Disclosed is a method for generating a time-dependent magnetic field gradient in diffusion weighted magnetic resonance imaging G(t)=[G.sub.x(t)G.sub.y(t)G.sub.z(t)].sup.T, which is asymmetric in time with respect to a refocusing pulse, by meeting one or more of the requirements: 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); minimize A or m=(Tr[AA]).sup.1/2 where A=∫.sub.P1G(t)G(t).sup.Tdt−∫.sub.P2G(t)G(t).sup.Tdt where P1 and P2 represent time intervals prior to and subsequent to the refocusing pulse; m is smaller than a threshold value. an attenuation factor ${\mathrm{AF}}_p=\exp \left(-\frac{t}{T2*}\right)$
due to T2* relaxation is one. Signal attenuation due to concomitant field gradients, regardless of the shape or orientation of the diffusion encoding b-tensor and the location of signal is hereby minimized.

The invention relates to a method of Dixon-type MR imaging of an object (10) placed in an examination volume of a MR device (1). It is an object of the invention to provide a method that enables an improved Dixon water/fat separation in combination with a dual-acquisition gradient-echo imaging sequence. The method comprises the steps of: subjecting the object (10) to a dual-acquisition gradient-echo imaging sequence comprising a series of temporally equidistant RF excitations, wherein one gradient echo is generated in each repetition time between successive RF excitations with the echo time alternating between a first and a second value (TE1, TE2), and wherein phase-encoding magnetic field gradients (P, S) are switched in each repetition time to sample a pre-defined region of k-space; acquiring echo signals from the object (10), wherein each gradient echo associated with either the first or the second echo time value (TE1, TE2) is sampled as a partial echo, and—reconstructing an MR image from the acquired echo signals, whereby signal contributions from water and fat are separated. Moreover the invention relates to an MR device (1) and to a computer program to be run on an MR device (1).

A method of medical imaging including receiving k-space data that is divided into multiple k-space data groups, selecting one of the multiple k-space data groups as a reference k-space data group, and calculating spatial transform data for each of the multiple k-space data groups by inputting the multiple k-space data groups and the reference k-space data group into a transformation estimation module. The spatial transformation estimation module is configured for outputting spatial transform data descriptive of a spatial transform between a reference k-space data group and multiple k-space data groups in response to receiving the reference k-space data group and the multiple k-space data groups as input. The method further comprises reconstructing a corrected magnetic resonance image according to the magnetic resonance imaging protocol using the multiple k-space data groups and the spatial transform data for each of the multiple k-space data groups.

The present disclosure provides a system and method for magnetic resonance imaging. The method may include obtaining a first set of imaging data, the first set of imaging data being sampled in multiple shots, each shot of the multiple shots corresponding to a plurality of echo times, the first set of imaging data including partially sampled data in a first k space; obtaining a second set of imaging data, the second set of imaging data including fully sampled data in a central region of a second k space; determining fitting data in the first k space based on the first set of imaging data and the second set of imaging data; and/or generating a target image based on the fitting data in the first k space and the first set of imaging data in the first k space.

A magnetic resonance imaging apparatus according to an embodiment includes a static magnetic field magnet, a plurality of radio frequency coils, and processing circuitry. The static magnetic field magnet generates a static magnetic field having a magnetic field strength that changes spatially. The plurality of radio frequency coils receive a nuclear magnetic resonance signal generated from a subject by an influence of a radio frequency pulse transmitted to the subject, the subject being placed in the static magnetic field having a magnetic field strength that changes spatially. The processing circuitry controls each of the plurality of radio frequency coils to receive the nuclear magnetic resonance signal at each of a plurality of frequencies tuned according to at least a distribution of the static magnetic field.

In a method for magnetic resonance imaging pseudorandomly undersampled k- space imaging data is acquired with multiple receiver coils of an MRI imaging apparatus. MR image reconstruction is performed to produce a reconstructed MR image from the k-space imaging data by iteratively solving sketched approximations of an original reconstruction problem. The sketched approximations use a sketched model matrix As that is a lower-dimensional version of an original model matrix A of the original reconstruction problem. The sketched model matrix As preserves the Fourier structure of the MR reconstruction problem and reduces the number of coils actively used during reconstruction.

Techniques for suppressing noise in an environment of a magnetic resonance (MR) imaging system having at least one primary coil and at least one auxiliary sensor. The techniques involve estimating a transform, that, when applied to noise received by the at least one auxiliary sensor, provides an estimate of noise received by the at least one primary coil. The transform is estimated from data obtained by the at least one primary coil and the least one auxiliary sensor, with the data being weighted prior to estimation to remove or suppress data in regions with a high signal to noise ratio. In turn, the estimated transform may be applied to noise measured by the at least one auxiliary sensor during imaging of a patient, to estimate and suppress noise present in the MR signals received by the at least one primary coil during imaging.

During obtaining a sensitivity distribution in a k-space, data based on which the sensitivity distribution is obtained is expanded with a mirror image to create an expanded image to prevent spectrum leakage, and the sensitivity distribution is stably calculated. During obtaining the sensitivity distribution in the k-space, image data based on which the sensitivity distribution is obtained is inverted as a mirror image to be made into the expanded image, the expanded image is transformed into k-space data, and a frequency component (frequency space data) of the sensitivity distribution is calculated. A region corresponding to the original image data is clipped from the calculated frequency space data, and the sensitivity distribution is obtained.

The present disclosure provides a system and method for magnetic resonance imaging. The method may include obtaining first k-space data collected from a subject in a non-Cartesian sampling manner. The method may also include generating second k-space data by regridding the first k-space data. The method may further include generating third k-space data by calibrating the second k-space data, wherein a calibrated field of view (FOV) corresponding to the third k-space data is constituted by a central portion of an intermediate FOV corresponding to the second k-space data. The method may still further include reconstructing, using at least one of a compressed sensing algorithm or a parallel imaging algorithm, a magnetic resonance (MR) image of the subject based at least in part on the third k-space data.

Disclosed herein is a medical system (100, 300). The execution of machine executable instructions (120) causes a processor (104) to: receive (200) measured gradient echo k-space data (122); receive (202) an off-resonance phase map (124); reconstruct (204) an initial image (126) from the measured gradient echo k-space data; calculate (206) an upsampled phase map (128) from the off-resonance phase map; calculate (208) an upsampled image (130) from the initial image; calculating (210) a modulated image (132) by modulating the upsampled image with the upsampled phase map; calculate (212) a corrected image (134) comprising iteratively. The iterative calculation comprises: calculating (214) updated k-space data by applying a data consistency algorithm (138) to a k-space representation of the modulated image and the measured gradient echo k-space data and calculating (216) an updated image (142) from the updated k-space data. Calculation of the updated image comprises demodulation by the upsampled phase map and applying a smoothing algorithm.