A system and method for more efficient data compression is provided, being particularly applicable to use in battery powered devices where there is a premium on minimizing the steps required and the amount of memory that must be dedicated to the task. The invention utilizes the technique of determining a delta or difference between each successive sample of the signal and the prior sample; examining the delta signals for a block comprising a predetermined number of such delta signals; determining the largest absolute delta value; determining the number of bits required to store such largest delta; and then storing both the determined number of bits and each delta value which is encoded with such determined number of bits. The block size is chosen to correspond to the type of signals being processed, and for typical medical applications is selected as a size within the range of 5-12 samples. The compressed data can be efficiently transmitted, such as from an implanted medical device to an external receiver, and decompressed by algebraically adding each delta to the value of the prior sample to recreate the respective samples and the signal.

System and method for compressing digitized signals in implantable and battery powered devices

http://diec.unizar.es/~laguna/personal/publicaciones/klnoise.pdf

ECG signal compression plus noise filtering with truncated orthogonal expansions

Data acquisition systems for non periodic signal with real-time data compression

To provide more convenient and comprehensive medical monitoring, especially to the out-of-hospital patients, this paper describes the implementation of a novel clustered real-time remote monitoring system. The manufacture of portable terminal device and development of hospital monitoring center system are introduced in detail. In addition, all-around tests are made to the whole system. The experimental results indicate that the system can afford a long-term, real-time and continuous monitoring and accurate positioning to multiple patients simultaneously. An automatic diagnosis can also be undertaken. It presents a good clinical application prospect.

A Clustered Real-Time Remote Monitoring System for Out-of-Hospital Cardiac Patients

Long-term ECG monitoring demands a bit rate of around 200 bps with acceptable distortion. Vector quantization (VQ) techniques allow one to reach that performance, despite the high computational effort. The most time-consuming stage in the VQ is the search for the best vector in the codebook, and, as a result, this makes real-time implementation infeasible. This paper evaluates the compression of ECG data using VQ with some techniques to optimize the searching for the best vector. The algorithm based on those techniques can be implemented in real-time using low-cost microprocessors. We have evaluated the VQ of the ECG signal and its first-difference using several codebook sizes. The results obtained are good enough to permit a real-time implementation. >

ECG data compression with vector quantization using k-dimensional tree for fast search

After having analyzed the recent electrocardiogram (ECG) data compression techniques, three algorithms (TRIM, AZTEC-VT, SAPA-2), which can be implemented on a real-time ambulatory ECG recording system, have been tested. The most suitable methods for reconstruction of the compressed signal have also been investigated. Particular attention has been paid to the definition of the performance indexes. Considerations on the filtering power of the algorithms have been made, using an ECG signal synthesizer. The results show that while TRIM and SAPA-2 may be considered at the same level, AZTEC-VT does not achieve similar performance. It is convenient to give a preference to SAPA-2, for online processing, because TRIM requires the input of four dimensional parameters in order to adapt the algorithm to the signal, while SAPA-2 requires only one input parameter. It is concluded that compression algorithms, considering processing time, compression ratio and the error introduced, allow performance that is adequate for real-time data compression in new generation Holter systems. >

G. Bortolan

Papers

Evaluation of algorithms for real-time ECG data compression