Asymmetric RF Pulse for a Magnetic Resonance Imaging System

A magnetic resonance (MR) imaging system comprising:

• a housing defining a bore;
• a main magnet arrangement configured to generate a main magnetic field within the bore;
• and
• one or more processors configured to:
• compute a first radio frequency (RF) amplitude for a predefined first part of a predefined time interval;
• receive an RF amplitude curve that depends on at least one RF curve parameter;
• compute a combined RF amplitude curve for the predefined time interval by combining the first RF amplitude for the predefined first part of the time interval and the RF amplitude curve for a predefined second part of the time interval that succeeds the predefined first part of the time interval;
• optimize the combined RF amplitude curve in accordance with a loss function that (i) comprises an energy loss term that depends on a pulse energy of the combined RF amplitude curve, and (ii) utilizes the at least one RF curve parameter as at least one optimization variable;
• and
• construct an asymmetric RF pulse,
• wherein a combined amplitude of the asymmetric RF pulse for the time interval is represented by the optimized combined RF amplitude curve;
• and
• an RF system configured to apply the asymmetric RF pulse to a target material disposed within the bore and to receive MR signals from the target material,
• wherein the one or more processors are further configured to reconstruct an MR image based upon the received MR signals.

A non-transitory computer-readable medium having instructions stored thereon that, when executed by one or more processors of a magnetic resonance (MR) imaging device, cause the MR imaging device to:

• compute a first radio frequency (RF) amplitude for a predefined first part of a predefined time interval;
• receive an RF amplitude curve that depends on at least one RF curve parameter;
• compute a combined RF amplitude curve for the predefined time interval by combining the first RF amplitude for the predefined first part of the time interval and the RF amplitude curve for a predefined second part of the time interval that succeeds the predefined first part of the time interval;
• optimize the combined RF amplitude curve in accordance with a loss function that (i) comprises an energy loss term that depends on a pulse energy of the combined RF amplitude curve, and (ii) utilizes the at least one RF curve parameter as at least one optimization variable;
• construct an asymmetric RF pulse,
• wherein a combined amplitude of the asymmetric RF pulse for the time interval is represented by the optimized combined RF amplitude curve;
• apply the asymmetric RF pulse to a target material;
• receive MR signals from the target material;
• and
• reconstruct an MR image based upon the received MR signals.