The present disclosure provides a system for MRI. The system may obtain MRI scan data of a subject by directing an MRI scanner to perform an MRI scan on the subject according to a first gradient waveform. The system may also determine a second gradient waveform based on the first gradient waveform and a gradient waveform determination model. The gradient waveform determination model may have been trained according to a machine learning algorithm. The system may further generate a target reconstruction image of the subject based on the second gradient waveform and the MRI scan data.

A method for avoiding artifacts in measurement data captured using a magnetic resonance system which has a gradient unit. The method includes loading data which characterizes the gradient unit of the magnetic resonance system; loading a measurement protocol to be used for capturing the measurement data, wherein the measurement protocol includes gradients to be switched and RF excitation pulses and RF refocusing pulses to be irradiated, wherein, after irradiation of an RF excitation pulse, a train of at least two RF refocusing pulses is irradiated and measurement data is captured after each RF refocusing pulse; determining compensation gradients which, after the capture of the measurement data, are to be switched after a final RF refocusing pulse of the train of RF refocusing pulses associated with the RF excitation pulse and before a following RF excitation pulse as a function of the loaded measurement protocol and of the data which characterizes the gradient unit; and carrying out the measurement protocol using the determined compensation gradients.

The invention relates to a method of MR imaging of an object (10) placed in an examination volume of an MR apparatus (1). It is an object of the invention to enable fast 3D MR imaging that provides motion-compensation and also allows a precise compensation for system imperfections. The method of the invention comprises the steps of: —subjecting the object (10) to a number of shots (S1-S4) of a 3D imaging sequence, wherein a train of MR signals is generated by each shot (S1-S4), each MR signal representing a k-space profile, wherein the set of k-space profiles of each shot (S1-S4) comprises at least one navigator profile and a number of imaging profiles; —acquiring the MR signals; —deriving motion information from the at least one navigator profile; and —reconstructing an MR image from the imaging profiles, wherein a motion-compensation is applied based on the motion information. Motion-induced phase errors can be derived from the navigator profiles, wherein the motion-compensation involves a corresponding phase-correction. Further, phase errors caused by magnetic field gradient imperfections and/or eddy currents can be derived from the navigator profiles and a corresponding phase-correction can be applied during image reconstruction. Moreover, the invention relates to an MR apparatus (1) for carrying out this method as well as to a computer program to be run on an MR apparatus (1).

A method for ascertaining a magnetic field of at least one magnetic coil unit of a magnetic resonance apparatus, a magnetic resonance apparatus, and a computer program product are provided. According to the method, the magnetic field is generated by the at least one magnetic coil unit. A plurality of magnetic field vectors are detected at different positions of the magnetic field by a magnetic field sensor unit, where each magnetic field vector of the plurality of magnetic field vectors describes a strength, such as a magnitude, and a direction of the magnetic field at the respective position. The magnetic field is ascertained. To ascertain the magnetic field based on the plurality of magnetic field vectors, a model of a vector field is ascertained.

In a computer-implemented method for setting a field of view for a magnetic resonance scan, exclusion information describing a region of the original field of view that is unmapped owing to the distortion is ascertained on the basis of the distortion map for at least one first set of field-of-view parameters describing a rectangular or cuboidal original field of view, the exclusion information is used to determine a second set of field-of-view parameters to be used for the magnetic resonance scan, and the magnetic resonance scan is performed using the second set of field-of-view parameters.

Disclosed is a method and apparatus for frequency drift correction of magnetic resonance CEST imaging, and a medium and an imaging device. The method comprises the following steps: firstly, in the frequency drift correction module, exciting a target slice by using a small flip-angle radio-frequency pulse, and acquiring a single line of free induction decay signals or two lines of non-phase encoding gradient echo signals; secondly, respectively calculating a value of the main magnetic field frequency drift according to phase information and an acquisition time of the single line of free induction decay signals or the two lines of non-phase encoding gradient echo signals; then adjusting the center frequency of the magnetic resonance device in real time according to the calculated value of the main magnetic field frequency drift, and achieving the real-time correction of main magnetic field frequency drift; and finally, performing CEST imaging.

In a method for generation of a homogenization field suitable for homogenization of magnetic resonance data of an examination object, first magnetic resonance data from an examination region of the examination object is provided, a trained function is provided, a homogenization field is extracted by processing the first magnetic resonance data by way of the trained function, and the homogenization field is provided.

A correction method for reducing temperature-related deviations in a gradient response of an MR pulse sequence in MR imaging is provided. An MR pulse sequence that includes at least one nominal test gradient is run. A gradient response to the at least one nominal test gradient is repeatedly acquired by a magnetic field measurement in an examination region. A gradient system transfer function is determined based on the gradient response. A corrected MR pulse sequence is determined based on the gradient system transfer function and of the at least one nominal test gradient.

In a method for determining at least one test position for a test measurement to be recorded by means of a magnetic resonance system, a test image is recorded, and at least one test position is selected based on the test image. With methods for the compensation of effects of deviations of gradients actually generated during a readout duration from gradients planned for this readout time duration, the selection of test positions according to the disclosure based on a test image advantageously ensures that the test positions lie in a recording region favorable for the test measurement, e.g. also within an examination object to be examined in the test image. A higher image quality in MR images, which were generated using test measurements carried out at test positions positioned according to the disclosure, can therefore be achieved.

In a method for correcting an influence of an interference effect on a gradient system of a MR apparatus during a MR scan, a gradient pulse is emitted by an amplifier of the gradient system, a gradient sequence is established, an output signal of the amplifier is captured for the gradient pulse, a transfer function is established, and an output signal of the amplifier is established such that the gradient system provides an expected gradient sequence.