Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Reexamination Certificate
2008-05-20
2008-05-20
Shrivastav, Brij B (Department: 2859)
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
C324S307000
Reexamination Certificate
active
11551413
ABSTRACT:
The present invention provides an apparatus for reducing acoustic noise in a magnetic resonance imaging device including passive shielding located outside the actively shielded gradient winding elements in order to reduce the magnitude of fields that spread outside the gradient coil assembly in unwanted directions and interact with the magnet cryostat or other metallic magnet parts, inducing eddy currents that cause consequent acoustic noise. The passive shielding elements are conducting layers located on the outer radius of the cylindrical gradient coil assembly in a cylindrical magnet system, conducting layers located at the ends of the gradient coil assembly in a cylindrical magnet system, and conducting layers located inside the actively shielded gradient winding inner elements in a cylindrical magnet system. The passive shielding could also be located on separate structures that are vibrationally isolated from the magnet cryostat. The actively shielded gradient winding can also be extended to portions at the ends of the actively shielded gradient winding and further to portions inside the inner radius of the inner portion of the actively shielded gradient winding. The actively shielded gradient windings and passive shielding should be designed concurrently in order to substantially optimize the gradient linearity and reduce the eddy currents generated in metallic parts of the magnetic resonance imaging system.
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Edelstein, W.A. et al., “Active-Passive Gradient Shielding for MRI Acoustic Noise Reduction”, Proc. Intl. Soc. Mag. Reson. Med. 11, 747 (2004) p. 1.
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Baig Tanvir N.
Brown Robert W.
Eagan Timothy P.
Edelstein William A.
Kidane Tesfaye K.
Hoffman Warnick & D'Alessandro LLC
Shrivastav Brij B
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