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).

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 for non-invasive quantification of organ fat using a magnetic resonance approach includes: constructing a detection system; connecting a detection area; detection system startup; acquiring data; analyzing data; and performing horizontal data analysis. An external computer, a radio frequency (RF) subsystem, and a portable magnet module are used to construct a system for non-invasive quantification of organ fat based on low-field nuclear magnetic resonance (LF-NMR,), which causes no damage, and achieves accurate and non-invasive quantification of organ fat. Specific pulse sequences are used to excite nuclear spin in a target region to generate LF-NMR, so as to achieve “one-click” detection, which is used for fast screening of related diseases such as non-alcoholic fatty liver disease (NAFLD). The system has accurate quantification, and is easy to operate without constraints of operator qualifications.

A method for NMR measurements on borehole materials, e.g., sidewall cores, is based on performing a standard measurement in substantially homogeneous magnetic fields with a sensitivity volume covering an entire sample and a measurement on a fragment of the sample (local measurement), the fragment having a predetermined volume independent of the irregularities of the sample shape (e.g., irregular shaped edges). The fragment of the sample is selected using a switchable static magnetic field gradient or a localized radio-frequency magnetic field. The homogeneous and the local measurement data are processed jointly to obtain volume normalized NMR relaxation data (in porosity units), the processing also using a calibration sample data. A measurement apparatus with an automated sample transfer can be used to implement the method in order to perform high-throughput NMR relaxation measurements that do not require independent measurement of the sample volume.

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.

Systems and methods for generative adversarial networks (GANs) to remove artifacts from undersampled magnetic resonance (MR) images are described. The process of training the GAN can include providing undersampled 3D MR images to the generator model, providing the generated example and a real example to the discriminator model, applying adversarial loss, L2 loss, and structural similarity index measure loss to the generator model based on a classification output by the discriminator model, and repeating until the generator model has been trained to remove the artifacts from the undersampled 3D MR images. At runtime, the trained generator model of the GAN can be generate artifact-free images or parameter maps from undersampled MRI data of a patient.

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.

Disclosed herein is a medical system (100, 300, 500) comprising a memory (110) storing machine executable instructions (120) and a magnetic resonance reconstruction module (122). The magnetic resonance reconstruction module is configured to reconstruct a motion corrected tracer-kinetic map (126) from measured k-space data (124). The measured k-space data is undersampled. The measured k-space data is T1 weighted. The measured k-space data is dynamic contrast enhanced k-space data. The medical system further comprises a processor (104) configured for controlling the medical system. Execution of the machine executable instructions causes the processor to: receive (200) the measured k-space data; and reconstruct (202) the motion corrected tracer-kinetic map by inputting the measured k-space data into the magnetic resonance reconstruction module. The magnetic resonance reconstruction module (122) is configured to reconstruct the motion corrected tracer-kinetic map as a direct model-based reconstruction from the measured k-space data (124).

Disclosed herein is a medical system (100, 300, 500) comprising a memory (110) storing machine executable instructions (120) and a magnetic resonance reconstruction module (122). The magnetic resonance reconstruction module is configured to reconstruct a motion corrected tracer-kinetic map (126) from measured k-space data (124). The measured k-space data is undersampled. The measured k-space data is T1 weighted. The measured k-space data is dynamic contrast enhanced k-space data. The medical system further comprises a processor (104) configured for controlling the medical system. Execution of the machine executable instructions causes the processor to: receive (200) the measured k-space data; and reconstruct (202) the motion corrected tracer-kinetic map by inputting the measured k-space data into the magnetic resonance reconstruction module. The magnetic resonance reconstruction module (122) is configured to reconstruct the motion corrected tracer-kinetic map as a direct model-based reconstruction from the measured k-space data (124).