Color Doppler velocity accuracy proximal to regurgitant orifices: influence of orifice aspect ratio.

Many noninvasive methodologies used for the accurate evaluation of valvular regurgitation require precise velocity measurements from ultrasound instruments. Previous studies have indicated that velocity measurements from color Doppler (CD) instruments are susceptible to errors due to the interaction of the ultrasound beam and the proximal orifice flow field. This study examined the influence of high aspect ratio (AR) orifices on the CD velocity error. Center line velocity error distributions for orifices ranging from 7.07 to 78.5 mm2, varying in shape from circular to an AR = 8 ellipse, were evaluated using a numerical model of the ultrasound beam and the simulated regurgitant flow field. An in vitro study was also performed and confirmed the findings of the numerical model. The study showed that increasing AR does not significantly change the error characteristics. The study confirmed that orifice size is the dominant factor in the error distribution, and that corrections speculated for circular orifices can be extended to elliptical orifices without significant errors.