  Background: Impedance Cardiogram (ICG) has impressive number of applications
in healthcare. However, its wider adoption is excessively limited due to the
well recognized challenges in ICG delineation. We present a simple, adaptive,
and efficient method for the most demanding ICG delineation task - detection of
less distinct B-point that marks the onset of the left ventricular ejection.
Method: The core of the new method is transformation of ICG time series by
weighted time window of an ICG segment preceding the maximal ICG peak (the
C-point) aiming at the B-point enhancement. The resulting Modified B-point
(MB-point) is then easily delineated. To evaluate the proposed workflow, the
dataset comprising 20 healthy participants and 21065 B-points are manually
annotated and openly shared with the software code. To the best of our
knowledge, our ICG dataset has the largest number of annotated B-points.
Detector performance is evaluated on two recorded segments with distinct
noises, as well as on an open dataset comprising ICG recorded in another set of
24 healthy subjects. Results: The results showed that the method was superior
to the competing methods when the tolerance for B-point detection was set to
+/-150 ms in all cases and for both datasets (>99.4%). Conclusions: Proposed
approach based on the weighted time windows presents a promising technique for
reliable ICG delineation that is instrumental for appropriate feature
extraction and ICG characterization. Further customization could incorporate
labeling of other pathological ICG segments, other biomedical signals, as well
as additional enhancements for improving robustness to noise.
