MEASUREMENT SCIENCE REVIEW              Volume 6, Section 2                          Main Page   

SECTION 2                            Download and print the front cover  ->>  

 No. 1

Čarnický J., Chorvát Jr.D.:

Three-dimensional measurement of human face with structured-light illumination

Abstract: The potential of three-dimensional scanning with structured-light illumination was evaluated for measurement of human face geometry. The aim was to create virtual human face models from the data scanned on real people, and to characterize the precision of such measurements. The quality of scanning with structured light proved to be sufficient to let us quantitatively parametrize the human face for anthropometric purposes. Values resulting from the distance measurements between the selected landmarks on obtained models were in agreement with the published data.

Keywords:  3D scanning, structured light, face anthropometry

Doležal L., Hálek J.:

A new method of sonograph lateral resolution measurement using PSF analysis of received signal

Abstract:  A number of quality parameters of ultrasound image have been defined. Their objective and accurate measuring, however, is relatively difficult. This is why we have developed a complex system, based on the point reflector principle, which enables us to analyze the point spread function (PSF) and measure this way a number of significant image quality parameters at any point of the area being imaged. A measuring system was designed and a program was developed for evaluation of lateral spatial resolution (LR) by 6dB drop method, enabling measuring of this parameter in a defined image area with any step of object shift in space, adjustable from 0.01mm.

By this method, we are able to determine LR numerically and accurately at any point of the area being imaged by sonograph. It enables us to image this function by three-dimensional graphics, including basic statistical measuring parameters. The method is a significant part of the complex of measuring of qualitative sonograph parameters which will be introduced by the Czech Metrology Institute within statutory regular quality control of specified medical equipment in the Czech Republic.   

Keywords:   ultrasonography, PSF analysis, lateral spatial resolution

Bartusek K., Smekal Z.:

Processing of MR images weighted by relaxation time T2 to increase their resolution           

Abstract:  The paper deals with the possibility to increase resolution in a measured MR image weighted by relaxation constant T2 of nuclei in the sample via suppressing spin density weighting. This method of image processing is based on measuring the MR of images by the spin echo technique for two time values (TE) and on the calculation of their quotient.

Keywords:  MR images, relaxation times, spin density suppression

Novak R., Hana K.:

The Base Neuronal Model of the Critical Physiological Mechanisms that Underlie the Electrical Signals Measured on the Scalp

Abstract:  The article presents the basic neuronal model of the cortex, that in a great deal takes part in the creation of the EEG activity of the brain scanned from the surface of the scalp. The proposed submodel comes out from the real physiology and anatomy of the human brain and is the basic building stone of the complex thalamocortical model producing the resulting EEG activity of the brain. Another part of the article points to the deeper physiological - anatomical mechanisms, that are related to the creation of EEG activity of the brain.

Keywords:  EEG, cortex, basic neuronal model, brain

 No. 2

Martinka J., Kozlíková K.:

Age Dependence of the Vulnerability Index in Young People

Abstract:  Index of vulnerabilty is a parameter evaluating the risk of arrhythmia development, which is derived from isointegral maps of QRST interval (IIM QRST). Individual characteristics of isointegral maps are influenced by different factors such as age or sex, which contribute to the relatively high variability among measured parameters of IIMs in patients or control subjects. In our study we wanted to establish age dependence of vulnerability index on age when using the same subjects as controls as well as tests. We found a non-significant increase of indexes of vulnerability in the older group of subjects.

Keywords:  isointegral map, index of vulnerability, healthy subjects

Starčuk Z, Bartušek K, Hubálková H, Bachorec T,  Starčuková J, Krupa P.:

Evaluation of MRI artifacts caused by metallic dental implants and classification of the dental materials in use

Abstract: Metallic objects (dental fillings, crowns, fixed bridges etc.), now found in many patients, may become a reason for the patient’s ineligibility for MR examination because of safety or image artifact concerns. The severity of the MRI artifacts caused by these objects depends primarily on the material, shape, position and orientation of the object, MRI method applied, and the location of the tissues of interest. The purpose of this work is to demonstrate the artifacts and describe a method of measuring the relevant material properties and the results. A method for the measurement of magnetic susceptibility based on field distortion simulation and field mapping based on MRI is described. Objects made of several materials were tested experimentally and these results were checked against simulated results. It has been found that among the more than 100 dental materials currently in use there are highly paramagnetic materials (Ni-Cr or Co-Cr based alloys), in which B0 inhomogeneity effects dominate, as well as slightly diamagnetic materials (alloys of precious metals and amalgams), which may cause artifacts due to the RF field inhomogeneity arising from induced RF currents. Spatial mapping of these effects may give indication of potential hot spots in these objects.

Keywords: magnetic resonance imaging, artifacts, metallic implants, dental alloys, magnetic susceptibility

Kozlíková K., Martinka J., Bulas J.:

Extrema of QRST Isointegral Maps in Left Ventricular Hypertrophy

Abstract: Left ventricular hypertrophy may both increase or decrease values of time integrals in QRST isointegral maps (IIM). We wanted to find out the change of IIM QRST in hypertensive patients with and without LVH. We analysed IIM QRST of 38 hypertensive patients – 15 without and 23 with left ventricular hypertrophy (left ventricular mass 107 ± 11 g/m2 versus 158 ± 29 g/m2, p < 0.0001) and compared their data with 12 controls of comparable age. We found significantly decreased mean maxima and peak-to-peak values in patients with hypertrophy in comparison to controls (maxima: 72.4 ± 37.3 mV.ms versus 100.6 ± 18.9  mV.ms, p < 0.05; peak-to-peak: 100.5 ± 45.6 mV.ms versus 136.2 ± 24.4 mV.ms, p < 0.05).  Minima increased not significantly. Any significant changes in map extrema values were found neither between patients with and without hypertrophy, nor between “pure” hypertensives and controls. As both possibilities, i.e. increased and decreased IIM QRST values were published, this topic needs more detailed studies.

Keywords: ECG body surface mapping, isointegral map, QT interval, hypertension, hypertrophy

 No. 3

Tomašovičová N., Koneracká M., Kopčanský P., Timko M., Závišová V.:

Infrared study of biocompatible magnetic nanoparticles

Abstract:  Magnetic fluids mainly consist of nano sized iron oxide particles (Fe₃O₄ or g--Fe₂O₃) that are suspended in carrier liquid. In recent years, substantial progress has been made in developing technologies in the field of magnetic nanoparticles, microspheres, magnetic nanospheres and ferrofluids. Techniques based on using of these biocompatible magnetizable complex systems have found application in numerous biological fields. Generally, the magnetic component of the particle is coated  by a biocompatible polymer such as  PEG, PLA or polysacharids as dextran, although recently inoganic coatings such as silica have been developed. The coating acts to shield the magnetic particle from the surrouding environment and can also be functionalized by attaching carboxyl groups, biotin, avidin, carbodi-imide and other molekules. These molecules then act as attachment points for the coupling of cytotoxic drugs or target antibodies to the carrier complex. This review is focused on describing the infrared spectrosopy as method that allow to check starting materials and follow reactions while work is in progress. 

Keywords: magnetic nanoparticles, infrared spectroscopy, biomedicine

36-39

Hlavačka F., Horak F.B.

Modeling of human balance control with somatosensory deficit in lower leg

Abstract:  We analyzed postural responses to galvanic vestibular stimulation in subjects with lower leg sensory deficit and age-matched control subjects. The aim was to determine whether subjects with somatosensory deficit show a sensory substitution with compensatory increase in sensitivity to vestibular stimulation. The pulse of galvanic current with duration 6s and intensity to 1 mA was applied to standing subjects so that forward body tilt was induced. Body lean was measured by force platform as center of foot pressure (CoP). Body tilt increased proportionately with increasing galvanic vestibular stimulation intensity for all subjects. Subjects with peripheral neuropathy showed larger forward CoP displacement in response to galvanic stimulation than controls. The largest differences between subjects with somatosensory deficit and controls were at the highest galvanic intensities, indicating an increased gain of vestibular loop. Simulations from a proposed model of postural control including vestibular and somatosensory feedback suggests that the increase in body lean in response to galvanic current in subjects with somatosensory deficit could be reproduced only if central vestibular gain was increased when peripheral somatosensory gain was decreased.

Keywords: human posture, vestibular stimulation, sensory substitution, posture model

Klima J, Ščehovič R.

The field strength measurement and SAR experience related to human exposure in 110 MHz to 40 GHz

Abstract: The actual discussions about exposure to electromagnetic fields mainly consider the radiation in lower microwave frequency bands originating from mobile cellular base station and mobile phones. As these base station are often connected to the core network via microwave links at higher microwave frequencies, their environmental influences has to be considered, too. This paper therefore investigates the characteristics radiation of lower (110 MHz to 2 GHz) and higher (2 GHz to 40 GHz) frequency bands and in terms of regulatory and legal aspects and looking at the physical and technological boundary conditions.

Keywords: SAR, mobile phones, radiation

 No. 4

Krishnaveni V., Jayaraman S., Aravind S., Hariharasudhan V., Ramadoss K.

Automatic Identification and Removal of Ocular Artifacts from EEG using Wavelet Transform

Abstract:  The Electroencephalogram (EEG) is a biological signal that represents the electrical activity of the brain. Eye-blinks and movement of the eyeballs produce electrical signals that are collectively known as Ocular Artifacts (OA). These are of the order of milli-volts and they contaminate the EEG signals which are of the order of micro-volts. The frequency range of EEG signal is 0 to 64 Hz and the OA occur within the range of 0 to 16 Hz. If the wavelet based EOG correction algorithm is applied to the entire length of the EEG signal, it results in thresholding of both low frequency and high frequency components even in the non-OA zones. This leads to considerable loss of valuable background EEG activity. Though the detection of OA zones can be done by visual inspection, the OA time zones need to be given as input to the EOG correction procedure, which is a laborious process. Hence there is a need for automatic detection of artifact zones. This paper discusses a method to automatically identify slow varying OA zones and applying wavelet based adaptive thresholding algorithm only to the identified OA zones, which avoids the removal of background EEG information. Adaptive thresholding applied only to the OA zone does not affect the low frequency components in the non-OA zones and also preserves the shape (waveform) of the EEG signal in non-artifact zones which is of very much importance in clinical diagnosis.

Keywords: EEG, EOG, OA, Adaptive Thresholding

Šušmáková K.

Correlation Dimension versus Fractal Exponent During Sleep Onset

Abstract: This study was concentrated on changes of complexity of EEG signals during the sleep onset process and the comparison of sleep onset with relaxation. The ability of two complexity measures - correlation dimension D₂ and fractal exponent γ - to distinguish these slightly distinct states was examined. Both measures confirmed decreased complexity of EEG signals during sleep onset process, on the contrary the complexity during the relaxation slightly increased. 

Keywords: sleep onset, relaxation, EEG, correlation dimension, fractal exponent

Krakovská A., Štolc S.

Fractal complexity of EEG signal

Abstract:  The paper deals with the presence of exponential or power-law decay in the power spectra of electroencephalogram (EEG). About 2300 EEG time series recorded during relaxed wakefulness were analysed. The whole spectrum of EEG was studied and power-law decay of about 2.28 prevailing over the exponential falling off was established. Correspondence between spectrum power-law decay and correlation dimension estimated for EEG was also validated

Keywords:  sleep onset, relaxation, EEG, correlation dimension, fractal exponent

Teplan M., Krakovská A., Štolc S.

Short-term effects of audio-visual stimulation on EEG

Abstract:  In order to identify direct and transient changes in human cortex under influence of the training with audio-visual stimulation (AVS) various EEG measures were estimated. In the course of 2 months, 25 repetitions of a 20 min AVS program with stimulation frequencies in the range 2-18 Hz were applied to 6 healthy volunteers. EEG data were recorded from 6 head locations during relaxed wakefulness prior, during and after AVS. Entrainment as a direct reaction to AVS was well developed in majority of cases, being strongest in backward regions and spreading also to other cortex locations. Transient effects displayed significant decreases in beta and gamma bands across head locations, and increase of theta-1 and alpha-1 coherence in central cortex regions.

Keywords: electroencephalography (EEG), audio-visual stimulation (AVS), spectral power

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