Koninklijke Philips Corporation N.v.

U.S. Philips Corporation

Jan Konijn

Gerardus Bernardus Jozef Mulder

Martijn Krelis Termeer

Johannes Adrianus Overweg

Cornelis Leonardus Gerardus Ham

Wilhelmus R Mens

Cornelis L G Ham

Theo Jenneskens

Guus Van Hest

Augustinus Bertus Petrus Van Hest

A shielded gradient coil assembly () to generate a gradient magnetic field, the assembly comprises on a plurality of radially inner and outer coaxial cylindrical surfaces a gradient field coil arrangement on the radially inner cylindrical surfaces including a longitudinal gradient field coil system () having one or more axial circumferential electrically conducting hollow z-field windings having a smaller transverse cross-section and a transverse gradient field coil system () having hollow (x,y)—field electrical conductors having a smaller transverse cross-section and arranged as saddle coils on the surfaces of the inner cylindrical surfaces. A gradient shield coil arrangement is provided on the radially outer cylindrical surfaces including a longitudinal gradient shield coil system () having one or more axial circumferential electrically conducting hollow z-shield windings having a larger transverse cross-section and a transverse gradient shield coil system () having solid electrical conductors arranged as saddle coils on the surfaces of the outer cylindrical surfaces. In this way an optimum combination is achieved of efficient direct and indirect cooling of the conductors while keeping eddy current effects at a low level.

Shielded gradient assembly

A gradient coil assembly for a magnetic resonance imaging system () includes at least one gradient coil () and a cooling arangement for cooling the gradient coil (). The gradient coil () includes a solid electrical conductor material forming one or more conductor lines () which are in direct contact with each other. The cooling arrangement includes a cooling channel () for guiding a cooling fluid (). The cooling channel () is arranged outside along the one or more conductor lines () in such a way that in a cross-sectional view one single continuous interface line between the cooling channel () and the one or more conductor lines () is formed. In this way efficient cooling of the gradient coil () may be achieved.

Cooling a gradient coil of a magnetic resonance imaging system

The present invention relates to a magnetic resonance imaging system comprising a main magnet (), the main magnet () comprising a magnet bore, the bore having a longitudinal axis () parallel to the main magnetic field of the main magnet (), the magnet bore comprising a gradient coil system, wherein the gradient coil system comprises a first () satellite coil and an inner coil (), wherein the first satellite coil comprises at least one pair of saddle coils () arranged oppositely over the magnet bore and wherein the inner coil () comprises at least two pairs of saddle coils () arranged oppositely over the magnet bore, wherein the inner coil () is located at a larger diameter from the central axis () than the first () satellite coil, wherein the first satellite coil and the inner coil form a stepped coil structure.

Magnetic resonance imaging system with satellite gradient coils

A tesseral shim coil for shimming the magnetic field of a magnetic resonance system by generating the spherical harmonics of the sine and cosine type of the magnetic field, the tesseral shim coil comprising at least four saddle coils, wherein the sum of the azimuthal span of the at least four saddle coils is less than 360 degrees. First and second sets of shim coils, respectively generating sine and cosine components of the shim fields are combined into a single coil layer, thereby reducing the radial thickness of the shim coil assembly.

Tesseral shim coil for a magnetic resonance system

A magnetic resonance imaging (MRI) system includes a main magnet system for generating a main magnetic field in an examination volume. A gradient coil system is arranged between the main magnet system and the examination volume and includes sub-gradient coils embedded in a binding material which has a glass temperature. A controller controls a temperature of the gradient coil system. A temperature-influencing unit influences the temperature of the gradient coil system on the basis of control signals supplied by the control unit. The control unit and the temperature-influencing unit control the temperature of the binding material of the gradient coil system to a value above the glass temperature during operation of the MRI system.

MRI apparatus with means for noise reduction

The invention relates to a magnetic resonance imaging (MRI) apparatus ( ) comprising a gradient coil assembly ( ) for generating gradient magnetic fields in an imaging volume, the gradient coil assembly ( ) comprising at least three gradient coils ( ) for generating three different gradient magnetic fields. In order to compensate self-induced eddy currents in the gradient coils it is proposed according to the invention to provide a conductive element ( ) in close proximity to at least one of the gradient coils ( ) in order to compensate self-induced eddy currents in the gradient coil assembly ( ). It is thus achieved that undesirable high-order behaviour of the gradient coils is suppressed and that conductive elements ( ) are provided in the gradient coil assembly ( ) such that undesirable high-order behavior of the gradient coils ( ) is suppressed and the nature of the short term self-eddy field becomes similar to that of the gradient coils ( ).

MRI apparatus

The invention relates to a coil system which includes a plurality of series-connected coils ( ) which are provided with parallel coil turn configurations ( ) which are insulated from one another and connected to those of the neighboring coil ( ) so as to form conductive paths ( ) which span coils. Conventional coil systems have the drawback of lack of flexibility in respect of the numbers of turns. It is an object of the invention to provide a coil system which does not have an integer effective number of turns and nevertheless satisfies the requirements imposed as regards the quality of the magnetic field. In accordance with the invention it is proposed that the individual coils ( ) are provided with at least two groups of coil turn configurations ( ) whose numbers of turns deviate from one another and which are connected to the coil turn configurations ( ) of the respective neighboring coil ( ) in such a manner that the summed number of turns of each conductive path ( ) is the same. An advantage is offered by the freedom achieved as regards the choice of the number of turns of the coils.

Coil system

In an rf coil of a magnetic resonance apparatus steps are taken to optimize a uniform rf measuring field. To this end, axially extending current conductors are provided with means for generating a non-constant effective current intensity in current paths extending across a cylindrical surface so as to be parallel with a symmetry axis of the coil. This can be realized by deflecting axial conductors away from the cylindrical surface, by partly shielding them, by adding auxiliary coils to be individually controlled, or by connecting L-C circuits across the current conductors.

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Eindhoven, Netherlands

Jan Konijn