Assessment of brain two-dimensional metrics in infants born preterm at term equivalent age: Correlation of ultrasound scans with magnetic resonance imaging

ContextDeveloping brain imaging is a critical subject for infants born preterm. Impaired brain growth is correlated with poor neurological outcomes, regardless of overt brain lesions, such as hemorrhage or leukomalacia. As magnetic resonance imaging (MRI) remains a research tool for assessing regional brain volumes, two-dimensional metrics (2D metrics) provide a reliable estimation of brain structures. In neonatal intensive care, cerebral ultrasound (cUS) is routinely performed to assess brain integrity. This prospective work has compared US and MRI accuracy for the measurement of 2D brain metrics and identification of overt injuries. MethodsMRI and cUS were performed at term equivalent age (TEA) in infants born before 32 weeks of gestation (GW). Demographical data and results of serial cUS (Neonatal Intensive Care Unit [NICU]-US) performed during hospitalization were gathered from medical charts. Blinded, experienced senior doctors reviewed the scans for both standard analysis and standardized, 2D measurements. The correlation of 2D metrics and inter-/intraobserver agreements were evaluated using Pearson's coefficient, Bland-Altman plots, and intraclass coefficient (ICC), respectively. ResultsIn total, 102 infants born preterm were included. The performance of TEA-cUS and NICU-cUS when compared to TEA-MRI and NICU-cUS was identical for the detection of high-grade hemorrhages and close for low-grade ones. However, TEA-MRI only detected nodular lesions of the white matter (WM). No infant presented a cerebellar infarct on imaging. Intra- and inter-observer agreements were excellent for all 2D metrics except for the corpus callosum width (CCW) and anteroposterior vermis diameter. MRI and cUS showed good to excellent correlation for brain and bones biparietal diameters, corpus callosum length (CCL), transcerebellar diameters (TCDs), and lateral ventricle diameters. Measures of CCW and vermis dimensions were poorly correlated. Conclusion and perspectiveThe cUS is a reliable tool to assess selected 2D measurements in the developing brain. Repetition of these metrics by serial cUS during NICU stay would allow the completion of growth charts for several brain structures. Further studies will assess whether these charts are relevant markers of neurological outcome.

Automated summary

This study compared the accuracy of ultrasound and magnetic resonance imaging (MRI) in measuring 2D brain metrics and detecting brain injuries in preterm infants. The results showed that ultrasound is a reliable tool for assessing selected 2D measurements, and repetitive ultrasound measurements during the neonatal intensive care unit (NICU) stay can be used to create growth charts for various brain structures. Further research will assess whether these charts are relevant markers of neurological outcomes.