Siemens Aktiengesellschaft

Siemens Healthcare Gmbh

Siemens Healthineers Ag

Siemens Aktiengesell Schaft

Forschungszentrum Julich Gmbh

Rene Gumbrecht

Hans-Peter Fautz

Holger Adolf

Thomas Benner

Jörg Ulrich Fontius

Dirk Diehl

Patrick Liebig

Armin Nagel

Jürgen Herrler

Patrick Gross

Joerg Ulrich Fontius

Markus Vester

Dominik Paul

Wolfgang Renz

Rainer Schneider

Matthias Gebhardt

Franz Schmitt

Nikolaus Demharter

Juergen Nistler

Rudi Baumgartl

Nadim Joni Shah

Michael Koehler

Theresa Bachschmidt

Sebastian Wolf

Kaveh Vahedipour

Tony Stoecker

Eva Schneider

Hans Peter Fautz

Tony STÖCKER

Nuclear spins are excited in a region of interest in an object under examination by a radio-frequency pulse. During at least one phase of the radio-frequency pulse, excitation fields are transmitted while magnetic field gradients are simultaneously applied so that the magnetization of the nuclear spins moves on a trajectory through a transmission k-space. In a first phase of the at least one phase of the radio-frequency pulse, the trajectory moves at a radial distance around the center of the transmission k-space. The radial distance corresponds to the radius of a sphere superimposed with at least one radial harmonic.

Method for exciting nuclear spins

A pulse-design unit for creating pulse data for controlling a magnetic resonance system includes a data interface configured for receiving an examination scheme, and a calculation module configured for generating pulse data based on an examination scheme. The pulse-design unit includes a data grid and/or parameter values created from map pairs of a plurality of patients and is configured to select and/or calculate pulse data using the data grid and/or parameter values and a provided examination scheme. A method and a control device for controlling a magnetic resonance imaging (MRI) system and a related magnetic resonance imaging system are also provided.

Method and device for controlling a magnetic resonance imaging system

A method is provided for calibration of a magnetic resonance device with a transmitting device for generating an excitation field. In a first acquisition phase, a first transmitting coil element is detuned, at least one second transmitting coil element is tuned, and an MR data set is acquired using the transmitting device. In a second acquisition phase, the first transmitting coil element, the at least one second transmitting coil element are tuned, and at least one further MR data set is acquired using the transmitting device. By an arithmetic unit, a calibration factor is determined based on the MR data set and the at least one further MR data set for calculating a total voltage value at a feeding point of the first transmitting coil element from voltage values, which may be measured at a measuring point of an electrical supply line of the first transmitting coil element.

Calibration of a magnetic resonance device and estimating a specific absorption rate

A computer-implemented method is disclosed for providing an actuation sequence which specifies transmit signals for at least one high-frequency transmit channel of an antenna arrangement of a magnetic resonance device for acquiring measurement data of an object under investigation by the magnetic resonance device. The method includes providing different actuation sequences, wherein each sequence is the result of an optimization method and which differs with regard to the value of an optimization parameter taken into account in the course of the optimization method. The method further includes providing a plurality of field distribution maps, (e.g., at least one Bmap and/or at least one Bmap), acquired by the or a further magnetic resonance device from the object under investigation. The method further includes selecting the actuation sequence to be used from the different actuation sequences depending on the field distribution maps and providing the actuation sequence to be used.

Computer-implemented method for providing an actuation sequence and method for acquiring measurement data by a magnetic resonance device

In order to reduce the memory footprint used for monitoring specific absorption rate (SAR) in a magnetic resonance imaging (MRI) system, a hybrid sliding window method is provided. The method includes receiving a measured value once every first time interval, processing the measured value, and storing a value resulting from the processing in a first memory element. Measured values stored in second memory elements are summed every second time interval, where the first time interval is less than the second time interval. A representation of SAR is calculated every first time interval based on the value resulting from the processing and the sum of the measured values of the second memory elements. When the second time interval is reached, the value stored in the first memory element is moved to one of the second memory elements, and the value stored in the first memory element is reset to zero.

Hybrid averaging method for specific absorption rate supervision

A method for controlling a magnetic resonance system outputs a pulse sequence including a first slice-selective excitation pulse that excites a first slice with a first magnetization. The pulse sequence includes a second slice-selective excitation pulse that excites a second slice with the first magnetization and a third slice-selective excitation pulse that excites the first slice with a second magnetization that cancels the first magnetization. The pulse sequence also includes and a fourth slice-selective excitation pulse that excites the second slice with a magnetization that cancels the first magnetization. The first slice and the second slice intersect.

Controlling magnetic resonance systems

A method for operating a transmission device of a magnetic resonance device is provided. In order to actuate coil elements of a radiofrequency coil with different phases, phase differences in a reference plane are taken into consideration. In a first calibration measurement to be performed once for each transmission path, a first phase of a transmitted radiofrequency signal is measured by an internal measuring device installed permanently in the transmission device spaced apart from the reference plane. A second phase of the transmitted radiofrequency signal is measured by a second, external measuring device to be connected to the reference plane for the first calibration measurement. At least one phase of the first phase and the second phase is taken into consideration in the phase-accurate actuating of the coil elements and/or for correcting further measurements with the internal measuring device.

Operation of a transmission device of a magnetic resonance device

A circuit arrangement for driving a transmission coil arrangement with at least two individual transmission coils of a magnetic resonance system for supplying a radiofrequency signal for producing alternating electromagnetic fields over at least two channels, with in each case a digital section and an analog section, is provided. In the digital section, in an envelope generator, base frequency signals that respectively generate an envelope are provided. The circuit arrangement also includes an intermediate frequency oscillator that generates a common intermediate frequency, a frequency mixer per channel for mixing the common intermediate frequency into the base frequency signals, and in the analog sections of the channels, respectively, second frequency mixers that mix a common radiofrequency signal into each base frequency signal. The envelope is transmitted, with the mixed-in intermediate frequency signal, and the total signal thus obtained is respectively conducted to an individual transmission coil via a respective amplifier.

Circuit arrangement for the driving electronics of a magnetic resonance system

In a method to determine a B1 phase map for at least two excitation modes of a radio-frequency coil arrangement of a magnetic resonance apparatus, the radio-frequency coil arrangement having multiple independently controllable transmission channels, and the B1 phase map describing, with spatial resolution, the phase of radio-frequency field this is generated in a respective excitation mode relative to a common reference phase map, first magnetic resonance data describing the phase change of a basic magnetic field of the magnetic resonance apparatus between a first echo time and a second echo time are acquired, and are evaluated to determine a spatially resolved Larmor frequency value that describes the deviation from a nominal Larmor frequency of the magnetic resonance apparatus. To correct raw phase maps derived from second magnetic resonance data acquired using a respective one of the excitation modes, a correction map, determined relative to the reference phase map, is calculated and subtracted from the raw phase map under consideration of the Larmor frequency value and the echo times in the acquisition of the second magnetic resonance data.

Method and magnetic resonance apparatus to determine a B1 phase map

An MR image is produced from data acquired by radiating an RF pulse and switching multiple bipolar magnetic field gradients to generate multiple gradient echoes that are acquired in a raw data set with multiple raw data lines by a reception coil, the multiple gradient echoes being acquired with bipolar magnetic field gradients of different polarity. Due to the bipolar magnetic field gradients of different polarity, in the raw data set first raw data lines are filled with MR signals in one direction in raw data space, and second raw data lines are filled with MR signals in the opposite direction. The MR image is reconstructed from MR signals that have simultaneously been acquired with at least two different reception coils, by generating a first coil raw data set from the raw data set in the image reconstruction, which coil raw data set has only the raw data lines of the raw data set that were filled with MR signals in one direction, and by selecting a second coil raw data set that has only the raw data lines of the raw data set that were filled with MR signals in the other set direction. The MR image is reconstructed from the two coil raw data sets using a parallel imaging reconstruction algorithm, under the assumption that the two coil raw data sets have been acquired by different reception coils.

Method and magnetic resonance apparatus for image reconstruction with multiple virtual coils

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

In a method for correction of a B0 field map measured with a magnetic resonance device, that describes deviations from a nominal field strength in the homogeneity area of the magnetic resonance device by deviations from a nominal frequency for protons bonded to water, the deviations being represented as Larmor frequency values for different picture elements shifted by chemical shifts, the B0 field map is recorded with spins of the fat and water protons not in phase. The B0 field map is segmented by evaluating the differences of the Larmor frequency values of adjacent picture elements of the B0 field map in at least two contiguous clusters. For each cluster, a decision is made on the basis of a smoothness criterion and a compactness criterion as to whether a cluster containing a majority of protons bonded into fat is involved. Clusters identified as containing a majority of protons bonded into fat are corrected by lowering the Larmor frequency values by the difference between the nominal frequency for protons bonded into water and the corresponding nominal frequency for protons bonded to fat.

Method and magnetic resonance apparatus for correction of a B0 map for chemical shifts

A method and control device operate a magnetic resonance system in order to execute a first pulse sequence that includes an excitation phase and an acquisition phase. In the excitation phase, a first gradient is applied in a gradient direction to generate a spatially dependent basic magnetic field. A selective radio-frequency excitation pulse is executed, wherein the selective radio-frequency excitation pulse excites a first material and does not excite a second material in a first partial region of an examination volume, and wherein the selective radio-frequency excitation pulse does not excite the first material and excites the second material in a second partial region of the examination volume. In the acquisition phase, non-selective refocusing pulses are executed in order to acquire raw data of the first and second partial region of the examination volume, which acquisition is spatially coded along the gradient direction.

Method and control device to control a magnetic resonance system

A method for generation of a radio-frequency (RF) pulse for excitation of nuclear spins in a predetermined layer of a specimen for magnetic resonance imaging and a magnetic resonance imaging device for performing the method are provided. The method includes determining a variation of a magnetic field in a measuring volume, and defining a spectral frequency distribution of the RF pulse. The RF pulse with the spectral frequency distribution is configured to excite nuclear spins in the specimen. The nuclear spins are polarized by the magnetic field at a predetermined flip angle in the measuring volume under a boundary condition of a substantially minimum energy content. The method also includes generating the RF pulse with the defined spectral frequency distribution.

Method and apparatus for SAR reduction using B0 specific RF excitation

In a computer-implemented method, device and system for controlling an imaging system, a specific absorption rate is calculated with a computation unit and an RF transmission signal of the imaging system is controlled with a control device. The process of controlling of the RF transmission signal includes disconnecting the RF transmission signal when a remaining period during which the RF transmission signal is harmless for the patient has been reduced to zero.

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Herzogenaurach, Germany

Rene Gumbrecht