Magnetic resonance spectroscopy with real-time correction of motion and frequency drift, and real-time shimming

摘要

This invention relates to localized magnetic resonance spectroscopy (MRS) and to magnetic resonance spectroscopic imaging (MRSI) of the proton NMR signal, specifically to a magnetic resonance spectroscopy (MRS) method to measure a single volume of interest and to a magnetic resonance spectroscopic imaging method with at least one spectral dimension and up to three spatial dimensions. MRS and MRSI are sensitive to movement of the object to be imaged and to frequency drifts during the scan that may arise from scanner instability, field drift, respiration, and shim coil heating due to gradient switching. Inter-scan and intra-scan movement leads to line broadening and changes in spectral pattern secondary to changes in partial volume effects in localized MRS. In MRSI movement leads to ghosting artifacts across the entire spectroscopic image. For both MRS an MRSI movement changes the magnetic field inhomogeneity, which requires dynamic reshimming. Frequency drifts in MRS and MRSI degrade water suppression, prevent coherent signal averaging over the time course of the scan and interfere with gradient encoding, thus leading to a loss in localization. It is desirable to measure object movement and frequency drift and to correct object motion and frequency drift without interfering with the MRS and MRSI data acquisition.