Systems and methods for suppressing Nyquist ghost for diffusion weighted magnetic resonance imaging are disclosed. An exemplary method includes acquiring multiple k-space data sets using multiple sets of diffusion weighted imaging pulse sequences, reconstructing a magnetic resonance image from each of the multiple k-space data sets respectively, and averaging magnitudes of the magnetic resonance images to generate an average magnitude magnetic resonance image.

Provided is an MRI image generation method including: acquiring first phase encoding lines obtained by undersampling along a first direction using an MRI device; acquiring second phase encoding lines obtained by undersampling in a second direction different from the first direction using the MRI device; generating a first MRI image based on the first phase encoding lines and the second phase encoding lines; and generating a second MRI image different from the first MRI image based on the first phase encoding lines and the second phase encoding lines.

The invention relates to a method of MR imaging of an object. It is an object of the invention to provide a multi-gradient echo imaging technique with increased acquisition speed and intrinsic suppression of artefacts from Bo inhomogeneities, T.sub.2* decay, chemical shift, motion, and/or flow, in particular in combination with radial or spiral k-space trajectories. The method of the invention comprises the steps of: —subjecting the object (10) to an imaging sequence comprising RF excitation pulses and switched magnetic field gradients, wherein multiple echo signals are generated at different echo times after each RF excitation pulse, —acquiring the echo signal data along radial or spiral k-space trajectories, wherefore the imaging sequence comprises magnetic field gradient blips in the x-/y- and/or z-directions; —separating signal contributions from water and fat to the echo signals and estimating a B.sub.0 map and/or an apparent transverse relaxation time map (T.sub.2* map) using a Dixon algorithm; and —synthesizing an image of a specified contrast from the echo signal data, the Bo map and/or the T.sub.2* map. Moreover, the invention relates to a MR device (1) and to a computer program for a MR device (1).

The invention relates to a method of Dixon-type MR imaging. It is an object of the invention to provide a method that enables efficient and reliable water/fat separation using bipolar readout magnetic field gradients and avoids flow-induced leaking and swapping artifacts. According to the invention, an object (10) is subjected to an imaging sequence, which comprises at least one excitation RF pulse and switched magnetic field gradients, wherein two echo signals, a first echo signal and a second echo signal, are generated at different echo times (TE1, TE2). The echo signals are acquired from the object (10) using bipolar readout magnetic field gradients. A first single echo image is reconstructed from the first echo signals and a second single echo image is reconstructed from the second echo signals. A zero echo time image is computed by extrapolating the phase of the first single echo image at each voxel position to a zero echo time using the phase difference between the first and the second single echo image at the respective voxel position. Flow-induced phase errors are identified and estimated in the zero echo time image, and the phase of the first single echo image is corrected according to the estimated flow-induced phase errors. Finally, a water image and/or a fat image are reconstructed from the echo signals, wherein signal contributions from water and fat to the echo signals are separated using the phase-corrected first single echo image and the second single echo image. Moreover, the invention relates to a MR device (1) and to a computer program to be run on a MR device (1).

In a method for determining imaging parameters for a Magnetic Resonance (MR) image, a set of image sequence parameters of the imaging sequence is determined, a frequency offset of off-resonant tissue potentially present in the object under examination is determined, an allowed maximum position shift of the off-resonant tissue along a slice selection direction is determined, a rotation angle which leads to the allowed maximum shift for the off-resonant tissue is determined based on the determined set of image sequence parameters, and the determined rotation angle is provided to the MR imaging system to allow the MR imaging system to generate the MR image using the determined rotation angle in the imaging sequence.

In a computer-implemented method of training a machine learning based processor, the processor can be trained to derive image data from signal data sets of multiple spin echo sequences. The trained processor can be configured to perform image processing for Magnetic Resonance Imaging (MRI) to derive the image data.

Techniques are disclosed for creating measurement data of an examination object by means of magnetic resonance technology in a plurality of repetitions according to a pulse sequence pattern, existing information about gradients that have already been switched is considered to determine compensation gradients that are possibly to be switched in a following repetition for compensating eddy current effects. Such dynamic determination and switching of compensation gradients make it possible to dynamically compensate eddy currents. Consequently, the image quality of image data reconstructed from measurement data acquired using inventive compensation gradients is increased.

A method for reducing N/2 ghost or Nyquist ghost in magnetic resonance (MR) images is provided The method includes acquiring k-space dataset for an object using an echo planar imaging (EPI) sequence, dividing the k-space dataset into first partial k-space subset data related to positive echoes and second partial k-space subset data related to negative echoes, obtaining third partial k-space subset data that is N/2 or Nyquist ghost-free subset data, respectively registering the first partial k-space subset data and the second partial k-space subset data to a first portion of the third partial k-space subset data corresponding to positive echoes and a second portion of the third partial k-space subset data corresponding to negative echoes, combining the registered first partial k-space subset data and the registered second partial k-space subset data to form full k-space dataset, and reconstructing an image for the object based on the full k-space dataset.

A magnetic resonance imaging system (200, 300, 400) includes a radio-frequency system (216, 214) with multiple coil elements (214) for acquiring magnetic resonance data (264) and a memory (250) for storing machine executable instructions (260) and pulse sequence commands (262). The pulse sequence commands are configured for controlling the magnetic resonance imaging system to acquire the magnetic resonance data according to a SENSE imaging protocol. Execution of the machine executable instructions causes a processor (244) to: control (500) the magnetic resonance imaging system to acquire the magnetic resonance data using the pulse sequence commands; reconstruct (502) a set of folded magnetic resonance images (266) from the magnetic resonance data; calculate (504) a voxel deformation map (270) from a magnetic field inhomogeneity map; and calculate (506) a set of unfolding matrices (274) using a least partially a coil sensitivity matrix (272) for the multiple coil elements, wherein the set of unfolding matrices includes at least one modified unfolding matrix which is calculated at least partially using the a coil sensitivity matrix and the voxel deformation map. Undistorted magnetic resonance image data (276) is calculated (508) using the set of folded magnetic resonance images and the set of unfolding matrices.

In a magnetic resonance readout-segmented diffusion-weighted imaging method, apparatus, and storage medium, a non-linear phase RF excitation pulse is applied to nuclear spins that exhibit a magnetization intensity vector, and applying, in a slice selection direction, a slice selection gradient pulse of duration corresponding to the non-linear phase RF excitation pulse, so as to flip the magnetization intensity vector into the X-Y plane. Diffusion weighting is performed on the magnetization intensity vector flipped into the X-Y plane. A readout-segmented sampling sequence is executed to read out raw data in a segmented manner from the magnetization intensity vector resulting from diffusion weighting. A view angle tilting gradient pulse is applied in the slice selection direction.