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Novel Tool for Complete Digitization of Paper Electrocardiography Data

Figure 1

Figure 1
Standard ECG paper with the information from 12 leads printed as a function of time. The regions with the test pulse for one of the leads and the patient demographic information are shown in boxes. The patient demographic information itself is redacted to protect patient privacy.

Figure 2

Figure 2
Outline of the ECG Digitization Process. The optional steps of the process are represented by dashed boxes.

Figure 3

Figure 3
A histogram of the grayscale ECG image where the separation between desired signal component (lower pixel intensity) and the graphical grid (higher pixel intensity) is observed in the range 130–160. Empirically, we determined that a threshold in this region will ensure efficient removal of the graphical grid from the ECG image.

Figure 4

Figure 4
(a) Sample ECG paper image. (b) Result of the thresholding for grid removal on the image shown in (a). (c) Digitized ECG signal obtained from the columnwise pixel scan on the image shown in (b).

Figure 5

Figure 5
Plot showing paper ECG signal (black) and digitized ECG signal (blue) for one lead. Note the similarity in the two signals, and the graininess in the paper ECG signal.

Figure 6

Figure 6
Three features of the ECG waveform used in the clinical validation: PR interval, QRS interval, QT interval.