Thomas M. Fiedler1, Mark E. Ladd1,2, and Andreas K. Bitz1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany
RF safety of Tx coils can
be assessed based on SAR or temperature limits; however, temperature is
directly correlated to tissue damage and enables a more precise RF exposure
assessment. Both safety assessments were compared for a 7T breast coil.
Temperature depends on the individual thermoregulation system and was taken
into account using three different temperature-dependent blood perfusions. Results
for a subject with impaired thermoregulation showed that temperature limits are
exceeded by up to 6.17 °C even when SAR limits are complied with. For a healthy
subject, up to 40% higher input power is allowed if temperature limits are
applied instead of SAR.