MEASUREMENT SCIENCE REVIEW              Volume 7, Section 2                          Main Page   

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 No. 1

Fereniec M., Kania M., Maniewski R.:

Optimal Leads Selection for Repolarization Phase Analysis

Abstract: The study aimed to identify 12 and 16 optimal recording sites in body surface potential mapping (BSPM) to assess repolarization phase differences between healthy volunteers and myocardial infarction groups. The Discriminant Index and Sequential Selection Algorithm were used to study averaged ST-T waveform in 61 surface leads. Two methods of selection of optimal recording sites gave two different lead sets. For diagnosis purpose leads selected by Discriminant Index value were better, for approximation of information content the Sequential Selection Algorithm allowed for selection better recording sites.
Keywords: BSPM, repolarization phase, optimal selection

Jamali Dinan F., Mosayebi P., Abrishami Moghaddam  H., Giti M.:

A Dynamic Surface Model for Segmentation of Cardiac MRI Images and its Usage in Cardiac Wall Motion Tracking

Abstract: This paper presents the application of a new active contour algorithm for object detection in 3D space. The introduced model is based on techniques of curve evolution for segmentation and level sets. We minimize an energy which can be considered as a particular case of the minimal partition problem. In the level set formulation, the problem becomes a “mean-curvature flow”-like evolving the active contour, which will stop on the desired boundary. However, the stopping term does not depend on the gradient of the image, as in the classical active contour models, but is instead related to a particular segmentation of the image. The method can be put into a 3D level-set framework using a Lipschitz function φ for automatic topology changes. The novel developed 3D algorithm was used for 3D segmentation of endocardial wall in the left ventricle. The experimental results demonstrated the
efficiency of the proposed scheme. The segmented cardiac image was then used by our previously developed 3D tracking algorithm to track the endocardial wall motion which resulted in a fully automatic 3D point-wise tracking software for analyzing 3D cardiac MRI images.
Keywords: deformable surface, level set, active mesh, cardiac image

 No. 2

Faktorová D.:

Complex Permittivity of Biological Materials Measurement at Microwave Frequencies

Abstract: The paper deals with complex permittivity measurement of biological materials. The
used methods are presented and their appropriateness for particular materials is given. The
achieved results are given in graphs and also similarities in courses of particular materials as
well as anomalies are discussed.
Keywords: dielectric constant, microwave measurement, Hippel´s method, Poley´s method

Titomir L.I., Trunov V.G., Aidu E.A.I., Sakhnova T.A., Blinova E.V.:

Recognition of Right Ventricular Hypertrophy Using the DECARTO
Images of the Cardioelectric Characteristics

Abstract: There are presented results of experimental-laboratory testing a new method to
diagnose the right ventricular hypertrophy. The method is based upon the dipole
electrocardiotopography (DECARTO) technique, proposed formerly by the authors and
successfully applied for recognition of the left ventricular hypertrophy. The results obtained
on reliably verified groups of normal and diseased persons show that this approach is
efficient for diagnosis of the right as well as the left hypertrophy.
Keywords: electrocardiotopography, ventricular hypertrophy, non-invasive diagnosis

 No. 3

Majer L., Stopjaková V., Vavrinský E.:

Sensitive and Accurate Measurement Environment for Continuous Biomedical Monitoring using Microelectrodes

Abstract: This paper presents a new non-invasive biomedical monitoring of selected psychosomatic processes. The proposed method measures human skin conductivity using the interdigitated array (IDA) microelectrodes, which allow continual monitoring and analysis of complicated physiological, pathophysiological, and therapeutic processes. The main goal is monitoring of psycho-galvanic reflex of the human skin that might be very useful for stress
identification in medical and psychological experiments. An integrated monitoring system, applicable also in portable measurement environment, was designed and developed. Comparison to a standard bridge-based measurement system was done in terms of accuracy, sensitivity and other main features. The measurement method itself as well as results achieved are discussed.
Keywords: non-invasive biomedical monitoring, skin conductivity measurement,
interdigitated array (IDA) microelectrodes, psycho-galvanic reflex

Přibil J., Frollo I :

Simple Method of Distributed Tuning of RF Sensor for NMR Imaging System

 No. 4

Kania M.,  Fereniec M.,  Maniewski R.:

Wavelet Denoising for Multi-lead High Resolution ECG Signals

Abstract: The aim of this study was to investigate the application of wavelet denoising in noise reduction of multichannel high resolution ECG signals. In particular, the influence of the selection of wavelet function and the choice of decomposition level on efficiency of denoising process were considered and whole procedures of noise reduction were implemented in MatLab environment. The Fast Wavelet Transform was use. The advantage of
used denoising method is noise level decreasing in ECG signals, in which noise reduction by averaging has limited application, i.e. in case of arrhythmia, or in presence of extrasystols.
Keywords: high resolution ECG, signal processing, wavelet denoising

Šušmáková K., Krakovská A.:

Classification of waking, sleep onset and deep sleep by single measures

Abstract:  The study analyses electrophysiological signals (EEG, EOG, ECG and EMG) to select measures and scoring methods suitable for the detection of sleep  stages from waking to deep sleep. 85 measures, selected from relevant spectral characteristics and measures inspired by dynamical systems theory are discussed. Some new characteristics proved to be more sensitive than the conventional scoring measures. Discriminant analysis done with Fisher quadratic classifier determined as the best measures power ratios in delta-alpha, theta-alpha, delta-sigma, delta-beta bands, relative power in delta band, fractal dimension, and coefficient of detrended fluctuation analysis.

Keywords: sleep, EEG, rules of Rechtschaffen and Kales, nonlinear, spectral measures

 No. 5

Juráš V.,  Bittšanský M.,  Majdišová Z.,  Trattnig S.:

In-Vitro Evaluation of Pre- and Post-Compression States of Human Articular Cartilage Using MRI at 3 Tesla

Abstract: The purpose of this study was to evaluate changes of several MR parameters (T1, T2 and ADC) before and after compression in human cartilage samples using unique microimaging compression system. Cartilage samples were prepared from joints of 10 patients, who underwent a total knee joint replacement. Study was performed on a Bruker 3T Medspec whole-body scanner (Bruker, Ettlingen, Germany) using BGA-12 micro-gradients with a special designed compression device built for this gradient system. Employing this equipment there is a possibility to reach accuracy of moving the compressive piston of 1/100 mm. T1 mapping was performed by the inversion recovery spin echo pulse sequence, for T2 mapping a multi-echo multi-slice spin echo sequence was used and ADCs were calculated from data collected from pulsed gradient spin echo (PGSE), all before and after compression. Fitting routines were written in IDL using mpcurvefit routine. Equipment for cartilage compression evaluation seems to be feasible for studying influence of static compression on cartilage tissue. Significant changes of T1, T2 and ADC parameters during compression were found. Biochemical imaging provided by multi-parametric MR improves biomechanical studies of articular cartilage.

Keywords: MRI, cartilage, biochemical testing

Kavitha A.,  Ramakrishnan S.:

Assessment of Human Red Blood Cell Aggregation Using Image Processing
and Wavelets

Abstract:  Aggregation of red blood cells which manifests in the form of rouleaux is a major determinant of flow behavior of blood in both micro and macro circulation. Any alteration in the normal behavior is found to be a critical factor in plugging of arterioles and venules forming irreversible clumps. In this work, the aggregation behavior of red blood cells is analyzed using Wavelet transforms. The artificially induced red cell aggregate images obtained from normal adult volunteers are used for the study. An arbitrary aggregation size index is derived using four different wavelet functions. The results demonstrate the ability of wavelets to precisely differentiate variations in degree of aggregation and their intercellular bonding. Also the aggregation size indices are found to be similar and consistent for a given aggregate for all wavelet functions. As the association and dissociation of red cells and the bonding strength during cluster formation are direct indicators of altered flow behavior of red cells in micro-vessels and large arteries such analysis seems to be clinically relevant. The methodology, algorithm and observations based on Wavelet transforms are discussed in detail.
Keywords: Red cell aggregates, Wavelet Transform, inter- erythrocytic cohesive forces, aggregation index

 No. 6

Hebláková E., Turzová M., Švehlíková J., Tyšler M.:

Model-based Assessment of Local Ischemia - Criteria for Localization Credibility

Abstract: A method for noninvasive identification of local ischemic lesions from difference integral (DI) maps, based on dipolar representation of the lesion, was previously reported. Aim of this study was to find some criteria enabling to recognize DI maps representing large or multiple ischemic lesions when the dipole-based method is not suitable for ischemia localization and to estimate the level of noise in DI maps. One or two simultaneous ischemic lesions with different sizes and positions in the myocardium were modeled and corresponding DI maps were computed and contaminated by various degree of random noise. Relative difference between square values of dipole and dipole-and-quadrupole residual maps (shares of DI maps not represented by a dipole or dipole and quadrupole) was proposed to identify large or multiple lesions while mean square value of gradients in dipole residual maps was proposed to estimate the noise level. According to our simulations, these criteria can help to estimate the credibility of the noninvasive assessment of local ischemia.

Keywords: body surface potential mapping, dipole model of cardiac generator, noninvasive assessment of ischemic lesions

Portable Device for High Resolution ECG Mapping

Abstract: Portable device for multi-channel ECG measurement and body surface potential (BSP) mapping is introduced and its possible application for cardiac diagnostic is presented. The device is designed for simultaneous measurement of up to 144 body surface potentials relatively to a relocatable reference electrode. Use of active electrodes, driven grounding electrode and battery operation of the device facilitate optimal signal quality.
Microprocessor controlled data acquisition unit is placed in a patient terminal and connected to the USB port of a hosting personal computer through an optical extension cable that minimizes capacitive coupling and guarantees high level of patient safety. Modular software for ECG recording and monitoring and for off-line ECG processing and BSP mapping was developed in Matlab environment. The device was used for testing of non-invasive identification of local ischemic lesions based on maps of BSP integrals and on dipolar model of the cardiac electric generator.
Keywords: multi-channel ECG measuring system, active ECG electrodes, body surface potential mapping, noninvasive identification of ischemic lesions.