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US 6,307,373 B1Granted
Anti-aliasing transmitter coil array for magnetic resonance
AssigneePicker International, Inc.
InventorIan Robert Young
Life of this patent
Estimating the term…
Abstract
In a magnetic resonance imaging apparatus 1 there is a region of good i.e. uniform field between A and B but, where the field falls off, say, at D, the r.f. excitation pulse can produce an alias image of D which overlies the desired image of say, B. To reduce this effect, the r.f. excitation coil 4 comprises an array of small coils, the amplitude and phase of the excitation of which is controlled so that the r.f. field collapses rapidly outside the region of good field.
Claims17
A magnetic resonance imaging apparatus comprising:
- means for generating an axially varying magnetic field distribution having a first field strength at a first region within an imaging region and a second field strength at a second region outside the imaging region, said first and second field strengths being equal and whereby image signals from the first region are subject to aliasing signals from the second region;
- r.f. excitation means for exciting nuclei to resonance, said means including
- an array of coils;
- and
- means for controlling the amplitude and phase of the signal transmitted by each coil so as to confine the r.f. field generated by the r.f. excitation means to the first region whereby the aliasing signals from the second region are reduced.
2 more elements
An apparatus for use in magnetic resonance imaging comprising:
- means for generating a varying magnetic field in an axial direction, the varying magnetic field having an equal field strength in at least first and second non-contiguous regions in the axial direction, whereby image signals from the first region are subject to aliasing signals from the second region;
- a plurality of r.f. coils;
- means for scaling at least one of signals (i) applied to the r.f. coils so as to preferentially excite magnetic resonance in nuclei located in the first region;
- and (ii) received by the r.f. coils so as to preferentially detect magnetic resonance relaxation signals from nuclei located in the first region, whereby the aliasing signals from the second region are reduced.
1 more element
A method comprising:
- generating a varying magnetic field distribution in an axial direction, the varying magnetic field distribution having an equal field strength in at least first and second non-contiguous regions in the axial direction, the first region being in an examination region, whereby image signals from the first region are subject to aliasing signals from the second region;
- using a plurality of r.f. coils to at least one of (i) generate an r.f. field, the phase and frequency of the signals applied to the coils being selected to preferentially excite nuclear magnetic resonance in nuclei located in the first region;
- and (ii) receive r.f. signals, the phase and frequency of the signals received by the coils being adjusted to preferentially detect nuclear magnetic relaxation signals from nuclei located in the first region, whereby the aliasing signals from the second region are reduced.
Dependencies are inferred from the claim text.