Composite spin locking pulse sequence and method of using the same

A magnetic resonance imaging method comprising:

• (a) performing a first magnetic resonance imaging sequence with a magnetic resonance imaging system, the sequence comprising:
• (i) a first preparatory composite spin locking pulse sequence having a spin lock pulse bounded by similarly oriented spin tipping pulses;
• and
• (ii) an acquisition pulse sequence to acquire first magnetic resonance data;
• (b) performing a second magnetic resonance imaging sequence with a magnetic resonance imaging system, the sequence comprising:
• (i) a second preparatory composite spin locking pulse sequence having a spin lock pulse bounded by oppositely oriented spin tipping pulses;
• and
• (ii) an acquisition pulse sequence to acquire second magnetic resonance data;
• (c) generating difference data on a pixel-by-pixel basis from the first and second data as the data is collected;
• (d) storing the difference data in a memory circuit.

A magnetic resonance imaging system comprising:

• a primary field magnet;
• a set of gradient field coils;
• a radiofrequency field coil;
• control circuitry coupled to the gradient field coils and to the radiofrequency field coil, the control circuitry configured to apply control signals to the gradient and radiofrequency coils in order to perform a magnetic resonance imaging sequence comprising:
• (a) a first magnetic resonance imaging sequence comprising:
• (i) a first preparatory composite spin locking pulse sequence having a spin lock pulse bounded by similarly oriented spin tipping pulses;
• and
• (ii) an acquisition pulse sequence in order to acquire first magnetic resonance data;
• (b) a second magnetic resonance imaging sequence comprising:
• (i) a second preparatory composite spin locking pulse sequence having a spin lock pulse bounded by oppositely oriented spin tipping pulses;
• and
• (ii) an acquisition pulse sequence in order to acquire second magnetic resonance data;
• and processing circuitry configured to determine difference data from the first and second magnetic resonance data in order to characterize T1ρ Data for a subject of interest.