52 results about "B1 field" patented technology

An apparatus, system, and method including a magnetic resonance imaging (MRI) apparatus includes a magnetic resonance imaging (MRI) system having a plurality of gradient coils positioned about a bore of a magnet, and an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly to acquire MR images, and a computer. The computer is programmed to apply a first off-resonant radio frequency (RF) pulse at a first frequency different than the resonant frequency to a plurality of nuclei excited at a resonant frequency, acquire a first signal from the plurality of nuclei after application of the first off-resonant RF pulse, determine a phase shift from the first signal based on the first off-resonant RF pulse, determine a B1 field based on the phase shift, and store the B1 field on a computer readable storage medium.

In a method and magnetic resonance system for homogenization of the B₁ field for a magnetic resonance data acquisition with a number of iteration steps. An iteration step includes the following sub-steps: Measurement data are acquired that represent a B₁ field distribution in at least one part of the examination volume of the magnetic resonance system. A B₁ homogeneity analysis based on the acquired measurement data is automatically implemented. A specific homogenization action is automatically selected from among a number of possible homogenization actions based on the B₁ homogeneity analysis, or the iterative homogenization method is ended if the diagnosed homogeneity is sufficient for an intended magnetic resonance measurement. The selected homogenization action is implemented.

In magnetic resonance tomography apparatus and method for determining the field strength of high-frequency pulses which are emitted during a magnetic resonance measurement by the antenna, a magnetic resonance signal excited by a radio-frequency pulse or a radio-frequency pulse sequence is measured, and a phase of the magnetic resonance signal is determined. Based on this phase, the field strength is then determined.

A RF coil compression system for use with an MRI system configured to image a patient's breast is disclosed. In one embodiment, the compression system comprises a first compression plate comprising a first plurality of RF coil elements, which is positioned in a plane oriented orthogonal to a direction of the main magnetic field and the first RF coil elements having a reception sensitivity to a B1 field and is orthogonal to a main magnetic field of the MRI system. The compresses system may further comprise a second compression plate, configured to be positioned opposing the first compression plate and orthogonal to the superior-inferior direction, the second compression plate comprising a second plurality of RF coil elements, the second RF coil elements having a reception sensitivity to a B1 field oriented in a direction substantially orthogonal to the first direction and to the main magnetic field of the MRI system.

The invention discloses a magnetic resonance system imaging method, which comprises the following steps: under a multichannel emission mode, according to spin echo signal intensity SSE and stimulated echo signal intensity SSTE, carrying out optimization on amplitude and phase parameters of a plurality of radio frequency emission channels to generate a target B1 field, wherein the target B1 field meets B1 field uniformity and radio frequency emission power optimization simultaneously; loading the optimized amplitude and phase parameters to a radio frequency pulse controller, and driving the plurality of radio frequency emission channels to generate the target B1 field; under the target B1 field, exciting a part to be scanned of a subject to obtain a magnetic resonance signal of the part to be scanned; and carrying out Fourier transform on the magnetic resonance signal to obtain a magnetic resonance image of the part to be scanned. The spin echo signal intensity and the stimulated echo signal intensity are collected to reflect distribution of the B1 field; and fast correction can be carried out to obtain a uniform B1 field, and radio frequency emission power can be corrected. The invention also provides a magnetic resonance system.

A method for determining the spatial distribution of the magnitude of the radio frequency transmission field B1 in a magnetic resonance imaging apparatus, wherein the method comprises performing an MRI experiment in which a B1-sensitive complex image (SI) of a sample is obtained, wherein the phase distribution within the B1-sensitive complex image (SI) depends on the spatial distribution of the magnitude of the field B1. For establishing the dependency of the phase distribution within the B1-sensitive complex image (SI) on the spatial distribution of the field B1, one or more adiabatic RF pulses are applied. The method provides a simple procedure for mapping the B1 field of a magnetic resonance imaging apparatus with an improved accuracy and a wider measurement range.

The invention discloses a magnetic resonance imaging method and system, wherein the method comprises: before imaging scanning, determining a preset deflection angle of a radio frequency pulse to excite specific tissues; analyzing a corresponding dual-saturated pulse deflection angle according to the preset deflection angle; combining a dual-saturated pulse and a gradient pulse to form a dual-saturated pulse saturation module, wherein the gradient pulse includes a layer-selecting gradient pulse that is used for exciting a corresponding layer of the specific tissues; executing an imaging scanning process, to be specific, applying the dual-saturated pulse saturation module and an imaging pulse sequence sequentially to a scanning area to perform magnetic resonance imaging. By carrying out magnetic resonance imaging through the dual-saturated pulse saturation module and the imaging pulse sequence, saturated band signal inhibition non-uniformity due to non-uniformity of B1 field can be overcome, and motion artifacts due to organ motion, tissue motion and other motions can be inhibited.

A local radio frequency (RF) transmitting coil (26) of a magnetic resonance imaging system (5) has a plurality of coil elements (100). Each coil element (100) has an adjustable load (62) which is adjusted by a control unit (60) to adjust a transmitted B1field distribution. The load can be adjusted to shim for a uniform B1 field distribution. Non-uniform B1 field distributions can be selected to perform magnetic resonance sequences that use such B1 field distributions, such as parallel imaging. The B1 field distribution can be changed during the magnetic resonance sequence to track a moving region of interest, time division multiplex parallel imaging, and the like.

An arrangement for radiation of a radio-frequency field into an examination subject has a local coil unit with a housing. An insulating dielectric material is embodied at least at one part of the housing in order to passively compensate an inhomogeneity of the B1 field that occurs in the examination subject. An adjustment arrangement allows for fixed but detachable provision of the insulating dielectric material at the housing part.

In a method and magnetic resonance examination apparatus wherein the field strength of radio-frequency pulses emitted by an antenna of the magnetic apparatus, the current flowing in the antenna upon the emission of the radio-frequency pulses is regulated by a predetermined nominal value by variation of a power fed into the antenna.

A local coil unit for a magnetic resonance apparatus, which radiates a radio-frequency field into an examination subject, has a housing and at least a part of the housing is formed of an insulating dielectric material that passively compensates for an inhomogeneity in the high-frequency field in the subject. The material has a relative dielectric value ε_r of greater than 50, preferably greater than 100, and a dielectric loss factor tan δ of less than 2.5×10⁻², preferably less than 1×10⁻³. In the dielectric material displacement currents are generated which create an additional magnetic field that compensates for the minima in the B1 field as a result of the eddy currents arising in the patient due to the radio-frequency radiation.

A dielectric element for positioning on an examination subject for locally influencing the B1 field distribution during magnetic resonance data acquisition contains a relaxation agent bound to mutually separated particles. The relaxation agent incorporates a paramagnetic substance. In a corresponding method for acquiring magnetic resonance data from an examination subject, such a dielectric element is positioned on the examination subject for locally influencing the B₁ field distribution, by homogenizing the B₁ field of a magnetic resonance apparatus.

In a method and arrangement for local manipulation of a B₁ field in a first region of an examination subject in an examination volume of a magnetic resonance system, a B₁ measurement value that represents the B₁ field in the sub-volume during an adjustment measurement is integrally determined, and in desired radio-frequency signal parameters for a subsequent magnetic resonance measurement are predetermined on the basis of the determined B₁ measurement value. At least during the adjustment measurement, the B₁ field is influenced within a second region counter to the manipulation intended in the first region by means of an auxiliary coil element which is arranged in or at the second region of the sub-volume remote from the first region.

Coil elements (18) generate a B1 excitation field in an examination region (14), which B1 excitation field is distorted by patient loading (e.g., wavelength effects). Passive shimming elements (22, 24) are disposed between the coil elements and the subject in order to improve the B1 field uniformity. In one embodiment, passive shimming elements include one or more dielectric rods (55) disposed below the subject which generate no substantial MR proton signal and which have a permittivity of at least 100 and preferably greater than 500. In another embodiment, tubes (24) adjacent each coil element are supplied with a dielectric liquid, a thickness of the dielectric liquid between the coil element and the subject adjusting a phase of the B1 field generated by the coil element. Active B1 shimming may be combined with passive shimming elements (22, 24) to effect an improved RF field homogeneity result.

A radio-frequency transmission arrangement for an MR system for generation of a total B1 field which has a first antenna device that generates a first portion of the total B1 field and at least one antenna insert that generates a second portion of the total B1 field, such that the resulting B1 field is generated by the first antenna device and the at least one antenna insert.

The invention relates to a high-dielectric-constant ultrahigh-field animal magnetic resonance radio frequency probe which comprises a coil unit, the coil unit comprises a cylindrical coil circuit substrate and a cylindrical inner wall substrate, and the inner wall substrate is arranged in the coil circuit substrate. The two ends of a high-dielectric-constant ceramic unit are fixed between the coilcircuit substrate and the coil inner wall substrate through a ceramic unit support. All the units are independent of one another, assembling is flexible, and the sensitivity of the radio frequency probe can be effectively improved. The plurality of high-dielectric-constant ceramic blocks can greatly improve the B1 field emission efficiency in the central region, and avoids the adverse effects ofcoil mode increase and disorder caused by complete cylindrical barium titanate ceramic.

In a method of performing magnetic resonance imaging and a magnetic resonance apparatus, first MR data are acquired of a region of interest of a subject in the absence of a B1 field. Second MR data are acquired of the region of interest in the presence of a B1 field, and within a short time interval after generation of the B1 field. The first and second MR data are processed to determine a B1 field map, and a T1 map is generated using the B1 field map. The T1 map is a B1 corrected T1 map. The first and second MR data 103, 109 may be acquired as part of a T1 mapping sequence, such as a MOLLI or SASHA type cardiac T1 mapping sequence.