A measurement volume is divided into multiple regions of interest (ROIs) and RF shimming parameters are independently selected for each of the ROIs. The ROIs have dimensions based on an RF wavelength in a specimen (i.e., based on RF frequency and specimen dielectric constant) and are selected to reduce wavelength-based nonuniformity in specimen excitation. For a multi-segment RF coil having segments situated about a cylindrical surface, ROI shapes include cylinders and cylindrical shells aligned along a coil axis.

A magnetic resonance imaging (MRI) system includes a plurality of transmitters to generate a parallel transmission radio frequency (RF) pulse, an array of coils coupled to the plurality of transmitters to apply the parallel transmission RF pulse to a subject, and a decoupling system connected to the plurality of transmitters and the array of coils. The decoupling system includes a plurality of hybrid couplers, each hybrid coupler of the plurality of hybrid couplers being coupled to a respective pair of the plurality of transmitters and to a respective pair of the array of coils. The plurality of hybrid couplers are configured to diagonalize an impedance matrix of the plurality of coils.

A method of MR imaging, wherein a portion of a body placed in the examination volume of a MR device is subjected to an imaging sequence of RF pulses and switched magnetic field gradients. The imaging sequence is a stimulated echo sequence including i) at least two preparation RF pulses () radiated toward the portion of the body during a preparation period, and ii) one or more reading RF pulses () radiated toward the portion of the body during an acquisition period temporally subsequent to the preparation period. One or more FID signals and one or more stimulated echo signals are acquired during the acquisition period. A B1 map indicating the spatial distribution of the RF field of the RF pulses within the portion of the body is derived from the acquired FID and stimulated echo signals.

The present disclosure relates to a system and method for MRI with respect to vessels and bleedings. The method may include exciting a region of interest by applying an RF pulse, wherein the region of interest includes a vessel region and a bleeding region. The method may further include acquiring a plurality of echo signals related to the region of interest. The method may further include generating one or more magnitude images based on the plurality of echo signals, generating a first image with respect to the vessel region based on the one or more magnitude images, generating one or more phase images based on the plurality of echo signals, and generating a second image with respect to a distribution of susceptibility of the bleeding region based on the one or more phase images.

A method of designing a refocusing pulse or pulse train for Magnetic Resonance Imaging comprises the steps of: a) determining a phase-free performance criterion representative of a proximity between a rotation of nuclear spins induced by the pulse and a target operator, summed or averaged over one or more voxels of an imaging region of interest; and b) adjusting a plurality of control parameters of the pulse to maximize the phase-free performance criterion; wherein each target operator is chosen so the phase-free performance criterion takes a maximum value when the nuclear spins within all voxels undergo a rotation of a same angle around a rotation axis lying in a plane perpendicular to a magnetization field B.sub.0, called a transverse plane, with an arbitrary orientation; wherein the angle is different from M radians, with integer M, preferably with < radians and even preferably with 0.9.Math. radians.

In a magnetic resonance (MR) apparatus and a method for operation thereof, the radio-frequency (RF) resonator of the scanner of the apparatus fed from a single RF source and is operated, during a total scan duration for acquiring MR scan data from a subject, so as to excite nuclear spins in the subject with respective RF fields having different B1+ field profiles that are radiated at respectively different times during the acquisition of the scan data. The scan data acquired during the scan thus are produced from MR signals caused by nuclear spins excited by at least two different B1+ field profiles. The scan can be used to acquire MR data for MR fingerprinting.

A method for magnetic resonance (MR) imaging is provided. A first sampling mask is provided for sampling along a first set of parallel lines extending in a first direction in k-space. A second sampling mask is provided for sampling along a second set of parallel lines extending in a second direction in k-space. The second direction is orthogonal to the first direction. A first set of MR k-space data is sampled using an MR scanner, by scanning a subject in the first direction using the first sampling mask. A second set of MR k-space data is sampled using the MR scanner, by scanning the subject in the second direction using the second sampling mask. An MR image is reconstructed from a combined set of MR k-space data including the first set of MR k-space data and the second set of MR k-space data.

A method for operating a transmission device of a magnetic resonance device is provided. In order to actuate coil elements of a radiofrequency coil with different phases, phase differences in a reference plane are taken into consideration. In a first calibration measurement to be performed once for each transmission path, a first phase of a transmitted radiofrequency signal is measured by an internal measuring device installed permanently in the transmission device spaced apart from the reference plane. A second phase of the transmitted radiofrequency signal is measured by a second, external measuring device to be connected to the reference plane for the first calibration measurement. At least one phase of the first phase and the second phase is taken into consideration in the phase-accurate actuating of the coil elements and/or for correcting further measurements with the internal measuring device.

A magnetic resonance imaging system acquires magnetic resonance data from a target volume in a subject. The magnetic resonance imaging system includes multiple excitation sources for generating a slice-selective or slab-selective spatial radio frequency (RF) excitation magnetic field targeting slice/slab spatial variations in the target volume, and a controller coupled to the excitation sources. The controller is adapted for: determining a power level required by the excitation sources for generating the slice-selective/or slab-selective spatial RF excitation magnetic field, decomposing the slice-selective or slab-selective spatial RF excitation magnetic field into respective RF excitation constituents of the excitation sources, controlling each of the excitation sources to simultaneously generate the respective RF excitation constituent, using the determined power level for acquiring the magnetic resonance data.

An asymmetric 3D shells k-space trajectory design with partial Fourier acceleration is described. A non-iterative homodyne reconstruction framework is also described.