Abstract: A method is presented for accelerating magnetic resonance imaging. In 3D MRI, the k-space in the phase encoding plane is divided into two symmetric parts and three asymmetric parts. Different sampling densities are applied in different parts. Images are reconstructed by iteratively minimizing a cost function when random sampling is applied in each part. A phase constraint term is added into the cost function to improve the quality of the reconstruction by exploiting the conjugate symmetry of k-space.

Abstract: A multi-channel switching system (100) for an MRI gradient coil system is characterized in that the number of channels controlled by the power amplifiers is smaller than the number of switches and the number of channels controlled by the power amplifiers is smaller than the number of coil elements in the coil system. Current in each of the coil elements can be switched to flow in either a positive or negative direction or to bypass the respective coil element and power to the switch elements is delivered via a smaller amount of power lines using a power distribution system providing floating power to each of the switches. This allows to electrically connect matrix coil elements dynamically within a pulse sequence to generate dynamically switched magnetic field profiles and therefore reduce the number of gradient power amplifiers, gradient cables and power supplies needed.

Abstract: A method of MR imaging and spectroscopy to reduce artifacts occurring due to the motion of an object to be represented, wherein the object position is determined quasi-continuously during the runtime of the MR acquisition, which includes one or more partial acquisitions (TA), and wherein motion correction is performed, which comprises dynamic adaptation of the frequency and phase settings of the RF system of the tomograph and of the orientation and amplitudes of the gradients during the runtime of the MR acquisition according to the current object position. The motion correction is thereby applied during a signal weighting period, during a signal read-out period, or between and/or during the two stated periods and the adaptations for motion correction are performed without interrupting or slowing the temporal progression of the MR acquisition. In this way, artifacts due to motion of the object to be represented can be further reduced.

Abstract: A method of MR imaging applies a magnetic field Bgrad1 having a spatially non-linear dependence to select a volume of at least one curved slice. The slice is described by its midsurface AM, a volume of the selected slice being made up of n? partial volumes in each of which gradients of at least one pair of remaining superimposed magnetic fields Bgradi (i>1) exhibit an angle dependence of 70° to 110° with respect to one another and with respect to the normal of the midsurface AM. At least one superimposed magnetic field of the respective pair exhibits a spatially non-linear dependence and combinations of these pairs are used for spatial encoding. In this way, curved surfaces can be mapped efficiently in high resolution and the method can be adapted to the slice shape.

Abstract: A method for magnetic resonance (=MR) imaging, wherein non-linear gradient fields are applied for the purpose of spatial encoding to acquire images of an object to be imaged and wherein the magnet resonance signal radiated from the object to be imaged is sampled on grids in time, to thereby obtain sampling points, is characterized in that the object to be imaged is mapped completely in regions of stronger gradient fields by increasing the density of the sampling points in the center of k-space, and additional sampling points are specifically acquired in the outer regions of k-space according to a k-space sampling pattern depending on the desired distribution of the resolution in the measurement, wherein the MR measurement is calculated with the additional sampling points. An MR imaging method is thereby provided by means of which homogenized resolution is achieved in the MR measurements using non-linear gradient fields for spatial encoding.

Abstract: A method of MR with spatial encoding to generate an image or spectroscopic data of an object of investigation inside an MR apparatus comprises the steps of (a) selecting a volume of interest within the object of investigation, (b) applying an RF pulse to generate a transverse magnetization within the object of investigation, (c) preparing a nonlinear phase distribution within the object of investigation by application of spatially encoding magnetic fields (SEMs), the SEMs comprising of a nonlinear gradient field or a combination of linear and nonlinear gradient fields, (d) effecting primary spatial encoding through application of SEMs, and (e) recording MR signals originating from the object of investigation. Step (c) or (d) thereby comprises applying a sequence of at least two SEMs, at least one of which contains a nonlinear field gradient and at least two of the SEMs having different field geometries.

Abstract: A method of MRI for reduction of motion artifacts in 3D MR data acquisition with multiple segments comprises: the complete acquisition being divided into two parts: basic acquisition and complementary acquisition. Basic acquisition is performed at the beginning. Complementary acquisition is performed after the basic acquisition is finished. View Reordering is prepared for basic acquisition and complementary acquisition separately. Motion monitoring is performed regularly during the data acquisition. Whenever motion is detected, data acquisition stops. Image reconstruction is performed when motion occurs in the phase of complementary acquisition. The final reconstructed image is free of motion artifacts.

Abstract: A method of MRI entails recording and storing MR signals from an object to produce an old set of data. A further measurement of the object is then initiated at a later time to record new MR data, whereby k-space is undersampled in the further measurement. The old data are corrected for changes in the new position of the object, for changes in the sensitivity and exact spatial positioning of the receiver coils as well as for changes in the actual field shimming. The old and new data are then combined to create a new, high resolution image of the object.

Abstract: A method for position dependent change in the magnetization in an object, according to a requirement in a magnetic resonance measurement, wherein radio-frequency pulses are irradiated in conjunction with supplementary magnetic fields that vary in space and over time and are superposed on the static and homogeneous basic field of a magnetic resonance measurement apparatus along a z-direction, is characterized in that non-linear supplementary magnetic fields are used, whose spatial gradient of the z-component is not constant at least at one instant of the irradiation, and that the radio-frequency pulses to be irradiated are calculated in advance, wherein progressions over time of the field strengths of the supplementary magnetic fields in the region of the object that are calculated and/or measured position-dependently are included in this calculation.

Abstract: A method of magnetic resonance imaging (MRI) is characterized by the following steps: a) forming a susceptibility model (305, 403) of at least a part of a subject (S), including an imaged body part (203), by using a structural magnetic resonance image (301) of the part of the subject (S) and/or prior knowledge of the anatomy of the subject (S); b) computing susceptibility-induced field deviations (404) present in the imaging volume at each time MR signals are acquired using the susceptibility model (305, 403) and the knowledge of a monitored position and monitored orientation (401) of the part of the subject (S) at that time; c) using the information about the susceptibility-induced field deviations (404) derived in b) for image correction (406), in particular correction of image distortions and/or intensity modulations. The quality of magnetic resonance imaging of moving subjects is thereby improved.

Abstract: A magnetic resonance method for using radio frequency pulses for spatially selective and frequency selective or multidimensionally spatially selective excitation of an ensemble of nuclear spins with an initial distribution of magnetization in a main magnetic field aligned along a z-axis, wherein a spin magnetization with a given target distribution of magnetization is generated, and for refocusing the spin magnetization, is characterized in that the radio frequency pulse is used as a sequence of sub-pulses of independent duration, courses of gradients and spatial and/or spectral resolution, comprising one or more large angle RF pulses with tip angles greater than or approximately equal to 15°, which generate a gross distribution of magnetization approximating the target distribution of magnetization or a desired modification of the distribution of magnetization with a mean deviation less than or approximately equal to 15°, wherein the actual effect of the LAPs on the distribution of spin magnetization before

Abstract: A method for accelerating data acquisition in MRI with N-dimensional spatial encoding has a first method step in which a transverse magnetization within an imaged object volume is prepared having a non-linear phase distribution. Primary spatial encoding is thereby effected through application of switched magnetic fields. Two or more RF receivers are used to simultaneously record MR signals originating from the imaged object volume, wherein, for each RF receiver, an N-dimensional data matrix is recorded which is undersampled by a factor Ri per selected k-space direction. Data points belonging to a k-space matrix which were not recoded by a selected acquisition schema are reconstructed using a parallel imaging method, wherein reference information concerning receiver coil sensitivities is extracted from a phase-scrambled reconstruction of the undersampled data matrix.

Abstract: A method of MR imaging and spectroscopy reduces artifacts occurring due to the motion of an object to be represented, wherein the object position is determined quasi-continuously during the runtime of the MR acquisition, which includes one or more partial acquisitions (TA), and wherein motion correction is performed, which comprises dynamic adaptation of the frequency and phase settings of the RF system of the tomograph and of the orientation and amplitudes of the gradients during the runtime of the MR acquisition according to the current object position. The motion correction is thereby applied during a signal weighting period, during a signal read-out period, or between and/or during the two stated periods and the adaptations for motion correction are performed without interrupting or slowing the temporal progression of the MR acquisition. In this way, artifacts due to motion of the object to be represented can be further reduced.

Abstract: A method of MR imaging applies a magnetic field Bgrad1 having a spatially non-linear dependence to select a volume of at least one curved slice. The slice is described by its midsurface AM, a volume of the selected slice being made up of n? partial volumes in each of which gradients of at least one pair of remaining superimposed magnetic fields Bgradi (i>1) exhibit an angle dependence of 70° to 110° with respect to one another and with respect to the normal of the midsurface AM. At least one superimposed magnetic field of the respective pair exhibits a spatially non-linear dependence and combinations of these pairs are used for spatial encoding. In this way, curved surfaces can be mapped efficiently in high resolution and the method can be adapted to the slice shape.

Abstract: A method to compensate for the magnetic field heterogeneity inside an object of investigation in a MR device obtains an uncorrected magnetic field distribution of the object and executes an MR sequence with a desired k-space coverage by applying RF pulses to generate a transverse magnetization within the object. MR signal data is recorded, magnetic field shimming parameters are dynamically updated and MR signal data are reconstructed to produce images or localized spectroscopic data. Artifacts in a reconstructed image resulting from an uncorrected magnetic field distribution are suppressed by temporally separating MR signals originating from at least two different sub-volumes within a volume of transverse magnetization by generating a nonlinear phase distribution within the object and by dynamically updating shimming parameters to compensate for the field inhomogeneity distributions within the different sub-volumes in the volume of transverse magnetization.

Abstract: A method of MR with spatial encoding to generate an image or spectroscopic data of an object of investigation inside an MR apparatus comprises the steps of (a) selecting a volume of interest within the object of investigation, (b) applying an RF pulse to generate a transverse magnetization within the object of investigation, (c) preparing a nonlinear phase distribution within the object of investigation by application of spatially encoding magnetic fields (SEMs), the SEMs comprising of a nonlinear gradient field or a combination of linear and nonlinear gradient fields, (d) effecting primary spatial encoding through application of SEMs, and (e) recording MR signals originating from the object of investigation. Step (c) or (d) thereby comprises applying a sequence of at least two SEMs, at least one of which contains a nonlinear field gradient and at least two of the SEMs having different field geometries.

Abstract: A method for magnetic resonance (=MR) imaging, wherein non-linear gradient fields are applied for the purpose of spatial encoding to acquire images of an object to be imaged and wherein the magnet resonance signal radiated from the object to be imaged is sampled on grids in time, to thereby obtain sampling points, is characterized in that the object to be imaged is mapped completely in regions of stronger gradient fields by increasing the density of the sampling points in the center of k-space, and additional sampling points are specifically acquired in the outer regions of k-space according to a k-space sampling pattern depending on the desired distribution of the resolution in the measurement, wherein the MR measurement is calculated with the additional sampling points. An MR imaging method is thereby provided by means of which homogenized resolution is achieved in the MR measurements using non-linear gradient fields for spatial encoding.

Abstract: The pursuit for ever higher field strengths and faster data acquisitions has led to the construction of coil arrays with high numbers of elements. With the SENSE technique it has been shown, how the sensitivity of those elements can be used for spatial image encoding. A method in accordance with the present invention, largely abstains from using encoding gradients. The resulting sensitivity encoded free induction decay (FID) data is then not used for imaging, but for determining field inhomogeneity distribution. The method has therefore been termed SSH for Sense SHimming.

Abstract: A method for accelerating data acquisition in MRI with N-dimensional spatial encoding has a first method step in which a transverse magnetization within an imaged object volume is prepared having a non-linear phase distribution. Primary spatial encoding is thereby effected through application of switched magnetic fields. Two or more RF receivers are used to simultaneously record MR signals originating from the imaged object volume, wherein, for each RF receiver, an N-dimensional data matrix is recorded which is undersampled by a factor Ri per selected k-space direction. Data points belonging to a k-space matrix which were not recoded by a selected acquisition schema are reconstructed using a parallel imaging method, wherein reference information concerning receiver coil sensitivities is extracted from a phase-scrambled reconstruction of the undersampled data matrix.

Abstract: A method for position dependent change in the magnetization in an object, according to a requirement in a magnetic resonance measurement, wherein radio-frequency pulses are irradiated in conjunction with supplementary magnetic fields that vary in space and over time and are superposed on the static and homogeneous basic field of a magnetic resonance measurement apparatus along a z-direction, is characterized in that non-linear supplementary magnetic fields are used, whose spatial gradient of the z-component is not constant at least at one instant of the irradiation, and that the radio-frequency pulses to be irradiated are calculated in advance, wherein progressions over time of the field strengths of the supplementary magnetic fields in the region of the object that are calculated and/or measured position-dependently are included in this calculation.