Method For Reducing Maximum Local Specific Absorption Rate In Magnetic Resonance Imaging

A method for producing a radio frequency excitation field with an RF coil that forms a part of an MRI system, the steps comprising:

• a) estimating an electric and a magnetic field produced by the RF coil;
• b) estimating an RF transmission profile of the RF coil using the estimated magnetic field;
• c) selecting locations in k-space to which RF energy is to be deposited;
• d) determining, using the estimated RF transmission profile and selected locations in k-space, a plurality of candidate RF pulse waveforms corresponding to a plurality of candidate RF pulses that have substantially similar excitation profiles but different specific absorption ratio (SAR) profiles;
• e) calculating a local SAR value at each spatial location within a selected portion of the subject for each candidate RF pulse waveform;
• f) calculating a plurality of weighting factors, using the determined plurality of candidate RF pulse waveforms and calculated local SAR values for each candidate RF pulse waveform, the plurality of weighting factors defining a number of times to apply RF pulses corresponding to selected ones of the plurality of candidate RF pulse waveforms in order to substantially minimize maximum local SAR in the selected portion of the subject;
• and
• g) directing the MRI system, using the calculated plurality of weighting factors and the associated selected ones of the plurality of candidate RF pulse waveforms, to produce a plurality of RF excitation pulses during a selected time period in order to produce an RF excitation field.