Fig. 3

Carotid ultrasound velocity waveform with landmarks used to compute the features. The peak systolic velocities (PSV) are indicated with red crosses. The systolic foot velocities (SFV) are marked with green crosses and divide the waveform into individual beats. The secondary systolic peaks (P2) are indicated with pink crosses. Yellow crosses indicate the dicrotic notch (DN). The dashed line indicates the mean velocity value over the entire velocity waveform (V_mean). The systolic flow time (T_syst), indicated by the thick, short, blue arrow, is the time from the SFV until the DN. The cycle time (T_cycle) is the duration of one heartbeat, indicated by the thick, long, blue arrow. The thin, purple arrows within the right beat indicate the full-width half-maximum (FWHM, bottom arrow) and full-width at 75% of the maximal amplitude (FWQ3, upper arrow). The dotted, light-blue arrows indicate the rise time (Trise, short arrow, from SFV to PSV) and fall time (T_fall, long arrow, from PSV to SFV). DN: dicrotic notch, FWHM: full-width half-maximum, FWQ3: full-width at 75% of the maximal amplitude, P2: secondary systolic peak, PSV: peak systolic velocity, SFV: systolic foot velocity, T_cycle: cycle time, T_fall: fall time, T_syst: systolic flow time, T_rise: rise time