Slice selective MRI excitation with reduced power deposition using multiple transmit channels
AssigneeUniversity of Utah Research Foundation
InventorGlen Morrell
Life of this patent
Estimating the term…
Abstract
Described are embodiments for slice-selective excitation for MRI that utilize multiple RF transmit coils, each of which are driven with a separate independent current waveform. These embodiments allow slice-selective excitation with slice profile and excitation time similar to other single-channel excitation, but with reduction in SAR caused by the transverse component of the RF field by a factor up to the number of excitation coils.
Claims20
A method, of emitting radio frequency (RF) pulses into an object during magnetic resonance imaging (MRI), comprising:
- emitting a first RF pulse into the object with a first RF excitation coil element, wherein the first RF pulse comprises a first RF waveform;
- emitting a second RF pulse into the object with a second RF excitation coil element, wherein the second RF pulse comprises a second RF waveform that is time shifted relative to the first RF waveform by 2nπ/γG, where G is a gradient strength of a slice-select gradient, γ is a gyromagnetic ratio in units of radians per unit gradient strength, and n is an integer;
- and
- emitting a third RF pulse into the object with a third RF excitation coil element, wherein the third RF pulse comprises a third RF waveform that is time shifted relative to the first RF waveform by −2nπ/γG.
A system, for emitting radio frequency (RF) pulses into an object during magnetic resonance imaging (MRI), comprising:
- a transmit module, programmed to:
- emit a first RF pulse into the object with a first RF excitation coil element, wherein the first RF pulse comprises a first RF waveform;
- emit a second RF pulse into the object with a second RF excitation coil element, wherein the second RF pulse comprises a second RF waveform that is time shifted relative to the first RF waveform by 2nπ/γG, where G is a gradient strength of a slice-select gradient, γ is a gyromagnetic ratio in units of radians per unit gradient strength, and n is an integer;
- and
- emit a third RF pulse into the object with a third RF excitation coil element, wherein the third RF pulse comprises a third RF waveform that is time shifted relative to the first RF waveform by −2nπ/γG.
A method, of emitting radio frequency (RF) pulses into an object during magnetic resonance imaging (MRI), comprising:
- emitting a first RF pulse into the object with a first RF excitation coil element, wherein the first RF pulse comprises a first RF waveform;
- emitting a second RF pulse into the object with a second RF excitation coil element, wherein the second RF pulse comprises a second RF waveform that is time shifted relative to the first RF waveform by 2nπ cos θ/γG, where θ is an angle between a selected slice and an axial plane, G is a gradient strength of a slice-select gradient, γ is a gyromagnetic ratio in units of radians per unit gradient strength, and n is an integer;
- and
- emitting a third RF pulse into the object with a third RF excitation coil element, wherein the third RF pulse comprises a third RF waveform that is time shifted relative to the first RF waveform by −2nπ cos θ/γG.
Dependencies are inferred from the claim text.