Method and system for converting paper ECG printouts to digital ECG files

1. A method for digitizing a two-dimensional ECG chart, comprising:

scanning the ECG chart, said ECG chart including an ECG wave, the ECG wave appearing on a background grid, the grid having generally horizontal and generally vertical grid lines;

detecting the background grid;

determining the number of pixels between grid lines; and

scaling a vertical axis of the scanned ECG chart in units of volts per pixel and scaling a horizontal axis of the scanned ECG chart in units of time per pixel.

2. The method of claim 1 , comprising the further step of detecting and correcting for tilt in the grid lines.

3. The method of claim 1 , comprising the further step of finding the location of each image pixel relative to the vertical axis as a function of the position of that image pixel relative to the horizontal axis.

4. The method of claim 3 , wherein the location of each image pixel relative to the vertical axis represents a voltage value and the location of each image pixel relative to the horizontal axis represents a time value.

5. The method of claim 4 , comprising the further step of storing data corresponding to the voltage of each image pixel as a function of time.

6. A computerized method of deriving a digital ECG waveform from a computer readable-file representing an optically-scanned ECG chart, said method comprising the processes of:

opening the computer readable-file representing the ECG chart;

displaying an image of the ECG chart;

selecting a portion of the displayed image of the ECG chart;

characterizing the displayed image;

detecting a plurality of grid lines appearing on the displayed image and being generally oriented in the horizontal and vertical directions; and

extracting and digitizing the ECG waveform appearing on the displayed image.

7. The method of claim 6 , wherein said characterizing process comprises at least one of inputting, selecting and confirming characteristics of the ECG chart corresponding to the displayed image.

8. The method of claim 7 , wherein said characteristics include one or more of paper speed and gain at which the ECG chart corresponding to the displayed image was produced, and the resolution with which the ECG chart corresponding to the displayed image was scanned.

9. The method of claim 6 , wherein said detecting a plurality of grid lines comprises one of a manual mode, a range mode, and an exact mode.

10. The method of claim 9 , wherein said manual mode comprises at least one of inputting, selecting and confirming input parameters of the ECG chart corresponding to the displayed image.

11. The method of claim 10 , wherein said input parameters include the paper speed at which the ECG chart corresponding to the displayed image was produced, the resolution with which the ECG chart corresponding to the displayed image was scanned, and the time interval represented by the distance between adjacent grid lines on the ECG chart corresponding to the displayed image.

12. The method of claim 11 , comprising the further process of mathematically deriving the distance in pixel units between adjacent grid lines.

13. The method of claim 9 , wherein said range mode comprises inputting a tolerance range for said detecting process.

14. The method of claim 9 , wherein said manual mode comprises selecting a region of the displayed image that includes a plurality of grid lines in each of the horizontal and vertical directions.

15. The method of claim 6 , further comprising the process of displaying one or more of the number of pixels between grid lines, the angle of the grid lines, and the reliability of the detecting process.

16. The method of claim 6 , wherein said extracting and digitizing process comprises:

selecting a region of the displayed image including at least a portion of the ECG waveform; applying a computer algorithm embodying an active contour and dynamic programming approach to derive a digitized ECG waveform.

17. The method of claim 16 , wherein said applying process includes representing the ECG waveform with an active contour having a vertical value corresponding to each horizontal pixel location within the selected region.

18. The method of claim 17 , wherein said applying process further comprises defining a cost function for at least the portion of the displayed ECG waveform within the selected region.

19. The method of claim 18 , wherein the solution to the cost function corresponds to a digital representation the displayed ECG waveform.

20. A system for deriving a digital ECG waveform, comprising:

a computer having a display, at least one storage device, memory, and at least one input device;

application software executable by said computer and being at least one of accessible to said computer and stored in said storage device or said memory of said computer, said application software configured for deriving a digital ECG waveform based upon an optically-scanned ECG chart;

an opening module enabling a user to open and display on said display the optically-scanned ECG chart;

a selecting module enabling a user to select a portion of the displayed image of the ECG chart;

a characterizing module enabling a user to characterize the displayed image;

a detecting module for detecting a plurality of grid lines appearing on the displayed image in both the horizontal and vertical directions; and

an extracting and digitizing module for extracting and digitizing the ECG waveform appearing on the displayed image.