Siemens Aktiengesellschaft

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Siemens Aktiengesell Schaft

Franz Schmitt

Hubertus Fischer

Stefan Nowak

Hans-Peter Fautz

Matthias Gebhardt

Ralph Kimmlingen

Winfried Arz

Joerg Ulrich Fontius

Herbert Bruder

Wolfgang Renz

Ralf Ladebeck

Johann Schuster

Juergen Nistler

Andrew Dewdney

Peter Schweighofer

Hans-Erich Reinfelder

Karsten Wicklow

Eva Eberlein

Michael Moritz

Mark A Griswold

Berthold Kiefer

Helmut Lenz

Rene Gumbrecht

Martin Harder

Thomas Benner

Georg Pirkl

Rudi Baumgartl

Oliver Schreck

Anders M Dale

Jeremiah A Heilman

Georg Goertler

Jörg Ulrich Fontius

Andre Van Der Kouwe

Holger Adolf

Mike Müller

Sabrina Harter

Ming Fang

Hans-Peter Hollenbach

Peter Havel

Lothar Regenfus

James W Goldfarb

Bernd Stoeckel

Marian Lattka

Ulrich Fontius

Ines Nimsky

Michael Stehling

Fischer

Piotr Wielopolski

A magnetic resonance RF field is produced in a magnetic resonance imaging system that includes a main magnetic field apparatus and an object-bearing table movable relative to the main magnetic field apparatus and on which a local coil system is arranged. The local coil system includes a plurality of transmission elements. A current location of the object-bearing table relative to the main magnetic field apparatus is established. The transmission elements are automatically connected based on the current location of the object-bearing table.

Method and local coil system for producing a magnetic resonance radio frequency field

Methods are provided for measurement of RF excitation pulses by a magnetic resonance device. The methods include the following acts: (1) sending of an RF excitation pulse by a radio-frequency system of the magnetic resonance device, (2) triggering of a receive event for capturing the RF excitation pulse by the control device of the magnetic resonance device, and (3) capturing of the sent RF excitation pulse in the form of excitation data by the radio frequency system. The excitation data may be used for checking process execution sequences.

Measurement of radio frequency excitation pulses

A gradient pulse generator generates reference current signals for a plurality of gradient coils of a gradient coil system of a magnetic resonance system and supplies each of the reference current signals to a controller assigned to one of the gradient coils. Also supplied to the respective controller is an actual current signal that is characteristic of the current flowing in the respective gradient coil. Each of the controllers generates a control signal and accordingly drives a gradient power amplifier assigned to the respective gradient coil. The gradient power amplifiers apply a current to the gradient coils assigned to the gradient power amplifiers in accordance with the generated control signals. Each of the controllers is also supplied with the reference current signal or the actual current signal of at least one other gradient coil or the time derivative of the reference current signal or the actual current signal.

Controlling gradient coils taking the inductive coupling into account

A controller of a magnetic resonance system determines an activation signal vector based on a target field predetermined for the controller in conjunction with field characteristics of field coils known to the controller. The activation signal vector includes a respective activation signal for each field coil. The controller determines the activation signal vector such that within a predetermined examination volume of the magnetic resonance system, any deviation of an ideal field that would result if ideal coils were subjected to the activation signals of the activation signal vector from the target field is minimized. The controller determines a compensation signal vector based on the activation signal vector in conjunction with eddy current characteristics of the field coils known to the controller. The compensation signal vector is used to minimize a deviation of an actual field from the target field within the predetermined examination volume of the magnetic resonance system.

Activation of field coils of a magnetic resonance system having eddy current compensation

In a method and apparatus to determine a predetermined signal amplitude of an examination subject in an MR measurement in which multiple RF pulses are radiated into the examination subject in a pulse sequence in a pulse series with a repetition time TR that is smaller than the Ttimes of the examination subject, a target magnetization is established for a predetermined point in time after radiation of the respective RF pulse for essentially all RF pulses from the pulse series, a target flip angle and a target phase are determined for different regions of the examination subject for essentially all RF pulses depending on the respective target magnetization, a respective amplitude and phase response is determined for essentially all RF pulses to generate the respective target magnetization after radiation of the respective RF pulse, and the RF pulses with the respective determined amplitude and phase response are radiated into the examination subject.

Method to determine a predetermined signal amplitude in MR measurements

Devices, systems, methods, and other embodiments associated with magnetic resonance imaging (MRI) are described. In one embodiment, an apparatus includes an RF coil for use in multi-nuclear excitation in magnetic resonance imaging (MRI). The RF coil includes a set of two or more L-C coils. Members of the set of two or more L-C coils have individual resonance frequencies. An RF amplifier is placed near the RF coil. The RF amplifier is controllable to selectively produce the individual resonance frequency of a member of the set of two or more L-C coils based, at least in part, on a digital input provided to the RF amplifier.

Multi-frequency excitation coils for MRI

A magnetic resonance device has a patient bed able to be automatically moved by means of a drive apparatus into a patient chamber, as well as a magnet arrangement for creating a magnetic field in the interior of the patient chamber. The drive apparatus is operated so as to move the patient bed at a speed determined as a function of the distribution of the magnetic field in the direction of movement of the patient bed.

Magnetic resonance apparatus with table movement controlled dependent on magnetic field distribution

In a method for adjustment of a B1 field in a magnetic resonance apparatus, the position of the measurement subject relative to a coordinate system is determined from a plurality of measurement subjects with a morphological magnetic resonance measurement. Respective tissue types of the measurement subject are determined using three-dimensional measurement subject data and a segmentation of the measurement subject into regions is effected using the tissue types having known dielectric properties. The segmentation and the association for all positions of the measurement subject are recorded for all subjects in respective entries of a database. A radio-frequency simulation for transmission coils is implemented with the entries of the database wherein electrical field distributions and/or B1 field distributions related to spatial elements are determined and are entered as results into the database, that is then used further magnetic resonance examinations.

Method for adjustment of a B1 field of a magnetic resonance apparatus

In a method for controlling a magnetic resonance system having a radio-frequency antenna structure and a number of individually controllable transmission channels, respective parallel radio-frequency signals are emitted via the transmission channels for generation of a desired radio-frequency field distribution in at least one specific volume region within an examination volume of the magnetic resonance system. A digital signal is generated for each of the transmission channels and is modulated on a carrier frequency. The radio-frequency signal so generated is transmitted via a radio-frequency signal path to the radio-frequency antenna structure and is amplified therein in a radio-frequency power amplifier. The digital signal is manipulated in a characteristic curve correction device on the basis of a correction characteristic curve predetermined for the respective radio-frequency signal path such that a distortion of the radio-frequency signal caused in the appertaining radio-frequency signal path is at least partially compensated. Respective individual correction characteristic curves for a specific measurement are predetermined for the various transmission channels dependent on a field distribution parameter that defines the desired radio-frequency field distribution. A magnetic resonance system implements such a method.

Method to control a magnetic resonance system with individually controllable RF transmission channels

In a method and device for monitoring the physiologically effective radio-frequency exposure in at least one specific volume region of an examination subject in a magnetic resonance data acquisition scan in a magnetic resonance system, amplitude values are acquired that respectively represent, at specific acquisition points in time, a signal amplitude of the radio-frequency signals emitted or to be emitted via the radio-frequency signal channels. Also, phase values are acquired that represent the phases of the appertaining radio-frequency signals at these points in time. Local exposure values are then determined on the basis of the amplitude values and phase values, respectively representing a physiological exposure that the radio-frequency pulses cause at the examination subject at a specific location at a specific time. Based on this, exposure control values are determined that are compared with predetermined exposure limit values. When an exposure limit values is reached or exceeded, a control signal is output.

Method and device for monitoring radio-frequency exposure in a magnetic resonance measurement

In a method for determination or adaptation of a shim for homogenization of a magnetic field of a magnetic resonance apparatus, which magnetic field is provided for the generation of magnetic resonance exposures of a specific examination region, an automatic determination, of a computer and/or supported by an operator on an image output unit of the computer, is made of a three-dimensional volume that is relevant for the determination or adaptation of the shim and that is matched to the examination region and/or an examination protocol by selection from an arbitrary morphology set of selectable volumes (which morphology set is not limited to specific shapes) and/or by generation of an arbitrarily three-dimensional volume not limited to specific shapes. The computer then automatically calculates the shim for the determined or selected three-dimensional volume.

Method and magnetic resonance apparatus for setting a shim to homogenize a magnetic field in the apparatus

In a method for adjustment of a shim device of a magnetic resonance apparatus before an image acquisition in a body region that has a volume of interest, a field distribution is measured in a region encompassing the volume of interest produced with a shim device set according to a basic shim data set. A shim data set that is optimized for the volume of interest is determined by a control device starting from the basic shim data set, dependent on the field distribution; and the optimized shim data set is used for adjustment of the shim device. The basic shim data set is selected from a databank of body region-specific input shim data sets.

Method for adjustment of a shim device of a magnetic resonance apparatus

In a magnetic resonance system and an operating method therefor, a number of independently operable radio frequency signal generator modules are provided or respectively connected to radio frequency coils. A control unit provides a synchronization signal to each of the radio frequency signal generator modules to selectively operate the modules to achieve different types of signal transmission. One of the radio frequency signal generator modules can serve as a master module, that receives the synchronization signal directly from the control unit, and supplies the synchronization signal to the other modules, functioning as slave modules.

Magnetic resonance RF transmission array

In a method and computer program product for operating a tomographic imaging apparatus, a standard measurement protocol is generated by displaying a planning representation of a standard object, defining a spatial position of a standard imaging area in the planning representation, and storing, as the standard measurement protocol for the standard object, a reference to the standard object and parameters of the standard imaging area. Such a standard measurement protocol can then be used in the slice position planning for an actual tomographic measurement, by obtaining data representing features of an examination object, corresponding to the standard object, determining a geometrical relation of the features of the examination object to features of the standard object, and generating an object-specific measurement protocol wherein the imaging area is positioned relative to the examination object by modification of the standard measurement protocol.

Method for slice position planning of tomographic measurements, using statistical images

A switchable longitudinal gradient coil with a cylindrical structure and windings that are symmetrically arranged around the Z-axis is composed of discrete windings or winding packets, or of continuous windings or continuous winding packets, which are provided with a separate supply line to an end face and which, outside of the coil, can be selectively connected to one another individually and/or in groups corresponding to the desired performance features.

Switchable longitudinal gradient coil

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Erlangen, Germany

Franz Schmitt