BULLETIN
of the
POLISH ACADEMY of SCIENCES TECHNICAL SCIENCES |
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Volume
53, Issue 3, September 2005
Biocybernetics, Bioengineering and Biotechnology |
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Aims&Scope, Subscription | Editors | Authors' guide | Vol 53-3 | mirror: http://fluid.ippt.gov.pl/~bulletin/ |
pp 223 - 229 |
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Analysis of bioelectrical signals of the human retina (PERG) and visual cortex (PVEP) evoked by pattern stimuli |
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K. PENKALA |
Purpose: to demonstrate the possibility of finding features reliable for more precise distinguishing between normal and abnormal
Pattern Electroretinogram (PERG) recordings, in Continuous Wavelet Transform (CWT) coefficients domain. To determine characteristic
features of the PERG and Pattern Visual Evoked Potential (PVEP) waveforms important in the task of precise classification and assessment of
these recordings. Material and methods: 60 normal PERG waveforms and 60 PVEPs as well as 47 PERGs and 27 PVEPs obtained in some retinal and optic
nerve diseases were studied in the two age groups (<= 50 years, > 50 years). All these signals were recorded in accordance with the guidelines
of ISCEV in the Laboratory of Electrophysiology of the Retina and Visual Pathway and Static Perimetry, at the Department and Clinic of
Ophthalmology of the Pomeranian Medical University. Continuous Wavelet Transform (CWT) was used for the time-frequency analysis and
modelling of the PERG signal. Discriminant analysis and logistic regression were performed in statistical analysis of the PERG and PVEP
signals. Obtained mathematical models were optimized using Fisher F(n1; n2) test. For preliminary evaluation of the obtained classification
methods and algorithms in clinical practice, 22 PERGs and 55 PVEPs were chosen with respect to especially difficult discrimination problems
(“borderline” recordings).
Results: comparison between the method using CWT and standard time-domain based analysis showed that determining the maxima and minima of the PERG waves was achieved with better accuracy. This improvement was especially evident in waveforms with unclear peaks as well as in noisy signals. Predictive, quantitative models for PERGs and PVEPs binary classification were obtained based on characteristic features of the waveform morphology. Simple calculations algorithms for clinical applications were elaborated. They proved effective in distinguishing between normal and abnormal recordings. Conclusions: CWT based method is efficient in more precise assessment of the latencies of the PERG waveforms, improving separation between normal and abnormal waveforms. Filtering of the PERG signal may be optimized based on the results of the CWT analysis. Classification of the PERG and PVEP waveforms based on statistical methods is useful in preliminary interpretation of the recordings as well as in supporting more accurate assessment of clinical data. |
Keywords: |
electrophysiology, visual system, Pattern Electroretinogram, PERG, Pattern Visual Evoked Potential, PVEP, Continuous Wavelet Transform, CWT, signal classification, discriminant analysis |
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Aims&Scope, Subscription | Editors | Authors' guide | Vol 53-3 |
Copyright
- Bulletin of the Polish Academy of Sciences: Technical Sciences
4 July 2005, site prepared by KZ |
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