The invention relates to a method of Dixon-type MR imaging. The method comprises the steps of:subjecting the object (10) to a first imaging sequence (31) comprising a series of refocusing RF pulses, wherein a single echo signal is generated in each time interval between two consecutive refocusing RF pulses,acquiring the echo signals from the object (10) at a first receive bandwidth using unipolar readout magnetic field gradients,subjecting the object (10) to a second imaging sequence (32), which comprises a series of refocusing RF pulses, wherein a pair of echo signals is generated in each time interval between two consecutive refocusing RF pulses,acquiring the pairs of echo signals from the object (10) at a second receive bandwidth using bipolar readout magnetic field gradients, wherein the second receive bandwidth is higher than the first receive bandwidth, andreconstructing a MR image from the acquired echo signals, whereby signal contributions from water protons and fat protons are separated. Moreover the invention relates to a MR device (1) and to a computer program to be run on a MR device (1).

In one embodiment, an MRI apparatus includes: a scanner for acquiring MR signals from an imaging region in which substances having different magnetic resonance frequencies are included; and processing circuitry. The processing circuitry is configured to: calculate phase correction data, which includes information on phase rotation amount due to non-uniformity of a static magnetic field, from MR signals; generate an image by using the phase correction data and the MR signals such that a signal from at least one of the substances in the imaging region is suppressed in the image; and perform decimation processing on first phase correction data to generate second phase correction data, based on information related to a component ratio of the plurality of substances in the imaging region and a plurality of MR signals, wherein resolution of the second phase correction data is lower than the first phase correction data.

A system for performing magnetic resonance imaging (MRI) of a subject has a pulse sequence system that generates a pulse sequence and has a gradient system, a plurality of gradient coils, a radio-frequency system, and a plurality of RF coils. The pulse sequence system causes the subject to emit MR signals which are captured as k-space data. The system also has a k-space ordering processor that collects first k-space data and second k-space data, an MR signal modeler that generates a signal variation model, and a compensation module that applies the signal variation model to the second k-space data collected to produce compensated k-space data. A display processor reconstructs the compensated k-space data into an image of the subject. The compensated data accounts for variation in magnetization during the pulse sequence and k-space data collection to reduce artifacts in the images.

The invention relates to a method of Dixon-type MR imaging. It is an object of the invention to provide an MR imaging technique using bipolar readout magnetic field gradients with an improved estimation of the main field inhomogeneity to eliminate residual artifacts. In accordance with the invention, a method of MR imaging of an object placed in a main magnetic field within an examination volume of a MR device is proposed, wherein the method comprises the steps of: subjecting the object (10) to an imaging sequence to generate at least two sets of echo signals at two or more different echo times using bipolar pairs of readout magnetic field gradients, one set of echo signals being generated at a first echo time (TE1) and the other set of echo signals being generated at a second echo time (TE2), acquiring the echo signals from the object (10), reconstructing a first image from the echo signals attributed to the first echo time (TE1) and a second image from the echo signals attributed to the second echo time (TE2), computing modified first and second images by compensating for a fat shift in the reconstructed first and second images respectively, estimating phase errors in the acquired echo signals on the basis of the first and second images and the modified first and second images using a signal model including the resonance spectra of fat and water and the spatial variation of the main magnetic field, andreconstructing a water image and/or a fat image by separating the signal contributions of fat and water to the acquired echo signals using the estimated phase errors. Moreover, the invention relates to a MR device (1) and to a computer program to be run on a MR device (1).

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 method for magnetic resonance imaging (MRI) includes steps of acquiring by an MRI scanner undersampled magnetic-field-gradient-encoded k-space data; performing a self-calibration of a magnetic-field-gradient-encoding point-spread function using a first neural network to estimate systematic waveform errors from the k-space data, and computing the magnetic-field-gradient-encoding point-spread function from the systematic waveform errors; reconstructing an image using a second neural network from the magnetic-field-gradient-encoding point-spread function and the k-space data.

In a magnetic resonance method and apparatus for generating diffusion-weighted image data, at least two recordings are implemented in which raw data are acquired at raw data points of a raw data memory weighted with a b-value. The raw data memory has a first subregion and a second subregion, the first subregion being more than half of the total raw data points of the raw data memory. In each of the at least two recordings of the first subregion, full sampling takes place, and the second subregion is differently undersampled in the respective recordings. The raw data are combined and reconstructed into image data weighted with the b-value.

The present invention is directed to enabling high-accuracy Nyquist ghost correction without using a reference image.

After at least one of a plurality of images for use in diagnosis is used to perform low-order phase correction without causing aliasing of an image, a 2D phase map including remaining high-order phase errors and phase errors in a phase encode direction is calculated. The low-order phase correction is performed on a pair of pieces of data for image obtained by inverting a readout gradient magnetic field as image data for use in 2D phase map calculation, and positive-polarity/negative-polarity errors of the readout gradient magnetic field are calculated with odd lines and even lines of the pair of pieces of data for image rearranged. In the case of DWI imaging, an image with b-value=0 can be used for 2D phase map calculation.

A storage medium, a magnetic resonance apparatus, and a method for obtaining a correction factor to balance a mismatch between gradient moments are disclosed herein. The method includes providing a magnetic resonance raw dataset, the generation of which includes acquiring the k-space of the magnetic resonance raw dataset in several partial measurements, wherein in each partial measurement, several k-space lines are at least partially sampled by setting a given set of acquisition parameters, applying at least one radio frequency excitation pulse, applying a first gradient in a predetermined direction, applying a second gradient in the predetermined direction, and reading out the magnetic resonance signals. The method further includes: changing the first gradient between at least two partial measurements; processing the magnetic resonance raw dataset several times to shifted raw datasets, each time using a different correction factor to shift the magnetic resonance signals in k-space in the predetermined direction; creating several magnetic resonance image datasets out of the shifted raw datasets; and determining the correction factor with respect to the image datasets.

Methods and systems are provided for hybrid slice encoding. In one embodiment, a method for magnetic resonance imaging comprises, during a scan with a pulse sequence, sampling k-space linearly for a predetermined number of echoes, and sampling k-space centrically for remaining echoes of the pulse sequence. In this way, blurriness along the slice direction may be reduced for 3D fast spin echo imaging.