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Objective: This study evaluated the productivity of computed tomography (CT) models and characterized their simplest (entry-level) models' supply in the world market. Methods: CT exam times were measured in eight health facilities in the state of Rio de Janeiro, Brazil. Exams were divided into six stages: (1) arrival of patient records to the examination room; (2) patient arrival; (3) patient positioning; (4) data input prior to exam; (5) image acquisition; and (6) patient departure. CT exam productivity was calculated by dividing the total weekly working time by the total exam time for each model. Additionally, an internet search identified full-body CT manufacturers and their offered entry-level models. Results: The time durations of 111 CT exams were obtained. Differences among average exam times were not large, and they were mainly due to stages not directly related to data acquisition or image reconstruction. The survey identified that most manufacturers offer 2- to 4-slice models for Asia, South America, and Africa, and one offers single-slice models (Asia). In the USA, two manufacturers offer models below 16-slice. Conclusion: Productivity gains are not linearly related to "slice" number. It is suggested that the use of "shareable platforms" could make CTs cheaper, increasing their availability.

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A simple experimental protocol applying a quantitative ultrasound (QUS) pulse-echo technique was used to measure the acoustic parameters of healthy femoral diaphyses of Wistar rats in vivo. Five quantitative parameters [apparent integrated backscatter (AIB), frequency slope of apparent backscatter (FSAB), time slope of apparent backscatter (TSAB), integrated reflection coefficient (IRC), and frequency slope of integrated reflection (FSIR)] were calculated using the echoes from cortical and trabecular bone in the femurs of 14 Wistar rats. Signal acquisition was performed three times in each rat, with the ultrasound signal acquired along the femur's central region from three positions 1 mm apart from each other. The parameters estimated for the three positions were averaged to represent the femur diaphysis. The results showed that AIB, FSAB, TSAB, and IRC values were statistically similar, but the FSIR values from Experiments 1 and 3 were different. Furthermore, Pearson's correlation coefficient showed, in general, strong correlations among the parameters. The proposed protocol and calculated parameters demonstrated the potential to characterize the femur diaphysis of rats in vivo. The results are relevant because rats have a bone structure very similar to humans, and thus are an important step toward preclinical trials and subsequent application of QUS in humans.

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A simple experimental protocol applying a quantitative ultrasound (QUS) pulse-echo technique was used to measure the acoustic parameters of healthy femoral diaphyses of Wistar rats in vivo. Five quantitative parameters [apparent integrated backscatter (AIB), frequency slope of apparent backscatter (FSAB), time slope of apparent backscatter (TSAB), integrated reflection coefficient (IRC), and frequency slope of integrated reflection (FSIR)] were calculated using the echoes from cortical and trabecular bone in the femurs of 14 Wistar rats. Signal acquisition was performed three times in each rat, with the ultrasound signal acquired along the femur's central region from three positions 1 mm apart from each other. The parameters estimated for the three positions were averaged to represent the femur diaphysis. The results showed that AIB, FSAB, TSAB, and IRC values were statistically similar, but the FSIR values from Experiments 1 and 3 were different. Furthermore, Pearson's correlation coefficient showed, in general, strong correlations among the parameters. The proposed protocol and calculated parameters demonstrated the potential to characterize the femur diaphysis of rats in vivo. The results are relevant because rats have a bone structure very similar to humans, and thus are an important step toward preclinical trials and subsequent application of QUS in humans.

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PURPOSE: This paper presents a comparative study of automatic thresholding algorithms for segmenting trabecular bone volume in x-ray microtomography (µCT). METHODS: First, a preprocessing stage was established, which considered noise reduction by applying anisotropic diffusion filtering and contrast enhancement by using morphological top-hats. Next, four automatic thresholding algorithms were implemented: clustering, maximum entropy, moment preservation, and concavity-based. These approaches analyze the preprocessed 3D µCT image histogram to optimize some parameters to find the best gray-level threshold. Thirty-eight vertebra bone samples were acquired from 19 normal Wistar rats, specifically the L3 and L4 vertebrae. The µCT images were acquired with a microfocus x-ray device at 100 slices/sample. Next, three human operators segmented the entire 3D µCT images manually to establish ground-truth segmentations so as to associate the segmentation problem with perceptual grouping. The normalized probabilistic Rand index (NPRI) was used to quantify the agreement between each computerized segmentation and the corresponding set of three ground-truth segmentations. Hence, the NPRI value should tend toward unity for an acceptable performance. Finally, a statistical analysis was done to determine which thresholding approach achieved the best performance. Besides, 3D morphometric indices were also measured. RESULTS: The Games-Howell test (α = 0.05) was used to compare the equality of means from the NPRI results considering the four thresholding algorithms (multiple comparisons). This statistical analysis indicated that the clustering and moment preservation techniques performed similarly, with NPRI values of 0.594 ± 0.126 and 0.607 ± 0.127, respectively. CONCLUSIONS: The main advantage of computerized segmentation is that it is fully automatic; that is, no interaction with the user is required. Thus, the method could be considered objective. Besides, the proposed preprocessing stage plays an important role in enhancing the µCT image quality to achieve better separation between the background volume and the trabecular bone volume.

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In this paper, we investigated the behavior of 22 co-occurrence statistics combined to six gray-scale quantization levels to classify breast lesions on ultrasound (BUS) images. The database of 436 BUS images used in this investigation was formed by 217 carcinoma and 219 benign lesions images. The region delimited by a minimum bounding rectangle around the lesion was employed to calculate the gray-level co-occurrence matrix (GLCM). Next, 22 co-occurrence statistics were computed regarding six quantization levels (8, 16, 32, 64, 128, and 256), four orientations (0° , 45° , 90° , and 135°), and ten distances (1, 2,...,10 pixels). Also, to reduce feature space dimensionality, texture descriptors of the same distance were averaged over all orientations, which is a common practice in the literature. Thereafter, the feature space was ranked using mutual information technique with minimal-redundancy-maximal-relevance (mRMR) criterion. Fisher linear discriminant analysis (FLDA) was applied to assess the discrimination power of texture features, by adding the first m-ranked features to the classification procedure iteratively until all of them were considered. The area under ROC curve (AUC) was used as figure of merit to measure the performance of the classifier. It was observed that averaging texture descriptors of a same distance impacts negatively the classification performance, since the best AUC of 0.81 was achieved with 32 gray levels and 109 features. On the other hand, regarding the single texture features (i.e., without averaging procedure), the quantization level does not impact the discrimination power, since AUC = 0.87 was obtained for the six quantization levels. Moreover, the number of features was reduced (between 17 and 24 features). The texture descriptors that contributed notably to distinguish breast lesions were contrast and correlation computed from GLCMs with orientation of 90° and distance more than five pixels.

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Bone quality is an evaluation index often applied in order to interpret clinical observations made upon bone health, such as bone mineral density, micro and macro architecture, and mineral content. Conventional inspection techniques do not provide full information on trabecular bone quality. This study shows the high resolution potential and the non-destructive character of X-ray microtomography and microfluorescence upon the application of such techniques for evaluating bone quality. The mineral content assessment was performed by two-dimensional concentration mappings of calcium, zinc, and strontium. The results showed significant changes in bone morphology.

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OBJECTIVE: To develop a computer model to analyse the performance of a standard physiotherapy clinic in the city of Rio de Janeiro, Brazil. DESIGN AND SETTING: The clinic receives an average of 80 patients/day and offers 10 treatment modalities. Details of patient procedures and treatment routines were obtained from direct interviews with clinic staff. Additional data (e.g. arrival time, treatment duration, length of stay) were obtained for 2000 patients from the clinic's computerised records from November 2005 to February 2006. METHODS AND MAIN OUTCOME MEASURES: A discrete-event model was used to simulate the clinic's operational routine. The initial model was built to reproduce the actual configuration of the clinic, and five simulation strategies were subsequently implemented, representing changes in the number of patients, human resources of the clinic and the scheduling of patient arrivals. RESULTS: Findings indicated that the actual clinic configuration could accept up to 89 patients/day, with an average length of stay of 119minutes and an average patient waiting time of 3minutes. When the scheduling of patient arrivals was increased to an interval of 6.5minutes, maximum attendance increased to 114 patients/day. For the actual clinic configuration, optimal staffing consisted of three physiotherapists and 12 students. According to the simulation, the same 89 patients could be attended when the infrastructure was decreased to five kinesiotherapy rooms, two cardiotherapy rooms and three global postural reeducation rooms. CONCLUSIONS: The model was able to evaluate the capacity of the actual clinic configuration, and additional simulation strategies indicated how the operation of the clinic depended on the main study variables.

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BACKGROUND: The ultrasound biomicroscopy (UBM) technique generates high-resolution echographic images using acoustic frequencies between 20 and 200 MHz. In dermatology, it enables non-invasive visualization of cutaneous structures. In this sense, several studies are being conducted for the measurement of cutaneous tumor sizes and for the evaluation of their response to therapeutic procedures. The present work was conducted to analyze the ability of UBM to identify diverse histological structures associated with cutaneous carcinomas ex vivo regarding the evaluation of the technique as a diagnostic tool that could, eventually, improve the patient's healthcare protocol. METHODS: Ex vivo human tissue samples, corresponding to basal cell carcinoma and squamous cell carcinoma cases, were studied. The ultrasonic system operated with a center frequency of 45MHz and the histological structures were identified by comparison with the light microscopy images. RESULTS: The histological components present in the tumors were identified by variations in the echogenicity level for several of the studied cases and particular characteristics were observed for the different tumor types. CONCLUSION: The possibility of differentiating the histological components associated with cutaneous carcinomas indicates the potential use of UBM for diagnostic applications. However, a larger number of specimens must be studied.

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PURPOSE: This paper presents a computerized segmentation method for breast lesions on ultrasound (US) images. METHODS: It consists of first applying a contrast-enhanced approach, i.e., a contrast-limited adaptive histogram equalization. Then, aiming at removing speckle and enhancing the lesion boundary, an anisotropic diffusion filter, guided by texture descriptors derived from a set of Gabor filters, is applied. To eliminate the distant pixels that do not belong to the tumor, the resulting filtered image is multiplied by a constraint Gaussian function. By doing so, both the segmentation and the marker functions are generated and could be used in the marker-controlled watershed transformation algorithm to create potential lesion boundaries. Finally, to determine the lesion contour, the average radial derivative function is evaluated. The proposed method was tested with 50 breast US images and 60 simulated "ultrasound-like" images. Accuracy and precision of the segmentation method were then assessed. For the accuracy, three parameters were used: Overlap ratio (OR), normalized residual value (nrv), and proportional distance (PD) between contours. RESULTS: The average results for US images were OR = 0.86 +/- 0.05, nrv = 0.16 +/- 0.06, and PD = 6.58 +/- 2.52%. For simulated ultrasound-like images, a better performance (OR = 0.92 +/- 0.01, nrv = 0.08 +/- 0.01, and PD = 3.20 +/- 0.53%) was achieved. CONCLUSIONS: The segmentation method proposed was capable of delineating the lesion contours with high accuracy in comparison to both the radiologists' delineations and the true delineations of simulated images. Moreover, this method was also found to be robust to human-dependent parameters variations.

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PURPOSE: To use the BI-RADS ultrasound classification in an intraobserver retrospective study of the interpretation of breast images. MATERIALS AND METHODS: The study used 40 breast ultrasound images recorded in orthogonal planes, obtained from patients with an indication for surgery. Eight professionals experienced in breast imaging analysis retrospectively reviewed these lesions, in three rounds of image interpretation (with a 3-6 months interval between rounds). Observers had no access to information from medical records or histopathological results, and, without their knowledge, in each new round were assigned the same images previously interpreted by them. Fleiss-modified Kappa measures were the study main concordance index. Besides the BI-RADS, a scale grouping its categories 2-3 and 4-5 was also used. The statistical analysis concerned the intraobserver agreement. RESULTS: Kappa values ranged from 0.37 to 0.75 (original categories) and from 0.73 to 0.87 (grouped categories). Overall, out of the 8 observers, 7 presented moderate to substantial concordance (Kappa values 0.51 to 0.74). CONCLUSION: The BI-RADS is a reporting tool that provides a standardized terminology for US exams. In this study, moderate to substantial concordance in Kappa values was found, in agreement with other studies of the literature.

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INTRODUÇÃO: O ultra-som é um recurso bastante utilizado em Fisioterapia. Entretanto, a aplicação inadequada pode promover aquecimento insuficiente ou causar danos aos tecidos biológicos. Por isso, é importante que se conheçam os parâmetros ótimos para atingir a temperatura adequada, dentro dos limites seguros. A geração de calor é função dos parâmetros do equipamento e das propriedades físicas dos tecidos. Este trabalho apresentou um software que simula a variação da energia e da temperatura nos tecidos ao longo do tempo, permitindo ao usuário visualizar o padrão de aquecimento nos tecidos em função dos parâmetros. MATERIAIS E MÉTODOS: O software foi implementado com base na equação biotérmica, supondo quatro camadas (pele, gordura, músculo e osso), das quais o usuário pode alterar espessura e propriedades acústicas e térmicas. Pode-se também escolher intensidade, freqüência e tempo de aplicação. São apresentados gráficos com o percentual de energia absorvida ao longo da profundidade e a respectiva variação de temperatura por cada milímetro de tecido. RESULTADOS: Foram realizadas simulações exemplificando situações de interesse para a terapia, variando tempo de aplicação, espessura e freqüência do ultra-som. Podem ser observadas as diferenças do padrão de aquecimento, em especial nas fronteiras das interfaces. CONCLUSÕES: O software permitiu o estudo do aquecimento de tecidos biológicos por ultra-som e pode ser usado tanto para fins didáticos como para planejamento de doses de aquecimento, para ondas contínuas. Numa próxima etapa, pretende-se adequá-lo para estimar qual dose deve ser regulada no aparelho, para manter a temperatura desejada pelo tempo escolhido. Software disponível em: http://www.peb.ufrj.br/lus.htm.

INTRODUCTION: Ultrasound is a resource commonly used in Physical Therapy. However, its inadequate application may produce insufficient heating or cause damage to biological tissues. Therefore, the knowledge on the optimum parameters for achieving the appropriate temperature, within safe limits, is necessary. Heat generation depends on equipment parameters and the physical properties of tissues. This study presented a software that simulates the energy and temperature variation in tissues over time, thus allowing users to view the heating patterns in tissues as a function of these parameters. METHODS: The software was implemented based on the bioheat transfer equation for four layers (skin, fat, muscle and bone), in which the user can change the thickness and thermal or acoustic properties of these tissues. The intensity, frequency and time of application can also be chosen. Graphs showing the percentage energy absorption in relation to depth and the respective temperature variation per millimeter of tissue are presented. RESULTS: Simulations were produced to give examples of situations of interest for therapy, by varying the time of application, thickness and ultrasound frequency. Differences in heating patterns are seen, especially at the interfaces. CONCLUSIONS: The software made it possible to study the heating of biological tissues by ultrasound and can be used both for teaching purposes and for planning heating doses for continuous waves. In the future, the software will be adapted, in order to estimate which dose should be regulated in the apparatus to maintain the desired temperature for the time chosen. Software available in: http://www.peb.ufrj.br/lus.htm.

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A modelagem da temperatura em tecidos humanos, quando os mesmos são sujeitos a ultra-som de terapia, é um aspecto essencial para um correto controle e calibração da instrumentação de terapia. A existência de modelos precisos possibilitaria um uso mais seguro e eficiente das terapias térmicas. O objetivo principal deste trabalho é a comparação entre a performance de um modelo linear e de um modelo não linear, na estimação pontual da temperatura num meio homogêneo. O objetivo final do trabalho é a construção de modelos para estimação in-vivo da temperatura. Os modelos lineares aplicados foram "autoregressive models with exogenous inputs" (ARX), enquanto que os modelos não-lineares aplicados foram "radial basis functions neural networks" (RBFNN). As melhores estruturas para as RBFNN foram selecionadas usando o "multi-objective genetic algoritm" (MOGA). A melhor estrutura RBFNN apresentou um erro máximo absoluto de 0,2ºC, que é inferior em uma ordem de grandeza ao erro cometido pelo melhor modelo ARX.

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The elaboration of a maintenance strategy is a main concern for hospital administrators. The strategies can be optimized through computational simulation of discrete events. The objective of this work is to present a model of a standard mammography clinic and to analyze the impact of different mammograph maintenance strategies on the clinic routine...

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Mean scatterer spacing (MSS) is a parameter that can be used to characterize the periodicity of biological tissues from ultrassound (US) signals. The present in vitro study uses the spectral autocorrelation function (SAC) to estimate the MSS of the human cancellous bone...

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Healthcare management is a dificult enterprise, which can be helped by modern computacional approaches such as the use of models based on computer simulation. The objective of this studt is to present an application of this tool to the analysis of the performance of a hospital clinic (an ophthalmologic clinic in a large hospital)...

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Temperature modeling of human tissue subjected to ultrasound for therapeutic use is essential for an accurate instrumental assessment and calibration. Prior studies with a homogeneous medium are hereby reported. Nonlinear punctual temperature modeling is proposed by means of Radial Basis Functions Neural Network (RBFNN) structures...

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O controle de qualidade da imagem em equipamentos ultra-sônicos de diagnósticos é baseado em parâmetros determinados por norma (IEC, 1996). Todos os parâmetros citados nesta norma, com exceção da Largura de Banda, podem ser avaliados utilizando-se de phantoms de tecidos biológicos. Baseado em normas e procedimentos internacionais, confeccionou-se um phantom para medição do parâmetro Faixa Dinâmica Exibida. Como material mimetizados de tecido, utilizou-se a solução matriz (agar, glicerina e água) adicionada de pó de grafite, apresentando coeficiente de atenuação (alfa 0) e velocidade da onda ultrasônica (c) compatíveis com a norma (alfa 0 = 0,7 dB.cm elevado a menos 1.MHz elevado a -0,83 e v = 1540 m.s elevado a menos 1). Adicionaram-se como conservantes, os antibióticos: clorafenicol, tetraciclina, penicilina G e os antifúngicos nistativa e anfotericina B. Foi também desenvolvido um protocolo detalhado para aplicação do phantom. Este protocolo foi testado em um aparelho comercial novo e os resultados iniciais apresentaram-se satisfatórios sugerindo sua adequação (tanto do phantom como do protocolo) numa aplicação rotineira em aparelhos comerciais

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Este trabalho apresenta a implementação de um protocolo para a aquisição dos parâmetros do feixe acústico de transdutores ultra-sônicos usados em medicina, baseado em normas nacionais e internacionais. O software ATUS (Avaliação de Transdutores Ultrs-Sônicos) foi desenvolvido em MATLAB (Mathworks, Natick, MA) e se apresenta como uma ferramenta amigável para visualização dos perfis do feixe (paralelo e perpendicular à face do transdutor) e para a obtenção e cálculo dos parâmetros de interesse, como intensidade acústica e características geométricas do feixe (distância focal, comprimento focal e área focal). O protocolo é aplicável ao feixe de transdutores usados tanto em diagnóstico como em fisioterapia. A interpolação de mapeamentos 2D sub-amostrados é apresentada como uma metodologia alternativa ao mapeamento 1D em diversas direções paralelas à face do transdutor, proposto pela Norma ABNT - IEC 1689 (1998)

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Foi implementado num microcomputador desenvolvido pelo Programa de Engenharia Biomédica da COPPE/UFRJ, um detector/delimitador de Complexos QRS em tempo-real que utiliza duas derivaçöes do eletrocardiograma (ECG). Ambas as derivaçöes säo comparadas entre si pelo algorítmo e é gerada uma "detecçäo resultante". A técnica de detecçäo para cada canal de ECG é baseada em compressäo de dados, identificaçäo de morfologias triangulares com cálculo de um "fator de qualidade" para as mesmas e sua conseqüente concatenaçäo para a formaçäo do QRS. A avaliaçäo do algorítmo é feita automaticamente pelo próprio microcomputador, utilizando-se um banco de dados de ECG do MIT-BIH ARRHYTHMIA DATABASE (1980), e permite que se observe tanto o desempenho do "detector resultante" como o de cada um dos outros dois canais. Numa primeira avaliaçäo, o desempenho do algorítmo para a derivaçäo de melhor relaçäo sinal/ruido no DATABASE, foi o seguinte: 0,63% de falsos negativos (FN) e 0,52% de falsos positivos (FP). Esse resultado é comparável ao obtido por outros grupos de pesquisadores para detectores de canal único. Para o "detector resultante" os resultados obtidos säo de 0,27% de falsos negativos e 5,44% de falsos positivos. A percentagem de FN é plenamente satisfatória. A de FP no entanto, ainda é elevada. Säo discutidas as vantagens potenciais de um detector/delimitador baseado em duas derivaçöes, bem como as melhorias que estäo em fase de implementaçäo no algorítmo

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A equipe vem há vários anos trabalhando no desenvolvimento de um monitor automático de arritmias cardíacas. Como subprodutos dessa linha de investigaçäo foram desenvolvidos microcomputadores de uso geral adequados ao processamento de sinais em tempo-real, bem como foi criada uma infra-estrutura que possibilita o desenvolvimento de microcomputadores dedicados a funçöes específicas de forma rápida e a baixo-custo. Vários recursos de "hardware" e "spftware" foram implementados com vistas a conferir maior capacidade de processamento a esses sistemas. Este trabalho apresenta alguns dos recursos mais úteis empregados, bem como procura analisar os efeitos da utilizaçäo dos mesmos sobre o desempenho geral dos sistema. Säo abordados os seguintes tópicos: conversores A/D com entrada multiplexada e um dispositivo de amostra e retençäo para cada entrada, técnica de exibiçäo de sinais em tempo-real baseada em memórias de duplo acesso, avaliaçäo de tempo de execuçäo de algoritmos para processamento em tempo-real, armazenadores circulares de amostras e programas monitores para desenvolvimento de sistemas

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