Measuring flow-mediated dilation through transverse and longitudinal imaging: comparison and validation of methods

Area of Science:

• Vascular Ultrasound
• Cardiovascular Imaging
• Biomedical Engineering

Background:

• Flow-mediated dilation (FMD) is a key indicator of endothelial function.
• Accurate and reproducible measurement of FMD is crucial for clinical and research applications.
• Traditional methods using longitudinal ultrasound images have limitations in precision and reproducibility.

Purpose of the Study:

• To compare the reproducibility and precision of different three-dimensional ultrasound imaging (3DUS) techniques for quantifying brachial artery FMD.
• To evaluate manual (TIMA) and semi-automated (TISA) vessel area measurements, and diameter measurements (TID) in transverse planes.
• To compare these transverse plane methods against the traditional longitudinal diameter measurement (LID).

Main Methods:

• 3DUS of the brachial artery was performed at baseline.
• Transverse images were analyzed using TIMA, TISA, and TID.
• Inter- and intra-observer variability, and transducer repositioning variability were assessed and compared to LID.

Main Results:

• All methods showed similar inter-observer variability.
• TID demonstrated the highest intra-observer precision (COV(intra)=0.31%, Δd(intra)=0.87%), while LID performed poorest (COV(intra)=0.57%, Δd(intra)=1.59%).
• TIMA (COV(rep)=2.35%, ΔFMD=6.52%) and TISA showed superior reproducibility over time compared to TID (COV(rep)=5.37%, ΔFMD=14.89%).

Conclusions:

• Transverse imaging planes offer equal or less variability than longitudinal planes for FMD assessment.
• TISA is recommended as the method of choice for FMD assessment due to its speed, simplicity, and high reproducibility, comparable to TIMA.
• Semi-automated measurement of vessel area in the transverse plane using 3DUS provides a reproducible and precise method for FMD quantification.