Quantiﬁcation of ventricular volumes from stacks of cine images contain the entire ventricular volumes and do not rely on assumptions of ventricular geometry which are unreliable in the newborn.12 While such analysis must be performed ofﬂine, analysis duration was only 10–15 min, which is not prohibitive, particularly in the research setting. This analysis also provides repeatable and previously unavailable data on cardiac ﬁlling (EDV) and EF in the newborn. The practical utility of CMR in preterm newborn infants is an important consideration. We have safely studied large num- ber of infants.16 While CMR cannot replace echocardiography, it does provide additional value in range of data provided and in repeatability. As in adults this improved repeatability should translate into increased power for clinical trials. For example, to demonstrate a 20% increase in total systemic per- fusion (SVC plus DAo, mean (SD) 224 (51) ml/kg/min) between treated and control groups with α=0.05 and β=0.80, requires just 16 infants per group. CMR could also increase insights into the pathophysiology of newborn circulatory failure and guide development of emerging echocardiographic techniques with greater applicability. Our study has produced initial reference data for newborn circulatory function. Mean LVO, RVO, SVC ﬂow and DAo ﬂow as assessed by PC in stable infants were 222, 219, 95 and 126 ml/kg/min, respectively. The combined volume of SVC and DAo ﬂow closely represents LVO when the ductus arte- riosus is closed, suggesting that this could act as a surrogate for total systemic perfusion. Measures of ﬂow tended to be higher at lower corrected gestational age, such that individual patients require gestation corrected normal ranges (ﬁgures 3 and 5A). Mean LVO as assessed by SSFP was 245 ml/kg/min, but again higher at lower corrected gestational age. Measures of left ventricular ﬁlling and ejection did not vary with gesta- tional age, with EDV <1.8 ml/kg, ESV <0.4 ml/kg and EF <58% all likely to be abnormally low in the newborn. This study has a number of limitations. The ﬁnal optimised imaging parameters were not implemented in all infants since an initial protocol development phase was required for the techniques. Echocardiographic quantiﬁcation of LVO was only introduced once the optimal cine and PC param- eters were identiﬁed, and even then many infants were too unsettled for repeated echocardiographic measurements to be performed. Without echo imaging the presence of sub-clinical ductal shunting cannot be excluded in the cohort of infants studied by cine CMR. We have not yet studied large number of extremely preterm infants, though this was not considered a priority during the optimisation process. We have not yet implemented an alternative approach (such as axial imaging) for the assessment of right ventricular function, but an alterna- tive to poorly repeatable short axis images will be required. CONCLUSIONS This study conﬁrms the feasibility of CMR in newborn infants and demonstrates that CMR provides additional value over echocardiography. Initial gestation-related reference values for cardiac ﬁlling, cardiac output and systemic perfusion are provided. CMR has the potential to measure cardiovascular function in preterm infants with sufﬁcient precision to allow appropriately powered trials of therapeutic intervention in fewer numbers of critically ill patients. Acknowledgements The authors are grateful to the families who took part in the study, to the nursing and medical staff who cared for the infants, and to the staff of the Imaging Sciences Department of Imperial College London. Arch Dis Child Fetal Neonatal Ed 2011;96:F86–F91. doi:10.1136/adc.2010.189142 Original article Funding This study was supported by the Garﬁeld Weston Foundation, the Medical Research Council, the Wellcome Trust, the Imperial College Comprehensive Biomedical Research Centre and a Dorothy Hodgkins Postgraduate Award (S.U.). Competing interests RR, JVH and ADE receive investigator-led research support from Philips. Ethics approval This study was conducted with the approval of the Hammersmith Hospital REC. Provenance and peer review Not commissioned; externally peer reviewed. REFERENCES 1. Mangham LJ, Petrou S, Doyle LW, et al. The cost of preterm birth throughout childhood in England and Wales. Pediatrics 2009;123:e312–27. 2. Doyle LW, Gultom E, Chuang SL, et al. Changing mortality and causes of death in infants 23-27 weeks’ gestational age. J Paediatr Child Health 1999;35:255–9. 3. Volpe JJ. Neurobiology of periventricular leukomalacia in the premature infant. 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