Kim Annink

229 Measurement of brain temperature using MRS a phantom study using a TE of 35ms on a 3.0T MRI scanner and tested this formula in neonates with NE, which is more similar to clinical practice. So, hospitals using 3.0T MRI can use their standard 1 H-MRS scan and no phantom study is needed before starting to measure brain temperature non-invasively. This will improve the feasibility of 1 H-MRS brain temperature measurements in clinical practice. Furthermore, in previous studies either short (8) or long (9,10) TE 1 H-MRS was used, but these two methods were never compared. This study found no statistical differences, but for some individuals there was a difference >1˚C, which is clinically significant. This difference cannot be technically explained. Further research using rectal temperature measurement during MRI in combination with short and long TE 1 H-MRS is essential to conclude which TE is more reliable. The possibility to measure brain temperature is important in clinical practice for the monitoring of safety, as an additional prognostic tool and for evaluation of the effect of therapeutic hypothermia. This study showed that brain temperature during MRI was not higher than rectal temperature measured within 3 hours before and after MRI in neonates with NE. This suggests that there is no heating of the brain during MRI, which is in accordance with the literature that MRI is safe in different neonatal populations (1,4,5). However, in this study brain temperature was compared to rectal temperature before and after MRI at the NICU. So, we cannot conclude that brain temperature itself did not increase during MRI because of the absence of a baseline measurement of brain temperature. Furthermore, brain temperature in normothermic infants with NE was even significantly lower during MRI compared to rectal temperature at the NICU, varying between minus 0.6 and 1.4˚C. These findings are in agreement with a study in preterm patients, scanned at 30 weeks of gestation within an MRI incubator, in which 17.3% of the preterm infants became hypothermic with a mean decline in temperature of 0.5˚C during MRI (5). The authors explained the lower temperatures by the cold air that was used for ventilation during MRI instead of the preheated air that is used on the NICU (21). This can also partly explain the decrease in temperature in especially the patients that still received therapeutic hypothermia, because all these infants were ventilated. The decrease in temperature was not statistically significant in infants with therapeutic hypothermia, 10