Imaging systems
AssigneeE M I Limited
InventorsMichael Burl, Hugh Clow, Colin G. Harrison, Ian R. Young
Life of this patent
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Abstract
In a medical NMR apparatus it is desirable that the axial magnetic field, Ho, is uniform. The result can in theory be obtained by accuracy of construction but in practice this cannot readily be achieved. It is now proposed to use a field sensing probe system which indicates the value of that field at a plurality of positions in the examined region and provides error signals indicating deviations from uniformity. The field is automatically corrected in response to the error signals by applying currents to field correcting coils. The errors may be considered as distinct gradient and dishing errors which are corrected individually.
Claims10
A medical nuclear magnetic resonance imaging apparatus for providing a nuclear magnetic resonance image of a cross-sectional part of the body of a patient, the apparatus including a coil system arranged to provide a substantially uniform magnetic field in a direction parallel to a chosen axis in the patient's body, probe means for providing signals indicative of values of the magnetic field at a plurality of positions in a region including the part to be imaged, means for determining, from said signals, deviations from uniformity of said magnetic field in the region and correction means responsive to said determinations for reducing said deviations from uniformity.
A method of reducing deviations from uniformity of a substantially uniform magnetic field produced in a nuclear magnetic resonance apparatus for producing an image of a cross-sectional part of the body of a patient, the method including:
- measuring values of the magnetic field at a plurality of positions in a region including the part to be imaged;
- determining, from the measurements, deviations from uniformity of said field;
- and reducing the deviations in response to the determination.
Dependencies are inferred from the claim text.