Time efficient multi-pulsed field gradient (mpfg) mri without concomitant gradient field artifacts

An MR apparatus, comprising:

• a gradient control system operable to apply a plurality of sets of diffusion-sensitizing gradient pulse pairs separated by a diffusion time to a sample to at least one gradient coil, wherein each of the diffusion-sensitizing gradient pulse pairs is associated with a respective random diffusion weighting;
• a receiver situated to receive MR signals responsive to the plurality of sets of diffusion-sensitizing gradient pulse pairs;
• and
• a processor coupled to the receiver and operable to determine at least one of a second-order mean diffusion tensor and a fourth-order covariance tensor associated with the second-order mean diffusion tensor based on the received MR signals.

A method, comprising:

• applying a first diffusion-sensitizing pulse to a specimen;
• applying a 180° RF pulse after the diffusion-sensitizing pulse during a diffusion time;
• after the diffusion time has elapsed, applying a second diffusion-sensitizing pulse to the specimen;
• and
• measuring MR signals responsive to application of the diffusion sensitizing pulses;
• and
• based on the measured MR signals, determining a second-order mean diffusion tensor associated with at least a portion of the sample.

A method of reducing concomitant field effects in diffusion weighted magnetic resonance measurement, comprising, within a single echo time:

• applying first multi-directional diffusion sensitizing gradient pulses to a specimen;
• applying a 180° pulse during a diffusion time;
• and
• applying second multi-directional diffusion sensitizing gradient pulses to the specimen after the 180° pulse, wherein the first multi-directional diffusion sensitizing gradient pulses and the second multi-directional diffusion sensitizing gradient pulses are symmetric with respect to the 180° pulse.