Objective: Ultrasound measurements of brachial arterial lumen dilatation following induced blood flow increase – brachial flow mediated dilatation (FMD) – describes endothelial function. FMD is known to have great differences in methods and variability. We therefore standardized the protocol and optimized instrumentation. Reproducibility was evaluated.

Methods: Room environmental conditions, positioning and preparation of subjects and instrumentation were defined. Subjects refrained from food, caffeine and exercise from the night before measurements. A stable, yet flexible, ultrasound probe holder and arm positioning/fixation device were used. Three sonographers investigated right brachial arteries of 35 healthy non-smoking young adults aged 23.8 (SD10.8) years on two separate occasions (Acuson Aspen, L7, 5–12MHz transducer). Blood flow was induced upon release of 5 minute fore arm cuff inflation (250 mmHg). Every third heart beat ECG-triggered DICOM still frames were captured on R-wave from start, 1 minute prior to forearm cuff inflation (250 mmHg), to 4 minutes after cuff release. Brachial lumen was measured continously with automated edge detection (Sonka, Brachial Analyzer, MIA, IA, USA). FMD was defined as % maximum lumen change after cuff release compared to start lumen diameter.

Results: For initial and replicates, the start lumen diameters were 3.88(SD0.64) and 3.89(0.65) mm; FMD’s 5.85(3.43) and 5.61(3.08)%. Mean paired difference between scans was 0.25(1.12)%: CV = 19.6%.

Conclusions: Standardization, stable setup of equipment and automated image analysis allow for consistent reproducible FMD measurements. Trial specific DICOM application protocols makes FMD fit for QAQC, applicable in multicentre studies on CVD risk and treatment regimens.