Caracterização tecnológica da mamografia digital em Portugal: progresso de um projeto em implementação

Introdução – A mamografia é o principal método de diagnóstico por imagem utilizado no rastreio e diagnóstico do cancro da mama, sendo a modalidade de imagem recomendada em vários países da Europa e Estados Unidos para utilização em programas de rastreio. A implementação da tecnologia digital causou alterações na prática da mamografia, nomeadamente a necessidade de adaptar os programas de controlo de qualidade. Objetivos – Caracterizar a tecnologia instalada para mamografia em Portugal e as práticas adotadas na sua utilização pelos profissionais de saúde envolvidos. Concluir sobre o nível de harmonização das práticas em mamografia em Portugal e a conformidade com as recomendações internacionais. Identificar oportunidades para otimização que permitam assegurar a utilização eficaz e segura da tecnologia. Metodologia – Pesquisa e recolha de dados sobre a tecnologia instalada, fornecidos por fontes governamentais, prestadores de serviços de mamografia e indústria. Construção de três questionários, orientados ao perfil do médico radiologista, técnico de radiologia com atividade em mamografia digital e técnico de radiologia coordenador. Os questionários foram aplicados em 65 prestadores de serviços de mamografia selecionados com base em critérios de localização geográfica, tipo de tecnologia instalada e perfil da instituição. Resultados – Foram identificados 441 sistemas para mamografia em Portugal. A tecnologia mais frequente (62%) e vulgarmente conhecida por radiografia computorizada (computed radiography) é constituída por um detector (image plate) de material fotoestimulável inserido numa cassete de suporte e por um sistema de processamento ótico. A maioria destes sistemas (78%) está instalada em prestadores privados. Aproximadamente 12% dos equipamentos instalados são sistemas para radiografia digital direta (Direct Digital Radiography – DDR). Os critérios para seleção dos parâmetros técnicos de exposição variam, observando-se que em 65% das instituições são adotadas as recomendações dos fabricantes do equipamento. As ferramentas de pós-processamento mais usadas pelos médicos radiologistas são o ajuste do contraste e brilho e magnificação total e/ou localizada da imagem. Quinze instituições (em 19) têm implementado um programa de controlo de qualidade. Conclusões – Portugal apresenta um parque de equipamentos heterogéneo que inclui tecnologia obsoleta e tecnologia “topo de gama”. As recomendações/guidelines (europeias ou americanas) não são adotadas formalmente na maioria das instituições como guia para fundamentação das práticas em mamografia, dominando as recomendações dos fabricantes do equipamento. Foram identificadas, pelos técnicos de radiologia e médicos radiologistas, carências de formação especializada, nomeadamente nas temáticas da intervenção mamária, otimização da dose e controlo da qualidade. A maioria dos inquiridos concorda com a necessidade de certificação da prática da mamografia em Portugal e participaria num programa voluntário. ABSTRACT - Introduction – Mammography is the gold standard for screening and imaging diagnosis of breast disease. It is the imaging modality recommended by screening programs in various countries in Europe and the United States. The implementation of the digital technology promoted changes in mammography practice and triggered the need to adjust quality control programs. Aims –Characterize the technology for mammography installed in Portugal. Assess practice in use in mammography and its harmonization and compliance to international guidelines. Identify optimization needs to promote an effective and efficient use of digital mammography to full potential. Methodology – Literature review was performed. Data was collected from official sources (governmental bodies, mammography healthcare providers and medical imaging industry) regarding the number and specifications of mammography equipment installed in Portugal. Three questionnaires targeted at radiologists, breast radiographers and the chief-radiographer were designed for data collection on the technical and clinical practices in mammography. The questionnaires were delivered in a sample of 65 mammography providers selected according to geographical criteria, type of technology and institution profile. Results – Results revealed 441 mammography systems installed in Portugal. The most frequent (62%) technology type are computerized systems (CR) mostly installed in the private sector (78%). 12% are direct radiography systems (DDR). The criteria for selection of the exposure parameters differ between the institutions with the majority (65%) following the recommendations from the manufacturers. The use of available tools for post-processing is limited being the most frequently reported tools used the contrast/ brightness and Zoom or Pan Magnification tools. Fifteen participant institutions (out of 19) have implemented a quality control programme. Conclusions – The technology for mammography in Portugal is heterogeneous and includes both obsolete and state of the art equipment. International guidelines (European or American) are not formally implemented and the manufacturer recommendations are the most frequently used guidance. Education and training needs were identified amongst the healthcare professionals (radiologists and radiographers) with focus in the areas of mammography intervention, patient dose optimization and quality control. The majority of the participants agree with the certification of mammography in Portugal.

Digital imaging systems for plain radiography

Advances in digital technology led to the development of digital x-ray detectors that are currently in wide use for projection radiography, including Computed Radiography (CR) and Digital Radiography (DR). Digital Imaging Systems for Plain Radiography addresses the current technological methods available to medical imaging professionals to ensure the optimization of the radiological process concerning image quality and reduction of patient exposure. Based on extensive research by the authors and reference to the current literature, the book addresses how exposure parameters influence the diagnostic quality in digital systems, what the current acceptable radiation doses are for useful diagnostic images, and at what level the dose could be reduced to maintain an accurate diagnosis. The book is a valuable resource for both students learning the field and for imaging professionals to apply to their own practice while performing radiological examinations with digital systems.

Image quality in diagnostic radiology

This chapter provides a theoretical background about image quality in diagnostic radiology. Digital image representation and also image quality evaluation methods are here discussed. An overview of methods for quality evaluation of diagnostic imaging procedures is provided. Digital image representation and primary physical image quality parameters are also discussed, including objective image quality measurements and observer performance methods.

Image enhancement for digital radiography

Once in a digital form, a radiographic image may be processed in several ways in order to turn the visualization an act of improved diagnostic value. Practitioners should be aware that, depending on each clinical context, digital image processing techniques are available to help to unveil visual information that is, in fact, carried by the bare digital radiograph and may be otherwise neglected. The range of visual enhancement procedures includes simple techniques that deal with the usual brightness and contrast manipulation up to much more elaborate multi-scale processing that provides customized control over the emphasis given to the relevant finer anatomical details. This chapter is intended to give the reader a practical understanding of image enhancement techniques that might be helpful to improve the visual quality of the digital radiographs and thus to contribute to a more reliable and assertive reporting.

Methods for automatic and assisted image annotation

Personal memories composed of digital pictures are very popular at the moment. To retrieve these media items annotation is required. During the last years, several approaches have been proposed in order to overcome the image annotation problem. This paper presents our proposals to address this problem. Automatic and semi-automatic learning methods for semantic concepts are presented. The automatic method is based on semantic concepts estimated using visual content, context metadata and audio information. The semi-automatic method is based on results provided by a computer game. The paper describes our proposals and presents their evaluations.

Otimização da imagem em tomografia computorizada no exame de tórax

Mestrado em Radiações Aplicadas às Tecnologias da Saúde. Área de especialização: Imagem Digital.

Otimização de dose em mamografia

Mestrado em Radiações Aplicadas às Tecnologias da Saúde. Área de especialização: Imagem Digital com Radiação X.

Image quality of myocardial perfusion-gated studies: effect of ingestion of different fat content in the reduction of extra-myocardial abdominal signal

Myocardial perfusion-gated-SPECT (MP-gated-SPECT) imaging often shows radiotracer uptake in abdominal organs. This accumulation interferes frequently with qualitative and quantitative assessment of the infero-septal region of myocardium. The objective of this study is to evaluate the effect of ingestion of different fat content on the reduction of extra-myocardial uptake and to improve MP-gated-SPECT image quality. In this study, 150 patients (65 ^ 18 years) who were referred for MP-gated-SPECT underwent a 1-day-protocol including imaging after stress (physical or pharmacological) and resting conditions. All patients gave written informed consent. Patients were subdivided into five groups: GI, GII, GIII, GIV and GV. In the first four groups, patients ate two chocolate bars with different fat content. Patients in GV – control group (CG) – had just water. Uptake indices (UI) of myocardium (M)/liver(L) and M/stomach–proximal bowel(S) revealed lower UI of M/S at rest in all groups. Both stress and rest studies using different food intake indicate that patients who ate chocolate with different fat content showed better UI of M/L than the CG. The UI of M/L and M/S of groups obtained under physical stress are clearly superior to that of groups obtained under pharmacological stress. These differences are only significant in patients who ate high-fat chocolate or drank water. The analysis of all stress studies together (GI, GII, GIII and GIV) in comparison with CG shows higher mean ranks of UI of M/L for those who ate high-fat chocolate. After pharmacological stress, the mean ranks of UI of M/L were higher for patients who ate high- and low-fat chocolate. In conclusion, eating food with fat content after radiotracer injection increases, respectively, the UI of M/L after stress and rest in MP-gated-SPECT studies. It is, therefore, recommended that patients eat a chocolate bar after radiotracer injection and before image acquisition.

Otimização do co-registo metabolismo-morfologia em estudos de PET/CT com 18F-DG de nódulos pulmonares: comparação de dois protocolos - 4D vs CT lento

Mestrado em Medicina Nuclear - Área de especialização: Tomografia por Emissão de Positrões.

Diagnosis of Tinea pedis and onychomycosis in patients from Portuguese National Institute of Health: a four-year study

ABSTRACT - Tinea pedis and onychomycosis are two rather diverse clinical manifestations of superficial fungal infections, and their etiologic agents may be dermatophytes, non-dermatophyte moulds or yeasts. This study was designed to statistically describe the data obtained as results of analysis conducted during a four year period on the frequency of Tinea pedis and onychomycosis and their etiologic agents. A questionnaire was distributed from 2006 to 2010 and answered by 186 patients, who were subjected to skin and/or nail sampling. Frequencies of the isolated fungal species were cross-linked with the data obtained with the questionnaire, seeking associations and predisposing factors. One hundred and sixty three fungal isolates were obtained, 24.2% of which composed by more than one fungal species. Most studies report the two pathologies as caused primarily by dermatophytes, followed by yeasts and lastly by non-dermatophytic moulds. Our study does not challenge this trend. We found a frequency of 15.6% of infections caused by dermatophytes (with a total of 42 isolates) of which T. rubrum was the most frequent species (41.4%). There was no significant association (p >0.05) among visible injury and the independent variables tested, namely age, gender, owning pet, education, swimming pools attendance, sports activity and clinical information. Unlike other studies, the variables considered did not show the expected influence on dermatomycosis of the lower limbs. It is hence necessary to conduct further studies to specifically identify which variables do in fact influence such infections.

Analysis and simulation of a-Si Ha-SiC HPINIP structures for color image detection

It is presented in this paper a study on the photo-electronic properties of multi layer a-Si: H/a-SiC: H p-i-n-i-p structures. This study is aimed to give an insight into the internal electrical characteristics of such a structure in thermal equilibrium, under applied Was and under different illumination condition. Taking advantage of this insight it is possible to establish a relation among-the electrical behavior of the structure the structure geometry (i.e. thickness of the light absorbing intrinsic layers and of the internal n-layer) and the composition of the layers (i.e. optical bandgap controlled through percentage of carbon dilution in the a-Si1-xCx: H layers). Showing an optical gain for low incident light power controllable by means of externally applied bias or structure composition, these structures are quite attractive for photo-sensing device applications, like color sensors and large area color image detector. An analysis based on numerical ASCA simulations is presented for describing the behavior of different configurations of the device and compared with experimental measurements (spectral response and current-voltage characteristic). (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Results of radiation protection programmes on mammography

In this paper, we present the results of mammography quality control tests related to the work with Portuguese mammography equipment, either in conventional or in digital mammography computed radiography, showing the main differences in the tested equipments. Quality control in mammography is a very special area of quality control in radiology, which demands relatively high knowledge on physics. Digital imaging is changing the standards of the radiographic imaging. Regarding mammography, this is yet a controversial issue owing to some limitations of the digital detectors, like the resolution for instance. A complete set of results regarding radiation protection of the patients submitted to mammography diagnosis is presented. A discussion of the quality image parameters and its interpretation in conventional and digital mammography is presented. In conclusion, we present a sample of results that can be considered as characteristics of mammography equipment in Portugal.

An ultrasound based computer-aided diagnosis tool for steatosis detection

Liver steatosis is a common disease usually associated with social and genetic factors. Early detection and quantification is important since it can evolve to cirrhosis. In this paper, a new computer-aided diagnosis (CAD) system for steatosis classification, in a local and global basis, is presented. Bayes factor is computed from objective ultrasound textural features extracted from the liver parenchyma. The goal is to develop a CAD screening tool, to help in the steatosis detection. Results showed an accuracy of 93.33%, with a sensitivity of 94.59% and specificity of 92.11%, using the Bayes classifier. The proposed CAD system is a suitable graphical display for steatosis classification.

Data mining framework for fatty liver disease classification in ultrasound: a hybrid feature extraction paradigm

PURPOSE: Fatty liver disease (FLD) is an increasing prevalent disease that can be reversed if detected early. Ultrasound is the safest and ubiquitous method for identifying FLD. Since expert sonographers are required to accurately interpret the liver ultrasound images, lack of the same will result in interobserver variability. For more objective interpretation, high accuracy, and quick second opinions, computer aided diagnostic (CAD) techniques may be exploited. The purpose of this work is to develop one such CAD technique for accurate classification of normal livers and abnormal livers affected by FLD. METHODS: In this paper, the authors present a CAD technique (called Symtosis) that uses a novel combination of significant features based on the texture, wavelet transform, and higher order spectra of the liver ultrasound images in various supervised learning-based classifiers in order to determine parameters that classify normal and FLD-affected abnormal livers. RESULTS: On evaluating the proposed technique on a database of 58 abnormal and 42 normal liver ultrasound images, the authors were able to achieve a high classification accuracy of 93.3% using the decision tree classifier. CONCLUSIONS: This high accuracy added to the completely automated classification procedure makes the authors' proposed technique highly suitable for clinical deployment and usage.

Chronic liver disease staging classification based on ultrasound, clinical and laboratorial data

In this work the identification and diagnosis of various stages of chronic liver disease is addressed. The classification results of a support vector machine, a decision tree and a k-nearest neighbor classifier are compared. Ultrasound image intensity and textural features are jointly used with clinical and laboratorial data in the staging process. The classifiers training is performed by using a population of 97 patients at six different stages of chronic liver disease and a leave-one-out cross-validation strategy. The best results are obtained using the support vector machine with a radial-basis kernel, with 73.20% of overall accuracy. The good performance of the method is a promising indicator that it can be used, in a non invasive way, to provide reliable information about the chronic liver disease staging.