Kim Annink

225 Measurement of brain temperature using MRS Calculation of brain temperature using MRS in neonates: comparing the formulas The formula of Wu et al. was compared to the calibrated formula to assess whether these were different in neonates, which would imply that calibration is necessary. The median brain temperature was 35.1˚C (IQR 33.6 – 36.1) according to the formula of Wu et al. and 35.0˚C (IQR 33.7 – 35.9) according to the calibrated formula using short TE 1 H-MRS (p=0.68). Using long TE 1 H-MRS, the median brain temperature assessed according to Wu et al. was 35.5˚C (IQR 34.4 – 36.2) and according to the calibrated formula 35.3˚C (IQR 34.4 – 35.9). This difference was just significant (p=0.048). The difference between the brain temperatures calculated with the two formulas varied for short TE 1 H-MRS between 0.01˚C and 0.67˚C (mean=0.06˚C) and for long TE 1 H-MRS this varied between 0.01˚C and 0.85˚C (mean=0.15˚C). See Figure 3. Figure 3: Comparison of the formulas for short and long TE. For each ΔH 2 O-NAA the tem- perature calculated with the formula of Wu et al. and the calibrated formula are shown for as well short TE (A) and long TE (B). The intersection point of both curves was (2.664; 34.507). Calculation of brain temperature using MRS in neonates: short versus long TE 1 H-MRS Twenty patients had both short TE and long TE 1 H-MRS available and brain temperatures derived from the different TEs were compared within patients. In normothermic and hypothermic patients, differences in brain temperatures derived from short and long TE 1 H-MRS according to Wu et al. were not statistically different. The differences in brain temperatures measured with short and long TE 1 H-MRS according to the calibrated formula were also comparable for normothermic 10