Calculations of B1 distribution, SNR, and SAR for a surface coil adjacent to an anatomically-accurate human body model

Abstract

Calculations of the radiofrequency magnetic (B1) field, SAR, and SNR as functions of frequency between 64 and 345 MHz for a surface coil against an anatomically-accurate human chest are presented. Calculated B1 field distributions are in good agreement with previously-published experimental results up to 175 MHz, especially considering the dependence of field behavior on subject anatomy. Calculated SNR in the heart agrees well with theory for low frequencies (nearly linear increase with B0 field strength). Above 175 MHz, the trend in SNR with frequency begins to depend largely on location in the heart. At all frequencies, present limits on local (1 g) SAR levels are exceeded before limits on whole-body average limits. At frequencies above 175 MHz, limits on SAR begin to be an issue in some common imaging sequences. These results are relevant for coils and subjects similar to those modeled here. © 2001 Wiley-Liss, Inc.