Cheng-Tung Ku

Wavelet-Based ECG Data Compression System With Linear Quality Control Scheme

Maintaining reconstructed signals at a desired level of quality is crucial for lossy ECG data compression. Wavelet-based approaches using a recursive decomposition process are unsuitable for real-time ECG signal recoding and commonly obtain a nonlinear compression performance with distortion sensitive to quantization error. The sensitive response is caused without compromising the influences of word-length-growth (WLG) effect and unfavorable for the reconstruction quality control of ECG data compression. In this paper, the 1-D reversible round-off nonrecursive discrete periodic wavelet transform is applied to overcome the WLG magnification effect in terms of the mechanisms of error propagation resistance and significant normalization of octave coefficients. The two mechanisms enable the design of a multivariable quantization scheme that can obtain a compression performance with the approximate characteristics of linear distortion. The quantization scheme can be controlled with a single control variable. Based on the linear compression performance, a linear quantization scale prediction model is presented for guaranteeing reconstruction quality. Following the use of the MIT-BIH arrhythmia database, the experimental results show that the proposed system, with lower computational complexity, can obtain much better reconstruction quality control than other wavelet-based methods.

A Novel ECG Data Compression Method Based on Nonrecursive Discrete Periodized Wavelet Transform

In this paper, a novel electrocardiogram (ECG) data compression method with full wavelet coefficients is proposed. Full wavelet coefficients involve a mean value in the termination level and the wavelet coefficients of all octaves. This new approach is based on the reversible round-off nonrecursive one-dimensional (1-D) discrete periodized wavelet transform (1-D NRDPWT), which performs overall stages decomposition with minimum register word length and resists truncation error propagation. A nonlinear word length reduction algorithm with high compression ratio (CR) is also developed. This algorithm supplies high and low octave coefficients with small and large decimal quantization scales, respectively. This quantization process can be performed without an extra divider. The two performance parameters, CR and percentage root mean square difference (PRD), are evaluated using the MIT-BIH arrhythmia database. Compared with the SPIHT scheme, the PRD is improved by 14.95% for 4lesCRles12 and 17.6% for 14lesCRles20

A linear quality control design for high efficient wavelet-based ECG data compression

In ECG data compression, maintaining reconstructed signal with desired quality is crucial for clinical application. In this paper, a linear quality control design based on the reversible round-off non-recursive discrete periodized wavelet transform (RRO-NRDPWT) is proposed for high efficient ECG data compression. With the advantages of error propagation resistance and octave coefficient normalization, RRO-NRDPWT enables the non-linear quantization control to obtain an approximately linear distortion by using a single control variable. Based on the linear programming, a linear quantization scale prediction model is presented for the quality control of reconstructed ECG signal. Following the use of the MIT-BIH arrhythmia database, the experimental results show that the proposed system, with lower computational complexity, can obtain much better quality control performance than that of other wavelet-based systems.

A Modified Run-Length Coding for the Realization of Wavelet-based ECG Data Compression System

With high compression performance, realization of wavelet-based data compression system is crucial for multi-lead ECG signal recording. In this paper, a modified run-length coding (MRLC) algorithm associated with an efficient quantization scheme is proposed for the realization of a RRO-NRDPWT-based ECG data compression system. The MRLC with regularity and low computational complexity is suitable for hardware implementation at a cost of compression performance. This sacrifice will be compensated by the new quantization scheme. By using the MIT-BIH arrhythmia database, the experimental results show that the proposed scheme can be competitive to other wavelet-based approaches in compression performance. In addition, the MRLC can improve traditional run-length coding by about 13%.

A Modified Run-Length Coding towards the Realization of a RRO-NRDPWT-Based ECG Data Compression System

The wavelet-based approach that combines a reversible round-off nonrecursive discrete periodized wavelet transform (RRO-NRDPWT) and the set partitioning in hierarchical trees (SPIHT) scheme is an efficient ECG data compression. However, this RRO-NRDPWT-based system suffers from the high complexity of the SPIHT scheme during realization. In this paper, a modified run-length coding (MRLC) algorithm is proposed towards the realization of a RRO-NRDPWT-based ECG data compression system. The MRLC with its regularity and low computational complexity is suitable for hardware implementation, but at a cost of compression performance. This sacrifice is compensated by an efficient quantization scheme. By using the MIT-BIH arrhythmia database, the experimental results show that the proposed scheme can compete with the SPIHT scheme for a compression ratio (CR) greater than 8. Hardware simulations are taken using both the Verilog logic simulator with Cadence design platform, and a Xilinx FPGA EP2C35F672C6.

Wavelet octave energy for breast tumor classification on sonography : A new shape feature

Infiltrative nature of lesions is a significant feature of malignant breast lesion in ultrasound images. Characterizing infiltrative nature is crucial for the realization of computer-aided diagnosis system. In this study, the infiltrative nature is regarded as an energy that produces irregularly and considerably local variances in a 1-D signal. The local variances can be enhanced by few high octave energies in 1-D discrete periodized wavelet transform (DPWT). A test dataset of breast sonograms with the lesion contour delineated by an experienced physician and two inexperienced students are built for feature efficacy evaluation. A high individual performance result implies that the proposed feature is well correlated with radiologists perception and closer to match those in trained physician than morphometric parameters. Experimental results also reveal that with a great performance improvement, the proposed feature is suitable for the combination with some morphometric parameters.

Realization of RRO-NRDPWT-based ECG signal compression with modified run-length coding

With high compression performance, realization of wavelet-based data compression system is significant for multi-lead ECG signal recording. In this paper, we proposed a modified run-length coding (MRLC) algorithm associated with an efficient quantization scheme for the realization of a RRO-NRDPWT-based ECG data compression system. The MRLC has the characteristics of regularity and low computational complexity which make it a suitable for hardware implementation at a cost of compression performance. This compromise will be compensated by the new quantization scheme. By using the MIT-BIH arrhythmia database, the experimental results show that the proposed scheme can be competitive comparing to other wavelet-based approaches in compression performance. In addition, the MRLC can improve traditional run-length coding by about 13%.

A fast quality-on-demand algorithm for wavelet-based electrocardiogram signal compression

In this paper, a fast quality-on-demand (QOD) algorithm for wavelet-based electrocardiogram (ECG) signal compression is proposed. The algorithm based on the 1-D reversible round-off non-recursive discrete periodized wavelet transform (1-D RRO-NRDPWT) and an approximately linear compression performance design to build a linear prediction model for quantization scale refinement. The convergence of quality control is verified to be always held. By using the MIT-BIH arrhythmia database, the experimental results show that the proposed method can effectively improved the computational complexity and convergence speed of quality control.

A High Efficient Quality Control Strategy for Wavelet-Based ECG Data Compression System

Maintaining retrieved signal with desired quality is crucial for ECG data compression. In this paper, a high efficient quality control strategy is proposed for wavelet-based ECG data compression. The strategy is based on a modified non-linear quantization scheme that can obtain a linear distortion behavior with respective to a control variable. The linear distortion characteristic supports the design of a linear control variable prediction algorithm. By using the MIT-BIH arrhythmia database, the experimental results show that the linear control variable prediction method can effectively improve the convergence speed than the previous literatures.

A single-variable non-linear quantization scheme for wavelet-based ECG data compression

In this paper, a non-linear quantization scheme with single control variable is proposed for wavelet-based ECG data compression. This scheme provides high and low octave coefficients with small and large decimal quantization scales, respectively. This method is based on the association of non-recursive 1-D discrete periodized wavelet transform (1-D NRDPWT) and a reversible round-off linear transformation (RROLT) theorem. The use of 1-D NRDPWT and RROLT is to resist error propagation effect and normalize the significance of octave coefficients, respectively. The two error control mechanisms can effectively reduce the searching area of quantization scales in an 11-D grid space. By using the MIT-BIH arrhythmia database, the experimental results show that this new approach can obtain a superior compression performance, particularly in high CR situations.