Summary
Objectives
: To develop a singular-spectrum analysis (SSA) based change-point detection algorithm
applicable to fetal heart rate (FHR) monitoring to improve the detection of deceleration
events.
Methods
: We present a method for decomposing a signal into near-orthogonal components via
the discrete cosine transform (DCT) and apply this in a novel online manner to change-point
detection based on SSA. The SSA technique forms models of the underlying signal that
can be compared over time; models that are sufficiently different indicate signal
change points. To adapt the algorithm to deceleration detection where many successive
similar change events can occur, we modify the standard SSA algorithm to hold the
reference model constant under such conditions, an approach that we term “base-hold
SSA”. The algorithm is applied to a database of 15 FHR tracings that have been preprocessed
to locate candidate decelerations and is compared to the markings of an expert obstetrician.
Results
: Of the 528 true and 1285 false decelerations presented to the algorithm, the base-hold
approach improved on standard SSA, reducing the number of missed decelerations from
64 to 49 (21.9%) while maintaining the same reduction in false-positives (278).
Conclusions
: The standard SSA assumption that changes are infrequent does not apply to FHR analysis
where decelerations can occur successively and in close proximity; our base-hold SSA
modification improves detection of these types of event series.
Keywords
Signal processing - computer-assisted models - statistical decision support techniques
- fetal heart rate - obstetrics