Doppler indices derived from the maximum frequency shift envelope

Derivation of the umbilical artery Doppler indices from maximum velocity envelope (bright yellow line contouring the waveform) as indicated by the white arrow heads. The vertical axis indicates the velocity scale, the horizontal axis indicates time.

S: peak-systolic velocity; D: end-diastolic velocity; A: temporal average of maximum velocity over one cardiac cycle; RI: resistance index; PI: pulsatility index.

Dotted horizontal double arrow red line = one cardiac cycle.

Courtesy of Dev Maulik, MD.

Graphic 73657 Version 7.0

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