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 a combination of at least two of the following:
performing the step on the set at each of the multiple parameter values and providing multiple processed results, respectively, comprising multiple respective feature values, respectively, comparing the feature values of the processed results, determining a chosen feature value among the multiple feature values based upon the comparison and corresponding to a chosen parameter value, setting the parameter to the chosen parameter value for performing the processing step to provide the post-processed MRS spectrum;
providing a first post-processed MRS spectrum, identifying a feature of a downfield region of the spectrum that is located downfield along a larger part per million (ppm) range than a water peak location, comparing the feature with a reference, performing a processing operation based on the comparison and related to the post-processed MRS spectrum;
determining a frequency shift error of an FID frame by performing spectral cross-correlation between the FID frame and a reference frame;
adjusting a phase of an FID frame by a phase shift configured to reduce an extent of the absorption spectrum having a negative value;
estimating a line width between two opposite walls of a water peak region of an FID frame of the series, comparing the estimated line width against a threshold value, and qualifying and including, or disqualifying and excluding, the FID frame from the set for further processing to provide the post-processed MRS spectrum based at least in part upon the comparison;
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; and
generating a first baseline estimate using a rank order filter (ROF) on a range of interest of an 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.
2. One or more non-transitory computer readable media comprising computer instructions configured to cause one or more computer processors to perform actions comprising the method of claim 1 .