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US 5,499,629 AGranted
Slice profile stabilization for segmented k-space magnetic resonance imaging
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsAdam B. Kerr, John M. Pauly
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Abstract
Selective RF pulses are applied for segmented k-space imaging sequences with the tip-angle profiles of the pulses varying for stabilizing the entire signal profile and reducing ghosting and blurring artifacts in slice images.
Claims10
A method of obtaining magnetic resonance imaging signals comprising the steps of
- a) placing an object to be imaged in a magnetic field (B.sub.0),
- b) applying a plurality of RF excitation pulses to said object to selectively excite nuclei in a slice through said object, one pulse of said plurality of RF excitation pulses serving as a template for other RF excitation pulses with said plurality of RF excitation pulses having varying tip-angle profiles for said nuclei whereby a stabilized signal profile is realized and wherein a tip-angle profile for the last pulse in the plurality of RF pulses is given, the required sequence of tip-angles to achieve a given signal level for all possible signal levels is known, and the tip-angle profiles .theta..sub.i-1 (x) for pulse i-1 are recursively determined from a known tip-angle profile .theta..sub.i (x) for pulse i, beginning with the last tip-angle profile, and
- c) detecting said signals from said nuclei.
Apparatus for obtaining magnetic resonance imaging signals comprising
- a) means for establishing a magnetic field, B.sub.O, through an object to be imaged,
- b) means for applying a plurality of RF excitation pulses to said object to selectively excite nuclei in a slice through said object, said plurality of RF pulses having varying tip-angle profiles for said nuclei whereby a stabilized signal profile is realized, and the tip-angle, .theta..sub.i, for pulse, i, is related to the tip angle, .theta..sub.i-1, for a preceding pulse, i-1, as follows:
- tan .theta..sub.i-1 (x)=e.sup.-TR.sub.R.sup./T.sub.1 sin .theta..sub.i (x)
- where T.sub.1 is the spin-lattice relaxation time of material in said object to be imaged, and TR.sub.R is the interval between pulses, and
- c) means for detecting said signals from said nuclei.
2 more elements
Dependencies are inferred from the claim text.