Techniques are disclosed for acquiring MR signals of an object under examination in an MR system using a multi echo imaging sequence. The method comprises the steps of applying an RF excitation pulse to the object to generate a transverse magnetization, applying at least two RF refocusing pulses for refocusing the transverse magnetization to generate at least two MR spin echoes for the RF excitation pulse, applying a first magnetic field gradient in a read out direction between the RF excitation pulse and the first of the at least two RF refocusing pulses, applying a second magnetic field gradient in the read out direction after each of the at least two RF refocusing pulses such that the zeroth and first gradient moment is substantially zero for the second magnetic field gradient, and acquiring the at least two MR spin echoes during the at least two second magnetic field gradients.

According to an aspect of the present inventive concept there is provided a method for diffusion weighted magnetic resonance imaging, comprising: generating by a gradient coil of a magnetic resonance imaging scanner a time-dependent magnetic field gradient G(t)=[G.sub.x(t)G.sub.y(t)G.sub.z(t)].sup.T, wherein the gradient G is asymmetric in time with respect to a refocusing pulse and wherein the gradient G is such that A=.sub.0.sup.TEh(t)G(t)G(t).sup.Tdt is zero, where TE is an echo time and h(t) is a function of time which is positive during an interval prior to the refocusing pulse and negative during a time interval after the refocusing pulse.

Systems and methods for performing concomitant field corrections in magnetic resonance imaging (MRI) systems that implement asymmetric magnetic field gradients are provided, in general, the systems and methods described here can correct for the effects of concomitant fields of multiple orders, such as zeroth order, first order, and second order concomitant fields.

Determining parameter values in image points of an examination object in an MR system by an MRF technique. Comparison signal waveforms, established using predetermined recording parameters, and each assigned to predetermined values of the parameters to be determined, are loaded. An image point time series of the examination object is acquired with an MRF recording method such that the acquired image point time series are comparable with the loaded comparison signal waveforms. A signal comparison of a section of the respective signal waveform of the acquired one image point time series is carried out with a corresponding section of loaded comparison signal waveforms to establish similarity values. The values of the parameters to be determined on the basis of the most similar comparison signal waveforms determined are determined, and then stored or output.

In diffusion-weighted magnetic resonance imaging, diffusion-encoded gradient pulses with an amplitude and a duration are activated. The amplitude and the duration of the gradient pulses are varied for various excitations of nuclear magnetization. The echo time for the various excitations of nuclear magnetization can be changed.

In a method and apparatus for acquiring magnetic resonance (MR) data, MR signals are acquired simultaneously from S slices, of a total of N slices of a subject, with S being an SMS factor. The N slices are respectively at different positions from an isocenter of the data acquisition scanner, thereby causing said MR signals to be affected differently by Maxwell terms of magnetic fields that give said MR signals respective signal dephasings that are dependent on the distance of a respective slice from the isocenter. The SMS MR data acquisition sequence is executed with a spacing between each pair of adjacent slices being less than N/S. Maxwell correction gradient moments are calculated at an average position between the S slices, thereby generating corrected k-space data wherein the signal dephasing of the MR signals from the S slices is reduced.

In one embodiment, an MRI apparatus, includes a static magnetic field magnet configured to generate a static magnetic field, a gradient coil configured to generate a gradient magnetic field, a transmission and reception coil configured to transmit an RF signal and receive a magnetic resonance signal, and processing circuitry. The processing circuitry determines whether or not a prescan for calculating a correction value that corrects a phase error is skippable or reducible based on an imaging condition of a main scan, and executes a scan including at least the main scan in accordance with a result of the determination.

A method for actuating a magnetic resonance device according to an MR control sequence, wherein the MR control sequence includes a bipolar gradient pulse between an excitation pulse and a first refocusing pulse, and the bipolar gradient pulse induces a defined Maxwell phase and generates a dephasing gradient moment for a readout gradient.

A magnetic resonance imaging apparatus according to an embodiment includes a calculation unit, a collecting unit, and an execution unit. The calculation unit calculates, based on a pulse sequence used in data collection by fast spin echo method, a phase shift amount on at least one echo component included in each of a plurality of echo signals. The correcting unit corrects, based on the calculated phase shift amount, phases of refocusing pulses applied in the pulse sequence such that phases match at least one of between spin echo components, between stimulated echo components, and between a spin echo component and a stimulated echo component. The execution unit executes the pulse sequence in which the refocusing pulses of the corrected phases are applied.

A magnetic resonance (MR) system for correcting concomitant field effects is provided. The MR system includes a gradient coil assembly including a plurality of gradient coils configured to apply at least one gradient field to a polarizing magnetic field of the MR system. The MR system also includes a second-order correction coil assembly including a first second-order correction coil configured to correct effects of a first term of second-order concomitant fields generated by the at least one gradient field. The system further includes a second-order correction computing device including at least one processor in communication with at least one memory device. The at least one processor is programmed to control the second-order correction coil assembly by instructing the MR system to apply a compensation field to the second-order correction coil assembly asynchronously with the at least one gradient field.