Kim Annink

241 7.0T MRI in neonates oxygen saturation, temperature (core temperature before and after and abdominal skin temperature during the scans) and comfort scales (20). This study was approved by the medical ethical committee of the UMC Utrecht (NL66198.041.18) and written informed consent was obtained from parents of all participants. RESULTS Preparations – SAR simulation The global SAR and peak local SAR of the virtual infant model in centered position and 50mm from isocenter in feet direction (-50mm FH) did not exceed the SAR of the adult models. However, when infant Charlie was positioned 50mm from isocenter in head direction (+50mm FH), global SAR levels and peak local SAR levels exceeded those of the adult models (by +13% and +12% compared to Duke, respectively) (Table 1). Table 1: Global and peak SAR levels. Duke centered Ella centered Charlie centered Charlie -50mm FH Charlie +50mm FH Global SAR levels Average SAR for 1 Watt input power (W kg -1 ) 0.066 0.069 0.062 0.050 0.075 Average SAR per B 1 2 (W kg -1 µT -2 ) 0.462 0.465 0.289 0.454 0.474 Average B 1 + in central slice for 1 Watt input power (µT)* 0.379 0.385 0.466 0.333 0.398 Peak local SAR levels Peak local SAR (10g average) for 1Watt input power (W kg -1 ) 0.435 0.398 0.321 0.213 0.487 Peak local SAR (10g average) per B 1 2 (W kg -1 µT -2 ) 3.04 2.63 1.48 1.92 3.08 *The power optimization procedure of the MR scanner software calibrates the needed input power to achieve a certain B 1 in the subject. This calibration is based on the average B 1 + in a central slice of the subject (brain in this case). The 10g-averaged local SAR in the head of the infant model was lower than in the adult head for all positions. When the infant model was positioned +50mm FH, the local SAR was highest in the neck/shoulder transitions (Figure 3). 11