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  1. 1. Er.Abdul Sayeed / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 1, January -February 2013, pp.422-425 ECG Data Compression Using DWT & HYBRID Er.Abdul SayeedABSTRACT Signal compression is an important innovations and to stimulate readers to investigateproblem encountered in many applications. the subject in greater depth using the extensive setVarious techniques have been proposed over the of references provide in outside world.years for addressing the problem. In this projectTransform based signal compression is proposed. II. ELECTROCARDIOGRAMThis method is used to exploit the redundancy in ECG or EKG from the Germanthe signal. This Paper uses Wavelet and Hybrid Electrocardiogram is a transthoracic (across theTransform to compress the signals. The well thorax or chest) interpretation of the electricalknown that modern clinical systems require the activity of the heart over a period of time, asstorage, processing and transmission of large detected by electrodes attached to the outer surfacequantities of ECG signals. ECG signals are of the skin and recorded by a device external to thecollected both over long periods of time and at body. An ECG test records the electrical activity ofhigh resolution. This creates substantial volumes the heart. ECG is used to measure the rate andof data for storage and transmission. Data regularity of heartbeats, as well as the size andcompression seeks to reduce the number of bits position of the chambers, the presence of anyof information required to store or transmit damage to the heart, and the effects of drugs ordigitized ECG signals without significant loss of devices used to regulate the heart, such as asignal quality. pacemaker. The ECG device detects and amplifies A wide range of compression techniques the tiny electrical changes on the skin that arebased on different transformation techniques like caused when the heart muscle depolarizes duringDCT, FFT; DST &DCT2 were evaluated to find each heartbeat. At rest, each heart muscle cell has aan optimal compression strategy for ECG data negative charge, called the membrane potential,compression. Wavelet and Hybrid compression across its cell membrane.techniques were found to be optimal in terms ofcompression.Index Terms-ECG, Compression, DWT, Hybrid,MSE, PSNR, CR.I INTRODUCTION: Transmission techniques of biomedicalsignals through communication channels arecurrently an important issue in many applicationsrelated to clinical practice. These techniques canallow experts to make a remote assessment of theinformation carried by the signals, in a very cost-effective way. However, in many situations this Fig 2.1Schematic Representation of Normal ECGprocess leads to a large volume of information. The The above diagram shows the Schematicnecessity of efficient data compression methods for Representation of Normal ECG waveform. Abiomedical signals is currently widely recognized. normal heartbeat has P wave, a QRS complex and a This chapter introduces the compression of T wave .A small U wave is sometimes visible in 50Electrocardiogram (ECG or EKG) signals using to 75% of ECGDiscrete Wavelet Transform (DWT) and Hybridtransform. Although storage space is currently III ECG COMPRESSION TECHNIQUErelatively cheap, electronic ECG archives could Many existing compression algorithm haveeasily become extremely large and expensive. shown some success in ECGG compressionMoreover, sending ECG recordings through mobile ,however algorithm that produces betternetworks would benefit from low bandwidth compression ratios and less loss of data in thedemands. ECG signal compression attracted recovered data is needed. The techniques used forconsiderable attention over the last decade. compression of ECG image is basically DWT. This The main goal here is to provide an up-to- technique uses transformed based method whichdate introduction to this fascinating field; through helps to convert time domain to frequency domain.presenting some of the latest algorithmic 422 | P a g e
  2. 2. Er.Abdul Sayeed / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 1, January -February 2013, pp.422-425This conversion help to form mathematical co-efficient in matrix form. This conversion helps toform the mathematical coefficient in the matrixform. For an image, high frequency componentdetermines insignificant information and lowfrequency determines significant information hence,we illuminate high frequency components. Finally,an easy to use computer program will be written in“MATRIX LABORATORY (MATLAB)”,whichwill allow its user to compare various compressionschemes and analyze reconstructedelectrocardiogram and Electroencephalographyrecords though a graphic interface without detailedknowledge of the mathematics behind thecompression algorithm. Fig 3.2.1 Block Diagram of ECG Compression technique3.1 Data compression technique By compressing the ECG Image moreinformation can be stored & processed for future IV ECG COMPRESSION ALGORITHMevaluation. The first sub goal of this project has The algorithm used for compression isbeen to investigate different compression methods transform based. The various transform can be givento find a potential candidate for future platform. as followsCOMPRESSION REQUIREMENTS:-The 4.1 ECG Compression using Wavelet Transformstrategy for compressing data must fulfill the  Image Resizing: First we take a JPEGfollowing requirements:- image. After that compiler will read it. Then it Information preservation: Due to convert color image to grey scale image. Then thediagnostic restriction ,it is imperative that the image converted to square image having pixel [512*information found in the original data is preserved 512]after compression .  DWT: We apply wavelet transform to the Control of compression degree: Another resize image. It will decompose image intopreference is the ability to control the amount of approximate image , vertical, horizontal, diagonaldata compression. Recent information is preferably component. Again we apply DWT andstored in an data exact form with low degree of decomposition takes place This is called 2nd levelcompression .However , with older data a more decomposition so in all 3 level decomposition takesaggressive compression strategy is accepted. place. Then we take all images in one window. Then Complexity Issue: Due to limited we apply compression technique with respect toprocessing capacity of the pacemaker , an algorithm compression in %for compressing data has to have low complexity.  Inverse DWT: On the compressed imageThis fact rules out many compression technique apply IDWT then we get 2nd level IDWT image.involving extensive calculation, which could be This process is repeated again then we getpotential candidates in other circumstances. compressed DWT image  Calculation of Compression Ratio(CR)3.2 ECG Compression scheme & Percentage RMS Difference(PRD) The objective of this project is to obtain atime domain approximation of the ECG signal usingcompression scheme based on a new emergingmethod of transformation i.e “Wavelet Transform”& “Hybrid Transform” RMS Value=√ [∑ (Vi) 2]/N PRD = (RMS Error) ¤ (RMS Value) ´ 100 % Where Vi is the i-th ECG value in the input source,Ri is the i-th value in the re constructed waveform N values in total 423 | P a g e
  3. 3. Er.Abdul Sayeed / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 1, January -February 2013, pp.422-425 Calculation of PSNR & MSE: Depending meaning "small wave" was used by Morlet andon compression we calculate the Peak signal to Grossmann in the early 1980s. Wavelet theory isnoise ratio(PSNR) & Mean square ratio(MSE) applicable to several subjects. All wavelet transforms may be considered forms of time- frequency representation for continuous-time (analog) signals and so are related to harmonic analysis. Almost all practically useful discrete wavelet transforms use discrete-time filter banks. Display the result These filter banks are called the wavelet and scaling coefficients in wavelets nomenclature. These filter banks may contain either finite impulse response (FIR) or infinite impulse response (IIR) filters. The wavelets forming a continuous wavelet transform (CWT) are subject to the uncertainty principle of Fourier analysis respective sampling theory: Given a signal with some event in it, one cannot assign simultaneously an exact time and frequency response scale to that event. The product of the uncertainties of time and frequency response scale has a lower bound. One use of wavelet approximation is in data compression. Like some other transforms, wavelet transforms can be used to transform data, then encode the transformed data, resulting in effective compression.Fig 4.1.1ECG Compressed image using wavelet Suppose DCT is currently used for compressing data such as images (JPEG), Video (MPEG) and4.2 ECG Compression using Hybrid Transform Audio (MP3). However , it can be used for It is the combination of DCT & compressing medical signals such as ECG dataWAVELET Transform for better compression ratio. using original data x with N points DCT can beIn this method we first apply DCT on ECG image defined as follows:-which apply convers image into frequencycomponents. Then we apply wavelet transform on X(k)= (k) x(n) cos[ ]frequency components which helps to obtain precise 0< k < N—1mathematical coefficient in matrix form. Now we Where,apply compression by eliminating high frequencycomponents. , For 1< k< N—1 Using this equation, it is possible to transform the original signal into a spatial domain. By truncating the signal in the transformed domain and then Run- Length encode the signal, it is possible to achieve high degree of compression. VII. RESULT AND CONCLUSION In this paper , we have represented an effective ECG data compression Algorithm to be implemented in MATLAB based on newly developed mathematical tool i.e wavelet and hybrid transformation. There exist many algorithm schemes based on different transformation scheme so for reliability & existence of our presented algorithm, we have compared it with other compressionFig 4.2.1 ECG Compressed image using Hybrid algorithm such as DCT. To achieve our goal we have followed certain steps which include analyzingV. WAVELET TRANSFORM AND WAVELET & observing the different transform and analyzingFAMILY the following parameters CR, PDR,MSE, PSNR The word wavelet has been used for obtaining in MATLAB using three techniquesdecades in digital signal processing and exploration In such compression it is found that the waveletgeophysics. The equivalent French word ondelette compression technique is very effective compared to 424 | P a g e
  4. 4. Er.Abdul Sayeed / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 1, January -February 2013, pp.422-425 that of DCT compression method .since using which can be implemented to save expensive disk wavelet high degree of compression; we get good space and to allow efficient use of available result but for large compression percent6age ,there bandwidth for remote ECG analysis . Moreover it is still some distortion involved in it. But Hybrid provides Excellent Reconstruction of ECG signals transformation is proved to be the best among all the to be used by physicians for correct diagnosis of three because it has the property of both WAVELET heart diseases and efficient storage of such & DCT . Using this method it has been viewed with information . In these areas are system proves to be both subjective and calculation ; this method invaluable. provides best possible compression even for larger compression degree REFRENCES TABLE I. [I] DWT Hybrid wavelet-transforms-theory-Compression Compression compression andapplications/ecg-signal-compression-CR=90% CR=95% CR=98% using-discrete-wavelet-transform.PRD about 1% PRD less than 1% PRD [II] Lindgren A, Jansson S. Heart physiology minimum and Simulation. Solna, Sweden: Siemens- Algorithm Algorithm Algorithm Elema AB.Execution Tim 7sec Execution time Execution [IV] Abenstein JP, Tompkins WJ. Anew Data- 3sec time less Reduction Algorithm for Real-Time ECG Analysis. IEEE Transactions on Biomedical Engineering. In the TABLE II,III.IV an effort is taken to [VII] Furth B, Perez A. An Adaptive Real-time compare the MSE & PSNR of all the three ECG Compression sampling on human transform to understand better about the transforms electrocardiograms. Medical & Biological and their efficiency Engineering & computing. TABLE II. DISCRETE COSINE TRANSFORMCompression MSE(mean PSNR(peak In % square error) signal to noise ratio) 10 0.9 111.8 5o 47.33 72.3 99 1.22e+3 41.49 TABLE III . DISCRETE WAVELET TRANSFORMCompression MSE(mean PSNR(peak signal In % square error) to noise ratio) 10 5.2 94.18 50 41.19 73.64 99 112.7 63.57 TABLE IV . HYBRID TRANSFORMCompression MSE(mean PSNR(peak signal In % square error) to noise ratio) 10 0.9 94.18 50 47.33 73.64 99 1.22e+3 65 A Computer based ECG system are used in hospitals for collection of patients medical history for reviewing patients present condition and continuously monitor ECG of heart patients .For this requirement, as the disk space in computer is limited an effective solution over this is utilized which is compression of such ECG Data , thus storing compressed ECG data reduces disk space .Thus from the obtain result it can be concluded that ECG compression based wavelet transform and hybrid transform is most appropriate and efficient method 425 | P a g e