摘要:
The invention relates to a sparger for introducing a gas or gas mixture into a liquid and to a method for sparging liquids. The sparger according to the invention comprises a cavity, a gas inlet for routing a gas into the cavity and two or more faces, which are or can be pressed onto one another in a positive fashion such that a gas pressed into the cavity through the gas inlet escapes through the gaps occurring between the pressed together faces.
摘要:
A magnetic resonance apparatus including transmission antennas that may be actuated in parallel by a control device of the magnetic resonance apparatus may be operated in a group mode. In the group mode, the transmission antennas are grouped into groups of transmission antennas. The actuation signals of transmission antennas within the respective group are in a respectively predefined relationship relative to one another. A respective group actuation signal for each of the groups of transmission antennas is prescribed for the control device by an operator. The control device carries out checks as to whether a group exposure value established based on the group actuation signals lies below a maximum admissible group exposure limit. If this is the case, the control device establishes the actuation signals for the individual transmission antennas based on the group actuation signals. If this is not the case, the control device carries out another measure.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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, the magnetic resonance system having a radio-frequency antenna structure with a number of individually controllable radio-frequency signal channels for generation of radio-frequency field distributions in an examination volume including the examination subject, 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 in the course of the magnetic resonance measurement. 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, these local exposure 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.
摘要:
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.
摘要:
In a method for operating a MR-tomography device, and MR-tomography device, the gradient coil system can be switched to different field qualities during a pulse sequence, so that an optimized field quality can be chosen during the individual measuring phases of a pulse sequence.
摘要:
A magnetic stimulation device has at least one stimulation coil, which is connected with its terminals to the output of at least one controllable electronic power converter and which has an inductance and current and voltage carrying capability, so that the stimulation pulses it generates permeate at least one volume on the order of magnitude of limbs, head or trunk of a patient. The controllable electronic power converter contains at least one activatable and deactivatable power semiconductor switch with short switching times. The electronic power converter is connected with its input to a voltage intermediate circuit. The voltage intermediate circuit and the controllable electronic power converter have a layout for high output voltages and currents, so that action potentials can be triggered even in deeper neuromuscular tissue of a patient, and the magnetic stimulation device offers wide freedom in the selection of the stimulation pulse shapes.
摘要:
A gradient coil for generating a periodically changing read-out gradient in a magnetic resonance imaging apparatus is operated in a series resonant circuit having a capacitor. One of the elements of the series resonant circuit is charged before the beginning of each read-out gradient. The gradient coil can be charged with current, or the capacitor can be charged with voltage. Such operation either avoids or significantly shortens the transient effect which occurs after excitation of the nuclear spins. The use of a series resonant circuit instead of a parallel resonant circuit significantly reduces the voltage load on the gradient amplifier, so that the gradient amplifier can be constructed simpler and more inexpensively.