Kim Annink

237 7.0T MRI in neonates INTRODUCTION Infants who are admitted to the neonatal intensive care unit are at risk for delayed or impaired neurodevelopmental outcome due to brain injury, cerebral malformations, genetic or metabolic disorders (1,2). MRI is the gold standard to assess brain development, malformations and injury in infants (3). The first neonatal 3.0 Tesla (T) field strength MRI scans were reported in 2004 (4), and 3.0T scanners are now routinely used by many centers. 3.0T MRI has several advantages compared to 1.5T MRI. The quality of the MR images improved because of the increased SNR leading to higher spatial resolution, improved susceptibility contrast and increased chemical shift dispersion leading to improved quality of MRS (5,6). The increased SNR in neonatal 3.0T MRI also led to shorter acquisition times (6). In adults, the introduction of ultra-high field MRI provided new opportunities, further improving the spatial resolution at 7.0T compared to 3.0T when the same acquisition times were used (7). This provided additional anatomical information (8). At 7.0T the sensitivity to susceptibility is strongly increased enabling the diagnosis of microbleeds and visualization of microvasculature. Due to the increased chemical shift dispersion at 7.0T, additional metabolite peaks could be detected with MRS (5,8–11). Nowadays, accessibility of 7.0T MR scanners in adult research is increasing rapidly and 7.0T MRI is more often used for clinical purposes. The initial safety concerns of using 7.0T MRI in adults were addressed in the past decades. The largest safety concern was an increase in body temperature because of the higher local and global specific absorption rate (SAR), for the same B 1 + at 7.0T. However, an increase in body temperature has not been reported in ultra-high field MRI in adults or children (5,12). Besides the increased SAR, a higher static magnetic field increases the risk of attracting ferromagnetic object, which can be prevented with screening for ferrometal before MRI (13). It also can potentially influence biological systems, as cardiac and neurophysiological responses, but harmful effects have never been described in follow-up studies in infants (13). Sensory symptoms such as vertigo, headaches and an iron taste due to the varying gradient field (5) were reported by patients undergoing a 7.0T MR scan, however, only 5% rated these symptoms as very unpleasant (14). Acoustic noise protection should be guaranteed during the MR scan, similar to 3.0T MRI. 11