Original article Figure 4 Bland-Altman plots of scan-rescan repeatability of assessment of left ventricular output performed by phase contrast (A) and cine (B) imaging, and of comparison of phase contrast and echo measures of left ventricular output (C). Table 1 Phase contrast measures of left ventricular output (LVO), right ventricular output (RVO) and superior vena caval (SVC) and descending aor- tic (DAo) ﬂow in 28 stable newborn infants LVO RVO SVC ﬂow DAo ﬂow SVC+DAo (ml/kg/min) (ml/kg/min) (ml/kg/min) (ml/kg/min) (ml/kg/min) Mean SD 222 45.8 219 46.9 95 27.0 Table 2 Repeatability of phase contrast measures of ﬂow in newborn infants n Limits of agreement (ml/kg/min) Repeatability index LVO 26 50.2 22.2% SVC ﬂow (p=0.03) and DAo (p<0.001) were lower at higher corrected gestational age (ﬁgure 3). Table 2 shows the number of infants studied, LOA and RI for scan–rescan PC measures of LVO, RVO, and SVC and DAo ﬂow indexed to weight within this group of 28 infants. Bland–Altman plot for scan–rescan repeatability of LVO by PC is shown in ﬁgure 4A. For most measures the scatter of the differences tends to increase as volume of ﬂow increases, such that the LOA may be slightly wider than necessary for lower ﬂows. Repeatability for LVO was similar when only preterm infants (<37 weeks) were included (n=13, LAO ±64.7 ml/kg/ min, RI 25.1%). Bland–Altman comparison of PC measures of combined systemic perfusion (SVC plus DAo ﬂow) versus LVO in 30 infants, with echocardiographic exclusion of pat- ent ductus arteriosus, showed mean difference 0.3 ml/kg/min, LOA ±46.7 ml/kg/min, RI 21.2%. Repeatability of analysis of LVO from a single PC sequence in 10 infants showed intra- observer RI 8.2%, inter-observer RI 8.3%. Analysis duration was 2–3 min per vessel. Cine imaging – normal ranges and repeatability SSFP stacks with optimised parameters were acquired in 82 stable infants, without clinical evidence of patent ductus arte- riosus. Thirty infants had proven ductal closure on echocar- diogram and no infant subsequently received treatment for a patent ductus arteriosus during their NICU admission. Of these 82 infants, 75 had SSFP stacks of sufﬁcient quality for analysis. These 75 infants had median birth weight 1886 (790–4140) g, birth gestation 33 (25–42) weeks. At scan postnatal age was 9 (1–73) days, weight 2192 (790–4140) g, gestation 35 (28–42) weeks. Forty-six infants had been admitted to the neonatal Arch Dis Child Fetal Neonatal Ed 2011;96:F86–F91. doi:10.1136/adc.2010.189142 126 32.1 RVO 9 55.5 22.5% 224 51.2 SVC 24 20.9 20.0% DAo 21 26.2 19.4% unit, 29 were term or near-term infants on the postnatal ward. Six infants were receiving supplemental oxygen at the time of the scan; one infant was on CPAP. SNR and CNR of the optimised SSFP images in 10 infants were SNRblood 50.2, SNRmyocardium 141.2; CNRblood-myocardium 91.0. Left ventricular functional parameters are shown in table 3. LVO was signiﬁcantly lower at higher corrected gestational age (p<0.001) (ﬁgure 5A). There was no signiﬁcant association between gestational age and left ventricular EDV (p=0.19), ESV (p=0.80) or EF (p=0.18) (ﬁgure 5B–D). The 2.5th centiles for EDV, ESV and EF were 1.8 ml/kg, 0.4 ml/kg and 58%, respectively. Table 4 shows the LOA and RI for scan–rescan cine mea- sures of left ventricular functional parameters within this group of 75 infants. Bland–Altman plot for scan–rescan repeatability of LVO by cine is shown in ﬁgure 4B. For most measures, the scatter of the differences tends to increase as volume increases such that again LOA may be wider than necessary for lower measures. Repeatability for assessment of LVO was similar when only preterm infants (<37 weeks) were considered in the analysis (n=12, LOA ±65.6 ml/kg/min, RI 22.8%). Repeatability of analysis of LVO from a single set of bFFE images using CMR Tools in 10 infants showed intra- observer RI 9.5%, inter-observer RI 22.4%. Analysis duration was approx 10–15 min per ventricle. Repeatability of right ventricular function from short axis stack cine images was poor (LOA ±126.3 ml/kg/min, RI 51.7%). Comparison with echo Echocardiography was performed in a total of 45 subjects. Scan–rescan repeatability of LVO by echocardiography in 10 infants who remained asleep or quietly awake throughout the echocardiogram showed LOA ±108.9 ml/kg/min, RI 49.2%. Bland–Altman comparison of LVO when measured by PC and echo in 10 infants showed mean difference 2.4 ml/kg/min, LOA +98.0 to −102.8 ml/kg/min, RI 44.4%, ﬁgure 4C). DISCUSSION Our group has developed a system for safely obtaining MR images in preterm and term infants.16 Having previously demonstrated feasibility of performing basic CMR in new- borns without sedation or anaesthesia,17 we now describe validation of optimised cine and PC techniques. High qual- ity images demonstrating cardiac ﬁlling, cardiac output and systemic perfusion can be obtained in newborns. SNR and CNR of these images are equivalent to those obtained at 3 T in adult subjects.20 Quantitative measures appear to be more repeatable than echocardiographic assessments; and CMR F89