Patent application number | Description | Published |
20080204018 | METHOD AND MAGNETIC RESONANCE APPARATUS FOR SETTING A SHIM TO HOMOGENIZE A MAGNETIC FIELD IN THE APPARATUS - 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. | 08-28-2008 |
20080231270 | METHOD FOR ADJUSTMENT OF A B1 FIELD OF A MAGNETIC RESONANCE APPARATUS - 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. Three-dimensionally associable measurement subject data are determined from the measurement subject. Respective tissue types of the measurement subject are determined using the three-dimensional measurement subject data and a segmentation of the measurement subject into regions is effected using the tissue types. Known dielectric properties are respectively associated with the tissue types. The segmentation and the association for all positions of the measurement subject are recorded in respective entries of a database, such that the database contains all entries of the measurement subjects. A radio-frequency simulation for an transmission coils is implemented with the entries of the database, with which electrical field distributions and/or B1 field distributions related to spatial elements are determined as a simulation result and are entered as results into the database. For further magnetic resonance examinations, the entries of the database are used for determination of an optimized current distribution for elements of a transmission coil with which the B1 field is ultimately adjusted. | 09-25-2008 |
20080231274 | METHOD TO CONTROL A MAGNETIC RESONANCE SYSTEM - 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. | 09-25-2008 |
20090134876 | Multi-frequency excitation coils for MRI - 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. | 05-28-2009 |
20100141252 | METHOD TO DETERMINE A PREDETERMINED SIGNAL AMPLITUDE IN MR MEASUREMENTS - 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 T | 06-10-2010 |
20110172515 | DYNAMIC CORRECTION OF HIGH FREQUENCY ADJUSTMENT DURING PARALLEL TRANSMISSION - The present embodiments relate to a system and a method for operating an imaging system, where a plurality of subvolumes of an examination volume of an examination object to be examined with the system is examined. The examination volume is assembled from the plurality of subvolumes, where to examine the subvolumes, at least one HF pulse is transmitted in each case. The at least one HF pulse is optimized for the subvolume that is to be examined therewith respect to specifications and basic conditions applicable for the subvolume. | 07-14-2011 |
20130181713 | CONTROLLING GRADIENT COILS TAKING THE INDUCTIVE COUPLING INTO ACCOUNT - 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. | 07-18-2013 |
20130187653 | ACTIVATION OF FIELD COILS OF A MAGNETIC RESONANCE SYSTEM HAVING EDDY CURRENT COMPENSATION - 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. | 07-25-2013 |
20140300355 | Method and Local Coil System for Producing a Magnetic Resonance Radio Frequency Field - 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. | 10-09-2014 |
20140306708 | Magnetic Resonance Apparatus with Group-by-Group Actuation of Transmission Antennas - 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. | 10-16-2014 |
20150077108 | Measurement of Radio Frequency Excitation Pulses - The embodiments relate to methods for measurement of RF excitation pulses by a magnetic resonance device including 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. In certain embodiments, the excitation data is used for checking process execution sequences. | 03-19-2015 |