A method for correcting concomitant gradient field effects in a magnetic resonance imaging (MRI) system includes determining a plurality of first phase difference measurements between two acquisitions using a plurality of first bipolar gradient waveforms applied to a first gradient coil. A first gradient coil constant is determined based on the plurality of first phase difference measurements and compensatory gradient waveforms are determined based on the first gradient coil constant. The compensatory gradient waveforms are applied to the gradient coils along with target gradient waveforms to compensate for a concomitant gradient field.

An asymmetric electromagnet system, method, and method of producing an asymmetric electromagnet system, wherein the asymmetric electromagnet system is for generating an imaging magnetic field in an imaging region with an imaging isocentre, the imaging region being asymmetrically positioned within a gradient coil bore inside a magnetic resonance imaging (MRI) system during imaging, the electromagnet assembly comprising: an asymmetric gradient coil configured to generate a gradient field in the asymmetrically positioned imaging region, at least one gradient axis having the gradient field with a constant offset component such that the position at which the gradient field passes through zero is offset with respect to the imaging isocentre of the asymmetrically positioned imaging region.

During operation, a computer system may acquire magnetic resonance (MR) signals associated with a sample from a measurement device or memory. Then, the computer system may access a predetermined set of coil magnetic field basis vectors associated with a surface surrounding the sample, where coil sensitivities of coils in the measurement device are represented by weighted superpositions of the predetermined set of coil magnetic field basis vectors using coefficients, and where the predetermined coil magnetic field basis vectors are solutions to Maxwell's equations. Next, the computer system may solve, on a voxel-by-voxel basis for voxels associated with the sample, a nonlinear optimization problem for MR information associated with the sample and the coefficients using: a forward model that uses the MR information as inputs and simulates response physics of the sample, the MR signals and the predetermined set of coil magnetic field basis vectors.

Measurements of an arbitrary magnetic field having one or more magnetic field components are acquired from a plurality of magnetometers, and a generic model of at least one of the one or more magnetic field components of the arbitrary magnetic field is generated in the vicinity of the magnetometers. The generic magnetic field model comprises an initial number of different basis functions. Maxwell's equations are applied to the generic magnetic field model to reduce the initial number of different basis functions, thereby yielding a Maxwell-constrained model of the magnetic field component(s) of the arbitrary magnetic field, and the magnetic field component(s) of the arbitrary magnetic field are estimated at each of at least one of the magnetometers based on the constrained magnetic field model and the arbitrary magnetic field measurements acquired from each magnetometer.

A computer that determines coefficients in a representation of coil sensitivities and MR information associated with a sample is described. During operation, the computer may acquire MR signals associated with a sample from the measurement device. Then, the computer may access a predetermined set of coil magnetic field basis vectors, where weighted superpositions of the predetermined set of coil magnetic field basis vectors using the coefficients represent coil sensitivities of coils in the measurement device, and where the predetermined coil magnetic field basis vectors are solutions to Maxwell's equations. Next, the computer may solve a nonlinear optimization problem for the MR information associated with the sample and the coefficients using the MR signals and the predetermined set of coil magnetic field basis vectors.

In a method for generating an image data set and a reference image data set: a first raw data set is provided that is acquired with a MR system and that includes measurement signals at read-out points in k-space that lie on a first k-space trajectory; a second raw data set is provided that is acquired with the same MR system and at the same examination object at read-out points that lie on a second, different k-space trajectory that is different from the first k-space trajectory; image data sets are reconstructed from the first raw data set; a reference image data set is reconstructed from the second raw data set; the reference image data set is compared with each image dataset to generate respective similarity values; and an image data set is selected having a greatest similarity value.

A method, electromagnet device, and system for reducing a higher order term of a concomitant field in an imaging magnetic field during magnetic resonance imaging is described. The electromagnet system has a first shim coil configured to be driven to generate a first compensation magnetic field during imaging according to a first second-order compensation term, the first compensation magnetic field having a similar amplitude but opposite direction as that of a first second-order concomitant magnetic field.

A computer that determines coefficients in a representation of coil sensitivities and MR information associated with a sample is described. During operation, the computer may acquire MR signals associated with a sample from the measurement device. Then, the computer may access a predetermined set of coil magnetic field basis vectors, where weighted superpositions of the predetermined set of coil magnetic field basis vectors using the coefficients represent coil sensitivities of coils in the measurement device, and where the predetermined coil magnetic field basis vectors are solutions to Maxwell's equations. Next, the computer may solve a nonlinear optimization problem for the MR information associated with the sample and the coefficients using the MR signals and the predetermined set of coil magnetic field basis vectors.

Methods, computing devices, and MRI systems that reduce artifacts produced by Maxwell gradient terms in TSE imaging using non-rectilinear trajectories are disclosed. With this technology, a RF excitation pulse is generated to produce transverse magnetization that generates a NMR signal and a series of RF refocusing pulses to produce a corresponding series of NMR spin-echo signals. An original encoding gradient waveform comprising a non-rectilinear trajectory is modified by adjusting a portion of the original encoding gradient waveform or introducing a zero zeroth-moment waveform segment at end(s) of the original encoding gradient waveform. During an interval adjacent to each of the series of RF refocusing pulses a first gradient pulse is generated. At least one of the first gradient pulses is generated according to the modified gradient waveform. An image is constructed from generated digitized samples of the NMR spin-echo signals obtained.

The present disclosure relates to operating an MR system in which MR signals of an object under examination are acquired in an examining region using a multi echo imaging sequence, in which an RF excitation pulse and a plurality of RF refocusing pulses are applied. The techniques include determining a first accumulated phase of a magnetization in the object under examination. Then, a second accumulated phase of the magnetization in the object under examination is determined due to concomitant magnetic fields occurring between a second pair of consecutive RF pulses. Finally, it is determined whether a deviation from the predefined relationship is larger than a threshold and, if this is the case, a measure is applied in view of the fact that the deviation is larger than the threshold.