Kim Annink

227 Measurement of brain temperature using MRS Table 2: Spearman’s Rho correlations between brain temperature and peripheral temperature before and after MRI are shown in this Table. The correlations have been tested for both formulas and TE. Formula Echo time (TE) Correlation with temperature before MRI Correlation with temperature after MRI Wu et al. Short TE (36ms) 0.648 (p=0.001) 0.617 (p=0.001) Long TE (288ms) 0.471 (p=0.009) 0.666 (p<0.001) Calibration Short TE (36ms) 0.650 (p=0.001) 0.612 (p=0.001) Long TE (288ms) 0.474 (p=0.008) 0.670 (p<0.001) Afterward, differences in temperatures before, during and after MRI were compared using the Kruskal-Wallis-H test and post-hoc tests for normothermic and hypothermic patients for the different methods (see Table 3). Table 3: The differences between temperature before, during and after MRI are shown for all methods. Formula Hypothermic neonates Normothermic neonates Before versus during MRI 1 During versus after MRI 2 Before versus during MR 1 During versus after MRI 2 Wu et al. Short TE -1.4°C +1.3°C -1.2°C * +0.9°C * Long TE -0.8°C +0.7°C -0.8°C +0.5°C Calibration Short TE -1.1°C +1.0°C -1.4°C * +1.1°C * Long TE -0.6°C +0.5°C -1.1°C * +0.7°C 1 the temperature difference between the temperature before MRI and during MRS 2 the temperature difference between the temperature after MRI and during MRS * p<0.05, corrected for multiple comparisons. In a multivariable linear regression model the association between therapeutic hypothermia, and head circumference as independent variables and the differences between the temperature before MRI and brain temperature as dependent variable was tested. Head circumference was significantly associated with difference in temperature in which brain temperature was measured using short TE and the formula of Wu et al. (head circumference: ß=-0.29, p=0.024) and in the model using short TE and the calibrated formula (head circumference: ß=-0.25, p=0.019). In the models using the brain temperature measured with long TE, none of the variables were associated with temperature differences. 10