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Peak systolic velocity, resistance index and pulsatility index. Variations in measuring a pre-recorded videotape
R H Mikkonen1, J M Kreula, P J Virkkunen
1Department of Radiology, University Central Hospital, Helsinki, Finland.
Purpose:
To study variation in the process of measuring Doppler ultrasound (US) wave forms.
Material And Methods:
Eleven radiologists measured peak systolic velocity (PSV), resistance index (RI), and pulsatility index (PI) from a pre-recorded videotape. The wave forms were taken from the carotid, brachial, celiac, and renal interlobar arteries in a healthy volunteer. Each radiologist obtained measurements 10 times from a freely chosen wave form of 10 wave forms (10-beat series) and then a further set of measurements also 10 times from a specific wave form (1-beat series).
Results:
There was a significant variation in all the PSV, RI and PI values measured, both in the 1-beat series and in the 10-beat series. The greatest variation was seen in the PI values: up to 5.1-fold. Both intraobserver and interobserver reproducibilities were poor.
Conclusion:
The process of obtaining measurements from an identified wave form is a major source of error in Doppler US studies. Special attention should be paid to this final phase of an examination. We recommend that measurements be obtained from more than one heart beat.