Phase-contrast MRI using phased-array multicoil
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsNorbert J. Pelc, Thomas J. Brosnan
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Abstract
MRI signals detected by a phased array of multicoils are combined to provide phase contrast image signals with improved signal-to-noise ratio. Detected complex image signals are obtained for different magnetic gradients and are combined to obtain phase, magnitude, and magnitude weighted image signals for imaging.
Claims18
In a multicoil magnetic resonance imaging system, a method combining signals detected by multicoils for phase-contrast imaging comprising the steps of
- a) detecting complex image signals Z.sub.1i and Z.sub.2i with each coil, i, in two excitation sequences with different magnetic gradients,
- b) obtaining a combined image C, as the summation of (Z.sub.1i Z.sub.2i *)/W.sub.i.sup.2 where
- Z.sub.2i * is the complex conjugate of Z.sub.2i
- W.sub.i is a gain factor for coil, i;
- and
- c) forming an output image dependent on C.
In apparatus for phase-contrast magnetic resonance imaging, the combination comprising:
- a) means for generating a magnetic field,
- b) means for generating at least one magnetic gradient field,
- c) multicoils for detecting complex image signals Z.sub.1i and Z.sub.2i with each coil, i, in two excitation sequences with different magnetic gradients;
- and
- d) means for obtaining a combined image C, as the summation of (Z.sub.1i Z.sub.2i *)/W.sub.i.sup.2 where
- Z.sub.2i * is the complex conjugate of Z.sub.2i
- W.sub.i is a gain factor for coil, i;
- and
- e) means for forming an output image dependent on C.
In a multicoil magnetic resonance imaging system, a method of combining signals detected by multicoils for phase-contrast imaging comprising the steps of
- a) detecting complex image signals Z.sub.1i and Z.sub.2i with each coil, i, in two excitation sequences with different magnetic gradients,
- b) determining velocity induced phase shift image, .DELTA..phi., as follows:
- ##EQU9## where M.sub.i =(.vertline.Z.sub.1i .vertline.+.vertline.Z.sub.2i .vertline.)/2
- .phi..sub.i =phase (Z.sub.1i Z.sub.2i *)
- *=complex conjugate
- W.sub.i =coil gain factor.
In apparatus for magnetic resonance imaging, the combination comprising:
- a) means for generating a magnetic field,
- b) means for generating at least one magnetic gradient field,
- c) multicoils for detecting complex image signals Z.sub.1i and Z.sub.2i with each coil, i, in two excitation sequences with different magnetic gradients, and
- d) means for determining velocity induced phase shift, .DELTA..phi., and M, magnitude multicoil image, as follows:
- ##EQU11## where M.sub.i =(.vertline.Z.sub.1i .vertline.+.vertline.Z.sub.2i .vertline.)/2
- .phi..sub.i =phase (Z.sub.1i Z.sub.2i *)
- *=complex conjugate
- W.sub.i =coil gain factor.
Dependencies are inferred from the claim text.