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2009 IEEE International Ultrasonics Symposium, IUS 2009

作者： Machado, Christiano Bittencourt Padilla, Frédéric Laugier, Pascal Pereira, Wagner Coelho De A. Meziri, Mahmoud Laboratoire d'Imagerie Paramétrique CNRS Université Pierre et Marie Curie Paris France Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Rio de Janeiro Brazil Département de Physique Université Badji Mokhtar BP12 Annaba Algeria

ISBN: (纸本)9781424443895

Mean scatterer spacing (MSS) has been used to characterize biological tissues, however it is not well explored yet. This study simulated ultrasound (US) propagation through a simple scatterer numerical model (first approach to trabecular bone), under variations of scatterer spacings, thickness and pulse frequency, and evaluated the capacity of spectral methods in estimating MSS. MSS values of 0.8 and 1.0 mm were simulated. The methods provided correct estimates for 3.5 MHz in all jitter values. For 1 MHz, only the MSS of 1.2 mm was identified. Variation of scatterer thickness did not alter significantly MSS estimates. For trabecular bone assessment, the best US frequency may be between the two tested frequencies in this work. ©2009 IEEE.

关键词： Ultrasonics

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NARX structures for non-invasive temperature estimation in non-homogeneous media

NARX structures for non-invasive temperature estimation in n...

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IEEE International Symposium on Intelligent Signal Processing

作者： C. A. Teixeira W. C. A. Pereira A. E. Ruano M. Graca Ruano Centre for Intelligent Systems Faculty of Sciences and Technology University of Algarve Portugal Biomedical Engineering Program-COPPE Federal University of Rio de Janeiro Brazil

ISBN: (纸本)1424408296;97

The safe and effective application of thermal therapies are limited by the existence of precise non-invasive temperature estimators. Such estimators would enable a correct power deposition on the region of interest by means of a correct instrumentation control. In multi-layered media, the temperature should be estimated at each layer and especially at the interfaces, where significant temperature changes should occur during therapy. In this work, a non-linear autoregressive structure with exogenous inputs (NARX) was applied to non-invasively estimate temperature in a multi-layered (non-homogeneous) medium, while submitted to physiotherapeutic ultrasound. The NARX structure is composed by a static feed-forward radial basis functions neural network (RBFNN), with external dynamics induced by its inputs. The NARX structure parameters were optimized by means of a multi-objective genetic algorithm. The best attained models reached a maximum absolute error inferior to 0.5degC (proposed threshold in hyperthermia/diathermia) at both the interface and inner layer points, at four radiation intensities. These models present also a small computational complexity as desired for real-time applications. To the best of ours knowledge this is the first non-invasive estimation approach in multi-layered media using ultrasound for both heating and estimation.

关键词： Temperature Nonhomogeneous media Medical treatment Ultrasonic imaging Instruments Feedforward systems Radial basis function networks Genetic algorithms Hyperthermia Computational complexity

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Analysis of the correlation between ventricular depolarization events and heart rate in normal subjects using signal-averaged ECG

Analysis of the correlation between ventricular depolarizati...

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Computers in Cardiology (CinC)

作者： P.R.B. Barbosa J. Barbosa-Filho J. Nadal Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Brazil Department of Cardiology Gama Filho University Rio de Janeiro Brazil

Electrical and mechanical events of cardiac activity must adapt to the time course between successive heart beats to allow the appropriate function of the heart as a pump. This study was conducted to evaluate the influence of resting instantaneous heart rate (HR) on the duration of the events of the ventricular depolarization, using SAECG. High resolution ECG signals of 12 normal adults (SEARCH data base) were analyzed and beats separated according to instantaneous HR histogram, which was divided into classes of 5 bpm width, ranging from 90 bpm to 65 bpm. For each subject, beats corresponding to a particular histogram class were signal-averaged together. The vector magnitude was assembled and analyzed according to conventional approach after bidirectional band-pass filtering. The present results indicate that ventricular depolarization events analyzed by signal-averaged ECG are dependent on instantaneous heart rate.

关键词： Heart rate Electrocardiography Signal analysis Histograms Heart beat Signal resolution Data analysis Assembly Band pass filters Filtering

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Anticipation mechanism and influence of fatigue in body sway control

Anticipation mechanism and influence of fatigue in body sway...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： R. Mello L.F. Oliveira J. Nadal Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Brazil Biomechanics Laboratory EEFD Federal University of Rio de Janeiro Brazil

The aim of this work was to identify the anticipatory mechanism and effects of fatigue of gastrocnemius muscle activity on the body sway control during quiet stance in upright position. Stabilometric and electromyographic (EMG) signals were synchronously collected from 23 subjects. The gastrocnemius fatigue was induced by a sustained plantar flexed posture until muscle failure. The acquisition lasted for 120 s before and after the induced fatigue. The stabilograms were subsampled to 5 Hz and the EMG was preprocessed to remove the 60 Hz mains noise and as its harmonics, by a tailor made digital Butterworth filter, order 20, band-pass with 10 and 300 Hz cut-of frequencies. After mean removal, the root mean square values of the EMG were calculated for each 200 ms window. The normalized cross correlation function was estimated between signals. Anticipation was verified before and after fatigue (p < 0.0001), and increased with fatigue (p < 0.02). Anticipation was identified as playing an important role in body sway regulation. The fatigue influence on the sway latency was not well established yet. A decrease on the rate of force production and the inertial moment of the body might contribute more to the increased latency than the posture control alterations itself.

关键词： Fatigue Electromyography Muscles Delay Power harmonic filters Band pass filters Digital filters Frequency Root mean square Production

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Semiautomatic contour detection of breast lesions in ultrasonic images with morphological operators and average radial derivative function

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Physics Procedia 2010年第1期3卷 373-380页

作者： W. Gómez L. Leija W.C.A. Pereira A.F.C. Infantosi Department of Electrical Engineering CINVESTAV-IPN Av. IPN 2508 Mexico City 07000 Mexico Biomedical Engineering Program COPPE/UFRJ Av. Horacio Macedo 2030 Rio de Janeiro 21941-914 Brazil

This work presents a computerized lesion segmentation technique on breast ultrasound images. There were applied known techniques such as morphological filtering, Watershed transformation and average radial derivative function. To evaluate the performance of the proposed method, two protocols were established. For the first, the resulting segmentation contours were compared with those of 24 gold standard simulated ultrasound-like images, and, for second, with 36 breast US images manually delineated by two senior radiologists. Further, two evaluation parameters were used: the percentage of coincidence (CP) and the proportional distance (PD). The former indicates the similarity between contours, while the latter express the dissimilarity. The accuracy of the proposed method was evaluated by considering images with CP>80% and PD<10% as adequately delineated. It was higher than 80% for real images and higher than 88% for simulated images.

关键词： Average radial derivative Breast ultrasound Morphological operators Segmentation

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Butterworth bi-directional and BiSpecTM filters in the assessment of ventricular late potentials: A comparative study

Butterworth bi-directional and BiSpecTM filters in the asses...

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The 26th Annual Meeting: Computers in Cardiology 1999

作者： Barbosa, Paulo Roberto Benchimol Barbosa, Eduardo Corrêa Ginefra, Paulo Nadal, Jurandir Biomedical Engineering Program COPPE Rio de Janeiro Federal University Rio de Janeiro Brazil Division of Cardiology Pedro Ernesto University Hospital UERJ Rio de Janeiro Brazil R. Pompeu Loureiro 36/702 C. 22061-000 Rio de Janeiro - RJ Brazil

The Ventricular Late Potentials (VLP) are low amplitude signals originated from electrically unstable regions of damaged myocardium. Due to low amplitude, VLP are detected on the body surface by statistical techniques and band-pass filtering to reduce the baseline noise and exclude high-energy components. BiSpecTM filter is currently in use as an alternative for VLP analysis, but no clinical study validating its application has been performed so far. To accomplish this task it was conducted a clinical study to compare BiSpec 40 Hz filter (BS) and four pole 40-250 Hz band-pass Butterworth bi-directional filter (BD) regarding their diagnostic properties. It was studied retrospectively 170 patients without bundle branch block, with signal-averaged ECG, using Predictor SAECG System (ART, Texas) and divided into three group The variables analyzed were DUR, RMST, RMS40 and LAS40. It was found significant differences between BS and BD for RMST in all groups (pO.001), DUR in GI (p<0.05) and LAS40 in GII (p<0.05). The distribution of diagnostic results were significantly different in GII and GIII (p<0.05) and linear correlation were <0.7 in GI and GII. Sensitivity was lower for BS than BD (p<0.05). This study demonstrates that BS and BD provide significantly different diagnostic results and suggests that normality intervals should be re-evaluated for BS.

关键词： Electrocardiography

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In Vitro Degradation of Polydioxanone (PDO) Lifting Threads in Microfocused Ultrasound

In Vitro Degradation of Polydioxanone (PDO) Lifting Threads ...

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Pan American Health Care Exchanges, PAHCE

作者： M. H. R. Silva A. Raybolt W. C. A. Pereira Biomedical Engineering Program - COPPE Federal University of Rio de Janeiro RJ Brazil School of Dentistry Federal University of Rio de Janeiro RJ Brazil

ISBN: (数字)9798350390490

ISBN: (纸本)9798350390506

Objective: Analyze the static degradation time of polydioxanone (PDO) threads with or without the association of microfocused ultrasound, which are techniques for aesthetic purposes. Materials and Methods: In vitro assays were conducted in isotonic solution using smooth polydioxanone (PDO) threads divided into 2 groups (n=3): FPL (Smooth Polydioxanone Thread) and FPLU (Smooth Polydioxanone Thread with Ultrasound). The FPLU group underwent microfocused ultrasound. Both groups endured the following analyses: UV spectroscopy Absorbance and Scanning Electron Microscopy (SEM). Results: Absorbance by UV spectroscopy: The concentration levels of molecules in the aliquots showed that at 8 days both FPL and FPLU groups exhibited absorbance levels of 0.0040 (mol −1 /*** −1 ) and 0.00585 (mol −1 /*** −1 ), respectively. At 30 days, these levels were 0.0799 (mol −1 /*** −1 ) and 0.0543 (mol −1 /*** −1 ). At 60 days, the FPLU group showed significant increase to 0.2039 (mol −1 /*** −1 ) compared to the FPL group at 0.1152 (mol −1 /*** −1 ) reaching a degradation peaks at 60 days. At 90 days, the FPL group presented 0.1299 (mol −1 /*** −1 ) and the FPLU group presented 0.2377 (mol −1 /*** −1 ). SEM: Morphological differences were observed in both groups. Conclusion: FPLU group showed higher absorbance over time. Microfocused ultrasound accelerated degradation time PDO threads, diminishing its functionality.

关键词： Degradation Scanning electron microscopy Spectroscopy In vivo Ultrasonic imaging In vitro Physics

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Temperature-induced changes in soft tissues analyzed by spectral methods and transient elastography: A comparative study

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AIP Conference Proceedings 2012年第1期1433卷 228-232页

作者： G. A. Cortela N. Benech W. C. A. Pereira C. Negreira Laboratorio de Acústica Ultrasonora Instituto de Física Facultad de Ciencias Montevideo Uruguay Biomedical Engineering Program COPPE/UFRJ Rio de Janeiro RJ Brazil

Some biological tissues, such as skeletal muscle, have regular or quasi-periodic structures. Periodicity of these structures can be investigated by spectral methods based on ultrasonic backscattered signals. These methods estimate the Mean Scatterer Spacing (MSS). In this work we analyzed the MSS dependence with temperature in bovine skeletal muscle tissue samples. Through spectral analysis we found that the relative variation of the MSS, in the temperature range 20 - 48°C was of ~ 2% /°C. For the same sample and under the same experimental conditions, we analyzed the propagation velocity of shear waves by transient elastography. It was determined that the relative variation of shear elastic modulus was ~ 3% /°C in the same temperature range. The repeatability of the results was tested in three tissue samples, with a set of 6 measurements on each. The relative variation is therefore similar for both parameters. Thus, this study shows that both techniques can be used as a method of noninvasive thermometry for small temperature range. In addition we emphasize the conceptual differences between both methods. As temperature changes, MSS estimation varies due to two physical phenomena. An apparent variation in mean spacing is produced because the sound speed is temperature-dependent, while tissue expansion produces a real change. In practice it is difficult to discriminate the weight of each component in the MSS variation. On the other side, transient elastography is less sensitive to thermal expansion. Thus it measures the actual shear wave speed change with temperature. This differentiation between both methods could be used to construct useful thermoelastic models for soft tissues in the future.

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Do FCU and ECU muscle architecture in children with hemiparetic cerebral palsy affect wrist functionality?

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Research on biomedical engineering 2019年第3-4期35卷 173-181页

作者： Barroso, Patricia Neto de Oliveira, Liliam Fernandes Amaral, Giovanna Mendes Gontijo, Ana Paula Bensemann Campos, Márcio Rodrigues Menegaldo, Luciano Luporini Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Av Horácio Macedo Rio de Janeiro2030 Brazil School of Physical Education and Sports Federal University of Rio de Janeiro Rio de Janeiro Brazil Belo Horizonte Brazil Department of Physical Therapy Federal University of Minas Gerais Belo Horizonte Brazil Department of Radiology and Image Diagnosis University Hospital Federal University of Minas Gerais Belo Horizonte Brazil

Purpose: In individuals with cerebral palsy (CP), wrist flexor and extensor muscles can have impaired tonus, strength, posture, and range of motion. Muscle force and movement generating capacity are related to muscle architecture. The purpose of the study was to measure muscle morphology of the flexor (FCU) and extensor carpi ulnaris (ECU) muscles and compare it with strength and passive stiffness in affected and unaffected forearms of children with hemiparetic CP. Methods: Nine children (MACS levels 1 and 2) were analyzed. Ultrasound was used to measure the maximal cross-sectional area, muscle thickness, and muscle perimeter of FCU and ECU. The strength of the wrist flexors and extensors muscles was measured using a manual dynamometer. Wrist flexion passive stiffness was evaluated using isokinetic dynamometry in passive mode. Results: No significant differences in cross-sectional area, anteroposterior distance, and perimeter between unaffected and affected forearm were observed. Flexion and extension isometric torques were reduced in the affected forearm compared with the unaffected, except the passive stiffness, which was increased. A correlation matrix analysis presented some significant correlations between morphological and functional outcomes. Conclusion: Wrist flexion and extension torques are reduced in the affected side of children with hemiparetic CP, and passive stiffness is increased, even without changes in FCU and ECU morphological parameters. © 2019, Sociedade Brasileira de Engenharia Biomedica.

关键词： Muscle

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Butterworth Bi-directional and BiSpec/sup TM/ filters in the assessment of ventricular late potentials: a comparative study

Butterworth Bi-directional and BiSpec/sup TM/ filters in the...

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Computers in Cardiology (CinC)

作者： P.R.B. Barbosa E.C. Barbosa P. Ginefra J. Nadal Division of Cardiology Pedro Ernesto University Hospital UERJ Rio de Janeiro Brazil Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Brazil

The Ventricular Late Potentials (VLP) are low amplitude signals originating from electrically unstable regions of damaged myocardium. Due to low amplitude, VLP are detected on the body surface by statistical techniques and band-pass filtering to reduce the baseline noise and exclude high-energy components. The BiSpec/sup TM/ filter is currently in use as an alternative for VLP analysis but no clinical study validating its application has been performed so far. To accomplish this task a clinical study was conducted to compare the BiSpec 40 Hz filter (BS) and four pole 40-250 Hz band-pass Butterworth bi-directional filter (BD) regarding their diagnostic properties. 170 patients were studied retrospectively without bundle branch blocks with signal-averaged ECG, using the Predictor SAECG System (ART, Texas) and divided into three groups. The variables analyzed were DUR, RMST, RMS40 and LAS40. Significant differences were found between BS and BD for RMST in all groups (p<0.001), DUR in GI (p<0.05) and LAS40 in GII (p<0.05). The distribution of diagnostic results were significantly different in GII and GIII (p<0.05) and linear correlation were <0.7 in GI and GII. Sensitivity was lower for BS than BD (p<0.05). This study demonstrates that BS and BD provide significantly different diagnostic results and suggests that normality intervals should be re-evaluated for BS.

关键词： Bidirectional control Filters Analysis of variance Testing Virtual manufacturing Cardiology Voltage Conducting materials Hospitals Heart

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