Magnetic resonance spectroscopy pulse sequence, acquisition, and processing system and method
Systems and methods are provided for processing a set of multiple serially acquired magnetic resonance spectroscopy (MRS) free induction decay (FID) frames from a multi-frame MRS acquisition series from a region of interest (ROI) in a subject, and for providing a post-processed MRS spectrum. Processing parameters are dynamically varied while measuring results to determine the optimal post-processed results. Spectral regions opposite water from chemical regions of interest are evaluated and used in at least one processing operation. Frequency shift error is estimated via spectral correlation between free induction decay (FID) frames and a reference spectrum. Multiple groups of FID frames within the acquired set are identified to different phases corresponding with a phase step cycle of the acquisition. Baseline correction is also performed via rank order filter (ROF) estimate and a polynomial fit. Sections of the ROF may be excluded from the polynomial fit, such as for example sections determined to be associated with relevant spectral peaks.
1. A method for processing a set of multiple serially acquired magnetic resonance spectroscopy (MRS) free induction decay (FID) frames from a multi-frame MRS acquisition series from a region of interest (ROI) in a subject, and for providing a post-processed MRS spectrum, comprising:
receiving the set of multiple serially acquired MRS FID frames from the multi-frame MRS acquisition series from the ROI in a subject;
associating first and second groups of FID frames within the set with first and second different relative phases, respectively, of a phase step cycle along the MRS acquisition series;
processing the first and second groups separately;
averaging the first and second groups separately to form first and second average interim spectra; and
averaging the first and second average interim spectra to provide the post-processed MRS spectrum.
2. The method of claim 1 , further comprising performing at least one of phase shift correction, frame editing, and frequency shift correction separately for the first and second groups.
3. The method of claim 1 , further comprising:
performing the method on a number equal to N groups of FID frames, the FID frames comprising similar phasing within each group but different than in other groups;
processing each of the N groups separately;
averaging the FID frames separately within each group;
averaging the group averages together; and
wherein N equals an integer more than two.
4. The method of claim 1 , wherein:
the MRS acquisition series comprises a number F of FID frames;
the different relative phases comprise a unique number S of phase steps; and
F divided by S equals N, which comprises a whole number.
5. A method performed according claim 1 using a processor, wherein the method further comprises controlling the processor to perform said method using a computer program stored in a non-transitory computer readable medium.
6. The method of claim 1 , wherein the ROI comprises a portion of a musculoskeletal joint.
7. The method of claim 6 , wherein the joint comprises a skeletal joint.
8. The method of claim 7 , wherein the skeletal joint comprises a spinal joint.
9. The method of claim 8 , wherein the ROI comprises at least a portion of an intervertebral disc.
10. A method performed according to claim 1 , wherein:
said MRS acquisition series is acquired from a single voxel positioned within the ROI according to a single voxel spectroscopy pulse sequence.
11. A method performed according to claim 1 , wherein said MRS acquisition comprises a multi-voxel spectroscopy acquisition comprising multiple said MRS acquisition series corresponding to each said voxel, and performing the method on each said MRS acquisition series.
12. A method for processing a set of multiple serially acquired magnetic resonance spectroscopy (MRS) free induction decay (FID) frames from a multi-frame MRS acquisition series from a region of interest (ROI) in a subject, and for providing a post-processed MRS spectrum, comprising:
receiving the set of multiple serially acquired MRS FID frames from the multi-frame MRS acquisition series from the ROI in a subject;
partially post-processing the set of FID frames to produce an interim MRS spectrum;
generating a first baseline estimate using a rank order filter (ROF) on a range of interest of the interim MRS spectrum partially post-processed from the set;
fitting a polynomial to at least a portion of the first baseline estimate to generate a baseline curve; and
subtracting the baseline curve from the interim MRS spectrum to provide the post-processed MRS spectrum.
13. The method of claim 12 , further comprising:
determining first and second regions of the first baseline estimate to be included and excluded, respectively, for the polynomial fit; and
fitting the polynomial to only the first regions of the baseline estimate.
14. A method performed according claim 12 using a processor, the method further comprising controlling the processor to perform said method using a computer program stored in a non-transitory computer readable medium.
15. The method of claim 12 , wherein:
the ROI comprises a portion of a musculoskeletal joint.
16. The method of claim 15 , wherein the joint comprises a skeletal joint.
17. The method of claim 16 , wherein the skeletal joint comprises a spinal joint.
18. The method of claim 17 , wherein the ROI comprises at least a portion of an intervertebral disc.
19. A method performed according to claim 12 , wherein:
said MRS acquisition series is acquired from a single voxel positioned within the ROI according to a single voxel spectroscopy pulse sequence.
20. A method performed according to claim 12 , wherein said MRS acquisition comprises a multi-voxel spectroscopy acquisition comprising multiple said MRS acquisition series corresponding to each said voxel, and performing the method on each said MRS acquisition series.