473 results about "Radiofrequency pulse" patented technology

A method of slice selective multiple quantum magnetic resonance imaging of an object is disclosed. The method is effected by implementing the steps of (a) applying a radiofrequency pulse sequence selected so as to select a coherence of an order n to the object, wherein n is zero, a positive or a negative integer other than ±1; (b) applying magnetic gradient pulses, so as to select a slice of the object to be imaged arid to create an image; and (c) acquiring a radiofrequency signal resulting from the object, so as to generate a magnetic resonance slice image of the object. The method provides slice selective multiple quantum magnetic resonance images of yet unprecedented quality in terms of contrast. The method is particularly useful for imaging connective tissues.

A system and method for facilitating RF pulse sequence generation and modification and for real-time sequence input modification for use in conjunction with magnetic resonance imaging equipment. A graphical user interface is provided through a display coupled to a digital computer operating as the primary control system for a magnetic resonance imaging scanner and associated hardware. Through the graphical user interface, an operator may choose or design sequences of radiofrequency pulses, gradient waveforms and other input parameters for the magnetic resonance imaging apparatus. Real-time information is also communicated to the operator through the graphical user interface allowing for real-time manipulation of the magnetic resonance imaging inputs and for displaying the magnetic resonance response thereto.

Method, systems and arrangements are provided for creating a high-resolution magnetic resonance image (“MRI”) or obtaining other information of a target, such as a cardiac region of a patient. Radio-frequency (“RF”) pulses can be transmitted toward the target by, e.g., an RF transmitter of an MRI apparatus. In response, multiple echoes corresponding to the plurality of pulses may be received from the target. Data from each of the echoes can be assigned to a single line of k-space, and stored in memory of the apparatus. An image of the target, acceleration data and/or velocity data associated with a target can be generated as a function of the data. In one exemplary embodiment, the data from different echoes may be assigned to the same k-space line, and to different cardiac phases. In one further embodiment, parallel processing may be used to improve the resolution of the image acquired during a single breath-hold duration. In yet another embodiment, utilizing a segmented implementation, multiples lines of k-space are acquired for a given cardiac phase (or time stamp) per trigger signal. The present invention may be utilized for the heart or for any other anatomical organ or region of interest for the evaluation and study of flow dynamics with very high temporal resolution.

In a method and device for monitoring the physiologically effective radio-frequency exposure in at least one specific volume region of an examination subject in a magnetic resonance data acquisition scan in a magnetic resonance system, the magnetic resonance system having a radio-frequency antenna structure with a number of individually controllable radio-frequency signal channels for generation of radio-frequency field distributions in an examination volume including the examination subject, amplitude values are acquired that respectively represent, at specific acquisition points in time, a signal amplitude of the radio-frequency signals emitted or to be emitted via the radio-frequency signal channels in the course of the magnetic resonance measurement. Also, phase values are acquired that represent the phases of the appertaining radio-frequency signals at these points in time. Local exposure values are then determined on the basis of the amplitude values and phase values, these local exposure values respectively representing a physiological exposure that the radio-frequency pulses cause at the examination subject at a specific location at a specific time. Based on this, exposure control values are determined that are compared with predetermined exposure limit values. When an exposure limit values is reached or exceeded, a control signal is output.

A method and apparatus are disclosed, for examining a substance of a given volume to characterize its type, with an integrated sensing head. The method comprises applying locally to the substance of the given volume a polarizing magnetic field, with a component defining a polarizing axis; applying locally RF pulses to the substance of the given volume, the RF pulses having a B component, orthogonal to the polarizing axis, such as to invoke EI response signals corresponding to the electrical impedance (EI) of the examined substance of the given volume, and magnetic resonance (MR) response signals corresponding to the MR properties of the examined substance of the given volume; detecting locally EI response signals from the substance of the given volume; and detecting locally MR response signals from the substance of the given volume. Two or more sensing heads may be used, both applying locally the RF pulses and detecting. Alternatively, one of the sensing heads may operate as a transmitter, while the other or others may operate as receivers.

The invention provides a high-precision inertial angular rate measurement method based on magnetic field compensation of an SERF (spin-exchange relaxation free) atomic device. The method comprises the steps that a glass gas chamber and a vacuum gas chamber which is filled with positive pressure gas and contains alkali metal are manufactured firstly, an oven is heated to make the temperature in the alkali metal gas chamber reach a temperature required by an SERF state; an operation period begins: pumping is conducted on the alkali metal gas chamber; pumping is interrupted, and 90-degree radio-frequency pulses act in the vertical pumping direction; radio frequency is interrupted, two times of probe light pulse detection are performed in the vertical pumping direction at an interval, and the magnetic field strength can be obtained according to the above measure experimental data; then, pumping is performed for a period of time by using circularly polarized light, then probe light detection is performed in the vertical pumping direction, the experimental data and measured magnetic field strength are compensated so that the high-precision inertial angular rate can be obtained, and pumping and detection are completed. The magnetic field measurement and inertial measurement are performed in the same experimental device under the same conditions, the measured magnetic field is utilized to compensate inertial angular rate errors caused by magnetic field interferences, and the measurement accuracy is improved.

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.

The invention provides a method for obtaining a high-resolution two-dimensional J decomposition spectrum, and relates to a nuclear magnetic resonance spectroscopy detection method. The method comprises: loading a sample to be detected into a standard nuclear magnetic test tube, and conveying into the detection chamber of a nuclear magnetic resonance spectrometer; sampling the one-dimensional hydrogen spectrum of the sample to be detected, and obtaining the signal peak distribution area and the spectral line width so as to provide the reference for the spectral width parameter setting, wherein the line width value reflects the magnetic field uniformity condition; measuring the pulse width of a radio frequency pulse required by excitation of the sample to be detected; introducing a compiled pulse sequence on the nuclear magnetic resonance spectrometer, opening the heteronuclear intermolecule multiple quantum coherent signal excitation module, the indirect dimensional evolving module, the spin echo fixed delay module and the J modulating fast sampling module of the pulse sequence, and setting the experiment parameters of various modules; skipping the artificial shimming operation process, and directly executing data sampling; and after completing the data sampling, calling data post-processing codes to carry out related data post-processing so as to obtain the high-resolution two-dimensional J decomposition spectrum being not affected by the inhomogeneous magnetic field.

The present invention discloses a method of simultaneously conducting more than one step of a radiofrequency phase cycle in a nuclear magnetic resonance (NMR) experiment. The method first involves providing a sample. Next, one or more radiofrequency pulses are applied to a plurality of spatially discrete slices of the sample under conditions effective to simultaneously conduct more than one step of a radiofrequency phase cycle in a single transient. Then, NMR signals generated from the step of applying the radiofrequency pulses are acquired. Finally, the NMR signals are processed to obtain an NMR spectrum.

In a method for adjustment of the field strength of radio-frequency pulses as well as a magnetic resonance measurement system, radio-frequency pulses are emitted by a radio-frequency antenna of a magnetic resonance measurement system in a magnetic resonance measurement A test volume slice is initially excited by emission of radio-frequency pulses with a defined pulse amplitude by the appertaining radio-frequency antenna and one-dimensional, spatially-resolved characteristic values are determined along an extent direction of the test volume slice. The one-dimensional, spatially-resolved characteristic values respectively represent a local field strength of the B₁ field in strips of the test volume slice running perpendicular to the extent direction. An average value of the determined characteristic values is then formed over at least over one determined segment along the extent direction of the test volume slice. A pulse amplitude of the radio-frequency pulses that is to be set for the magnetic resonance measurement to be implemented is determined on the basis of the average value.

Apparatus for producing magnetic resonance (MR) images of a subject over a limited volume, including a patient table, and a shielded unit housed under the patient table, the shielded unit including an RF pulse generator module, a magnet assembly for producing a static magnetic field in magnetic structure including a shaped magnetic “C” core, a gradient field generating assembly for generating magnetic field gradients in two orthogonal planes for producing MR images, a radiofrequency (RF) coil assembly for transmitting a broad band radiofrequency pulse and a RF field matching structure to simulate an infinite volume to the RF coil assembly, wherein the RF coil assembly detects a plurality of MR signals induced from a subject in response to RF pulses from the RF pulse generator.

A nuclear magnetic resonance (NMR) method is used to determine a velocity distribution or velocity image of a flowing fluid in a downhole environment. The method comprises applying a radio frequency pulse sequence; applying a magnetic field gradient magnetic field and a gradient pulse duration; measuring a NMR signal; determining a phase characteristic of the NMR signal; and determining the velocity distribution or image of the fluid using the determined phase characteristic, the magnetic field gradient pulse parameters, and a time delay between gradient pulses.

In a method for acquiring magnetic resonance data with a magnetic resonance system using a magnetic resonance sequence, the sequence has a first partial sequence in which magnetic resonance data are acquired for multiple slices that have to be acquired simultaneously, from which image data for the individual slices are calculated by a reconstruction algorithm. The sequence also has a second partial sequence for determining additional data, which are used to evaluate and/or assess the magnetic resonance data, and which have a spatial resolution that is lower than the magnetic resonance data, in which radio-frequency pulses and readout processes take place in a slice-specific manner through a time offset within a single measuring process, in which a single continuous excitation period with the radio-frequency pulses and a single continuous readout period with the readout processes follow one another, so that separate additional data are directly determined for each slice.

In a method for controlling a radio-frequency device, and a magnetic resonance tomography system and a radio-frequency control device wherein the method is implemented, the RF device of a magnetic resonance tomography system is emitted during a magnetic resonance measurement of an examination subject that is moving relative to the transmission field of the RF device. The RF device emits RF pulses at chronological intervals, and measurement values are measured at chronological intervals. At chronological intervals, position values are determined that represent a current position of the examination subject relative to the transmission field. On the basis of the measurement values and the position values, exposure values are determined that represent a physiological degree of effectiveness that the RF pulses have on the subject exposed to the RF pulses. Based on a multiplicity of exposure values, exposure control values are respectively formed. The RF device is limited in its functioning if an exposure control value reaches or exceeds an exposure limit value.

A method for establishing a magnetic resonance system actuation sequence is described. A first number of field distribution maps are acquired for slices of the measurement region, and a radiofrequency pulse train is established on the basis thereof for the magnetic resonance system actuation sequence. This acquisition of the first number of field distribution maps may be brought about on the basis of an acquisition scheme. A reduced number of field distribution representation maps are established on the basis of the acquired field distribution maps, which field distribution representation maps represent the first number of acquired field distribution maps in accordance with a predetermined optimization criterion, and the radiofrequency pulse train is established on the basis of the field distribution representation maps.

Small and inexpensive probeheads for use in nuclear magnetic resonance systems, in particular, magnetic resonance relaxometry systems are provided. The design of the magnet-radiofrequency coil configurations within the probeheads is guided by an excitation bandwidth associated with radiofrequency pulses to be applied to a sample.