SAR reduction in MR imaging with parallel RF transmission

An MR apparatus comprising:

• an MR system that comprises a magnet to impress a polarizing magnetic field, a plurality of gradient coils positioned about a bore of the magnet to induce a magnetic field gradient, a parallel RF transmit coil array having a plurality of transmit coils, and an RF transceiver system and an RF switch to transmit RF pulses and to acquire MR images, wherein the RF switch is controlled by a pulse module;
• and
• a computer programmed to:
• design an RF pulse waveform for each transmit coil of a plurality of transmit coils of the parallel RF transmit coil array such that RF pulse length is managed and possible excitation profile side lobes are reduced;
• and
• regulate SAR during MR imaging through independent control of the plurality of transmit coils of the parallel RF transmit coil array based on an RF pulsing sequence optimization algorithm, wherein said RF pulsing sequence optimization algorithm combines said RF pulse waveform design and said SAR regulation.

A method of MR imaging comprising

• determining at least one of a region-of-interest in and an excitation profile over an imaging volume;
• determining an excitation pulse scheme for a target excitation profile based on at least one effective B1 field map for a parallel RF transmit coil array, wherein each effective B1 field map reflects possible inductive coupling effects that exist between a transmit coil and at least another transmit coil;
• and
• independently controlling RF pulsing of a plurality of transmit coils of the parallel RF transmit coil array such that RF power deposition is reduced, wherein said RF pulsing is integrated as part of said excitation pulse scheme.