Other

Koninklijke Philips Corporation N.v.

Case Western Reserve University

Timothy P Eagan

Thomas Chmielewski

Robert L Brown

William A Edelstein

Robert W Brown

Tesfaye Kebede Kidane

Yong Wu

Tanvir Baig

Victor Taracilla

Zhen Yao

Gordon D DeMeester

Michael Andrew Morich

Shmaryu M Shvartsman

Shmaryu Shvarstsman

James A Flock

Gordon D Demeester

Radio frequency (RF) shields used with magnetic resonance imaging (MRI) apparatus may experience gradient field induced eddy currents and RF field induced eddy currents. These eddy currents can cause the RF shield to heat up at an undesirable rate. RF shields are designed to have a desired degree of RF shielding and a desired heating attribute. Design goals for RF shields include gradient field transparency and RF field opacity, both of which can be influenced by eddy currents. Example methods identify a gradient field that will induce eddy currents and identify an RF field that will induce eddy currents. If a region on the RF shield is identified where the desired heating attribute will not be achieved, then a pattern of axial cuts and azimuthal cuts can be made in the RF shield to reduce gradient eddy current heating in the RF shield while maintaining desired RF shielding.

Optimized RF shield design

In preparation for acquiring PET image data, subject motion models are built based on physiologic signal monitoring and MR data is collected and used for improved PET imaging. The physiologic signal monitoring is also used during PET imaging, and the acquired MR data is used for prospective or retrospective gating of the PET image acquisition, or in the PET reconstruction for improved correction/imaging.

MR-PET cyclic motion gating and correction

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.

Active-passive electromagnetic shielding to reduce MRI acoustic noise

A birdcage coil () used in conjunction with a magnetic resonance imaging apparatus includes a first conductive loop (), a second conductive loop (), and a plurality of first conductor rungs () disposed between the first and second conductive loops. A third conductor () is coupled to the second conductive loop at resonance frequencies, such as by second conductor rungs (). The birdcage coil also includes switches () for switching the birdcage coil at least among: 1) an RF transmit mode to operate as an RF transmit coil; and 2) an RF receive mode to operate as an RF receive coil.

Degenerate birdcage coil and transmit/receive apparatus and method for same

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Shaker Heights, OH, United States of America

Timothy P Eagan