Calculated Local and Average SAR in Comparison with Regulatory Limits
Liu W, Mao W, Smith M, Collins C
University of Minnesota
Here we discuss some recent experiences in attempting to compare SAR calculated in the human head and body to regulatory limits. Importantly, even in volume coils at commonly-used frequencies, calculated maximum SAR in any one gram of tissue will exceed FDA limits long before whole-head or whole-body SAR averages. This raises questions about either the interpretation of local SAR calculations in light of the limits, or about interpretation of the limits in light of common practice and new local SAR calculations. Finally, use of numerical calculations for comparison to regulatory limits on local temperature show fairly poor spatial correlation between SAR and temperature, indicating a need for more meaningful regulatory limits.