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Publications

Publications by BIO

2011

A Novel Dry Active Biosignal Electrode Based on an Hybrid Organic-Inorganic Interface Material

Authors
Dieteren Ribeiro, DMD; Fu, LSS; Carlos, LD; Silva Cunha, JPS;

Publication
IEEE SENSORS JOURNAL

Abstract
In this paper, we describe the design, implementation and testing of a dry active flexible electrode with a novel interface material for wearable biosignal recording. The new interface material takes the form of a gel and is highly bendable and comfortable on the wearer's skin. A comparison between common Ag/AgCl and our dry active electrode was performed on seven healthy volunteers. The presented prototype was designed for ECG signals but this technology can be modified for other biosignals. Our results show that the new dry active electrode presents better electrical characteristics than the common Ag/AgCl electrode, namely less power-line interference and better response in the signal band. We can conclude that our novel dry active flexible electrode outperforms the traditional Ag/AgCl wet electrode with the advantages of being dry and comfortable. Some future applications of this biodevice are discussed.

2011

Autonomic correlates of attachment insecurity in a sample of women with eating disorders

Authors
Dias, P; Soares, I; Klein, J; Cunha, JPS; Roisman, GI;

Publication
ATTACHMENT & HUMAN DEVELOPMENT

Abstract
This study examined associations between attachment insecurity and autonomic response during the Adult Attachment Interview (AAI) in a sample of 47 women with eating disorders using a new system for the synchronous acquisition of behavioral and physiological data: the Bio Dual-channel and Representation of Attachment Multimedia System (BioDReAMS; Soares, Cunha, Zhan Jian Li, Pinho, Neves, 1998). Consistent with the emerging literature on the psychophysiology of adult attachment, insecurity was positively correlated with electrodermal reactivity during the AAI. Furthermore, relatively secure patients showed some evidence of parasympathetic withdrawal, which can be conceptualized as evidence of more effective emotion regulation. Results suggest that, even among women with diagnosed psychopathology, security is associated with moreproductive patterns of psychophysiological response to attachment-related challenges.

2011

3D-Video-fMRI: 3D Motion Tracking in a 3T MRI Environment

Authors
Fernandes, JM; Tafula, S; Silva Cunha, JPS;

Publication
IMAGE ANALYSIS AND RECOGNITION: 8TH INTERNATIONAL CONFERENCE, ICIAR 2011, PT II: 8TH INTERNATIONAL CONFERENCE, ICIAR 2011

Abstract
We propose a technical solution that enables 3D video-based in-bore movement quantification to be acquired synchronously with the BOLD function magnetic resonance imaging (fMRI) sequences. Our solution relies on in-bore video setup with 2 cameras mounted in a 90 degrees angle that allows tracking movments while acquiring fMRI sequences. In this study we show that using 3D motion quantification of a simple finger opposition paradigm we were able to map two different finger positions to two different BOLD response patterns in a typical block design protocol. The motion information was also used to adjust the block design to the actual motion start and stop improving the time accuracy of the analysis. These results reinforce the role of video based motion quantification in fMRI analysis as an independent regressor that allows new findings not discernable when using traditional block designs.

2010

Programmable Test Bench for Hemodynamic Studies

Authors
Pereira, HC; Cardoso, JM; Almeida, VG; Pereira, T; Borges, E; Figueiras, E; Ferreira, LR; Simoes, JB; Correia, C;

Publication
WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, VOL 25, PT 4: IMAGE PROCESSING, BIOSIGNAL PROCESSING, MODELLING AND SIMULATION, BIOMECHANICS

Abstract
The non-invasive assessment of hemodynamic parameters has been a permanent challenge posed to the scientific community. The literature shows many contributions to this quest expressed as algorithms dedicated to revealing some of its characteristics and as new probes or electronics, featuring some enhanced instrumental capability that can improve their insight. A test system capable of replicating some of the basic properties of the cardiovascular system, especially the ones related with the propagation of the arterial pressure wave (APW), is a powerful tool in the development of those probes and in the validation of the various algorithms that extract clinically relevant information from the data that they can collect. This work describes a test bench system, based on the combination of a new programmable pressure wave generator with a flexible tube, capable of emulating some of these properties. It discusses its main characterization issues and demonstrates the system in a relevant case study. Two versions of the system have been set up: one that generates a short duration pulse-like pressure wave from an actuator operated in a switched mode, appropriate to system characterization; a second one, using a long stroke actuator, linearly operated under program control, capable of generating complex, including cardiac-like, pressure waveforms. This configuration finds its main use in algorithm test and validation. Tests with a new piezoelectric probe, designed to collect the APW at the major artery sites are shown, demonstrating the possibility of non-invasive precise recovery of the pressure waveform.

2010

Characterization of a double probe for local pulse wave velocity assessment

Authors
Pereira, HC; Pereira, T; Almeida, V; Borges, E; Figueiras, E; Simoes, JB; Malaquias, JL; Cardoso, JMR; Correia, CMB;

Publication
PHYSIOLOGICAL MEASUREMENT

Abstract
Local pulse-wave velocity (PWV) is an accurate indicator of the degree of arteriosclerosis (stiffness) in an artery, providing a direct characterization of the properties of its wall. Devices currently available for local PWV measurement are mainly based on ultrasound systems and have not yet been generalized to clinical practice since they require high technical expertise and most of them are limited in precision, due to the lack of reliable signal processing methods. The present work describes a new type of probe, based on a double-headed piezoelectric (PZ) sensor. The principle of PWV measurement involves determination of the pulse transit time between the signals acquired simultaneously by both PZs, placed 23 mm apart. The double probe (DP) characterization is accomplished in three main studies, carried out in a dedicated test bench system, capable of reproducing a range of clinically relevant properties of the cardiovascular system. The first study refers to determination of the impulse response (IR) for each PZ sensor, whereas the second one explores the existence of crosstalk between both transducers. In the last one, DP time resolution is inferred from a set of three different algorithms based on (a) the maximum of cross-correlation function, (b) the maximum amplitude detection and (c) the zero-crossing point identification. These values were compared with those obtained by the reference method, which consists of the simultaneous acquisition of pressure waves by means of two pressure sensors. The new probe demonstrates good performance on the test bench system and results show that the signals do not exhibit crosstalk. A good agreement was also verified between the PWV obtained from the DP signals (19.55 +/- 2.02 ms(-1)) and the PWV determined using the reference method (19.26 +/- 0.04 ms(-1)). Although additional studies are still required, this probe seems to be a valid alternative to local PWV stand-alone devices.

2010

SYNTHESIZED CARDIAC WAVEFORM IN THE EVALUATION OF AUGMENTATION INDEX ALGORITHMS Case Study for a New Wavelet based Algorithm

Authors
Almeida, V; Pereira, R; Borges, E; Figueiras, E; Cardoso, J; Correia, C; Pereira, HC; Malaquias, JL; Basilio Simoes, JB;

Publication
BIOSIGNALS 2010: PROCEEDINGS OF THE THIRD INTERNATIONAL CONFERENCE ON BIO-INSPIRED SYSTEMS AND SIGNAL PROCESSING

Abstract
We developed and tested the performance of a new wavelet based algorithm for Augmentation Index (AIx) determination. The evaluation method relies on reference cardiac-like pulses that are synthesized using a weighted combination of exponentially shaped sub-pulses that represent the three main components of real pulses: the systolic stroke, its reflected replica and the carotid reservoir or windkessel effect. The pulses are parameterized so as to reproduce the main types of cardiac waveforms. The values of AIx yielded by the new algorithm are compared with the ones computed directly from the synthesized waveform and with the values produced by standard Probability Density Function (PDF) analysis.

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