Analysis on Conversion Process from Paper Record ECG to Computer based ECG

Abstract

Introduction An ECG is simply a representation of the electrical activity of the heart muscle as it changes with time, usually printed on paper for easier analysis. Like other muscles, cardiac muscle contracts in response to electrical depolarization of the muscle cells. The sum of this electrical activity is amplified and recorded for just a few seconds that know as an ECG. The electrocardiogram (ECG) represents a graph of variation in electrical potential generated by the heart and recorded at the body surface. Recently, exchanging patients' clinical information between healthcare facilities has become very important. Measurements of parameters from electrocardiograms (ECGs) are still largely performed from paper ECG records. It will be very helpful, if plane paper type of ECG could be converted to digital form. At the same time, the new requirements justify the need for tools to convert existing paper ECG records into digital format, particularly for retrospective studies. A computer application was developed for the conversion of paper ECG records to digital ECG files [1-6]. In general, the background of ECG paper charts can be divided into three types: uniform background, background with colored grid and background with black grid. Electrocardiogram (ECG) signals are usually recorded onto standard grid papers in hospitals as a routine clinical examination for diagnosis of possible cardiac failure. There is a need to convert the existing ECG paper records into electronic forms for efficient retrieval for clinical uses. It is to be noted that printed ECG reports include some characters as well as annotations while taking an image of such ECG strips. It is desirable to remove these printed characters. Efficient noise removal and image enhancing algorithms are also required so as to increase overall digitization process accuracy [7-10]. This research work proposes an effective algorithm for extracting the digitized signal from ECG paper strips. A system prototype is designed to convert ECG paper records into electronic ECG recording forms so that they can be either efficiently retrieved as needed, or analyzed by ECG signal processing algorithms, or transmitted through computer networks for clinical purposes. In the research, the scanned binary images of ECG paper records are analyzed using image processing techniques, such as filtering and morphological procedures. The direction of digitizing the ECG paper records is referred in which morphological approach is used to remove the background grid and isolated pixels such as characters from the paper recorded ECG. System Description The ECG charts were scanned into images using a commercial A4 scanner with 600dpi gray scale settings. Before the operation, a region of interest is being defined that will help in reducing the processing time and much more it will allow a specific selection of a particular part of the waveform (Figure 1). The algorithm starts with reading an image and converts it from gray scale to binary image in order to prepare it for the binary morphological operation. A threshold is applied with image to binary conversion then the segments that are less than a specified number of pixels can be removed. The binary image is processed with a particular neighborhood morphological binary operation that will estimate the background of the image that will be subtracted from the selected image. The result image contains residual effects from the subtraction of the background. To reduce these effects, region based segmentation is applied. Then, the segments that represent the ECG wave and background are separated. Region based segmentation is applied for more isolated pixels that represent printed characters or noise reduction [8-12]. The final image will contain the waveform with minimal effect on the boundary. The next step is to smooth the boundary of the ECG wave with a binary morphological thicken. The final step is to convert the Abstract The capacity of electrocardiograms (ECG) recorded in hospital is increasing. Although modern electrocardiographs have digital output, most of ECG's are still recorded on grid papers. Recently, exchanging patients' clinical information between healthcare facilities has become very important. It will be very helpful if paper type of ECG could be converted to digital form. In this study, a morphological method is developed to digitize ECG signal from the paper charts. The results show that the method can erase the background noise and provide the digital ECG signal from ECG paper charts correctly. ECG signal digitization is practically used in ECG data exchanging between healthcare providers. Experimental results on sample ECG paper records are very encouraging and show the promise of efficiency in ECG data storage and retrieval and easy manipulation for clinical uses.