Guenther Pausch

GRADIENT COIL SYSTEM FOR A NUCLEAR MAGNETIC RESONANCE TOMOGRAPHY APPARATUS WHICH REDUCES ACOUSTIC NOISE

The supply of current pulses to gradient coils in a magnetic resonance imaging tomography apparatus results in physical vibration of the coils, causing acoustic noise. For reducing such acoustic noise, a gradient coil system is disclosed wherein the individual gradient coils are secured on a tubular carrier formed by a two concentric shells. The two shells are joined to each other in a manner which is rigid against shearing in the longitudinal direction by connector elements. The self-excited vibrational behavior of the gradient coil system is thereby tuned to lower vibrational amplitudes and to higher vibrational frequencies, so that a more effective damping can be achieved with acoustic damping measures.

Actively shielded transverse gradient coil for nuclear magnetic resonance tomography apparatus

An actively shielded transverse gradient coil arrangement contains a primary coil and a secondary coil that are arranged at a radial spacing from one another. Turns of the primary coil and the secondary coil disposed farther from the center of the examination volume in an axial direction of the gradient coil arrangement have a smaller radial spacing from one another than do turns lying close to the center. The parasitic flux density can thus be minimized. This is particularly important in EPI sequences for avoiding physiological stimulations in the examination subject.

Method for constructing a transversal gradient coil in a magnetic resonance imaging system

For the purpose of constructing a transversal gradient coil, formed by a conductor, for producing a target field distribution with a prescribed current in a magnetic resonance imaging system, a series of points defining the locations of the coil conductor on a carrier are identified by placing a grid mesh network of elementary saddle coils over the carrier, calculating the magnetic field of these elementary saddle coils and defining a number of ampere-turns for each elementary saddle coil with a fit algorithm on the basis of the target field distribution. The discrete conductor position points are then identified by integration which, in combination, define the path of the coil conductor on the carrier.

Actively shielded planar gradient coil for pole plate magnets of a magnetic resonance imaging apparatus

Each pole plate of a pole plate magnet of a magnetic resonance imaging apparatus has a sub-coil of the gradient coil allocated to it. Each sub-coil is composed of a primary and a secondary coil, respectively lying on one of two overlapping surfaces of a frustrum. The winding curve of each sub-coil changes multiply over a surface of the frustrum between the surfaces. The gradient coil can thus be optimized such that the required, maximum current densities become significantly lower compared to conventional, actively shielded arrangements.

Local gradient coil arrangement for nuclear magnetic resonance tomography apparatus

A local gradient coil arrangement having an essentially hollow-cylindrical geometry can be separated at at least one side along a separating line proceeding in the axial direction of the arrangement. All gradient coil conductors that would cross the separating line are interrupted at the separating line. The currents at each side of the separating line are carried via connecting lines that proceed parallel to the separating line. The gradient coil arrangement can thus be divided into two parts without having to provide contacts between these two parts.

NMR tomography apparatus with combined radio frequency antenna and gradient coil

In a combined radiofrequency antenna and gradient coil in a magnetic resonance imaging apparatus, radiofrequency signals are coupled into conductor loops of the gradient coil so that these loops are operated as elements of a radiofrequency antenna. The installation space for a separate radiofrequency antenna can thus be saved. Given the same patient-receiving volume, the diameter of the cylindrical opening of a magnet or the spacing between pole shoes can be reduced, so that the magnets can be more economically built.