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[Computerized transformation of the cardiotocographic paper record to its digital equivalent for computerised
Objective:
To analyze cardiotocograph by computer, the tracings recorded in paper form must first be converted into their digital equivalent. We developed a method by which this process may be performed.
Methods:
Paper recordings were first scanned using a conventional flat bed scanner to obtain a digital image. Each image was firstly corrected for rotational misalignment error during scanning and, sceondly the grid was removed by performing logistic contrast enhancement to leave the discrete fetal heart rate and tocographic tracings. The method was validated by comparing differences between the fetal heart rate obtained from the paper record with that directly obtained from the fetal monitor.
Results:
Forty recordings were analyzed. The mean difference per recording between the actual and derived values ranged from -0.26(-)-1.26 beats per minute. The 95% confidence interval for the pooled differences between the derived and actual fetal heart rate values was--7-5 beats per minute.
Conclusion:
By using the techniques described in this paper, it is now possible to convert the large number of paper records available so that they can be analyzed by computerized cardiotocograph interpreters.