The invention relates to a method of Dixon-type MR imaging. The object (10) is subjected to at least two shots of an imaging sequence, each shot comprising an excitation RF pulse followed by a series of refocusing RF pulses, wherein at least a pair of phase encoded echoes, a first echo at a first echo time and a second echo at a second echo time, is generated in each time interval between two consecutive refocusing RF pulses. Two sets of echo signal pairs, a first set and a second set, are acquired using in bipolar pairs of readout magnetic gradients in two respective shots of the imaging sequence. The bipolar pair of readout magnetic field gradients in the acquisition of the second set has an opposite polarity to that of the bipolar pair of readout magnetic field gradients in the acquisition of the first set. Alternatively or additionally the temporal course of the readout magnetic field gradients in the acquisition of the second set is reversed with respect to the temporal course of the readout magnetic field gradients in the acquisition of the first set. Alternatively or additionally the acquisitions of the first and second sets are different from each other with respect to the gradient areas of magnetic field gradients in the readout direction (M) preceding respectively succeeding the bipolar pair of readout magnetic field gradients. Finally, an MR image is reconstructed from the acquired first and second sets of echo signal pairs, whereby signal contributions from water protons and fat protons 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 for measuring water exchange across the blood-brain barrier includes acquiring diffusion weighted (DW) arterial spin labeling (ASL) magnetic resonance imaging (MRI) signals. The method further includes determining optimal parameters to separate labeled water in capillary and brain tissue compartments. The method further includes estimating water exchange rate across the blood-brain barrier based on the DW ASL MRI signals and the optimal parameters, using a total generalized variation (TGV) regularized single-pass approximation (SPA) modeling algorithm.

Magnetic resonance imaging (“MRI”) data are corrected from corruptions due to physiological changes using a self-navigated phase correction technique. Unlike motion correction techniques, the effects of physiological changes (e.g., breathing and respiration) are corrected by making the MRI data self-consistent relative to an absolute uncorrupted phase reference. This phase correction information can be extracted from the acquisition itself, thereby eliminating the need for a separate navigator scan, and establishing an accelerated acquisition. This absolute reference can be computed in a data segmented space, and the subsequent data can be corrected relative to this absolute reference with low-resolution phases.

The invention relates to a method of MR imaging of an object (10). It is an object of the invention to enable MR imaging using radial acquisition with a reduced level of phase distortions and corresponding image artefacts. The method of the invention comprises the steps of: a) generating MR signals by subjecting the object to an imaging sequence comprising RF pulses and switched magnetic field gradients; b) acquiring the MR signals as radial k-space profiles, wherein pairs of spatially adjacent k-space profiles are acquired in opposite directions and wherein k-space profiles acquired in temporal proximity are close to each other in k-space; c) reconstructing an MR image from the acquired MR signals. Moreover, the invention relates to a MR device (1) and to a computer program for a MR device (1).

A pulse sequence generation computing device for a magnetic resonance imaging (MRI) system includes a processor in communication with a memory device. The processor is programmed to receive a pulse sequence including a plurality of gradient pulses and provide a pulse sequence threshold function corresponding to an acoustic noise reduction level. For each gradient pulse in the pulse sequence, the processor is programmed to determine an amplitude and a slew rate of the gradient pulse, determine a threshold amplitude and slew rate of the gradient pulse, and compare the determined amplitude and slew rate to the threshold amplitude and slew rate. If either the determined amplitude or slew rate exceeds the threshold amplitude or slew rate, the processor adjusts at least one of the amplitude and the slew rate of the gradient pulse to an amplitude and a slew rate as defined by the pulse sequence threshold function.

Techniques are disclosed for acquiring at least two measurement datasets, each consisting of measurement data. The two measurement datasets are recorded at points in time at which spins of a first spin species present in the examination object have different phase positions from spins of a second spin species present in the examination object. Moreover, the two measurement datasets are recorded in each case while switching readout gradients of different polarity, and thus the desired measurement datasets may be recorded faster than conventional approaches.

In a method and system for the generation of measurement data required k-space is read out in the readout direction in k-space rows such that at least a first k-space row of the k-space rows does not cover the k-space to be read out in the readout direction in full and at least a second k-space row of the k-space rows covers the k-space to be read out in locations in the readout direction at which the first k-space row does not cover the k-space to be read out. Measurement data that is missing in the k-space is completed in this way on the basis of recorded echo signals stored as measurement data.

The present invention is directed to a system and method for determining blood volume in a subject. Blood volume is an important hemodynamic parameter for monitoring many disorders, such as stoke and cancer. Current MRI techniques for quantification of absolute blood volume for such clinical applications all require injecting exogenous contrast agents. To reduce associated safety risks and cost, the present invention is directed to a non-contrast-enhanced MRI method for blood volume mapping on MRI. The technique of the present invention employs velocity-selective (VS) pulse trains in paired control and label modules for separating vascular signal by subtraction. The Fourier-transform based VS saturation pulse train (FT-VSS) of the present invention has improved performance over conventional VS pulse trains for the blood volume measurement.

A method of Dixon-type MR imaging includes subjecting the object (10) to a first imaging sequence (31) including a series of refocusing RF pulses. A single echo signal is generated in the time interval between two consecutive refocusing RF pulses. The first echo signals from the object (10) are acquired at a first receive bandwidth using unipolar readout magnetic field gradients. The object (10) is further subject to a second imaging sequence (32), which includes a series of refocusing RF pulses. A pair of second echo signals is generated in each time interval between two consecutive refocusing RF pulses. The pairs of second echo signals from the object (10) are acquired at a second receive bandwidth using bipolar readout magnetic field gradients. The second receive bandwidth is higher than the first receive bandwidth. Signal contributions from water protons and fat protons are separated and an MR image is reconstructed.

A method and system for improving the quality of MR images acquired with optimal variable flip angles includes receiving MRI parameters for a target tissue, selecting at least one objective function from a plurality of objective functions, simulating a relationship between each flip angle and the at least one objective functions based on the MRI parameters, determining optimal variable flip angle distribution to reach optimization of the at least one objective function for whole acquisition of the MR image, selecting or optimizing a k-space strategy, applying a plurality of radio frequency (RF) pulses with the optimal variable flip angle distribution and the k-space strategy to a target area in an object, receiving MR signals from the target area, the MR signals corresponding to the plurality of RF pulses, acquiring, in the k-space strategy, k-space lines based on the MR signals, and reconstructing the MR image from the k-space lines.