Comparison among Short Time Fourier Transform and Continuous Wavelet Transform Techniques in Flash Erg Signals Processing

Abstract

Flash Electroretinogram signals are the electrical potentials that result from the stimulation of the retina layer of the eye with a flash light. The two main components of these signals, "a" and "b" waves, are great of significance in the evaluation of the retina layer. Therefore, different signal processing techniques are utilized. In this study, the analysis of ‘a’ and ‘b’ waves in the rod, maximum combined and cone responses of flash Electroretinogram signals recorded from healthy individuals have been performed by using the Short Time Fourier Transform and Continuous Wavelet Transform methods. In this context, it has been studied which method is more proper in determining the waves localizations. As a result of analyses, it has been determined that the Continuous Wavelet Transform is more successful for all three responses. In addition, it has been found that the localizations of the waves can be determined more accurately by using Coiflet, Gauss, Mexican hat and Morlet wavelets in rod and cone responses, and Morlet wavelet in maximum combined response.

Keywords

• Electroretinogram
• Continuous wavelet transform
• Short time fourier transform

Flaş ERG Sinyallerinin İşlemesinde Kısa Zamanlı Fourier Dönüşümü ve Sürekli Dalgacık Dönüşümü Tekniklerinin Karşılaştırılması

Abstract

Flaş Elektroretinogram sinyalleri gözün retina tabakasının flaş bir ışık ile uyarılması sonucu ortaya çıkan elektriksel potansiyellerdir. Bu sinyale ait iki temel bileşeni olan ‘a’ ve ‘b’ dalgaları retina tabakasının değerlendirilmesinde önem arz etmektedir. Bunun için farklı sinyal işleme tekniklerinden yararlanılmaktadır. Yapılan bu çalışmada sağlıklı bireylerden kaydedilen flaş Elektroretinogram sinyallerinin rod, maksimum kombine ve kon yanıtları kullanılarak Kısa Zamanlı Fourier Dönüşümü ve Sürekli Dalgacık Dönüşümü yöntemleriyle sinyallerin ‘a’ ve ‘b’ dalgaları analizi edilmiştir. Bu doğrultuda dalgaların lokasyonlarının tespit edilmesinde hangi yöntemin daha başarılı olduğu irdelenmiştir. Gerçekleştirilen analizler sonucunda her üç yanıtta da dalgaların analizi için Sürekli Dalgacık Dönüşümünün daha başarılı bir yöntem olduğu tespit edilmiştir. Bunun yanı sıra Sürekli Dalgacık Dönüşümünde rod ve kon yanıtları için Coiflet, Gauss, Meksika şapka ve Morlet dalgacıklarının, maksimum kombine yanıtı için ise Morlet dalgacığının kullanılması halinde dalgaların lokasyonlarının daha doğru bir şekilde tespit edebileceği saptanmıştır.

Keywords

• Sürekli dalgacık dönüşümü
• Elektroretinogram
• Kısa zamanlı fouirer dönüşümü

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