M-Sequences Related to the Multifocal Electroretinogram: Identification of Appropriate Primitive Polynomials to Avoid Cross-Contamination in Multifocal Electroretinogram Responses

Ireland, Jillian M (2001) M-Sequences Related to the Multifocal Electroretinogram: Identification of Appropriate Primitive Polynomials to Avoid Cross-Contamination in Multifocal Electroretinogram Responses. MSc(R) thesis, University of Glasgow.

Abstract

The basis of multifocal ERG is the use of a decimated m-sequence for simultaneous and independent stimulation of many areas of the visual pathway. The purpose of this thesis is to investigate the effects of cross contamination from higher orders of the response. To examine the effects of cross contamination a series of primitive polynomials were found by constructing finite fields. The first order ERG response is formed by cross correlating the m-sequence with the physiological response. A second order response is formed by investigating particular flash sequences of the stimulation sequence and is formed by cross correlation of a second order m-sequence with the physiological response. Zech Logarithms were used to identify cross contamination between the various first and second order sequences. Tables of good and bad primitive polynomials were constructed for degree 12 to degree 16 and the effects of window length and decimation length examined. If we decimate the sequence into 128 areas, and look at a window of length 16, cross-contamination occurs in all sequences generated from primitive polynomials of degree less than or equal 12, but only 26% in the case of degree 14, and 5.6% for degree 16. Finally, selected good and bad primitive polynomials were used to generate decimated m-sequences for a multifocal electrophysiological experiment to demonstrate the practical effects of cross-contamination. Trace arrays showing uncontaminated discreet physiological responses from 61 individual elements were recorded using the example good primitive polynomial whereas additional waveforms were present on the trace array when the same experiment was repeated with a bad primitive polynomial. The use of finite field theory to generate primitive polynomials and zech logorithm analysis enables us to predict which primitive polynomials are suitable for m- sequence generation for multifocal electroretinography. Practical investigations support the theoretical analysis. This has important implications for developers of multifocal electrophysiology systems.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Additional Information: Adviser: Ian Anderson
• Keywords: Medicine, Ophthalmology
• Date of Award: 2001
• Depositing User: Enlighten Team
• Unique ID: glathesis:2001-76405
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 14:43
• Last Modified: 19 Nov 2019 14:43
• URI: https://theses.gla.ac.uk/id/eprint/76405