System and method for controlling concomitant gradient phase errors in chemical-shift encoded imaging

1. A magnetic resonance imaging (MRI) system comprising:

a magnet system configured to generate a polarizing magnetic field about at least a portion of a subject arranged in the MRI system;

a plurality of gradient coils configured to apply magnetic gradients to the polarizing magnetic field;

a radio frequency (RF) system configured to apply an excitation field to the subject and acquire MR image data from the subject;

a computer system programmed to:

control the plurality of gradient coils and the RF system to perform a multi-pass, chemical shift-encoded (CSE)-MRI acquisition of imaging data from the subject;

perform a complex, joint estimation of phase terms in the imaging data for each pass of the multi-pass, CSE-MRI acquisition to account for concomitant gradient (CG)-induced phase errors of different passes;

generate at least one of a proton density fat fraction (PDFF) estimate or an R2* estimate that is unbiased by CG-induced phase errors using the phase terms; and

communicate a report that includes at least one of the PDFF estimate or the R2* estimate.

2. The system of claim 1 wherein complex, joint estimation of phase terms is part of a CSE-MRI signal model that includes pass-specific phase terms.

3. The system of claim 1 wherein the multi-pass, CSE-MRI acquisition includes uniformly spaced echoes.

4. The system of claim 1 wherein the polarizing magnetic field has a strength of at least 3.0 Tesla.

5. The system of claim 1 wherein the computer system is further programmed to perform the complex, joint estimation of phase terms without a model of imaging gradient waveforms applied by the plurality of gradient coils when performing the multi-pass, CSE-MRI acquisition.

6. The system of claim 1 wherein the computer is further configured to perform a mixed fitting to compensate for eddy currents induced during the multi-pass, CSE-MRI acquisition.

7. The system of claim 1 wherein the complex, joint estimation of phase terms is configured to account for bias in fat and R2* estimation caused by errors in the MRI signal induced by concomitant gradients during the multi-pass, CSE-MRI acquisition.

8. A method comprising:

acquiring multi-pass, chemical shift-encoded (CSE)-MRI imaging data of a subject;

performing a complex, joint estimation of phase terms in the imaging data for each pass of the multi-pass, CSE-MRI imaging data to account for concomitant gradient (CG)-induced phase errors of different passes;

generating at least one of a proton density fat fraction (PDFF) estimate or an R2* estimate that is unbiased by CG-induced phase errors using the phase terms; and

communicating a report that includes at least one of the PDFF estimate or the R2* estimate.

9. The method of claim 8 wherein acquiring the multi-pass CSE-MRI imaging data includes controlling an MRI system to perform a spoiled gradient echo (SGRE) pulse sequence.

10. The method of claim 9 wherein the SGRE pulse sequence includes uniformly sampling spaced echoes.

11. The method of claim 9 wherein the MRI system has a strength of at least 3.0 Tesla.

12. The method of claim 8 wherein complex, joint estimation of phase terms includes applying a CSE-MRI signal model that includes pass-specific phase terms.

13. The method of claim 8 further comprising performing the complex, joint estimation of phase terms without a model of imaging gradient waveforms applied by the plurality of gradient coils when acquiring the multi-pass, CSE-MRI imaging data from the subject.

14. The method of claim 8 further comprising performing a mixed fitting to compensate for eddy currents induced during acquisition of the multi-pass, CSE-MRI imaging data from the subject.

15. The method of claim 8 wherein the complex, joint estimation of phase terms is configured to account for bias in fat and R2* estimation caused by errors in the MRI signal induced by concomitant gradients during the multi-pass, CSE-MRI acquisition.

16. The method of claim 8 wherein acquiring the multi-pass, CSE-MRI imaging data includes accessing the multi-pass CSE-MRI imaging data from a storage medium.