Improved analysis of brachial artery ultrasound using a novel edge-detection software system

Brachial artery ultrasound is commonly employed for noninvasive assessment of endothelial function. However, analysis is observer dependent and suscep tible to errors. We describe studies on a computerized edge-detection and w all-tracking software program to allow more accurate and reproducible measu rement. In study 1, three purpose-built Perspex phantom arteries, 3.00, 4.0 0, and 6.00 mm in diameter, were measured with the software. There was a me an bias of 11 mum (P < 0.001 at each level) between known and measured valu es; the mean resolving power of the software was estimated as 8.3 <mu>m. In study 2, the mean intraobserver coefficient of variation of repeated measu res of flow-mediated dilation (FMD) using the software (6.7%) was significa ntly lower than that for traditional manual measurements using the intima-l umen interfaces (24.8%, P < 0.05) and intima-media interfaces (32.5%, P < 0 .05). In study 3, 24 healthy volunteers underwent repeat testing twice with in 1 wk; the coefficients of variation for between-visit reproducibility of FMD and response to glyceryl trinitrate using the software were 14.7 and 1 7.6%, respectively. Assuming 80% power and an a of 0.05, eight subjects wit h matched controls would be required, in a parallel designed study, to dete ct an absolute 2.5% change in FMD. In summary, we have developed a semiauto mated computerized vascular ultrasound analysis system that will improve th e power of clinical intervention studies to detect small changes in arteria l diameter.