Quantification of left to right shunt in patent ductus arteriosus by color Doppler

Ultrasound is a reliable tool to diagnose patent ductus arteriosus in premature infants but no reliable noninvasive method exists to quantify ductal flow. The aim of this study was to quantify the size of the shunt via persistent ductus arteriosus from pixel counts in color Doppler flow images. A cotton band was placed around the ductus arteriosus of newborn lambs to adjust the magnitude of flow. For flow measurements, ultrasonic transit time flow probes were applied around the ascending aorta and ductus arteriosus. Twenty-four different flow states were attained in four newborn lambs. An Acuson Sequoia scanner equipped with a 7 MHz transducer was used to register Doppler data and images with maximal color distribution during diastole in the pulmonary artery longitudinal sections (PALS). Each image-pixel was matched with the color velocity bar and the pixels were assigned to the corresponding flow velocity. The total area showing color relative to the area of the PALS correlated well with the amount of ductal flow (r = 0.87, r(2) = 0.75, p < 0.001). When Qp/Qs was >1.4:1, more than 40% of the area in PALS in diastole exhibited color information. Similarly, the color pixel velocities squared correlated with the size of the shunt. Quantification of the percentage of pixels in a color Doppler registration via a computer-based analysis shows a high correlation with the size of ductal shunting.