Siemens Aktiengesellschaft

Horst Siebold

Ralph Oppelt

Georg Frese

Wilhelm Duerr

Helmut Forster

Karl-Georg Heinzelmann

Konrad Meier

Herbert Bruder

Bernd Granz

Arnulf Oppelt

Fritz Breimesser

Guenter Ries

Wilfried Loeffler

Heinrich Seifert

Arnolf Maurer

Wolfgang Frie

Franz Strahwald

Jurgen Vetter

In a computed tomography system equipped with a data-acquisition system and a method for operating such a computed tomography system, the computed tomography system has a radiation detector with at least one linear detector array composed of a row several detector elements aligned adjacent to one another. The data-acquisition system reads out the detector elements and forms difference signals from signals read out from pairs of adjacent detector elements.

Computed tomography apparatus and method for operating same

A magnet arrangement for a diagnostic nuclear magnetic resonance apparatus has a first system for generating a uniform magnetic field in a first imaging volume, the first imaging volume being arranged inside the first system, and a second system for generating a uniform magnetic field in a second imaging volume is in interactive connection with the first system. The second imaging volume is arranged between the first system and the second system.

Magnet arrangement for a diagnostic nuclear magnetic resonance apparatus

A magnet contains a magnetic yoke and two pole shoes, between which a magnetic field of great homogeneity is formed. The pole shoes are provided with special pole plates. At least one pole plate (11d) is separated from a base part (11b) facing the yoke by a narrow correction air gap (15), and can be aligned by means of mechanical setting devices. According to the invention, each pole shoe (11) has a bead-like edge piece (11c) for field correction at its edge area (17b), which surrounds an inner pole shoe area (17a). In this region, the pole plate (11d), which can be aligned laterally separated from the edge piece (21).

Homogeneous field magnet with at least one pole plate to be mechanically

In a magnet arrangement for a diagnostic magnetic resonance apparatus, first and second units operate in combination to generate a magnetic field, the second unit being arranged at a distance from the first, the units determining a region having a substantially homogeneous magnetic field, which is arranged between the two magnetic field-generating units. An access to the region is oriented obliquely to the spacing of the two magnetic field-generating units. The magnetic field-generating units respectively have first and second outer transversal dimensions with the second outer transversal dimension being smaller than the first outer transversal dimension. The first magnetic field-generating unit has an opening that is fashioned as an additional access to the region.

Magnet arrangement for a diagnostic magnetic resonance apparatus

Ultrasound imaging system having a reduced number of lines between the

The magnet contains a magnetic yoke and two pole shoes between which a magnetic field of high homogeneity is formed. The pole shoes are provided with special pole piece device. Each pole piece device is spaced from a base part facing the yoke by a narrow correction air gap. In accordance with the invention, each pole piece device contains two plate-like pole piece elements which are parallel to each other and spaced apart by a gap of predetermined width. In this connection, the plate element facing the base part has a relative permeability (.mu..sub.r 1) which is smaller by at least a factor of 5 than the plate element facing the useful volume, the relative permeability (.mu..sub.r 2) of which element is at least 10,000.

Homogeneous field magnet having pole shoes with pole piece means which

A magnetic resonance imaging apparatus for producing tomograms has a C-magnet with substantially planar pole faces for generating a magnetic field in the direction of the z-axis of a Cartesian coordinate system, for examining a human body having a body axis extending in the direction x-axis, the region to be examined being disposed between the pole pieces, gradient coils substantially parallel to the pole pieces, and a regulator for controlling the gradient currents of the gradient coils using the magnetic flux associated with each gradient coil as the measure value effecting such control. The gradient currents are adjusted dependent on disturbances in the magnetic flux which are caused by eddy currents and saturation effects in the ferromagnetic material in the proximity of the pole faces. Such a regulator can also be used in combination with gradient coils for generating a gradient in the z-direction for compensating for transient inhomogeneities in the main magnetic field.

Magnetic resonance imaging apparatus with regulator for reducing eddy

A surface resonator for use in a magnetic resonance imaging apparatus having a transversal fundamental magnetic field is composed of two sub-systems, each generating a magnetic field with the magnetic fields being perpendicular relative to each other. Each sub-system contains two current loops, both of which enclose the magnetic field allocated to them in the same plane. A circularly polarizing surface resonator is thus obtained for the transversal fundamental magnetic field.

Surface resonator for a magnetic resonance imaging apparatus

A circularly polarizing RF antenna suitable for use in a magnetiic resonance imaging tomography apparatus has four current loops, each formed by two U-shaped conductors with the ends of the lateral legs of the U-shaped conductors disposed opposite to each other in mirror-symmetric fashion, and the ends of the lateral legs being bridged by a resonant capacitor. The current loops are arranged on a carrier which forms a portion of a hollow cylinder, and which is divided in an axial direction between two of the current loops, so that at least one of the current loops is removable without electrical contacts. A divisible RF antenna is thus achieved into which a head or a knee joint can be easily introduced for imaging.

Circularly polarizing RF antenna for an MRI apparatus

A circularly polarizing RF antenna suitable for use in an MRI apparatus for obtaining tomograms of an examination subject includes two antenna systems, each having a winding, having two lateral legs and a middle leg, and a return path which form a resonant circuit in combination with one or more resonant capacitors. The middle legs of the two antenna systems are disposed so that they cross one another. One or more decoupling capacitors are provided between the two antenna systems. A circularly polarizing antenna for a magnetic resonance imaging system is thus obtained having a magnetic field vector in the imaging region which rotates in planes parallel to the pole surfaces of a C-shaped magnet which generates the fundamental magnetic field in the magnetic resonance imaging apparatus.

Circularly polarizing RF antenna for an MRI apparatus having a C-magnet

A resonator for use in a magnetic resonance imaging apparatus for transmitting and receiving high frequency signals is formed by a combination of two antenna sub-systems, which generate respective magnetic fields which are perpendicular to each other, with the currents in the sub-system being phase-shifted by 90.degree. relative to each other, and each sub-system includes a capacitance which defines the resonant frequency. Each of the sub-systems forms a current loop, the current loops containing a common current network and a common base plate, which serves as a return path for both current loops. The junctions of the current network are connected via the resonant capacitances to the base plate, which consists of electrically conductive material. A circularly polarizing resonator is achieved for the transversal, fundamental field of the imaging apparatus, with the resonator also being capable of use as a surface resonator if the spacing between the current network and the base plate is small.

Resonator for a magnetic resonance imaging apparatus

A gradient coil system for a nuclear magnetic resonance tomography apparatus has a set of saddle coils disposed on a first cylindrical surface for generating the x-gradient, and a set of saddle coils disposed on a second, separate cylindrical surface for generating the y-gradient. The saddle coils in each set include three sub-coils having predetermined ampere turns, and formed by cable conductor wound exclusively by convex turns arranged in the same cylindrical surface. A middle coil of the three sub-coils has an arced portion facing the z=0 plane in an x-y-z coordinate system which approximates an arc of an ellipse.

Method for manufacturing gradient coil system for a nuclear magnetic

A magnetic resonance imaging apparatus generates tomograms according to the echo planar imaging method (EPI), with at least one of the gradient coils having a resonant circuit allocated thereto which is excited by an amplifier. A capacitor forms a series resonant circuit with the gradient coil, and a controlled gain amplifier which is operated as a current regulator, such as a switched current regulator, is connected to this series resonant circuit. The read-out gradient G.sub.x is switched on at a time t.sub.0, the gradient G.sub.x having a transient region .tau..sub.1 beginning at t.sub.0 and ending at a time t.sub.2. The gradient current I(t) is steady in this transient region .tau..sub.1, and the integral of the gradient current I(t) over t.sub.0 through t.sub.2 is zero.

Magnetic resonance imaging apparatus and method for operating same

A gradient coil system for a nuclear magnetic resonance tomography apparatus has a set of saddle coils disposed on a first cylindrical surface for generating the x-gradient, and a set of saddle coils disposed on a second, separate cylindrical surface for generating the y-gradient. The saddle coils in each set include three sub-coils having predetermined ampere turns, and formed by cable conductor wound exclusively by convex turns arranged in the same cylindrical surface. A middle coil of the three sub-coils has an arced portion facing the z.dbd.0 plane in an x-y-z coordinate system which approximates an arc of an ellipse.

Gradient coil system for a nuclear magnetic resonance tomography

A gradient coil system for a nuclear magnetic resonance tomography apparatus has main x and y coils, which are split arc saddle coils. The coil arcs are split so that their coupling increases with increasing distance from the plane of symmetry. The x and y main coils have respective x and y auxiliary coils allocated to them, which are also saddle coils and which have an aperture angle less than 90.degree., and which are arranged on the same cylindrical surface. The characteristics of the elementary saddle coils which define the gradient coil field are matched so that the noise terms of the series development of the gradient field are at least partially eliminated.

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Erlangen, Germany

Horst Siebold