Method in the form of a pulse sequence for fast nuclear magnetic resonance imaging
AssigneeSiemens Aktiengesellschaft
InventorOliver Heid
Life of this patent
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Abstract
Radiofrequency pulses are emitted to the examination subject with a repetition time that is shorter than the spin grid relaxation time and that is also dimensioned such that the phase deviation between nuclear spins in the examination volume due to magnetic field inhomogeneities is less than 180.degree.. A readout gradient with sub-pulses with changing polarity is activated between two radiofrequency pulses and a nuclear magnetic resonance signal in the form of an echo arises under each sub-pulse. All gradients activated between two successive radiofrequency pulses comprise a gradient-time integral equal to zero.
Claims6
A method for operating a nuclear magnetic resonance tomography apparatus for obtaining a tomographic image of an examination subject disposed in an examination volume, comprising the steps of:
- (a) generating a uniform magnetic field in said examination volume for aligning nuclear spins in said examination subject to a predetermined direction;
- (b) exciting said nuclear spins in said examination subject by generating successive radiofrequency pulses with a repetition time which is shorter than a spin grid relaxation time of said nuclear spins and said repetition time having a duration for maintaining a phase difference during a repetition time, arising between nuclear spins in said examination subject due to magnetic field inhomogeneities, smaller than 180.degree.;
- (c) generating at least a readout gradient, composed of a plurality of sub-pulses with alternating polarity, between two successive radiofrequency pulses, with a nuclear magnetic resonance signal in the form of a gradient echo arising under each sub-pulse, and reading out at least a portion of the nuclear magnetic resonance signals in respective readout intervals;
- and
- (d) dimensioning any gradients generated between two successive radiofrequency pulses to have a gradient time integral of zero.
Dependencies are inferred from the claim text.