Fig. 2.

Calculated difference in Temperature increase (°C) with and without consideration of physiological response (with minus without) for a human head in a volume coil for 30 minutes at 300 MHz with a head-average SAR of 3.0 W/kg, 6.0 W/kg, 9.0 W/kg and 12.0 W/kg (left to right) on an axial plane passing through the eyes (top), an axial plane passing through the center of the coil and brain (2^nd row), and sagittal and coronal planes passing through the center of the coil and brain (3^rd and bottom rows). Positive values generally occur where slight temperature increases cause small increases in metabolic rate, but where the temperature does not exceed 39°C enough to cause a significant thermoreglatory increase in perfusion. Negative values occur where thermoregulatory increases in perfusion have a notable effect.