) in order to improve the image acquisition technique that will provide the best compromise between image quality and the average glandular dose (AGD). METHODS A contrast-detail analysis, employing the test object CDMAM, was carried out for the digital mammography unit manufactured by Lorad Hologic - model Selenia. We simulated two breast thicknesses using phantoms and a Figure of Merit as optimization tool, which includes an indicator of image quality, the IQFinv and the average glandular dose. Images of the ACR and TORMAM phantoms were obtained with both, automatic and optimized exposure parameters. In order to compare the image quality, the SNR (Signal to Noise Ratio) was measured in each image. RESULTS In the two phantoms, for both 4.5 and 7.5cm thicknesses, the AGDs obtained with the optimized parameters show a reduction. In addition, the images obtained with the optimized exposure parameters, had the same or a better image quality when compared to the images obtained using the automatic mode. CONCLUSIONS The proposed optimization methodology proved to be an effective tool to improve the digital mammography unit, due to the use of objective metrics for evaluation and validation of the results.

Coefficient of permeability for fluid in saturated means (Ks): estimate by flow columns and variable matrix potential

The coefficient of permeability (Ks) is a very important parameter in the environmental risk modeling processes and its measurement is aimed at subsidizing the contamination of soil and groundwater studies. It has the function of characterizing the driving limits amid saturated solute contaminants in various soil textures, allowing analysis of a greater or lesser degree of percolation of the soil matrix. It is noted that for each soil texture, there are distinct Ks bands, for sandy soils the values can reach 102 cm/day and for clay soils these values are only 10-1 cm/day. The methods used for measuring the Ks are varied and costly. It can be observed that in many scientific studies, techniques for field and laboratory measurement are used, and in both cases the devices used are called permeameters. In addition, there are also indirect measurement techniques of Ks, applying theoretical equations using physicochemical input parameters such as soil moisture limits. Thus, due to the many techniques used, there are different Ks values for the same type of soil, given that the coefficient Ks is the most adequate for bands ranging between maximum and minimum values. Therefore, the objective of this study was to create a Ks estimation technique, integrating two methods of easy application and low cost, that could take into account the load transient patterns and distinct output flow of organic fluids and water in a sandy soil.

Variação espaço-temporal do índice de qualidade de água e índice de estado trófico do reservatório público de Ceraíma, Guanambi, Bahia

O trabalho teve por objetivo a avaliacao espaco-temporal do Indice de Qualidade de Agua (IQA) e Indice de Estado Trofico (IET) do Acude Publico de Ceraima, Guanambi (BA) visando caracterizar a qualidade da agua, avaliar o nivel de eutrofizacao e analisar a da dinâmica da agua no acude levando em consideracao informacoes relativas a bacia hidrografica do rio Carnaiba de Dentro e parâmetros morfologicos e climatologicos. Desta forma, foi desenvolvida a analise fisiografica da bacia hidrografica com o auxilio do ArcGis 9.2 a qual mostrou que a bacia hidrografica apresenta baixa capacidade de drenagem sendo alongada e apresentando pouca possibilidade de enchentes rapidas em condicoes normais de precipitacao. A analise da morfologia do acude indicou um elevado desenvolvimento do perimetro e boa capacidade de assimilacao de impactos poluidores e resistencia ao estabelecimento da eutrofizacao. Quatro pontos amostrais foram selecionados no sentido longitudinal do acude tendo sido realizadas tres campanhas para coleta de amostras de agua. Foram tambem coletadas informacoes meteorologicas referentes a temperatura media do ar nos dias das coletas, a lâmina de precipitacao ocorrida nos sete dias anteriores as coletas e os volumes de agua armazenados no acude nos dias das coletas. A media dos parâmetros relativos ao IQA indicou condicoes estatisticamente iguais de qualidade de agua nos locais amostrados sendo que a o IQA variou de condicoes otimas a boas. Os valores obtidos para o IET nos pontos de coleta tambem nao apresentaram diferencas significativas, sendo todos os locais amostrados classificados como ambientes mesotroficos. Devido a grande variacao de volume de agua entre as coletas 1 e 2, a qualidade de agua na coleta 2 foi boa e o ambiente eutrofizado devido provavelmente a lixiviacao de fertilizantes utilizados na agricultura praticada no entorno do acude e o aporte de esgotos domesticos.

Revisão integrativa sobre aplicação das metodologias de avaliação de riscos à saúde e ao ambiente

E consenso, na literatura, que nao existe uniformizacao de metodologias e processos para avaliacao de risco na area da saude e do meio ambiente. Neste trabalho foi realizada uma ampla revisao da producao cientifica nacional e internacional sobre a aplicacao das principais metodologias de avaliacao de risco. E apresentada uma analise comparativa detalhada do processo avaliativo de risco, considerando principalmente as metodologias USEPA, ATSDR e OMS, as quais revelaram ter a maior aplicacao em artigos reportados na literatura nos ultimos anos. O proposito central deste estudo foi abrir, em um marco unico, as vantagens, desvantagens e as ferramentas incluidas nas metodologias reportadas. Esta analise visa, por um lado, oferecer subsidios para a possivel elaboracao de padroes de novas metodologias de avaliacao de riscos a saude e meio ambiente; e por outro lado, disponibilizar suporte informativo para a selecao das metodologias mais adequadas a serem aplicadas em cada caso. Sao discutidas as areas cobertas por cada metodologia, suas diferencas e procedimentos comuns, assim como questoes do processo avaliativo de risco que ainda permanecem em aberto. A analise realizada na presente pesquisa podera contribuir na possivel uniformizacao de metodos de avaliacao de risco as condicoes da saude coletiva e aos ecossistemas brasileiros, e para subsidiar a formulacao de uma nova metodologia mais adequada e completa.