Siemens Aktiengesellschaft

Georg Frese

Horst Siebold

Gerhard Brinker

Franz Hebrank

Michael Sellers

Eckart Stetter

Karl-Georg Ladwein

In a the method for determining distortions in an image that can be generated with an imaging system from a subject arranged in an imaging volume of the imaging system, a first region of the imaging volume is presented undistorted in the image and a second region of the imaging volume is presented distorted in the image. Using the imaging system, an image of at least three markings that have a known spatial position relative to one another is produced. A first and a second of the three markings are arranged in the first region and a third of the three markings is arranged in the second region. The position of the imaged markings in the image is determined. An ideal position of the third marking in the image is determined from its known spatial arrangement with respect to the first and second markings. A positional difference of the imaged third marking from its ideal position is identified. The positional difference represents a criterion for the distortion.

Method for determining distortions in an image and calibration object therefor

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

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

A magnet arrangement for a diagnostic magnetic resonance apparatus has an electromagnet arrangement for the production of a homogeneous magnetic field oriented along an axis in an imaging volume. The electromagnet arrangement has first and second windings arranged opposite one another at a distance from one another, transverse to the axis. In relation to the axis, an axial access and a transverse access to the imaging volume are present between the first and second windings.

A tesseral gradient coil for use in a nuclear magnetic resonance tomography apparatus is disposed in the hollow-cylindrical interior of the magnet system which generates the fundamental magnetic field, with one segment of each turn of the gradient coil lying on a small radius and one segment lying on a large radius, with reference to the cylinder access. The parasitic magnetic field which is unavoidably generated by the gradient coil, and which induces currents in the examination subject and in the cryostat of the fundamental field magnet system, is significantly reduced by this coil arrangement. The structure of the gradient coil is particularly suitable for use in the echo planar method, wherein the gradients must be switched rapidly and induced currents are therefore especially disturbing.

Tesseral gradient coil for a nuclear magnetic resonance tomography

A structure for homogenizing the fundamental field in a nuclear magnetic resonance examination apparatus has a plurality of rods consisting at least partially of ferromagnetic material and a structure for supporting the rods in the fundamental magnetic field. The supporting structure may be in the form of rings with the rods extending therethrough at selected positions, either individually or in groups. The location, cross-section, length, shape and number of rods are selected as needed for homogenizing the fundamental field.

Structure for homogenizing the fundamental field in a nuclear magnetic

The invention relates to a nuclear spin tomograph in which means for the homogenization of the normally present magnetic fields are provided. These means are formed by iron plates (24a, 26a, 28a), whose form, size, arrangement and number are chosen accordingly. The iron plates (24a, 26a, 28a) may be applied parallel to the longitudinal direction of the housing on the housing sides and in star form on one of the end walls (20) of the housing (23).

Nuclear spin tomograph

A gradient coil system for an image-generating, nuclear magnetic resonance tomographic apparatus, particularly a zeugmatographic apparatus. The gradient coil system is arranged on a hollow cylindrical support body having an axis which extends along the z-direction of an x, y, z coordinate system which has an origin in the center of an imaging region. The gradient coil system contains, in addition to ring-shaped individual coils for generating field gradients which are substantially constant in the imaging region, a plurality of saddle-shaped coils which are symmetrically arranged through the imaging center for generating field gradients in the x and y directions. The saddle-shaped coils have straight conductor sections extending in the z-direction and arc-shaped conductor sections which extend perpendicularly with respect to the z-axis and along the circumferential direction of the support body. In accordance with the invention, a further arc-shaped conductor section is connected in parallel with the arc-shaped conductor sections, the further arc-shaped conductor section facing a plane of symmetry. All of the arc-shaped conductor sections are displaced in the z-direction from the plane of symmetry by predetermined distances, and each arc-shaped conductor section has an electric linkage factor which is responsive to the distance between the particular arc-shaped conductor section and the plane of symmetry.

Gradient field coil system for nuclear spin tomography

A gradient coil system for an image-generating, nuclear magnetic resonance tomographic apparatus, particularly a zeugmatographic apparatus. The gradient coil system is arranged on a support body of rotational symmetry, illustratively a hollow cylindrical support body, having an axis which extends along the z-direction of an x, y, z coordinate system which has an origin in the center of an imaging region. The gradient coil system contains two pairs of toroidal individual coils which are arranged symmetrically with respect to an x-y plane which extends through the center of the imaging region and which are arranged perpendicular to the z-axis. The direction of current flow in the individual coils of a coil pair is opposite to the direction of flow in the individual coils of the other coil pair. Moreover, further sets of coils are provided for generating field gradient G.sub.x in the x-direction, and G.sub.y in the y-direction. The hollow cylindrical shape of the support body on which the individual coils are arranged permit an imaging region having a substantially spherical volume with a substantially constant field gradient G.sub.z to be achieved. Each of the coils has a predetermined linkage factor which corresponds to the product of the current flowing through the number of coil turns of the coil. Those coils which are arranged further from the plane of symmetry have a substantially larger linkage factor than the coils which are nearer to the plane of symmetry.

Growing community of inventors

Herzogenaurach, Germany

Georg Frese