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1

Accuracy of the electrodes location method for simultaneous SPECT and EEG examinations

Kowalczyk L., Goszczyńska H., Zalewska E.

Biocybernetics and Biomedical Engineering

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2015

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Vol. 35, no. 3

176--184

EN

A simultaneous SPECT and EEG examination allows for a combined analysis of brain structural and functional changes. The examinations can be visualized as 3D maps of overlapping SPECT (radiopharmaceutical concentration) and EEG (bioelectric potential) data. Synchronization of both maps is difficult, as SPECT shows neither the skull outline nor the EEG electrodes. Thus a technique to reflect electrodes placement in SPECT data was needed. Earlier we devised a method to make a small number of electrodes visible in SPECT without compromising SPECT accuracy. We also proposed a procedure approximating coordinates of the 10–20 system EEG electrodes in a 3D space using only 5 electrodes coordinates, while assuming that all electrodes are placed on 9 intersecting ellipses. Here we used 20 phantoms of real heads from the BrainWeb project and the Oostenveld calculation of electrodes canonical placement in an averaged head model. We divided the electrodes placement error into an easy-to-assess ‘‘distance error’’ (distance from the head surface) and a difficult-to-assess ‘‘angular error’’ (a wrong direction in relation to the symbolic head center). Applying our procedure to the Oostenveld data set, we assessed the ratio between the distance and the angular error and showed that a majority part of the entire approximation error results from the distance error. Our approximation procedure was applied to the BrainWeb phantoms and the distance error was computed allowing estimation of the entire error of electrodes placement. The estimated average error of the electrodes coordinates' approximation procedure was 4.2 mm and the maximum error was 15.4 mm.

2

Histograms of selected EEG maps sequences

Goszczyńska H., Podsiadły-Marczykowska T.

Journal of Medical Informatics & Technologies

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2011

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Vol. 18

19--27

EN

The aim of the study was analysis of histograms of selected sequences of EEG maps to assess variability of isopotential areas. In clinical practice this variability is evaluated using visual inspection that is subjective and may be difficult in revealing of subtle differences. Variability of isopotential areas is manifested by changes of isopotential areas as well as changes of their topolocalisation. The histograms of total map areas include the information concerning the ispotential area variability, while histogram analysis of particular areas of map may be useful for evaluation of variability of isopotential areas configuration. Basing on the examples containing the period before, during and after generalized seizure activity, the variability of constellations of isopotential areas in EEG maps and related to that diversity of their histogram types were presented. The work includes examples of series of EEG map histograms with their statistical analysis and the description of method used for the quantitative assessment of the histogram series variability for the maps sequences containing seizure activity.

3

A method for densitometric analysis of moving object tracking in medical images

Goszczyńska H.

Machine Graphics and Vision

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2008

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Vol. 17, No. 1/2

69-90

EN

The aim of this work is to develop a method of automatic data collection for coronary blood flow estimation based on computer analysis of angiographic image sequences. In the methods of coronary flow measurements, apart from problems involving densitometric analysis, there is also the problem of cyclic movement of the measurement field, i.e. of an artery segment or part of the myocardium. The system of automatic artery segment tracking presented in this paper does not only reduce the "manual effort" of the operator to establish the region of interest in the frame sequence, but also makes it possible to plot a densitometric curve with the time resolution equal to that of the frame sequence. The algorithm thus implemented, based on a template matching method, makes it also possible to trace the results of automatic detection of some characteristic points within the structure of arteries and to correct any faulty matching. The incorporation of the movement trajectories obtained allows us to trace the movement of the part of the myocardium close to the characteristic points of the artery with the aim of estimating the degree of myocardium perfusion. This relatively simple algorithm is acceptable for routine clinical testing due to the short time of frame sequence analysis (few minutes) and its relatively small error (the maximum estimated error of the automatic analysis is less than 11%). The comparative analysis of the results obtained for the template matching algorithm based on several criteria of similarity failed to establish any specific criterion with regard to acceleration or matching accuracy.

4

Clinical study on the coronary flow measurements method based on coronarographic image sequences

Goszczyńska H., Kowalczyk L., Rewicki M.

Biocybernetics and Biomedical Engineering

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2006

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Vol. 26, no. 2

63-73

EN

Many studies concerning evaluation of the artery blood flow based on coronarographic images have been made. Application of the indicator-dilution technique allows calculation of absolute values of the blood flow in the coronary arteries based on the densitometric analysis of coronarographic image sequences under some specific conditions imposed on injections of the contrast medium and digital image sequences registration. This method is based on densitometric measurements carried out in two sequences of images of the same artery. The first sequence is recorded during the routine injection of the contrast, and the other is recorded during the slow test injection of the contrast with a reduced amount of the indicator. The method was tested on coronarographic images obtained in routine examinations in two groups of control patients. The comparative analysis of 18 patients indicates that there exists a moderate consistency between the results of this method and the clinical assessment. The results of our studies are strongly dependent on the accuracy of the measurements and the method of recording. Proposed method, tested on the model of artery and measurements obtained from coronarographic examinations of control groups of patients, provides grounds for future studies.