Abstract: A system and method is provided for simultaneously designing a radiofrequency (“RF”) pulse waveform and a magnetic field gradient waveform in a magnetic resonance imaging (“MRI”) system. The method includes determining a desired pattern of RF excitation and determining, from the desired pattern of RF excitation, a plurality of k-space locations indicative of the magnetic field gradient waveform and a plurality of complex weighting factors indicative of RF energy deposited at each k-space location. The method also includes calculating, from the determined k-space locations, the magnetic field gradient waveform and calculating, from the complex weighting factors, the RF pulse waveform that will produce the desired pattern of RF excitation when produced with the calculated magnetic field gradient.

Abstract: A method for reducing maximum local specific absorption rate (“SAR”) in a magnetic resonance imaging (“MRI”) system is disclosed. More specifically, a plurality of candidate radio frequency (“RF”) pulses are designed and the manner in which they are applied to a subject is determined such that the maximum local SAR is substantially reduced relative to applying the candidate RF pulse that produces the lowest maximum local SAR alone. Put another way, this “time-multiplexing” of a set of RF pulses that each produce approximately the same excitation pattern yields a lower maximum local SAR than does transmitting the individual RF pulse having the lowest local SAR over many repetition times (“TRs”). A convex optimization method is utilized to determine the manner in which the RF pulses are multiplexed in time such that a substantially lower maximum local SAR is achieved.

Abstract: A method for target-dependent, sparsity-enforced selection for choosing a substantially optimal connection of radiofrequency (“RF”) transmitters to the elements of the RF coil array is provided. In particular, a method is provided that selects the linear combinations of the “N” spatial mode profiles of a transmission RF coil array, such that the k-space trajectory and pulse duration acceleration capabilities of the array are advantageously utilized. A sparsity-enforcement method that determines a subset of the available spatial modes for a parallel transmission RF coil array is employed to this end. In this manner, the utilization of the encoding power of a highly-parallel N-mode coil array in a system with only “P” available excitation channels is enabled.

Abstract: A method for reducing maximum local specific absorption rate (“SAR”) in a magnetic resonance imaging (“MRI”) system is disclosed. More specifically, a plurality of candidate radio frequency (“RF”) pulses are designed and the manner in which they are applied to a subject is determined such that the maximum local SAR is substantially reduced relative to applying the candidate RF pulse that produces the lowest maximum local SAR alone. Put another way, this “time-multiplexing” of a set of RF pulses that each produce approximately the same excitation pattern yields a lower maximum local SAR than does transmitting the individual RF pulse having the lowest local SAR over many repetition times (“TRs”). A convex optimization method is utilized to determine the manner in which the RF pulses are multiplexed in time such that a substantially lower maximum local SAR is achieved.

Abstract: A method for target-dependent, sparsity-enforced selection for choosing a substantially optimal connection of radiofrequency (“RF”) transmitters to the elements of the RF coil array is provided. In particular, a method is provided that selects the linear combinations of the “N” spatial mode profiles of a transmission RF coil array, such that the k-space trajectory and pulse duration acceleration capabilities of the array are advantageously utilized. A sparsity-enforcement method that determines a subset of the available spatial modes for a parallel transmission RF coil array is employed to this end. In this manner, the utilization of the encoding power of a highly-parallel N-mode coil array in a system with only “P” available excitation channels is enabled.

Abstract: A system and method is provided for simultaneously designing a radiofrequency (“RF”) pulse waveform and a magnetic field gradient waveform in a magnetic resonance imaging (“MRI”) system. The method includes determining a desired pattern of RF excitation and determining, from the desired pattern of RF excitation, a plurality of k-space locations indicative of the magnetic field gradient waveform and a plurality of complex weighting factors indicative of RF energy deposited at each k-space location. The method also includes calculating, from the determined k-space locations, the magnetic field gradient waveform and calculating, from the complex weighting factors, the RF pulse waveform that will produce the desired pattern of RF excitation when produced with the calculated magnetic field gradient.