Method to improve uniformity of magnetization and MR image at 7T human MRIs
AssigneeThe United States of America, as represented by the Secretary, Department of Health and Human Services
InventorBu S. Park
Life of this patent
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Abstract
A measurement volume is divided into multiple regions of interest (ROIs) and RF shimming parameters are independently selected for each of the ROIs. The ROIs have dimensions based on an RF wavelength in a specimen (i.e., based on RF frequency and specimen dielectric constant) and are selected to reduce wavelength-based nonuniformity in specimen excitation. For a multi-segment RF coil having segments situated about a cylindrical surface, ROI shapes include cylinders and cylindrical shells aligned along a coil axis.
Claims21
A method of magnetic resonance imaging (MRI) a specimen, comprising:
- selecting at least two regions of interest (ROIs) of the specimen having dimensions based on a wavelength of RF pulses to be applied to the specimen, wherein the dimensions are less than the wavelength;
- establishing MRI pulse sequences for each of the at least two ROIs, the MRI pulse sequences including RF pulses associated with the wavelength;
- and
- applying the established MRI pulse sequences to the specimen to obtain respective images for each of the at least two ROIs.
A magnetic resonance imaging system, comprising:
- an RF transmit coil operable to apply RF pulses to a specimen;
- an RF receive coil operable to receive a magnetic resonance signal in response to the RF pulses from the RF transmit coil;
- and
- a controller operable to assign a plurality of regions of interest (ROIs) in the specimen and obtain images associated with each of the plurality of ROIs based on the received magnetic resonance signal, wherein the controller is operable to provide RF pulses having different wavelengths to the specimen for each of the plurality of ROIs, each of the wavelengths of the RF pulses determined from a frequency of the RF pulses and electromagnetic properties including a dielectric constant associated with the specimen at the frequency of the RF pulses.
Dependencies are inferred from the claim text.