Claims
- 1. A method for acquiring image data with a magnetic resonance imaging system using an imaging pulse sequence that establishes a steady-state level of longitudinal magnetization in spins being imaged, the steps comprising:applying an RF saturation pulse to the spins to drive their longitudinal magnetization to a level below the steady-state level; delaying the acquisition of image data for a recovery period Trec having a duration determined by a flip angle (α) of an RF excitation pulse in the imaging pulse sequence and a transmit repeat period (TR) of the imaging pulse sequence during which recovery period Trec the longitudinal magnetization of the spins recovers to substantially the steady-state level; and acquiring image data using the imaging pulse sequence.
- 2. The method as recited in claim 1 in which the RF saturation pulse produces a flip angle of substantially 90° in the spin magnetization.
- 3. The method as recited in claim 2 in which the imaging pulse sequence is a spoiled, gradient-recalled echo pulse sequence.
- 4. The method as recited in claim 3 in which the length of the recovery period Trec is determined by the expression: Trec=TR1-cos αwhere α is the flip angle of an RF excitation pulse applied during each imaging pulse sequence and TR is the transmit repeat period (TR) of the imaging pulse sequence.
- 5. A method for acquiring image data with a magnetic resonance imaging system, the steps comprising:a) producing an RF excitation pulse having a flip angle (α); b) producing a slice select magnetic field gradient pulse; c) producing a phase encoding magnetic field gradient pulse; d) producing a readout magnetic field gradient pulse; e) acquiring an NMR signal during the production of the readout magnetic field gradient pulse; f) producing a spoiler magnetic field gradient pulse after acquiring the NMR signal; g) repeating steps a)-f) a plurality of times with a transmit repeat period (TR) less than a spin relaxation time T2, and in which a different phase encoding magnetic field gradient pulse value is employed during each repeat; and h) applying an RF saturation pulse before step a) is performed and delaying the performance of step a) for a recovery period Trec having a duration determined by the flip angle (α) and the transmit repeat period (TR).
- 6. The method as recited in claim 5 in which the RF saturation pulse produces a flip angle of substantially 90°.
- 7. The method as recited in claim 5 in which the length of the recovery period Trec is determined by the expression: Trec=TR1-cos αwhere α is the flip angle of the RF excitation pulse applied during step a) and TR is the transmit repeat period (TR) of the imaging pulse sequence.
GOVERNMENT LICENSE RIGHTS
The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of CA37993 awarded by the National Institutes of Health.
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