Phase contrast imaging After initial survey for determination of cardiac position, steady-state free procession (SSFP) short axis and vertical and horizontal long axis views were obtained from initial axial scan through the heart (ﬁgure 1 with video links). Aortic and pulmonary outﬂow tracts were imaged using two orthogo- nal SSFP sequences. Left and right ventricular output (LVO and RVO) were assessed using through-plane phase contrast (PC) techniques with slice positioned immediately distal to the aortic and pulmonary valves.18 Since patency of the duc- tus arteriosus or foramen ovale prevent LVO and RVO from indicating systemic perfusion in the newborn, volumes of ﬂow in the superior vena cava (SVC) and descending aorta (DAo) were also assessed as markers of upper and lower body perfusion.10 11 Axial stacks of T1-weighted spin echo images were taken and multiplanar reformatted into sagittal and coro- nal planes showing the SVC and DAo, with ﬂow assessed by PC at the level of the pulmonary bifurcation and diaphragm, respectively. Acquisition parameters for PC imaging were rep- etition time 8.4 ms, echo time 4.9 ms, ﬂip angle 10°, slice thick- ness 4 mm, acquired voxel size 1.2 mm, 20 phases/cycle, scan duration 57 s. Velocity encoding was set at the minimum level to prevent aliasing, generally 100 cm/s for LVO, RVO and DAo ﬂow, 60 cm/s for SVC ﬂow. PC analysis and validation All PC sequences were analysed using an in-built workstation (Philips ViewForum). Automated vessel edge detection was used for pulmonary and descending aortic contours, with manual adjustment where necessary. Aortic contour was traced using a visually applied ellipse function. SVC contour was traced man- ually. PC sequences were externally validated against a ﬂow phantom with 8 mm internal diameter, which approximates the size of the newborn aorta,19 with non-pulsatile ﬂow rates of 0–1200 ml/min, and using automated vessel edge detection. Cine imaging Cine imaging was performed using SSFP. From vertical and horizontal long axis views obtained as above, a contiguous stack of short axis images (5–7 slices) was obtained to cover the left ventricle from atrioventricular (A-V) valve to cardiac apex. Acquisition parameters for cine imaging were repetition time 4.1 ms, echo time 2.1 ms, ﬂip angle 45°, slice thickness 3–5 mm, acquired voxel size 1.5 mm, 32 phases/cycle, scan duration 29 s/slice. Cine image analysis Cine images were analysed using semiautomated segmenta- tion software (CMR Tools; CVIS, London, UK). Left and right ventricular end-diastolic (EDV) and end-systolic (ESV) volumes, stroke volume and EF were calculated by tracing the endocardial Figure 1 Four chamber (A) and short axis (B) views obtained with balanced fast ﬁeld echo sequences in a newborn infant (view also video links at http://adc.bmj.com). Arch Dis Child Fetal Neonatal Ed 2011;96:F86–F91. doi:10.1136/adc.2010.189142 Original article border at end-systole and end-diastole at each level of the short axis stack. The ﬁrst image after the R wave was considered to be end-diastole. The end-systolic phase was determined as the slice with the smallest ventricular cavity. Volumes of the papil- lary muscles and moderator band were excluded from the ven- tricular volumes. The A-V valve planes were tracked through the cardiac cycle from two chamber and four chamber views. Measures of signal to noise ratio (SNR) in the myocardium and blood; and contrast to noise ratio (CNR) between myocardium and blood were taken by standard means.20 Echocardiographic imaging CMR was also used to study a sub-cohort of infants who had cardiac structure and function assessed by echocardiography within 24 h of CMR. Echocardiography scans were performed by a neonatologist with 10 years’ echo experience (AMG) using an Antares system (Siemens, Mountain View, California, USA) with a 10 MHz linear array transducer. Cardiac struc- tural abnormalities, signiﬁcant intra- and extra-cardiac shunts and A-V valve regurgitation were excluded. LVO was quanti- ﬁed to allow comparison with CMR. Left ventricular outﬂow tract diameter was assessed at the level of the aortic valve on 2D imaging at end-systole, aortic blood ﬂow velocity was assessed using pulsed wave Doppler placed at the level of the aortic valve from a modiﬁed apical view.21 Repeatability analysis Where possible CMR scans were repeated using the initial imaging geometry (scan–rescan repeatability) after 5–15 min. Repeatability of analysis was also assessed from a single set of images by the same (intra-) and a different (inter-) observer. Echocardiographic quantiﬁcation of LVO was repeated where satisfactory views were obtained and where infants slept or were quietly awake throughout the echocardiogram. In all cases, observers were blinded to prior data when analysing ﬂow volumes. Statistical analysis Bland–Altman analysis was used for assessment of repeatabil- ity and to compare methodologies.22 The mean bias and limits of agreement (LOA or ‘repeatability coefﬁcient’, 1.96 × SD of differences) were calculated, as was repeatability index (RI, limits of agreement/mean of measures) to allow comparison of repeatability between different measures.23 Associations between continuous variables were assessed by simple linear regression. A probability value of <0.05 was considered signiﬁ- cant. Demographic data are presented as median and range. Hemodynamic variables are presented as mean and SD, with the 2.5th centile (equivalent to 2 SD below the mean) taken as the lower limit of normal. RESULTS Subjects In total 108 infants were studied. A range of imaging sequences were employed in each infant to optimise SSFP and PC imaging, such that all sequences were not attempted in all infants. Median birth weight was 1627 (580–4140) g, birth gestation 32 (25–42) weeks, 53 infants were male. At scan postnatal age was 11 (1–94) days, weight 1845 (590– 4600) g and gestation 34 (26–42) weeks. Seventy-four infants had been admitted to the neonatal unit, the remaining 34 received care on the postnatal ward. Twelve infants were receiving supplemental oxygen at the time of the scan; three F87