Siemens Aktiengesellschaft

Siemens Healthcare Gmbh

Helmut Lenz

Dirk Schneiderbanger

Matthias Gebhardt

Lennart Kilian

Daniel Niederlöhner

Markus Vester

Dominik Paul

Jürgen Nistler

Swen Campagna

Franz Schmitt

Nikolaus Demharter

Ralph Kimmlingen

Peter Schweighofer

Gerhard Brinker

Wolfgang Bielmeier

Gudrun Ruyters

Carsten Prinz

Mihail Boguslavskij

Eva Eberlein

Franz Hebrank

Axel Friedrich

Roland Werner

Bernd Erbe

Stephan Stöcker

Robert Bleisteiner

Walter Burger

Harald Hofmann

Christian Schwingenschloegl

Christian Plewa

Daniel Scheit

A method for operating an MR system with a gradient pulse amplifier unit that has an end stage connected to a gradient coil with switching elements is provided. The gradient pulse amplifier unit includes a modulator for actuating the switching elements, and lockout switches interconnected in signal paths from the modulator to the switching elements. The gradient pulse amplifier unit includes feeder circuit breakers interconnected in at least some signal paths from the modulator to the switching elements. The circuit breakers are connected in the associated signal paths downstream of the lockout switches. A gradstop unit configured to receive at least one shut-off signal and actuate the lockout switches and the feeder circuit breakers. When the gradstop unit receives a shut-off signal, the gradstop unit actuates the lockout switches to lock out and the feeder circuit breakers to output an actuation signal to the switching elements.

MR system with improved protection against cardiostimulation

A magnetic resonance apparatus with a safety structure for monitoring a safety-related function is provided. The safety structure includes a control path that is configured to control the safety-related function, and a first protect path and a second protect path. The first protect path and the second protect path are configured to acquire a safety-related parameter of the safety-related function. The first protect path is configured to identify a hazardous situation, independently of the control path and the second protect path, based on the safety-related parameter that the first protect path acquires. The second protect path is configured to identify a hazardous situation, independently of the control path and the first protect path, based on the safety-related parameter that the second protect path acquires. The first protect path and the second protect path are each configured to transfer the magnetic resonance apparatus into a safe state in a hazardous situation.

Safety structure of a magnetic resonance apparatus

A method for operating an MR system with a gradient power amplifier having at least one output stage that is connectable to a gradient coil, and having four switching elements connected to one another as an H-bridge includes, to operate the gradient coil, in alternation: switching the switching elements attached to a common first pole of a voltage supply to conductive and switching the switching elements attached to a common second pole of a voltage supply to blocking by inverting power drivers; and switching the switching elements attached to a common first pole of a voltage supply to blocking and switching the switching elements attached to a common second pole of a voltage supply to conductive by inverting power drivers. The switching elements attached to the first pole are switched by non-inverting power drivers, and the switching elements attached to the second pole are switched by inverting power drivers.

MR system with improved protection against cardiac stimulation

A method for actuating a gradient coil can include the provision of a target value for a manipulated variable, the output of the manipulated variable according to the target value to the gradient coil, the capture of an actual value of the output manipulated variable, the scaling of the captured actual value taking into consideration a scaling characteristic depending on the target value, and the transformation of the actual value captured in a scaled manner into a digital actual value.

Method and system for actuation of a gradient coil

A method for monitoring a temporal change in a magnetic field in a magnetic resonance device, as well as an evaluation unit, a magnetic resonance device, and a computer program product for performing the method are provided. The method provides that a position-dependent magnetic field distribution that is produced by the plurality of gradient coils is provided with a plurality of monitoring points. In addition, time-dependent gradient values of the plurality of gradient coils are ascertained. Based on position-dependent magnetic field distribution and the time-dependent gradient values, the temporal change in the magnetic field is ascertained. The temporal change in the magnetic field is monitored by comparing the temporal change in the magnetic field with at least one limit value.

Monitoring of a temporal change in a magnetic field in a magnetic resonance device

A circuit arrangement for an MRT system and a method for operating an MRT system are disclosed. The circuit arrangement includes a gradient amplifier having a switch-mode output stage, a regulator device, and a modulator connected therebetween in the circuit. To ensure patient safety, a control path is integrated into a drive path of the circuit arrangement or the MRT system provided for driving a gradient coil, the gradient coil being connected to an output of the switch-mode output stage. The control path includes a limiter stage connected downstream of the regulator device, the modulator, the switch-mode output stage and its supply voltage. The limiter stage is connected in the circuit between the regulator device and an input of the modulator, to limit a control signal output by the regulator device and limit the voltage for the gradient coil provided by the switch-mode output stage at its output.

Circuit arrangement for an MRT system, MRT system and method for operating an MRT system

A circuit arrangement for generating a current for an inductive load is provided. The circuit includes a switched output state, a modulator, a current measuring device, a controller, a compensator, and a summer. The switched output stage is configured to generate the current from a supply voltage. The modulator is configured to modulate the supply voltage of the output stage depending on a modulator input signal of the modulator. The current measuring device is configured to determine the actual value of the current. The controller is configured to generate a controller signal depending on a setpoint value of the current and the actual value of the current. The compensator is configured to generate from the setpoint value of the current at least one compensation control signal that compensates for nonlinearities of the output stage. The summer is configured to generate the modulator input signal additively from the controller signal and the at least one compensation control signal.

Circuit arrangement, gradient amplifier, and method for compensating for nonlinearities of an amplifier output stage

A circuit arrangement is provided for suppressing offset, offset drift, and 1/f noise during analog/digital conversion. The arrangement includes an analog/digital converter configured to convert an analog input signal into output data, an inverter configured to invert the input signal, a switching element connected upstream of the analog/digital converter and downstream of the inverter and configured to periodically change over between the input signal and the inverted input signal at a predefinable switching frequency, and a switchable negator circuit connected downstream of the analog/digital converter and configured to periodically negate the output data from the analog/digital converter at the switching frequency, the output data being negated when the inverted input signal is applied to the analog/digital converter. An analog/digital converter is also provided with suppression of offset, offset drift, and 1/f noise during analog/digital conversion. A gradient amplifier having a circuit arrangement or an analog/digital converter is also provided.

Suppressing offset, offset drift, and 1/f noise during analog/digital conversion

A control apparatus for a gradient amplifier includes a differentiation unit. The differentiation unit forms a differentiation signal by differential processing from a current desired value signal of the gradient amplifier. At least one electrical low pass filter unit is connected in series with the differentiation unit, and/or at least one electrical high pass filter unit is connected in parallel with the differentiation unit.

Control apparatus with differential control in a magnetically coupled coil system for a current-regulated amplifier powering field coils of a magnetic resonance tomograph

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 method for generating at least one modulator input signal from at least one regulator signal is provided. The method comprising: generating at least one dither signal based on the periodic output of elements of a discrete dither sequence of the basic form DF=0, 1, 2 . . . 2&#x2212;1; and adding the at least one dither signal to the regulator signal. The regulator signal comprises a digital regulator signal with a length of m bits, and the modulator input signal comprises a digital modulator input signal with a length of n bits, where m&#x3e;n.

Method for generating a modulator input signal and premodulator

A method for controlling an electric amplifier is provided. The method includes monitoring a closed-loop control signal of a regulator, which triggers an end stage of the amplifier; adjusting the closed-loop control signal as a function of an output signal of the end stage; comparing the closed-loop control signal with a reference signal; triggering the end stage when an amplitude limit value and a period length limit value are exceeded or undershot by the amplitude value and period length value, respectively, of the closed-loop control signal; and blocking an input side and/or the regulator when the end stage is triggered.

Electric amplifier and method for the control thereof

An electrical amplifier comprising an output stage that can be supplied by an electrical energy source, is connected to a control device on the input side, the control signal of the control device controlling an output signal of the output stage dependent on a parameter value of the energy source. The amplifier is has a compensation device that is connected to the energy source and the control device, and is used to modify the control signal according to the parameter value of the energy source which can be, for example, the network voltage of the energy source. A method for controlling an electrical amplifier comprising an output stage supplied by an electrical energy source includes, determining parameter value of the energy source, deriving a compensation signal therefrom, and a control signal for the output stage is generated according to the compensation signal. The amplifier and method can be used in a gradient amplifier for a magnetic resonance appliance.

Amplifier having a regulation system controlled by the output stage

A stabilization circuit wherein voltages of the secondary winding of a transformer are stabilized with respect to mains voltage fluctuations and load fluctuations, an auxiliary voltage is derived either from a secondary winding of the transformer or an auxiliary transformer. Together with the mains voltage portion of this auxiliary voltage acquired by pulse-width modulation forms the primary voltage of the transformer such that the desired stabilization is achieved.

Stabilization circuit for compensating fluctuations in a voltage at a user

A power amplifier, particularly a gradient amplifier of a magnetic resonance tomography apparatus, has at least one switched output stage containing a power bridge circuit formed by a number of switch elements and connected to a floating intermediate circuit voltage, as well as at least one digital pulse width modulator that generates pulse-width-modulated control signals for all switch elements from a digital input signal in order to generate at least one output stage voltage according to an output stage switch clock. The digital pulse width modulator is preceded by a pre-modulator for forming the digital input signals, with at least one of the digital input signals containing an offset, preferably corresponding to half an LBS.

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Oberasbach, Germany

Helmut Lenz