Multiscale representation for automatic identification of structures in medical images.

The identification of structures is a key step in several applications of medical imaging. In this work we propose a method for the identification of structures using a multiscale approach with inclusion of a priori information about the searched objects. After describing the image structures in the multiscale representation, a matching step determines which structure most likely corresponds to the target. Patterns are generated by previous application of the method to a set of images. We present a prototype for identifying structures in 2D images. A set of experiments was carried out to evaluate the prototype leading to encouraging results.

Prontuário eletrônico de pacientes: integrando informações clínicas e imagens médicas / Eletronic patient record: integrating clinical information and image data

O Instituto do Coração tem envidado esforços para integrar todas as informações clínicas dentro da Instituição. Nos últimos anos o InCor implementou com sucesso um sistema para transmissão, arquivamento, recuperação, processamento e visualização de Imagens Médicas e um Sistema de Informações Hospitalares (HIS) que armazena as informações administrativas e clínicas. A integração desses subsistemas forma o Prontuário Eletrônico do Paciente (PEP). O InCor é um dos seis Institutos que compõem o Hospital das Clínicas da Universidade de São Paulo. Como cada um dos Institutos possui o seu próprio sistema de informações, a troca de informações entre os Institutos é também uma questão muito relevante. Este trabalho apresenta a experiência no desenvolvimento de um Prontuário Eletrônico funcional e completo, que inclui controle de acesso, exames laboratoriais, imagens (estáticas, dinâmicas e 3D), laudos, documentos e mesmo sinais vitais de tempo real. Este artigo também discute a modelagem e implantação de um protótipo de um PEP distribuído e homogêneo. Atualmente, um volume superior a 2,5 TB de imagens DICOM já foi armazenado utilizando a arquitetura proposta. Diariamente, o PEP armazena mais de 5GB de dados e tem uma quantidade de acessos superior a 300 usuários. O sistema de armazenamento permite uma visibilidade de seis meses para acesso imediato e mais de dois anos para acesso automático utilizando uma jukebox

The Heart Institute (InCor) of São Paulo has been committed to the goal of integrating all clinical information within the institution. In the last few years, InCor has successfully created a system for transmission, archiving, retrieval, processing and visualization of Medical Images and a Hospital Information System (HIS) that stores the institution administrative and clinical information. These integrated subsystems form InCor's Electronic Patient Record (EPR). Since InCor is one of the six institutes of the University of São Paulo Medical School Hospital (HC) and each institute has its own information system, exchanging information among the institutes is also a very important issue. This work describes the experience in the effort to develop a functional and comprehensive EPR, which includes access control, lab exams, images (static, dynamic and 3D), clinical reports, documents and even real-time vital signals. This paper addresses also the design and prototype for integration of distributed and heterogeneous EPR. Currently, more than 2.5 TB of DICOM images, have been stored using the proposed architecture. The EPR stores more than 5 GB/day of data and presents more than 300 hits per day. The proposed storage subsystem allow six months of visibility for rapid retrieval (online mode) and more than two years for automatic retrieval using the jukebox

Relation between medial temporal atrophy and functional brain activity during memory processing in Alzheimer's disease: a combined MRI and SPECT study.

OBJECTIVE: To investigate the relation between atrophy of the hippocampal region and brain functional patterns during episodic memory processing in Alzheimer's disease. PATIENTS AND METHODS: Whole brain structural magnetic resonance imaging (MRI) data and single photon emission computed tomography (SPECT) measures of regional cerebral blood flow (rCBF) were obtained during a verbal recognition memory task in nine subjects with mild Alzheimer's disease and 10 elderly healthy controls. Using the statistical parametric mapping approach, voxel based comparisons were made on the MRI data to identify clusters of significantly reduced grey matter concentrations in the hippocampal region in the Alzheimer patients relative to the controls. The mean grey matter density in the voxel cluster of greatest hippocampal atrophy was extracted for each Alzheimer subject. This measure was used to investigate, on a voxel by voxel basis, the presence of significant correlations between the degree of hippocampal atrophy and the rCBF SPECT measures obtained during the memory task. RESULTS: Direct correlations were detected between the hippocampal grey matter density and rCBF values in voxel clusters located bilaterally in the temporal neocortex, in the left medial temporal region, and in the left posterior cingulate cortex during the memory task in the Alzheimer's disease group (p < 0.001). Conversely, measures of hippocampal atrophy were negatively correlated with rCBF values in voxel clusters located in the frontal lobes, involving the right and left inferior frontal gyri and the insula (p < 0.001). CONCLUSIONS: Hippocampal atrophic changes in Alzheimer's disease are associated with reduced functional activity in limbic and associative temporal regions during episodic memory processing, but with increased activity in frontal areas, possibly on a compensatory basis.

Correspondência de pontos em seqüência de artérias coronárias / Correspondence of points in sequence of coronary arteries

Nos últimos vinte anos, a análise de movimento tem sido um problema importante em imagens médicas. Em imagens cardíacas, um dos objetivos, por exemplo, é análise de movimento não rígido e a estimativa das características de deformação das artérias coronárias. Este trabalho mostra uma metodologia para o problema de correspondência de pontos em movimento não rígido das artérias coronárias. Ele está baseado em um problema de otimização que assume que o contorno da coronária não muda sua forma instantaneamente. Quando um objeto é adquirido por um equipamento de imagem em uma amostragem temporal alta, o movimento entre quadros será pequeno para uma translação, uma rotação e uma deformação do objeto. Correspondência de pontos de vasos é realizada usando dois quadros sucessivos e está baseado na minimização de uma medida de deformação entre as curvas. A função custo considera vetor desparidade entre pontos mapeados e informação de curvatura. Programação dinâmica é utilizada como estragégia de busca do mapeamento ótimo. São apresentados os resultados do método aplicado a imagens sintéticas e reais. Avaliações realizadas com dados simulados fornecem resultados muito bons, com erro médio quadrático menor do que um pixel. Em imagens de angiografia de raios X da coronária, a inspeção visual das posições dos pontos detectados mostra que os resultados são bastante promissores. Contudo, avaliação exaustivas do método proposto sobre numerosos conjuntos de dados reais são necessárias para posterior utilidade clínica em estudos cardíacos.

Refinamento da segmentação do ventrículo cardíaco esquerdo em imagens de ressonância magnética baseado em simulated annealing / Left cardiac ventricle refinement of magnetic resonance images based on simulated annealing

Neste trabalho apresentamos uma metodologia para o refinamento de segmentações 2D de imagens de ressonância magnética. Os algoritmos implementados partem de uma segmentação inicial e, através de inclusões e exclusões de pixels na borda da segmentação ativa, obtêm asegmentação desejada. A cada passo dos algoritmos, duas segmentações estão disponíveis: uma segmentação atual e uma candidata. A escolha de uma delas é feita de acordo com critérios determinísticos (refinamento por técnica híbrida) ou estocásticos (refinamento utilizando simulated annealing), mediante a minimização de uma função de energia. Esta função é composta por termos que medem o constraste na borda, a variância da intensidade do sinal e a forma. A metodologia foi avaliada sobre phantoms núméricos e aplicada com sucesso em imagens de ressonância magnética. Esta metodologia pode ser facilmente estandida para outas modalidades de imagens.

A voxel-based investigation of regional cerebral blood flow abnormalities in obsessive-compulsive disorder using single photon emission computed tomography (SPECT).

Several functional imaging studies have reported abnormalities of the orbitofrontal and anterior cingulate cortices, striatum and thalamus in obsessive-compulsive disorder (OCD). These studies have often been limited by small patient samples and image analysis methods that rely on region-of-interest (ROI) approaches. We have assessed resting regional cerebral blood flow with 99mTc-ECD SPECT in 26 unmedicated OCD patients and 22 healthy control subjects using the voxel-based Statistical Parametric Mapping method for data analysis. We found a significantly reduced ECD uptake in OCD patients relative to the control subjects in the right lateral orbitofrontal cortex, and in the left dorsal anterior cingulate cortex (P<0.001 two-tailed, uncorrected for multiple comparisons). There were significant positive correlations in the OCD group between the ECD uptake in the left lateral orbitofrontal cortex and ratings for obsessive-compulsive symptoms (OCS), and between the ECD uptake in the right medial orbitofrontal cortex and the ratings for both OCS and depressive symptoms. There were also unpredicted significant ECD uptake increases in the cerebellum in OCD patients, as well as a negative correlation between posterior cingulate ECD uptake and OCS severity (P<0.05, corrected for multiple testing). These results implicate specific subregions of the orbitofrontal and anterior cingulate cortices in the pathophysiology of OCD, as well as suggesting the involvement of other areas not usually included in ROI-based imaging studies. With the incorporation of voxel-based methods and the use of large patient samples, rCBF-SPECT studies may continue to provide valuable information about the functional anatomy of OCD.

Lossy compression techniques, medical images, and the clinician.

There has been increasing interest in the storage and retrieval of medical images in hospitals and clinics here in Brazil and elsewhere. At the Heart Institute of São Paulo, with thousands of image-based procedures performed each month, the pursuit of optimal transmission and storage methods for digital images is a major concern. The use of data-compression techniques can reduce the enormous amount of imaging data to be stored or transmitted across a computer network, so that the efficiency of the computing system is preserved. The techniques for image compression can be categorized as "lossless" or "lossy," with "lossy" techniques being those in which some, supposedly irrelevant information is lost. Lossy techniques are much more efficient than lossless ones, achieving data-compression ratios as high as 100:1.

Relevance of statistically significant differences between reconstruction algorithms.

When comparing reconstruction algorithms, differences in figures of performance merit that are too small to be of any practical relevance may still be statistically significant. We formalize the notion of "relevance" and propose an evaluation methodology in which statistical significance is retained for relevant improvements, but not for irrelevant ones.

Segmentaçäo de imagens médicas 3D baseado em vetor de atributos e conectividade competitiva / Segmentation of the 3D medical images based on vector of features and competitive connectivity form

Propõe-se uma técnica verdadeiramente 3D para a classificação de elementos de imagens médicas baseado em vetor de atributos, levando-se em conta a conectividade de forma competitiva. O valor da conectividade reflete-se - no sentido "fuzzy" - simultaneamente a afinidade do voxel ao objeto considerando-se o vetor de atributos, e a conectividade espacial do mesmo à região inicial fornecida pelo usuário. As vantagens desta abordagem são: a) segmentação verdadeiramente n-dimensional, exigindo mínima interação com o usuário; b) independência do órgão ou da modalidade de imagem, uma vez que o sistema depreende as características estatísticas das classes pela amostra; c) assegura a conectividade espacial; d) permite segmentação competitiva entre diversos objetos. A maior limitação é assumir que o vetor de atributos para um dado objeto tem distribuição normal multivariada. Alguns resultados são mostrados em imagens de Ressonância Magnética do coração.

Hypermedia patient data retrieval and presentation through WWW.

WWW can be a helpful tool for PACS and HIS data retrieval and presentation. The use of gateways to access both text and hypermedia databases (images and video) enables fetched data to be presented in virtually any computer system. WWW browsers provide a very friendly interface and require little training to operate. This paper presents a prototype that uses a SQL gateway for accessing relational patient databases. The dataset used here include text data from reports of diagnostic procedures as well as pointers to the corresponding images. Images can be displayed by the browsers' viewers.

A methodology for testing for statistically significant differences between fully 3D PET reconstruction algorithms.

We present a practical methodology for evaluating 3D PET reconstruction methods. It includes generation of random samples from a statistically described ensemble of 3D images resembling those to which PET would be applied in a medical situation, generation of corresponding projection data with noise and detector point spread function simulating those of a 3D PET scanner, assignment of figures of merit appropriate for the intended medical applications, optimization of the reconstruction algorithms on a training set of data, and statistical testing of the validity of hypotheses that say that two reconstruction algorithms perform equally well (from the point of view of a particular figure of merit) as compared to the alternative hypotheses that say that one of the algorithms outperforms the other. Although the methodology was developed with the 3D PET in mind, it can be used, with minor changes, for other 3D data collection methods, such as fully 3D cr or SPECT.

Evaluation of task-oriented performance of several fully 3D PET reconstruction algorithms.

The relative performance of five fully 3D PET reconstruction algorithms is evaluated. The algorithms are a filtered backprojection (FBP) method and two variants each of the EM-ML and ART iterative methods. For each of the iterative methods, one variant makes use of voxels and the other makes use of 'blobs' (spherically symmetric functions smoothly decaying to zero at their boundaries) as basis functions in its discrete reconstruction model. The methods are evaluated from the point of view of the efficacy of the reconstructions produced by them for three typical medical tasks--estimation of the average activity inside specific regions of interest, detection of hot spots, and detection of cold spots. A free parameter is allowed in the description of each of the five algorithms; the parameters are determined by a training process during which a value of the free parameter is selected which (nearly) maximizes a technical figure of merit. Such training and the actual comparative evaluation is done by making use of randomly generated phantoms and their projection data. The methodology allows assignation of levels of statistical significance to claims of the relative superiority of one algorithm over another for a particular task. We find that using blobs as basis functions in the iterative algorithms is definitely advantageous over using voxels. This result has high statistical significance. (We also include a visual illustration of it.) Comparing FBP, EM-ML using blobs, and ART using blobs, we do not find a clear difference in the overall performance of the investigated variants of the methods. If anything, our results suggest that ART using blobs may be the most efficacious of the three.

Lossy compression in nuclear medicine images.

The goal of image compression is to reduce the amount of data needed to represent images. In medical applications, it is not desirable to lose any information and thus lossless compression methods are often used. However, medical imaging systems have intrinsic noise associated to it. The application of a lossy technique, which acts as a low pass filter, reduces the amount of data at a higher rate without any noticeable loss in the information contained in the images. We have compressed images of nuclear medicine using the discrete cosine transform algorithm. The decompressed images were considered reliable for visual inspection. Furthermore, a parameter was computed from these images and no discernible change was found from the results obtained using the original uncompressed images.

Safety in medical signal analysis.

A number of issues are raised about the possibility of erroneous results obtained from signal analysis techniques that could lead to an incorrect diagnosis or an inadequate decision. An example is the use of a filter to attenuate interference when the (unidimensional) signal of interest contains wavelets. The output wavelets may be distorted by the filter in such a way that their interpretation leads to an incorrect diagnosis. In medical imaging, peripheral hot spots and sunburst streaking in computed tomography, blurring of tomographic reconstruction of cardiac images (as in single-photon-emission computed tomography, or SPECT) due to organ movement, and artifact due to image enhancement are among the difficulties introduced by signal analysis methodology. Some general recommendations are put forward as to how to deal with these kinds of problems.

Method to localise myocardial infarction using magnetocardiography: simulation studies.

The work presents a method for localising regions of myocardial infarction (MI) using magnetocardiography, which is validated by simulation techniques. We have verified that the first two principal components of magnetocardiographic signals obtained from torso mapping within a normal group are very similar even in experimental measurements. So, if we have the temporal eigenvectors of a normal group, these can be used as an orthonormal basis for estimating the signals of a patient being tested. Analysis of the residual signals using singular value decomposition (SVD) allows the localisation of regions of MI. Comparisons are made with a similar method which uses spatial eigenvectors as its basis. It is shown that our approach is able to localise the equivalent current dipoles which generate MI even when they are not orthogonal to the spatial eigenvectors.

Collagen fibril diameters in arteries of mice. A comparison of manual and computer-aided morphometric analyses.

Arteries of mice were studied by a silver impregnation technique, by the Picrosirius-polarization method and by transmission electron microscopy. The histochemical results obtained coincided with the electron-microscopic observations in showing the presence of two distinct collagen populations, segregated into different compartments of each artery. The fibrous component of the tunica media was comprised of reticulin fibers, which displayed a distinct argyrophilia when studied by means of the silver impregnation technique, and showed up as thin, weakly birefringent, greenish fibers when examined with the aid of the Picrosirius-polarization method. In addition, the electron-microscopic studies disclosed the presence of thin collagen fibrils in the tunica media, contrasting with the thicker fibrils that could be localized ultrastructurally to the tunica adventitia where nonargyrophil, coarse collagen fibers had been characterized by the histochemical methods used. In this respect, collagen distribution in arteries of mice is very similar to the pattern that was consistently observed in the other species studied, which argues in favor of the existence of a uniform structural pattern of collagen distribution that is a general phenomenon in vertebrate arteries. Experimental results comparing the traditional method and the computer-aided measurement of collagen fibril diameters showed that the system provides results equivalent to those produced by manual execution. In addition, the advantage in speed of the computer-aided method should prove useful in complicated studies where numerous structures are involved.