Original article infants were on continuous positive airway pressure (CPAP). No scan was complicated by signiﬁcant desaturation, brady- cardia or hypothermia. PC imaging – external validation Quantiﬁcation of ﬂow in an external phantom by optimised PC sequences was highly correlated with actual ﬂow (r2=0.995, ﬁgure 2). PC imaging – normal ranges and repeatability Optimised PC sequences were performed in 28 stable infants, with normal echocardiograms and proven ductal closure. Images of sufﬁcient quality for quantiﬁcation of LVO, SVC and DAo ﬂow were obtained in all 28 infants, images of sufﬁcient quality for quantiﬁcation of RVO were obtained in 22 infants. The 28 infants had median birth weight 1856 (965–4140) g, birth gestation 33 (28–41) weeks. At scan postnatal age was 10 (2–22) days, weight 2055 (1015–4140) g, gestation 34 (29–41) weeks. Seventeen infants had been admitted to the neonatal unit, 11 were term or near-term infants on the postnatal ward. One infant was receiving supplemental oxygen at the time of the scan; no infant was on CPAP. Mean and SD of LVO, RVO, and SVC and DAo indexed to weight are shown in table 1. LVO (p=0.005), RVO (p=0.11), Figure 2 Regression plot of external validation of phase contrast ﬂow quantiﬁcation versus ﬂow phantom. Line of unity shown. Figure 3 Normal ranges by corrected gestational age at scan for phase contrast assessment of left ventricular output (A), right ventricular output (B), superior vena caval ﬂow (C) and descending aortic ﬂow (D). F88 Arch Dis Child Fetal Neonatal Ed 2011;96:F86–F91. doi:10.1136/adc.2010.189142