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T Palko

Publications and source records attributed to T Palko.

12 recordsLinked to original sources
PubMed2002

The discrimination of stenosed carotid bifurcation models with smooth and irregular plaque surface. Part I. Laser and ultrasonic Doppler flow studies.

Irregular carotid lesion surface is considered as a factor increasing the risk of the cerebral embolism. The objective of the study was to investigate the possibility to distinguish models of stenosed carotid bifurcation with lesion irregularity on the basis of the properties of flow velocity distributions. Two groups of elastic replicas of carotid bifurcations with different stenosis degree were investigated. Each group consisted of three models with different severity of plaque surface irregularity and one with smooth wall. Velocity data were collected using a one-component laser Doppler anemometer (LDA) system and a pulsed Doppler flowmeter. The LDA velocity distributions and Doppler spectral broadening index, turbulence intensity index and coefficient of skewness were analysed. The lesion irregularity resulted in change of the size and/or shape of reversed/reduced flow areas and of the position of the jet with respect to those observed in a smooth wall model. The flow features observed in the ultrasonic Doppler spectra were generally coherent with the axial LDA velocity distributions. Doppler spectral parameters demonstrated different sensitivities to the severity of the wall irregularity, however, the complexity of curves of these indices versus time did not allow to draw decisive conclusions and implied use of a more sensitive tool of analysis.

Blood Flow Velocity↗
PubMed2002

The discrimination of stenosed carotid bifurcation models with smooth and irregular plaque surface. Part II. The multivariate statistical analysis of ultrasonic Doppler velocity data.

According to the conclusion of the first part of the paper the Doppler spectral indices were analyzed in a detailed manner to provide a means to differentiate bifurcation models with different irregularities. Autoregressive (AR) models using the Akaike FPE criterion were fitted to the curves of the spectral broadening index, turbulence intensity index and coefficient of symmetry. These curves were also submitted to the data reduction significant point extraction algorithm. The multivariate discriminant analysis was performed on parameter vectors containing coefficients of AR models, data reduction rate and data reduction error. The discriminant analysis allowed distinguishing models with the same degree of stenosis and different plaque surface characteristics on the basis of these vectors. The highest discrimination efficiency was observed for parameter vectors obtained from TBI and SKEW curves. The efficiency of discrimination was slightly higher for more severely stenosed models.

Algorithms↗
PubMed1998

Platform independent implementation of DICOM-based miniPACS.

Platform independence is an important issue for a software designed to run across a hospital environment which is practically always heterogeneous one. This paper presents a simple miniPACS solution designed over an existing Intranet (Internet limited to a local area network). Platform independence is achieved with Java programming language which allows resulting code to be executed on virtually all machines. System consists of a server application providing DICOM (Digital Imaging and Communications in Medicine) services and clients that can use these services over a TCP/IP connection. The server application is capable of an image storage and supports a query mechanism to allow access to stored data, thus the clients may perform two major functions: providing image data for archiving or image retrieval for viewing. Presented client application provides both these functions. It retrieves stored images for further processing and returns calculated results to the archive. The parts of the system are connected through a DICOM interface. Consequently the system architecture is open and any devices like scanners or viewing stations supporting specific DICOM services may be attached.

Humans↗
PubMed1993

Detection of fetal breathing and cardiac movements and rhythms in ultrasonic Doppler signal recorded on the surface of the maternal abdomen.

It is proposed to use information on the direction of reflector movement and extensive filtering in the detection of fetal breathing and cardiac movements in the ultrasonic Doppler signal recorded on the surface of the material abdomen. The method appears fairly insensitive to spurious signals and allows those of interest to be distinguished without any reference technique. A decision rule for breathing and cardiac rhythm detection, incorporating movement direction, amplitude, shape and periodicity criteria, is also proposed.

Female↗
PubMed1993

Effect of method and parameters of spectral analysis on selected indices of simulated Doppler spectra.

The sensitivity of Doppler spectral indices (mean frequency, maximum frequency, spectral broadening index and turbulence intensity) to the conditions of spectral analysis (estimation method, data window, smoothing window or model order) increases with decreasing signal bandwidth and growing index complexity. The bias of spectral estimate has a more important effect on these indices than its variance. A too low order, in the case of autoregressive modeling and minimum variance methods, and excessive smoothing, in the case of the FFT method, result in increased errors of Doppler spectral indices. There is a trade-off between the errors resulting from a short data window and those due to insufficient temporal resolution.

Arteries↗