Systems and methods for radio frequency (rf) based spatial encoding in magnetic resonance imaging using frequency-modulated rf pulses

A method for magnetic resonance imaging, the method comprising:

• (a) acquiring magnetic resonance data from a subject using a magnetic resonance imaging (MRI) system by:
• generating a pulse sequence with the MRI system, the pulse sequence comprising:
• a radio frequency (RF) excitation pulse;
• a first frequency-modulated RF pulse having a first time-bandwidth product, wherein the first frequency-modulated RF pulse is generated after the RF excitation pulse;
• a second frequency-modulated RF pulse having a second time-bandwidth product, wherein the second frequency-modulated RF pulse is generated after the first frequency-modulated RF pulse;
• acquiring magnetic resonance data with the MRI system by sampling magnetic resonance signals formed in response to the RF excitation pulse, wherein a phase whose value is dependent on the first time-bandwidth product and the second time-bandwidth product is imparted to magnetic resonance signals formed in response to the RF excitation pulse, and a difference between the first time-bandwidth product and the second time-bandwidth product is changed at least one of within the pulse sequence or in repetitions of the pulse sequence in order to phase encode the magnetic resonance data;
• (b) reconstructing an image from the acquired magnetic resonance data.