Background and aims Magnetic resonance imaging (MRI) is considered imaging method of choice for high-risk preterm infants to assess brain injury. However, MRI scanning in preterm infants is particularly challenging due to safety, logistical and quality issues that limit clinical feasibility. Meanwhile, due to ongoing technical developments and by using additional acoustic windows, advanced serial cranial ultrasonography (CUS) has acquired great clinical value. We hypothesised that dedicated serial CUS is equally effective in diagnosing preterm brain damage as a routine MRI scan at 30 weeks postmenstrual age and excels in clinical feasibility.

Methods We prospectively collected data of 307 infants born <29 weeks gestational age. Serial CUS and MRI were performed according to standard clinical protocol. In case of instability, MRI was postponed or cancelled. Brain images were assessed by independent experts and compared between modalities.

Results Serial CUS was performed in all infants, MRI was often postponed (n = 58) or cancelled (n = 127). Injury was found in 146 infants (47.6%). Clinical characteristics differed significantly between groups that were subdivided according to timing of MRI. 61 discrepant imaging findings were found. MRI was superior in identifying cerebellar haemorrhages; CUS in detection of acute intraventricular haemorrhage and cerebral sinovenous thrombosis.

Conclusion Advanced serial CUS seems highly effective in diagnosing preterm brain injury, but may miss cerebellar abnormalities. Although MRI does identify these lesions, clinical additional value is limited. Improved safety, better availability and tailored procedures are essential for MRI to increase its value in clinical care.