Biomedical subjects

N Nithiyanandam

Publications and source records attributed to N Nithiyanandam.

4 recordsLinked to original sources

PubMed1998

Genetic-algorithm cancellation of sinusoidal powerline interference in electrocardiograms.

The paper describes a method, based on a genetic algorithm, to remove sinusoidal powerline interference in electrocardiograms. There is a report on the use of the genetic algorithm to remove powerline interference for two different types of interference, powerline interference with frequency drift, and interference with frequency drift as well as third- harmonic distortion. The studies are conducted on electrocardiograms with simulated interference and also on actual noisy electrocardiogram records. The results obtained using the genetic algorithm in these cases of interference are presented.

Algorithms↗

PubMed1997

ECG compression and recognition using complete tree representation.

This paper deals with a novel method of Electrocardiogram (ECG) representation, compression and recognition using Complete Tree algorithm. The construction of Complete Tree is like overlaying a ECG waveform on a grid. The waveform is observed through the grid structure with vertical and horizontal grid lines. In addition to nodes created for each interval enclosed by that waveform on a quantisation level, nodes are also created for each point where the waveform cuts the vertical grid line between the current quantisation level and the next quantisation level. A leaf node represents the data sample of ECG at that position. For reconstruction of this ECG waveform, only the leaf nodes are used resulting in ECG compression. This representation is also useful in ECG pattern matching and recognition without reconstructing the original waveform. The ECGs with sampling rate of 500 sps are used. A compression ratio (CR) of 4.8:1 with percent RMS difference (PRD) of 8.45% is obtained. The reconstruction of original ECG waveform from its tree representation shows high fidelity in all its complexes of ECG. The results are compared with all other compression techniques such as AZTEC, TP, FAN, DPCM etc. By using Tree merging and splitting algorithms, the matching and recognition of ECG is implemented.

Algorithms↗

PubMed1997

Equivalent tree representation of electrocardiogram using genetic algorithm.

Electrocardiogram (ECG) gives the electrical activity of the heart. The number of data points required to represent the ECG signal is reduced by using a complete-tree representation. This reduced data structure (ECG Tree) is obtained by fitting the ECG signal in a grid structure consisting of both horizontal and vertical lines. The leaf nodes are the points where the vertical grid lines intersect with the ECG signal. These leaf nodes now form the features of the ECG signal. Some of these leaf nodes may be redundant and hence the reduction in the number of leaf nodes and thus optimization of the tree (equivalent tree) is done using a novel technique based on the Genetic Algorithm (GA). In this work, the equivalent tree is formed using GA consisting of four stages. First, from the group of generated leaf nodes various combinations of strings are constructed to form the population. Second, the fitness function is taken as the measure of the vertical distances between two neighbouring leaf nodes in order to evaluate the population with respect to their fitness values. Third, the selection procedure is used to give offsprings based on an assigned threshold value. Finally, crossover and mutation operations are performed repeatedly till an optimized population is obtained. The optimal nodes represent the equivalent tree. The Backpropagation Neural Network as a classifier is used to test the efficacy of the GA in this optimization problem.

Algorithms↗

PubMed1995

Integrating the ECG power-line interference removal methods with rule-based system.

The power-line frequency interference in electrocardiographic signals is eliminated to enhance the signal characteristics for diagnosis. The power-line frequency normally varies +/- 1.5 Hz from its standard value of 50 Hz. In the present work, the performances of the linear FIR filter, Wave digital filter (WDF) and adaptive filter for the power-line frequency variations from 48.5 to 51.5 Hz in steps of 0.5 Hz are studied. The advantage of the LMS adaptive filter in the removal of power-line frequency interference even if the frequency of interference varies by +/- 1.5 Hz from its normal value of 50 Hz over other fixed frequency filters is very well justified. A novel method of integrating rule-based system approach with linear FIR filter and also with Wave digital filter are proposed. The performances of Rule-based FIR filter and Rule-based Wave digital filter are compared with the LMS adaptive filter.

Algorithms↗