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11th Mediterranean Conference on Medical and Biomedical Engineering and Computing 2007: MEDICON 2007, 26-30 June 2007, Ljubljana, Slovenia

Tomaz Jarm ; Peter Kramar ; Anze Zupanic (eds.)

Resumen/Descripción – provisto por la editorial

No disponible.

Palabras clave – provistas por la editorial

Biomedical Engineering

Institución detectada Año de publicación Navegá Descargá Solicitá
No detectada 2007 SpringerLink


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ISBN electrónico


Editor responsable

Springer Nature

País de edición

Reino Unido

Fecha de publicación

Información sobre derechos de publicación

© Springer-Verlag 2007

Cobertura temática

Tabla de contenidos

Assessing FSP Index Performance as an Objective MLAEP Detector during Stimulation at Several Sound Pressure Levels

Antonio Fernando Catelli Infantosi; M. Cagy; E.J.B. Zaeyen

The need for a better approach for auditory screening is due to pathologies that can affect higher auditory centers. Therefore, the Middle Latency Auditory Evoked Potential (MLAEP) was investigated by using the statistical index. The EEG of ten adults during click stimulation with different sound pressure levels was collected. With the critical value for the statistical null hypothesis (absence of response), particularly considering EEG as a colored noise and fitting the number of degrees of freedom of the index distribution, objective detection of MLAEP resulted in a better performance than the threshold of 3.1, commonly employed in the literature. This finding suggests the for detecting MLAEP response as an auxiliary tool for determining objectively the neurophysiologic acoustical threshold level.

- Brain Research and Analysis of EEG | Pp. 492-496

The Colorful Brain: Compact Visualisition of Routine EEG Recordings

M.J.A.M. van Putten

Clinical EEG recordings are typically evaluated by visual analysis of the various waveforms Besides the long learning curve, it is rather subjective and prone to human error. To assist in the visual interpretation, various quantitative techniques have been proposed. Here, we describe a triplet of features that quantify the spatial distribution of the various EEG waveforms and their coherence, represented as three time-frequency plots. The technique allows compression of 20 minutes of EEG recordings into a single picture, that captures various essential elements, including anterior-posterior differentiation, reactivity to eyes opening and closing, and photic drving. In addition, it may detect disorders, including various manifestations of epileptiform discharges.

Palabras clave: Photic Stimulation; Background Pattern; Neighbor Coherence; Photic Driving; Medisch Spectrum.

Pp. 497-500

Using ANN on EEG signals to predict working memory task response

Vito Logar; A. Belic; B. Koritnik; S. Brezan; V. Rutar; J. Zidar; R. Karba; D. Matko

Many authors have shown that performing working-memory tasks causes an elevated neuronal activity in several areas of the human brain, which suggests information exchange between them. Since the information exchanged, encoded in brain waves is measurable by electroencephalography (EEG) it is reasonable to assume that it can be extracted with an appropriate method. In this paper we present a method for extracting the information using an artificial neural network (ANN), which we consider as a stimulusresponse model. The EEG was recorded from three subjects while they performed a modified Sternberg task that required them to respond to each trial with the answer "true" or "false". The study revealed that a stimulus-response model can successfully be identified by observing phase-demodulated theta-band EEG signals 1 second prior to a subject's answer. The results showed that the model was able to predict the answers from the EEG signals with an average reliability of 75% for all three subjects. From this we concluded that stimulus-response model successfully observes the system states and consequently predicts the correct answer using the EEG signals as inputs.

Palabras clave: Artificial Neural Network; Theta Rhythm; Response Prediction; Theta Frequency Band; Sternberg Task.

- Brain Research and Analysis of EEG | Pp. 501-504

Cross-correlation based methods for estimating the functional connectivity in populations of cortical neurons

Alessandro Noriaki Ide; M. Chiappalone; L. Berdondini; V. Sanguineti; C. Martinoia

In this paper we estimate the functional connectivity in in-vitro cultured cortical neurons plated into highdensity passive microelectrodes arrays. We compare standard and partial correlation methods in order to find out the main pathways between two electrodes. In summary, while standard correlation considers just pairs of electrodes, giving a general overview of the network, partial correlation can give more details about the connectivity map due to the cancellation of indirect connections.

Palabras clave: Cortical Neuron; Functional Connectivity; Partial Correlation; Spike Train; Cortical Network.

Pp. 525-528

Extracellular ATP-Purinoceptor Signaling for the Intercellular Synchronization of Intracellular Ca2+ oscillation in Cultured Cardiac Myocytes

Koichi Kawahara; Y. Nakayama

Isolated and cultured neonatal cardiac myocytes contract spontaneously and cyclically. The contraction rhythms of two isolated cardiac myocytes, each of which beats at different frequencies at first, become synchronized after the establishment of mutual contacts, suggesting that mutual entrainment occurs due to electrical and/or mechanical interactions between two myocytes. The intracellular concentration of free Ca also changes rhythmically in association with the rhythmic contraction of myocytes (Ca oscillation), and such a Ca oscillation is also synchronized among cultured cardiac myocytes. In this study, we investigated whether intercellular communication other than via gap junctions was involved in the intercellular synchronization of intracellular Ca oscillation in spontaneously beating cultured cardiac myocytes. Treatment with either blockers of gap junction channels or an un-coupler of E-C coupling did not affect the intercellular synchronization of Ca oscillation. In contrast, treatment with a blocker of P2 purinoceptors resulted in the asynchronization of Ca oscillatory rhythms among cardiac myocytes. The present study suggested that the extracellular ATP-purinoceptor system was responsible for the intercellular synchronization of Ca oscillation among cardiac myocytes.

- Cardiovascular System | Pp. 537-540

Computer Assisted Optimization of Biventricular Pacing Assuming Ventricular Heterogeneity

Raz Miri; M. Reumann; D. Farina; B. Osswald; O. Dössel

Reduced cardiac output, dysfunction of the conduction system, atrio-ventricular block, bundle branch blocks and remodeling of the chambers are results of congestive heart failure (CHF). Biventricular pacing as Cardiac Resynchronization Therapy (CRT) is a recognized therapy for the treatment of heart failure. The present paper investigates an automated non-invasive strategy to optimize CRT with respect to electrode positioning and timing delays based on a complex threedimensional computer model of the human heart. The anatomical model chosen for this study was the segmented data set of the Visible Man and a set of patient data with dilated ventricles and left bundle branch block. The excitation propagation and intra-ventricular conduction were simulated with Ten Tusscher electrophysiological cell model and adaptive cellular automaton. The pathologies simulated were a total atrioventricular (AV) block and a left bundle branch block (LBBB) in conjunction with reduced interventricular conduction velocities. The simulated activation times of different myocytes in the healthy and diseased heart model are compared in terms of root mean square error. The outcomes of the investigation show that the positioning of the electrodes, with respect to proper timing delay influences the efficiency of the resynchronization therapy. The proposed method may assist the surgeon in therapy planning.

Pp. 541-544

Power density spectra of the velocity waveforms in Artificial heart valves

A. A. Sakhaeimanesh

To find the possible frequencies induced by the vibration of the flexible membrane of the Jellyfish valve, power density spectra of the the valvular velocity waveforms were carried out. Most of the spectral energy was contained in frequencies lower than 11 Hz and all spectra exhibited pronounced peaks which implied wave motions in the preferred frequency range. Two distinct peak frequencies, 1.2 and 2.4 Hz, were observed downstream of the Jellyfish valve which qualified as the frequencies of fundamental harmony of the waveform velocity and one of its sub harmonics. Effect of oscillation on elevating turbulent shear stresses through the jellyfish and St.Vincent valves has also been investigated. Laser Doppler Anemometry (LDA) was employed to determine the velocity and shear stress distributions at various locations downstream of the valves. Comparison between two valves revealed that at 0.5D downstream of the valves the magnitude of shear stresses in the Jellyfish valve were much higher than those of the St. Vincent valve at cardiac outputs of 4, 5.5 and 6.5 l/min. The cause of high shear stresses in close proximity to the Jellyfish valve could be attributed to the oscillation of the membrane which in turn generated a wake downstream of the valve (in the core of valve chamber) and produced a wide region of disturbance further downstream. This resulted in further pressure drag and consequently, higher pressure drops across the valve and higher shear stresses downstream of the valve.

Palabras clave: Turbulent Intensity; Power Density Spectrum; High Shear Stress; Shear Stress Distribution; Laser Doppler Anemometry.

- Cardiovascular System | Pp. 545-548

Method for Reducing Pacing Current Threshold at Transesophageal Stimulation

Andres Anier; J. Kaik; K. Meigas

In order to reduce pacing current threshold at transesophageal stimulation use of additional chest electrode was studied. The study was performed in 34 patients aged 19 to 66 years using standard transesophageal pacing equipment. Use of chest electrode lowered pacing current over standard bipolar transesophageal methods.

Palabras clave: Supraventricular Tachycardia; Atrial Pace; Sick Sinus Syndrome; Interelectrode Spacing; Pace Threshold.

Pp. 554-557

User–centered system to manage Heart Failure in a mobile environment

Elena Villalba Mora; D. Salvi; M. Ottaviano; I. Peinado; M.T. Arredondo; M. Docampo

In Western world, the prevalence of chronic diseases is highly increasing due to the increase in the life expectancy. Besides, cardiovascular diseases (CVD) are the leading source of death, causing 45% of all deaths and Heart Failure (HF), the paradigm of CVD, mainly affects people older than 65. This paper focuses on the latest advances in the design and development of the user interaction system to manage Heart Failure Management in a mobile environment, based on daily monitoring of Vital Body Signals, with wearable and information technologies, for the continuous assessment of this chronic disease.

Palabras clave: User Interaction; Mobile Environment; Research Phase; Manage Heart Failure; Heart Failure Care.

Pp. 558-561

Cell membrane fluidity at different temperatures in relation to electroporation effectiveness of cell line V79

Masa Knaduser; Marjeta Sentjurc; Damijan Miklavcic

When cell is exposed to short electric pulses with high amplitudes its membrane is transiently permeabilised. Characteristics of the cell play important role in this process. In the present study the effect of cell membrane fluidity on electroporation was investigated. To obtain significant differences in cell membrane fluidity cell suspension was exposed to different temperatures for five minutes before and during the pulse application. To exclude the effect of the temperature on cell membrane resealing only a small droplet of cell suspension was used for cell membrane permeabilization assay as it reached room temperature in few seconds after it was removed from electroporated sample. It was found that the decrease in cell membrane fluidity caused by exposure of cells to low temperature during electric pulse application significantly reduces electroporation effectiveness of the cell line V79.

Palabras clave: Electric Pulse; Spin Probe; Pulse Application; Reach Room Temperature; Cell Membrane Fluidity.

Pp. 570-573