Compression of high-density EMG signals for trapezius and gastrocnemius muscles.

BACKGROUND: New technologies for data transmission and multi-electrode arrays increased the demand for compressing high-density electromyography (HD EMG) signals. This article aims the compression of HD EMG signals recorded by two-dimensional electrode matrices at different muscle-contraction forces. It also shows methodological aspects of compressing HD EMG signals for non-pinnate (upper trapezius) and pinnate (medial gastrocnemius) muscles, using image compression techniques. METHODS: HD EMG signals were placed in image rows, according to two distinct electrode orders: parallel and perpendicular to the muscle longitudinal axis. For the lossless case, the images obtained from single-differential signals as well as their differences in time were compressed. For the lossy algorithm, the images associated to the recorded monopolar or single-differential signals were compressed for different compression levels. RESULTS: Lossless compression provided up to 59.3% file-size reduction (FSR), with lower contraction forces associated to higher FSR. For lossy compression, a 90.8% reduction on the file size was attained, while keeping the signal-to-noise ratio (SNR) at 21.19 dB. For a similar FSR, higher contraction forces corresponded to higher SNR CONCLUSIONS: The computation of signal differences in time improves the performance of lossless compression while the selection of signals in the transversal order improves the lossy compression of HD EMG, for both pinnate and non-pinnate muscles.

Objective color calibration for manufacturing facial prostheses.

SIGNIFICANCE: Rehabilitation through facial prostheses' main goal is to aid individual's social reintegration as well as improving their quality of life. However, this treatment is not yet widely available in Brazil due to the lack of specialized clinics and the cost associated with the high number of necessary medical appointments until the final result. One of the steps in the process consists of measuring skin color, which is observer-dependent and may suffer from the effect of metamerism. AIM: The methodology of our work aims to obtain a standard between different devices and greater fidelity to the color seen in person in order to reduce face-to-face iterations, reduce costs, and ensure better final results. APPROACH: A physical device and a computer program were improved from previous projects. The changes included implementing the Thin-Plate Spline 3D algorithm for color calibration, in addition to an optional non-uniform illumination correction in the process. We also aim to improve the project's accessibility using a colorimeter. The methodology and the algorithms were both compared to readings from direct skin measurements as well as color references. RESULTS: After processing, the ΔEab* metric between images from the same segments is taken with different cameras and conditions of illumination decreased from 18.81 ± 4.85 to 4.85 ± 1.72. In addition, when the images were compared to colorimetric readings of the skin, the difference went from 14.93 ± 4.11 to 5.85 ± 1.61. It was also observed that using a less expensive device did not impact the readings. The project is open source and available at Github. CONCLUSIONS: The results demonstrate the possibility of applying the methodology to assist in the manufacturing of facial prostheses to decrease the total number of consultations, in addition to providing greater reliability of the final result.

Proposal for DICOM multiframe medical image integrity and authenticity.

This paper presents a novel algorithm to successfully achieve viable integrity and authenticity addition and verification of n-frame DICOM medical images using cryptographic mechanisms. The aim of this work is the enhancement of DICOM security measures, especially for multiframe images. Current approaches have limitations that should be properly addressed for improved security. The algorithm proposed in this work uses data encryption to provide integrity and authenticity, along with digital signature. Relevant header data and digital signature are used as inputs to cipher the image. Therefore, one can only retrieve the original data if and only if the images and the inputs are correct. The encryption process itself is a cascading scheme, where a frame is ciphered with data related to the previous frames, generating also additional data on image integrity and authenticity. Decryption is similar to encryption, featuring also the standard security verification of the image. The implementation was done in JAVA, and a performance evaluation was carried out comparing the speed of the algorithm with other existing approaches. The evaluation showed a good performance of the algorithm, which is an encouraging result to use it in a real environment.

Managing medical images and clinical information: InCor's experience.

Patients usually get medical assistance in several clinics and hospitals during their lifetime, archiving vital information in a dispersed way. Clearly, a proper patient care should take into account that information in order to check for incompatibilities, avoid unnecessary exams, and get relevant clinical history. The Heart Institute (InCor) of São Paulo, Brazil, has been committed to the goal of integrating all exams and clinical information within the institution and other hospitals. Since InCor is one of the six institutes of the University of São Paulo Medical School and each institute has its own information system, exchanging information among the institutes is also a very important aspect that has been considered. In the last few years, a system for transmission, archiving, retrieval, processing, and visualization of medical images integrated with a hospital information system has been successfully created and constitutes the InCor's electronic patient record (EPR). This work describes the experience in the effort to develop a functional and comprehensive EPR, which includes laboratory exams, images (static, dynamic, and three dimensional), clinical reports, documents, and even real-time vital signals. A security policy based on a contextual role-based access control model was implemented to regulate user's access to EPR. Currently, more than 10 TB of digital imaging and communications in medicine (DICOM) images have been stored using the proposed architecture and the EPR stores daily more than 11 GB of integrated data. The proposed storage subsystem allows 6 months of visibility for rapid retrieval and more than two years for automatic retrieval using a jukebox. This paper addresses also a prototype for the integration of distributed and heterogeneous EPR.

Guidewire path determination for intravascular applications.

Vascular diseases are among the major causes of death in developed countries and the treatment of those pathologies may require endovascular interventions, in which the physician utilizes guidewires and catheters through the vascular system to reach the injured vessel region. Several computational studies related to endovascular procedures are in constant development. Thus, predicting the guidewire path may be of great value for both physicians and researchers. However, attaining good accuracy and precision is still an important issue. We propose a method to simulate and predict the guidewire and catheter path inside a blood vessel based on equilibrium of a new set of forces, which leads, iteratively, to the minimum energy configuration. This technique was validated with phantoms using a ∅0.33 mm stainless steel guidewire and compared to other relevant methods in the literature. This method presented RMS error 0.30 mm and 0.97 mm, which represents less than 2% and 20% of the lumen diameter of the phantom, in 2D and 3D cases, respectively. The proposed technique presented better results than other methods from the literature, which were included in this work for comparison. Moreover, the algorithm presented low variation (σ=0:03 mm) due to the variation of the input parameters. Therefore, even for a wide range of different parameters configuration, similar results are presented for the proposed approach, which is an important feature and makes this technique easier to work with. Since this method is based on basic physics, it is simple, intuitive, easy to learn and easy to adapt.

A contextual role-based access control authorization model for electronic patient record.

The design of proper models for authorization and access control for electronic patient record (EPR) is essential to a wide scale use of EPR in large health organizations. In this paper, we propose a contextual role-based access control authorization model aiming to increase the patient privacy and the confidentiality of patient data, whereas being flexible enough to consider specific cases. This model regulates user's access to EPR based on organizational roles. It supports a role-tree hierarchy with authorization inheritance; positive and negative authorizations; static and dynamic separation of duties based on weak and strong role conflicts. Contextual authorizations use environmental information available at access time, like user/patient relationship, in order to decide whether a user is allowed to access an EPR resource. This enables the specification of a more flexible and precise authorization policy, where permission is granted or denied according to the right and the need of the user to carry out a particular job function.

Edge-preserving speckle texture removal by interference-based speckle filtering followed by anisotropic diffusion.

Ultrasonography has an inherent noise pattern, called speckle, which is known to hamper object recognition for both humans and computers. Speckle noise is produced by the mutual interference of a set of scattered wavefronts. Depending on the phase of the wavefronts, the interference may be constructive or destructive, which results in brighter or darker pixels, respectively. We propose a filter that minimizes noise fluctuation while simultaneously preserving local gray level information. It is based on steps to attenuate the destructive and constructive interference present in ultrasound images. This filter, called interference-based speckle filter followed by anisotropic diffusion (ISFAD), was developed to remove speckle texture from B-mode ultrasound images, while preserving the edges and the gray level of the region. The ISFAD performance was compared with 10 other filters. The evaluation was based on their application to images simulated by Field II (developed by Jensen et al.) and the proposed filter presented the greatest structural similarity, 0.95. Functional improvement of the segmentation task was also measured, comparing rates of true positive, false positive and accuracy. Using three different segmentation techniques, ISFAD also presented the best accuracy rate (greater than 90% for structures with well-defined borders).

Evaluation of plaque composition by intravascular ultrasound "virtual histology": the impact of dense calcium on the measurement of necrotic tissue.

AIMS: We aimed to evaluate if the co-localisation of calcium and necrosis in intravascular ultrasound virtual histology (IVUS-VH) is due to artefact, and whether this effect can be mathematically estimated. METHODS AND RESULTS: We hypothesised that, in case calcium induces an artefactual coding of necrosis, any addition in calcium content would generate an artificial increment in the necrotic tissue. Stent struts were used to simulate the "added calcium". The change in the amount and in the spatial localisation of necrotic tissue was evaluated before and after stenting (n=17 coronary lesions) by means of a especially developed imaging software. The area of "calcium" increased from a median of 0.04 mm2 at baseline to 0.76 mm2 after stenting (p<0.01). In parallel the median necrotic content increased from 0.19 mm2 to 0.59 mm2 (p<0.01). The "added" calcium strongly predicted a proportional increase in necrosis-coded tissue in the areas surrounding the calcium-like spots (model R2=0.70; p<0.001). CONCLUSIONS: Artificial addition of calcium-like elements to the atherosclerotic plaque led to an increase in necrotic tissue in virtual histology that is probably artefactual. The overestimation of necrotic tissue by calcium strictly followed a linear pattern, indicating that it may be amenable to mathematical correction.

Medical Image distribution and visualization in a hospital using CORBA.

In this work it is presented the solution adopted by the Heart Institute (InCor) of Sao Paulo for medical image distribution and visualization inside the hospital's intranet as part of the PACS system. A CORBA-based image server was developed to distribute DICOM images across the hospital together with the images' report. The solution adopted allows the decoupling of the server implementation and the client. This gives the advantage of reusing the same solution in different implementation sites. Currently, the PACS system is being used on two different hospitals each one with three different environments: development, prototype and production.

Um modelo de autorização e controle de acesso para o prontuário eletrônico de pacientes em ambientes abertos e distribuídos / An authorization and access control model for electronic patient record in open distributed environments

Conceber modelos para autorização e controle de de acesso para prontuário eletrônico do paciente (PEP) é indispensável para viabilizar o uso em larga escala do PEP em grandes instituições de saúde. Este trabalho propõe um modelo de autorização adequado às exigências de controle de acesso ao PEP, buscando assegurar a privacidade do paciente e a segurança de acesso aos seus dados, mas flexível o suficiente para tratar casos de exceção com base em informações constextuais. O modelo permite regular o acesso dos usuários ao PEP com base nas funções (papéis) que estes exercem numa organização, estendendo e refinando o modelo de referência para controle de acesso baseado em papéis do tipo simétrico definido pelo NIST (National Institute of Standards and Techology). Suporta hierarquia de papéis com herança de autorizações; controle de acesso seletivo aos recursos do PEP; autorizações positivas e negativas; exceções estáticas e dinâmicas baseadas em contextos; separação de responsabilidades estática e dinâmica baseadas em conflitos fortes e fracos entre papéis. Uma arquitetura é proposta para implementar este modelo usando o serviço de diretório LDAP (Lightweight Directory Access Protocol), a linguagem de programação Java, e os padrões CORBA/OMG CORBA Security Service e Resource Access Decision Facility. Com estes padrões abertos e distribuídos, os componentes heterogêneos do PEP podem solicitar serviços de autorização de acesso de modo unificado e consistente a partir de múltiplas plataformas. O PEP na WEB do InCor foi selecionado como aplicação piloto para emprego deste modelo e hoje cerca de 780 usuários o acessa com diferentes privilégios, dependendo dos papéis associados a cada um deles. Desenvolvimentos futuros incluem a especificação de modelos contextuais para criação de autorizações dinâmicas para o PEP e a utilização de mecanismos mais robustos de autenticação do usuário

Aplicações de telemedicina em redes de alta velocidade / Telemedicine applications in high speed networks

A distribuição dos serviços de saúde e o compartilhamento de informações clínicas, utilizando sistemas de telecomunicação, envolvem um conjunto diverso e complexo de tecnologias. Além disso, se a informação a ser compartilhada contém imagens, um problema especial em cardiologia é como distribuir imagens dinâmicas obtidas em estudos de ecocardiografia e de angiografia com qualidade de serviço. As imagens individuais são facilmente transmitidas, mas o volume total, considerando todas as imagens em uma seqüência, é enorme, podendo chegar facilmente à ordem de gigabytes por paciente. Os avanços em tecnologias de comunicações e em informática facilitam a médicos e especialistas localizados em um centro de referência a troca de informações com médicos e profissionais de saúde em local distante, em outro centro ou mesmo com o próprio paciente. Embora em especialidades como cardiologia, radiologia e patologia as informações relevantes sobre o paciente sejam inerentemente digitais, a necessidade de alta qualidade associada ao volume de dados impõe limitações à prática de ações de Medicina a distância por intermédio dos meios de comunicação convencionais.

Vetorcardiografia de esforço / Exercise vectocardiography

Neste trabalho apresentamos estudos preliminares na pesquisa de parâmetros e/ou métodos que melhoram a sensibiliade e especificidade do teste ergométrico. Adotamos a configuraçäo ortogonal de FRANK de eletrodos para aquisiçäo das projeçöes X, Y e Z do ECG. O índice IND incorpora variaçöes, com exercício, da área do segmento ST-T em relaçäo ao repouso, e é independente da posiçäo do coraçäo na caixa torácica ou volume torácico. Mostra-se que as médias do IND säo estatisticamente diferentes entre os grupos de normais e isquêmicos. empregando-se a Regressäo Logística, foram selecionadas variáveis capazes de diferenciar estes grupos com sensibilidade de 81,3% e especificidade de 91,4%

Automaçäo das provas de funçäo pulmonar: aquisiçäo e análise da espirometria em microcomputador / Automation of pulmonary function tests: acquisition and analysis of spirometry by microcomputers

Este trabalho apresenta o Sistema Computadorizado de Provas de Funçäo Pulmonar (SOFO), idealizado e desenvolvido para aquisiçäo e análise de provas espirométricas. O SPFP realiza as funçöes de aquisiçäo dos sinais de fluxo e volume respiratórios, análise computadorizada dos sinais com cálculos de parâmetros espirométricos, formaçäo de Banco-de-Dados clínico-diagnóstico, e emissäo de relatórios e laudos. O SPFP foi desenvolvido segundo sugestöes e normas internacionais ((ATS) de aquisiçäo, análise e representaçäo dos dados de Espirometria. O equipamento básico de processamento utilizado, foi um microcomputador comercial de baixo custo. O "software" é modular, sendo portanto atualizável e expansível segundo novas necessidades

Quantificaçäo do movimento 3D do miocárdio em Gated SPECT / Quantifies 3D motion of myocardial in Gated SPECT

Os métodos convencionais para análise do movimento do ventrículo esquerdo (VE) são baseados em imagens planas e considerações geométricas que, em geral, são inválidas em ventrículos anormais. Propõe-se, neste trabalho, a quantificação do movimento 3D do VE em imagens de Medicina Nuclear (gated-SPECT), através da técnica de Fluxo Óptico estendida para o espaço voxel. O movimento das paredes do VE é representado por uma série de campos de vetores de velocidade 3D, os quais são calculados automaticamente para cada voxel na seqüência de volumes cardíacos.

The conventional methods for analysis of L V wall motion abnormalities are based on planar images and geometrical analysis with many hardly fulfilled assumptions. This work describes a method which quantifies 3D L V motion by means of the optical flow technique extended to the voxel space. The LV wall motion is represented by a series of 3D velocity vector field which is computed automatically by the proposed method for each voxel on the sequence of cardiac volumes.

O projeto Pacs: um sistema para visualizaçäo dinâmica e armazenamento de imagens de angiografia digital no Incor / Pacs project: a system to dynamic visualization and image storage of digital angiography in Incor

Este trabalho descreve a solução encontrada para um sistema PACS totalmente em padrão DICOM, esclarecendo as técnicas de desenvolvimento do sistema, métodos de compressão e visualização dinâmica para os estudos de cine-angiografia, o que permitirá, num futuro breve, a qualquer PC conectado à rede de computadores do InCor buscar, e visualizar sequências de imagens de forma segura, eficiente, com boa resolução espacial e temporal.