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Observer variability in volumetric blood flow measurements in leg arteries using duplex ultrasound
S T Hussain1, R E Smith, R F Wood
1Professorial Surgical Unit, Medical College of St. Bartholomew's Hospital, London, UK.
Insights
Duplex ultrasound
Area of Science:
- Vascular Ultrasound
- Hemodynamics
- Medical Imaging
Background:
- Duplex ultrasound's clinical utility is limited by variability in cross-sectional area (CSA) and time-averaged mean velocity (TAMeV) estimation.
- Accurate volumetric flow measurement is crucial for assessing vascular health.
Purpose of the Study:
- To determine inter- and intraobserver variation in volumetric blood flow measurements in the common femoral artery (CFA) and its branches (SFA, PFA).
- To assess the reliability of duplex ultrasound for hemodynamic monitoring.
Main Methods:
- Volumetric blood flow calculated as the product of TAMeV and CSA.
- Measurements taken at rest in the CFA, SFA, and PFA of 20 normal subjects.
- Inter- and intraobserver variability assessed for both CSA and TAMeV.
Main Results:
- The coefficient of variation for TAMeV was consistently higher than for CSA.
- Interobserver variation in blood flow was greater than intraobserver variation (e.g., 40.3% vs. 21.2% for PFA).
- Defined minimum detectable changes in volumetric flow (VQ).
Conclusions:
- Modern duplex Doppler equipment allows for reliable hemodynamic measurements using volumetric flow.
- Volumetric flow can be a dependable tool for monitoring patients pre- and post-intervention.
- The study quantifies variability, establishing a baseline for clinical application.
Abstract:
Duplex ultrasound volumetric flow measurements have not found a major clinical use because of variability caused by errors in estimating cross-sectional area (CSA) and in measuring time averaged mean velocity (TAMeV). We determined inter- and intraobserver variation in volumetric blood flow measured at rest in the common femoral artery (CFA) and its main branches, the superficial femoral (SFA) and profunda femoris (PFA) arteries, in 20 normal subjects. The product of TAMeV and CSA was taken as volumetric flow. The coefficient of variation of TAMeV was consistently greater than that of CSA. Interobserver variation for blood flow (16.2%, 20.2% and 40.3% for CFA, SFA and PFA, respectively) was larger than intraobserver variation (13.0%, 15.1%, 21.2%). In conclusion, these data define the minimum changes in VQ that can be realistically detected and indicate that, with modern duplex Doppler equipment, volumetric flow can be used as a reliable haemodynamic measure for monitoring patients before and after surgical or radiological intervention.