Bruker Biospin Ag

Thomas Speck

Michael Fey

Dirk Wilhelm

Markus Weiger

Oskar Schett

Werner H Tschopp

Schimun Denoth

Silvia Buttazzoni

Jacco Douwe Van Beek

Werner Tschopp

A method for homogenizing the static magnetic field with a distribution B(r) in the active volume of a magnetic resonance apparatus having a number N of shim coils defines a target field distribution BT(r) using a filter method in which a norm of the shim currents is influenced by means of filter factors. An optimization procedure works in a parameter space having M control parameters, wherein 2&#x2266;M&#x3c;N. One of the control parameters is used as a weighting parameter for modification of a spatial weighting function and another control parameter is used to control the filter factors. Using this method the hardware limitations can be taken into account when determining the target field distribution, without a significant increase in the computational effort to determine the target field distribution during optimization.

Shimming procedure that includes determination of the target field by optimization in a parameter space of reduced dimensionality

In a coil arrangement for nuclear magnetic resonance comprising a main coil (), a shielding coil (), and at least one correction coil (), the function of which consists in forming a magnetic field gradient with eddy current properties which are as good as possible, the main coil () and the shielding coil () are electrically connected in series with the correction coil (). The deviations of the residual field from the desired design generated by production tolerances are thereby modified by the correction coil in such a fashion that the long-lasting eddy currents are suppressed. This either reduces the waiting time that must lapse after a gradient pulse before a predetermined field homogeneity is achieved or e.g. the deviations from the desired field are minimized in imaging applications.

Gradient coil with correction windings and method for production thereof

A sample container () for NMR measurements defines a volume (V) of sample substance. The sample container () has a first interface (G) towards an environment () and a second interface (G) towards the sample substance (). A susceptibility jump at the second interface Gis sufficiently large that the maximum value of |B'/B| within the volume (V) is at least 0.5 ppm. The geometry of the sample container () is selected in such a fashion that, when a homogeneous magnetic field Bhas been applied, a location-dependent relative field change F is present in the volume (V), which is larger than 20 ppb at least at one point in a center partial volume (V) and a first residual field (R) in the center partial volume (V) is smaller than 1.6 ppb. A second residual field (R) in the lower partial volume (V) is smaller than 30 ppb.

NMR measuring configuration with optimized sample container geometry and method for calculating the shape of the sample container

A sample vessel () made of material with magnetic susceptibility &#x3c7;, for containing a sample substance () with magnetic susceptibility &#x3c7;&#x2260;&#x3c7;to be analyzed in a nuclear magnetic resonance (NMR) spectrometer, has an inner interface Gtoward the sample substance and an outer interface Gtoward the environment () that exhibits magnetic susceptibility &#x3c7;. The shape of the interface toward the sample substance and the interface toward the environment are coordinated to match the discontinuities in susceptibility at the interfaces in such a way that on introduction of the sample tube filled with sample substance into the previously homogeneous magnetic field of an NMR spectrometer, the magnetic field inside the sample substance remains largely homogeneous.

Sample holder for NMR measurements with field homogenization in the sample volume by means of the bordering surfaces of the sample holder

A method for homogenizing a static magnetic field with a magnetic field distribution B(r) for nuclear magnetic resonance spectroscopy by adjusting the currents Cthrough the shim coils, thus creating spatial field distributions C&#xb7;S(r), where r stands for one, two, or three of the spatial dimensions x, y, and z, and said magnetic field distribution B(r) has only a field component along z, in a working volume of a magnetic resonance apparatus with one or more radio frequency (=RF) coils () for inducing RF pulses and receiving RF signals within a working volume, said RF coils having a spatial sensitivity distribution of magnitudes B(r), and with shim coils () for homogenizing the magnetic field within the working volume, said shim coils () being characterized by their magnetic field distributions per unit current S(r) and having components only along z, includes the following steps: In this way a direct one-to-one link is obtained between a set of shim currents and the associated NMR spectrum The quality of the desired NMR spectra can be improved with this method.

Method for automatic shimming for nuclear magnetic resonance spectroscopy

A method for homogenizing a static magnetic field with a magnetic field distribution B(r) for nuclear magnetic resonance spectroscopy by adjusting the currents Cthrough the shim coils, thus creating spatial field distributions C&#xb7;S(r), where r stands for one, two, or three of the spatial dimensions x, y, and z, and said magnetic field distribution B(r) has only a field component along z, in a working volume of a magnetic resonance apparatus with one or more radio frequency (=RF) coils () for inducing RF pulses and receiving RF signals within a working volume, said RF coils having a spatial sensitivity distribution of magnitudes B(r), and with shim coils () for homogenizing the magnetic field within the working volume, said shim coils () being characterized by their magnetic field distributions per unit current S(r) and having components only along z, includes the following steps:

A matrix shim system for generating magnetic field components superimposed on a main static magnetic field, comprising a plurality of annular coils, is characterized in that it comprises g groups G. . . Gof coils, with g being a natural number &#x2267;1, wherein each group Gconsists of at least two single annular coils connected in series, wherein each group Gis designed to generate, in use, a magnetic field For each group G, there are at least two values of n for which with N: the total number of current supplies of the matrix shim system, and R: smallest inside radius of any of the annular coils of the matrix shim system. An individual, adjustable electrical current supply is provided for each group Gof coils. The inventive matrix shim system is both simple in design and stable against current fluctuations.

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Thalwil, Switzerland

Thomas Speck