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Improved range resolution and side lobe level of ultrasound echoes using nonlinear frequency-modulated excitation signal and modified compressing filter

Improved range resolution and side lobe level of ultrasound ...

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IEEE Symposium (IUS) Ultrasonics

作者： Tarcisio M. Dantas Rodrigo P. B. Costa-Felix João C. Machado Telecommunication Engineering Department of Federal Fluminense University Niteroi Rio de Janeiro Brazil Laboratory of Ultrasound Division of Acoustic and Vibration Metrology Directory of Scientific and Industrial Metrology INMETRO Duque de Caxias Rio de Janeiro Brazil Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Rio de Janeiro Brazil

ISBN: (纸本)9781457712531

Linear frequency modulated (LFM) pulses are used as excitation for ultrasonic imaging systems. Temporal sidelobes, due to echo compression, are generated and impart a degradation of the range resolution. This work proposes a compensated frequency-modulated (CFM) excitation signal that improves the range resolution of compressed pulses, keeping low the sidelobe levels. An experimental pulse-eco system setup was used employing a 2.25 MHz transducer (-3 dB relative bandwidth of 45%) excited with a CFM signal, with a duration of 20 μs, immersed in a water tank containing a flat aluminum reflector. The spectrum magnitude of the CFM signal was determined as the nth power of the pseudo-inverted pulse-echo system transfer function magnitude. Its phase was calculated from the group delay determined from the CFM power spectrum. The echoes were compressed with a modified Wiener filter and the best range resolution of 0.47 mm, measured in -30 dB level, was achieved. This result is superior to the latest best published result, which is 42% larger than the one from this present work.

关键词： Signal resolution Image resolution Ultrasonic imaging Image coding Frequency modulation Wiener filters

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Automatic microcalcifications segmentation procedure based on Otsu's method and morphological filters

Automatic microcalcifications segmentation procedure based o...

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Pan American Health Care Exchanges, PAHCE

作者： M. A. Duarte A. V. Alvarenga C. M. Azevedo A. F. C. Infantosi W. C. A. Pereira Electronic Engineering Department Gama Fiho University Rio de Janeiro Brazil Laboratory of Ultrasound National Institute of Metrology Standardization and Industrial Quality (Inmetro) Brazil Gaffrée & Guinle University Hospital University of Rio de Janeiro Rio de Janeiro Brazil Biomedical Engineering Program/COPPE Federal University of Rio de Janeiro Rio de Janeiro Brazil

Microcalcifications are present in a great number of malignant lesions, being considered as a significant sign of malignancy. However, they are detected in less than 50% of mammograms with carcinomas. Given this scenario, systems to highlight infra-clinic lesions, aiding the specialists to make diagnostics, have been studied. These Computer-aided diagnosis systems have been developed based on parameters extracted from microcalcifications. They are basically composed of three parts: segmentation, parameters calculation and lesions classification. This paper presents an automatic microcalcification segmentation method, based on Otsu's method and morphological filters. The proposed method was assessed with 236 regions of interest, captured from 54 images (300 dpi, 8 bits). Based on the joint opinion of two experienced radiologists, the algorithm adequately segmented at least 88.6% of the cases.

关键词： Image segmentation Image reconstruction Pixel Breast cancer biomedical imaging

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12th Mediterranean Conference on Medical and Biological engineering and Computing, MEDICON 2010

作者： Da-Silva, P.J.G. Infantosi, A.F.C. Nadal, J. Biomedical Engineering Program COPPE Federal University of Rio de Janeiro P. O. Box 68.510 21941-972 - Rio de Janeiro - RJ Brazil

ISBN: (纸本)9783642130380

In the present work, the Event-Related Synchronization and Desynchronization (ERD/ERS) index was used for evaluating the cortical response to dynamic visual stimulation in an postural control protocol. EEG signals (O1, P3, P4 and O2 derivations) of 33 healthy subjects were acquired during stabilometric test. The trials were conducted with the subject observing a white wall (WW) and a virtual scene on static (SS) and dynamic (DS) conditions. The power spectra estimates were compared using the Spectral F-Test (SFT, α = 0.05 and Bonferroni correction) and the ERD/ERS index. The SFT results indicate no difference between the EEG power contribution of WW and SS, and decreased power within alpha band during DS for all derivations. The ERD/ERS index allowed successfully detecting above 83% of the desynchronization within the alpha band during dynamic stimulation. Moreover, it also promotes postural instability. This finding indicates the potentiality of the ERD/ERS technique in studies of postural control assessed by dynamic visual stimulation. © 2010 International Federation for Medical and Biological engineering.

关键词： Virtual reality

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A numerical model of the respiratory modulation of pulmonary shunt and PaO2 oscillations for acute lung injury

A numerical model of the respiratory modulation of pulmonary...

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作者： Beda, Alessandro Jandre, Frederico C. Giannella-Neto, Antonio Pulmonary Engineering Lab Biomedical Engineering Program COPPE - Federal University of Rio de Janeiro Rio de Janeiro Brazil Pulmonary Engineering Group University Clinic Carl Gustav Carus Technical University Dresden Dresden Germany

It is an accepted hypothesis that the amplitude of the respiratory-related oscillations of arterial partial pressure of oxygen (ΔPaO2) is primarily modulated by fluctuations of pulmonary shunt (Δs), the latter generated mainly by cyclic alveolar collapse/reopening, when present. A better understanding of the relationship between ΔPaO2, Δs, and cyclic alveolar collapse/reopening can have clinical relevance for minimizing the severe lung damage that the latter can cause, for example during mechanical ventilation (MV) of patients with acute lung injury (ALI). To this aim, we numerically simulated the effect of such a relationship on an animal model of ALI under MV, using a combination of a model of lung gas exchange during tidal ventilation with a model of time dependence of shunt on alveolar collapse/opening. The results showed that: (a) the model could adequately replicate published experimental results regarding the complex dependence of ΔPaO2 on respiratory frequency, driving pressure (ΔP), and positive end-expiratory pressure (PEEP), while simpler models could not;(b) such a replication strongly depends on the value of the model parameters, especially of the speed of alveolar collapse/reopening;(c) the relationship between ΔPaO2 and Δs was overall markedly nonlinear, but approximately linear for PEEP ≥ 6 cmH2O, with very large ΔPaO2 associated with relatively small Δs. © 2009 biomedical engineering Society.

关键词： Ventilation

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Simples coherence vs. multiple coherence: A somatosensory evoked response detection investigation

Simples coherence vs. multiple coherence: A somatosensory ev...

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12th Mediterranean Conference on Medical and Biological engineering and Computing, MEDICON 2010

作者： Melges, D.B. De Sá, A. M. F. L. Miranda Infantosi, A.F.C. Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Av. Horácio Macedo 2030 Sala 327 CEP 21941-914 Rio de Janeiro Brazil

ISBN: (纸本)9783642130380

In this work the performance of two techniques useful for detecting the somatosensory evoked potential (SEP), namely the Magnitude-Squared Coherence (MSC or Simple Coherence) and its multivariate version, the Multiple Coherence (MC), was compared. Electroencephalographic (EEG) signals during somatosensory stimulation were collected from forty adult volunteers without history of neurological pathology using the 10-20 International System. All leads were referenced to the earlobe average. The stimulation was carried out throughout current pulses (200 μs width) applied to the right posterior tibial nerve (motor threshold intensity level) at the rate of 5 Hz. The response detection was based on rejecting the null hypothesis of response absence (M = 100 epochs and significance level α = 0.05). The MSC was applied to the derivations [Cz], [Fz], [C3] and [C4], usually employed in the SEP recordings when bipolar derivations are used. The MC was applied to the pairs [Cz][Fz] and [C3][C4]. The results indicated that if two derivations are available, it should be better to use the MC applied to both leads than the MSC applied to each one. © 2010 International Federation for Medical and Biological engineering.

关键词： Electroencephalography

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Active contours without edges applied to breast lesions on ultrasound

Active contours without edges applied to breast lesions on u...

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作者： Gómez, W. Infantosi, A.F.C. Leija, L. Pereira, W.C.A. Department of Electrical Engineering CINVESTAV-IPN Mexico D.F. Mexico Biomedical Engineering Program COPPE/UFRJ Cidade Universitária Horácio Macedo Ave. 2030 Rio de Janeiro Brazil

ISBN: (纸本)9783642130380

A computerized lesion segmentation technique for breast ultrasound images is proposed. It uses a deformable model based on active contours without edges. The performance of this technique was accessed by comparing the resulting contours of 50 ultrasonographies with those manually delineated by two radiologists. For the boundary, the error metrics used were the Hausdorff distance (HD) and the mean absolute distance (MD). The error area was assessed by using the percentage of false positive (FP), false negative (FN), and true positive (TP) pixels. The results were HD = 8.76±6.04, MD = 2.78±1.20, FP = 4.98±3.83, FN = 16.19±6.85, and TP = 83.86±6.75. These findings indicate that the proposed technique was capable to reach high detailed contours. © 2010 International Federation for Medical and Biological engineering.

关键词： Image segmentation

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Principal components clustering through a variance-defined metric

Principal components clustering through a variance-defined m...

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12th Mediterranean Conference on Medical and Biological engineering and Computing, MEDICON 2010

作者： Costa, J.C.G.D. Melges, D.B. Almeida, R.M.V.R. Infantosi, A.F.C. Biomedical Engineering Program COPPE-Federal University of Rio de Janeiro Av. Horacio Macedo 2030 Bl. H Rio de Janeiro Zip code 21941-972 Brazil

ISBN: (纸本)9783642130380

This work aims at proposing a clustering procedure through a new metric, a weighted Euclidean distance, in which the weights are the ratio of corresponding eigenvalues and the largest eigenvalue found after a Principal Components Analysis. In order to illustrate the method, the procedure was carried out on twenty-one newborn EEG segments, classified as TA (Tracé Alternant) or HVS (High Voltage Slow) patterns. The observed clustering structure was assessed by the cophenetic and agglomerative coefficients. Results showed that, despite its unlikely existence, a clustering structure was suggested by the traditional approach. This structure, however, was not confirmed by the proposed method. © 2010 International Federation for Medical and Biological engineering.

关键词： Principal component analysis

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Investigating the EEG alpha band during kinesthetic and visual motor imagery of the spike volleyball movement

Investigating the EEG alpha band during kinesthetic and visu...

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12th Mediterranean Conference on Medical and Biological engineering and Computing, MEDICON 2010

作者： Stecklow, M.V. Cagy, M. Infantosi, A.F.C. Biomedical Engineering Program Federal University of Rio de Janeiro COPPE Av. Brigadeiro Trompowsky Rio de Janeiro Brazil Fluminense Federal University Department of Epidemiology and Biostatistics Niterói Brazil

ISBN: (纸本)9783642130380

Motor Imagery (MI) is the mental simulation of motor tasks and its execution may recover a motor planning in the central nervous system. The purpose of this study was to analyze the changes along trials of Motor Imagery (MI) in Kinesthetic (KMI) and Visual (VMI) modalities. The casuistry initially consisted of 15 right-handed male volleyball athletes (AG) and 18 non-athletes (NAG). By previously applying MIQ-R, 3 subjects from NAG were dismissed of the study due to their low questionnaire score. Both groups performed 30 trials of KMI and VMI of spike volleyball movement, intermixed with mental countdown (REF). The t-test (α = 0.05) resulted in similar MIQ-R mean scores for both groups, although AG demonstrated greater facility to imagine the volleyball task than NAG. Each EEG free-artifact signal was subdivided in three sequences (S1, S2 and S3) with 8 epochs each. Wilcoxon paired tests (α = 0.05) of the EEG power spectrum in the vicinity of alpha peak (ABP) suggests habituation during initial trial (S1) mainly for athletes. The comparisons between REF and KMI using the spectral F-test (SFT with α = 0.05) indicates the left occipital (athletes) and parietal (non-athletes) sites as those in which SFT>SFTcrit. Based on such results, one can conclude that the KMI modality promotes more cortical changes than VMI, particularly for non-athletes. These findings suggest a different learning process of MI execution of repetitive sequences, related to previous knowledge of the real task. © 2010 International Federation for Medical and Biological engineering.

关键词： Testing

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Breast ultrasound imaging phantom to mimic malign lesion characteristics

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Physics Procedia 2010年第1期3卷 421-426页

作者： I.M. de Carvalho R.L.Q. Basto A.F.C. Infantosi M.A. von Krüger W.C.A. Pereira Biomedical Engineering Program COPPE/UFRJ Av. Horacio Macedo 2030 Rio de Janeiro 21941-914 Brazil

Ultrasound (US) phantoms are used to simulate the main acoustic properties of human soft tissues and are usually applied in guided biopsy training and equipment calibration. In this work it is presented an ultrasound phantom that mimics breast lesions with irregular edge, which is a typical feature related to malignancy. The phantom matrix was made of a mixture of water, agar, glycerine and graphite and PVC powders and the lesions were of silicon and polyacrylamide. The mimicking properties were US attenuation, propagation speed and density. The images obtained were visually compatible to malignant and benign lesions and are meant to be used as references for evaluation of segmentation algorithms for image processing.

关键词： Breast Phantom Ultrasound

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A fractional electrical impedance model in detection of occlusal non-cavitated carious

A fractional electrical impedance model in detection of occl...

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

作者： Andréa P. Morais Alexandre V. Pino Mãrcio N. Souza Biomedical Engineering Program COPPE Centro de Tecnologia Federal University of Rio de Janeiro Rio de Janeiro Brazil

Identification of occlusal caries remains a major concern for the diagnosis, which is still highly subjective and presents a considerable variability among clinicians. Dentists have been observed an increase of a specifically type of caries lesion, the hidden caries. Among the available techniques to assess the hidden caries, the measurement of electrical impedance has been shown to be one of the most promising. This paper presents a fractional electrical model for the tooth and uses such a model associated to a BioImpedance Spectroscopy (BIS) method based on the current response to a step voltage excitation. An analytical solution for the current response is presented based on a fractional calculus approach. Estimate parameters of the proposed model achieved using an in vitro data acquired in a protocol performed to collect bioimpedance data showed that it seems possible to detect occlusal non-cavitated caries, and that the principal confounding factor in the diagnosis of the incipient occlusal caries, the pigmented areas, can also be differentiated.

关键词： Teeth Dentistry Impedance Biological system modeling Bioimpedance Lesions Bioinformatics

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