Magnetic resonance spectroscopy with real-time correction of motion and frequency drift, and real-time shimming
First Claim
1. An MRI apparatus that permits collecting a complete spectroscopic image with one spectral dimension and up to three spatial dimensions in a single signal excitation comprising:
- an RF pulse transmitting device to excite nuclear spins in a circumscribed region;
a gradient pulse application device to encode k-space;
an NMR signal receiving device;
a spatial-spectral data collection, reconstruction and storage device; and
a pulse sequence control device to generate a magnetic resonance spectroscopy pulse sequence and a magnetic resonance spectroscopic imaging pulse sequence containing a modified water suppression module.
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Abstract
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.
19 Citations
20 Claims
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1. An MRI apparatus that permits collecting a complete spectroscopic image with one spectral dimension and up to three spatial dimensions in a single signal excitation comprising:
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an RF pulse transmitting device to excite nuclear spins in a circumscribed region; a gradient pulse application device to encode k-space; an NMR signal receiving device; a spatial-spectral data collection, reconstruction and storage device; and a pulse sequence control device to generate a magnetic resonance spectroscopy pulse sequence and a magnetic resonance spectroscopic imaging pulse sequence containing a modified water suppression module. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An MRI apparatus that permits collecting a complete spectroscopic image with one spectral dimension and up to three spatial dimensions in a single signal excitation comprising:
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an RF pulse transmitting device to excite nuclear spins in a circumscribed region; a gradient pulse application device to encode k-space; an NMR signal receiving device; a spatial-spectral data collection, reconstruction and storage device; and a pulse sequence control device to generate a magnetic resonance spectroscopy pulse sequence and a magnetic resonance spectroscopic imaging pulse sequence containing a real-time data analysis device and a feedback device to modulate the pulse sequence control device. - View Dependent Claims (15, 16, 17)
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18. A method of magnetic resonance spectroscopic imaging with real-time motion and frequency drift correction comprising the steps of:
- providing a cloverleaf navigator designed and tested for use in gradient echo imaging sequences;
modifying the behavior navigators across the train of echoes water suppression;
modifying modules to include a short navigator immediately after the RF pulse; and
providing a dephasing gradient. - View Dependent Claims (19, 20)
- providing a cloverleaf navigator designed and tested for use in gradient echo imaging sequences;
Specification