55 results about "Flip angle" patented technology

A time-efficient diffusion magnetic resonance imaging systems and methods are provided that can produce multiple diffusion-weighted images with different b-values in one repetition time, and / or multiple diffusion-weighted images with different diffusion times in one repetition time, both by utilizing a train of stimulated echoes. Each stimulated echo in the train of stimulated echoes is generated by a re-excitation radio-frequency (RE) pulse with a variable flip angle, following an initial 90° excitation RE pulse and a subsequent 90° restoration RE pulse.

The invention relates to the field of detection, in particular to a food detection method based on low-field nuclear magnetic resonance, which can monitor the fluctuation of an applied pulse so as to determine the deviation of the overturning angle of a hydrogen atom nucleus in a sample caused by the fluctuation of the pulse and further determine the actual overturning angle. Furthermore, the interference of pulse fluctuation on an external magnetic field is also considered, and the influence of the pulse fluctuation on the relaxation duration is fully eliminated according to the actual relaxation duration determined by the actual overturning angle and the interference of the external magnetic field, so that the performance of the hydrogen nucleus in the sample can be accurately represented; further, the substance state of the sample can be accurately determined.

A method for optimizing flip angles in a magnetic resonance variable flip angle pulse sequence, a CEST imaging method, a medium, and a device are presented. A signal-to-noise ratio (SNR) enhancement problem is modeled as a flip angle optimization problem, and a total objective function composed of an SNR maximization objective term and a resolution penalty term is constructed, wherein the total objective function may be solved for an optimal solution by finding derivatives with respect to flip angles, so as to obtain an optimal flip angle capable of maximizing SNR. The objective function includes the resolution penalty term, so that resolution may also be considered in variable flip angle CEST when the SNR is optimized. Compared with a conventional filtering method, the present disclosure avoids noise amplification caused by filtering, and does not require manual presetting of a window function.

In a method for improving the recording of measurement data of an object under inspection, the method includes loading desired imaging parameters and a desired flip angle for recording the measurement data by means of a recording method, wherein the gradient to be switched for position encoding of the measurement data has its full intensity during the incident RF excitation pulse. A quantization value of a desired interference for the recording method is determined based on the desired imaging parameters, and a check on the feasibility of correcting for the interference is performed based on the quantization value and the desired flip angle.

Techniques are described for acquiring data of an examination object and imaging parameters for an acquisition of measured data via an acquisition method in which gradients to be switched for position encoding of the measured data have their full strength during an irradiation of the RF excitation pulses, and a desired flip angle are loaded. The feasibility of the correction, the acquisition method is selectively performed with the loaded imaging parameters and the loaded flip angle. If a feasibility check is negative, a pulse duration of the RF excitation pulses to be irradiated in the acquisition method and / or of the desired flip angle are adjusted into an adjusted flip angle and / or at least one of the desired imaging parameters into an adjusted imaging parameter, and the acquisition method is performed with an adjusted pulse duration and / or with an adjusted flip angle and / or with an adjusted imaging parameter.

The application belongs to the technical field of magnetic variable measurement, and solves the technical problem of poor magnetic field measurement precision caused by single attitude adjustment of the existing Hall measurement system. The vacuum Hall measurement system for the in-vacuum undulator comprises a vacuum chamber, a Hall probe and a motion execution mechanism. The motion execution mechanism comprises a guide rail and a pose adjustment mechanism. The Hall probe is movable along the extension direction of the guide rail. The pose adjustment mechanism drives the Hall probe to move three-dimensionally to measure the magnetic field distribution through the guide rail. The pose adjustment mechanism comprises a Z-direction swing platform to adjust the pitch angle of the guide rail, a Y-direction swing platform to adjust the roll angle of the guide rail, a Y-direction moving platform, an X-direction moving platform and a Z-direction moving platform. The application can adjust the attitude in two directions and the position in three directions in space, reduce the parasitic displacement, make the Hall probe move three-dimensionally in the undulator and improve the magnetic field measurement precision.

The invention discloses a magnetic resonance imaging method and device and MRI equipment, and relates to the technical field of magnetic resonance. According to the method, the steady-state value of the tissue set can be obtained, the first overturning angle and the target duration of the steady-state catalysis module are determined based on the steady-state value of the tissue set, then the steady-state catalysis module is applied to the tissue set, and the difference value between the signal value of each imaging tissue passing through the steady-state catalysis module and the steady-state value of the imaging tissue is smaller than a difference value threshold value. The method can then apply an imaging sequence to the set of tissues to acquire magnetic resonance signals for each imaged tissue. Therefore, according to the method, the steady-state catalysis module can be calculated and applied to the tissue set before imaging, so that the signal value of each imaging tissue tends to a steady-state value to the maximum extent, artifacts introduced due to large difference between the signal value of the imaging tissue and the steady-state value can be effectively reduced during imaging, and the imaging quality is improved.

The invention relates to a radio frequency pulse flip angle determination method and device and computer equipment. And according to the actual scanning parameter and the signal amplitude function of the magnetic resonance scanning sequence, determining the candidate signal amplitude of each candidate flip angle corresponding to the radio frequency pulse under the actual scanning parameter, and according to the candidate signal amplitude of each candidate flip angle, determining a target flip angle corresponding to the radio frequency pulse. In the embodiment of the invention, the candidate signal amplitudes of the plurality of candidate flip angles under the actual scanning parameter are determined through the signal amplitude function, and the target flip angle of the radio frequency pulse under the actual scanning parameter is determined according to the plurality of candidate signal amplitudes, so that the flip angle of the radio frequency pulse in the spin echo sequence is optimized, the longitudinal magnetization vector is recovered more quickly, and the accuracy of the spin echo sequence is improved. Therefore, the signal amplitude generated by excitation each time is improved, and the signal-to-noise ratio of a magnetic resonance image is finally improved.

A method for equilibrium phase contrast-enhanced magnetic resonance (MR) angiography using an extracellular MR contrast agent administered to a subject includes performing a balanced T1 relaxation enhanced steady-state (bT1RESS) pulse sequence to acquire MR data from a region of interest of the subject during an equilibrium phase of contrast enhancement after a first pass of the extracellular contrast agent through the region of interest. The bT1RESS pulse sequence includes a T1-weighted magnetization preparation including at least one contrast modifying (CM) radio frequency (RF) pulse, a single-shot balanced steady-state free precession (bSSFP) readout, and a time interval between the T1-weighted magnetization preparation and the acquisition of a center of k-space. The time interval is determined based on a T1 relaxation time of a contrast-enhanced blood pool and a flip angle of the at least one CM RF pulse. The method further includes generating an angiographic image of the region of interest.

The invention relates to magnetic resonance, MR, imaging, comprising: subjecting one portion of an object (10) to a preparation sequence (PRE) comprising a spectrally selective adiabatic inversion radiofrequency, RF, pulse (21) having a flip angle (a) to selectively invert nuclear magnetization associated with fat protons; after a delay time (TD), subjecting the portion to an imaging sequence (IM) comprising one excitation RF pulse (28) to generate MR signals (27), wherein the delay time and / or the flip angle are determined such that contributions from a first spectral species of fat protons affected by the inversion RF pulse and a second spectral species of fat protons not affected by the inversion RF pulse to the MR signals substantially cancel each other out; acquiring the MR signals; and reconstructing an MR image from the MR signals, wherein contributions from both the first and second spectral species of fat protons are suppressed in the MR image.

The application relates to a radio frequency transmit field detection method and device, a radio frequency transmit field correction method, a magnetic resonance system, a storage medium and a computer program product. The method comprises: acquiring at least two groups of magnetic resonance echo signals. Each group of magnetic resonance echo signals is generated by exciting a detection object by a radio frequency transmit pulse with a different preset flip angle, and the different preset flip angles conform to a predetermined relationship. According to each group of magnetic resonance echo signals, a flip angle probability density distribution function corresponding to a radio frequency transmit field is determined. The flip angle probability density distribution function represents the probability density distribution of the flip angle of the radio frequency transmit field in the case that a characteristic quantity of the magnetic resonance echo signal is at a set value. According to the flip angle probability density distribution function and the magnetic resonance echo signal, the distribution of the radio frequency transmit field is determined. By using the method, the actual offset of the radio frequency transmit field is detected to determine the uniformity of the radio frequency transmit field.

The invention discloses a low-field NMR relaxation time rapid measurement method, and the method comprises the steps: designing an IR-bSSFP pulse sequence which comprises a 180-degree reversal pulse and an excitation pulse sequence, and enabling the flip angle of a radio frequency excitation pulse in the excitation pulse sequence to be a pseudo-random flip angle; the radio-frequency phases of the adjacent radio-frequency excitation pulses are linearly changed by a fixed phase increment; based on the IR-bSSFP pulse sequence, obtaining a component MRF signal sequence of a measured object, and simulating a magnetization vector evolution process to obtain a dictionary matrix; matching the component MRF signal with a dictionary matrix pattern in combination with a smooth constraint term to obtain corresponding longitudinal relaxation time and transverse relaxation time; the invention also discloses low-field NMR relaxation time rapid measurement equipment, which comprises a pulse sequence construction module, a dictionary generation module and a mode matching module. Multi-parameter information can be obtained through single scanning, the measurement time is remarkably shortened, the experiment complexity is reduced, and the precision and repeatability of a measurement result are improved.

The application discloses a kind of based on signal phase's magnetic resonance radio frequency gain calibration method, comprising the following steps: S1: design a fermi pulse, calculate corresponding radio frequency amplitude;S2: design pre-scan sequence;S3: the actual maximum radio frequency amplitude of fermi pulse under fixed radio frequency gain is measured to the data acquisition;S4: according to the actual maximum radio frequency amplitude measured and the maximum integer value of fermi pulse waveform file, the radio frequency conversion coefficient of radio frequency system at this time is calculated;S5: predict the flip angle of any radio frequency pulse under a certain radio frequency gain preset value;S6: according to multiple radio frequency gain preset values and corresponding flip angle, the radio frequency gain value required for target flip angle is predicted.The application is also disclosed a kind of based on signal phase's magnetic resonance radio frequency gain calibration system.The radio frequency conversion coefficient of radio frequency system is indirectly measured by more stable signal phase information, and will not be influenced by background magnetic field inhomogeneity, tissue signal attenuation and other environments.

The invention belongs to the technical field of magnetic variable measurement, and provides an in-vacuum Hall measurement system for an in-vacuum undulator, which solves the technical problem of poor magnetic field measurement precision caused by single attitude adjustment of an existing Hall measurement system. The in-vacuum Hall measurement system for the in-vacuum undulator comprises a vacuum chamber, a Hall probe and a motion executing mechanism, the motion executing mechanism comprises a guide rail and a pose adjusting mechanism, the Hall probe can move in the extending direction of the guide rail, and the pose adjusting mechanism drives the Hall probe to move in a three-dimensional mode through the guide rail to measure magnetic field distribution. The pose adjusting mechanism comprises a platform swinging around the Z direction so as to adjust the pitch angle of the guide rail; swinging the platform around the Y direction to adjust the overturning angle of the guide rail; a Y-direction moving platform, an X-direction moving platform and a Z-direction moving platform. According to the invention, the attitude in two directions and the position in three directions in the space can be adjusted, the parasitic displacement is reduced, the Hall probe is enabled to perform three-dimensional motion in the undulator, and the magnetic field measurement precision is improved.

The present disclosure provides a single-sided magnetic resonance imaging system comprising a plurality of components. The present disclosure also provides a method for generating a multi-dimensional image by using an imaging system. The present disclosure also provides a process of applying multiple xSPEN readout gradients on the single-sided magnetic resonance imaging system disclosed herein. There are several techniques for collecting dynamic magnetic resonance (MR) images. The fast pulse sequence may be used to fast sample the entire k-space, thereby generating images acquired within a small time window. For example, a spiral trajectory gradient echo sequence may be used to sample the entire k-space within tens of milliseconds. Another method is to use small flip angle excitation to quickly collect lines in k-space. These methods may also be combined with undersampling to collect images more quickly.

A computer-implemented method is proposed for providing a control sequence (25) to be used, which predetermines respective transmission signals (29-31) to be emitted for the acquisition of measurement data (32) of an examination subject (2) by a magnetic resonance device (1) for at least one radio-frequency transmission channel (5) of an antenna arrangement (4) of the magnetic resonance device (1). The method comprises the following steps: providing a B 1 field distribution map for the examination subject (2), wherein the amplitudes and phases are determined with spatial resolution for each radio-frequency transmission channel (5); providing a reference image which has no inhomogeneities, wherein the reference image is estimated from the provided B 1 field distribution map and / or generated from an image and / or created synthetically;Carrying out an optimization process in which the phase and flip angle for each radio-frequency transmission channel (5) and each pulse of the complex sequence are varied iteratively until the homogeneity of the simulated image of the examination object (2) corresponds to the homogeneity of the reference image for the target phases and target flip angles resulting from the optimization process; and providing the determined target phases and target flip angles for each radio-frequency transmission channel (5) and pulse as a control sequence.

The invention discloses a multi-parameter quantitative imaging method and device, nuclear magnetic resonance equipment and a storage medium, the multi-parameter quantitative imaging method is applied to the nuclear magnetic resonance equipment, and the nuclear magnetic resonance equipment comprises a T2 preparation sequence module and a variable flip angle multi-echo gradient echo sequence module connected with the T2 preparation sequence module. Comprising the steps that equivalent echo time is controlled through a T2 preparation sequence module, a flip angle is controlled through a variable flip angle multi-echo gradient echo sequence module, a target object is scanned, and a multi-parameter echo signal is obtained; and performing imaging processing on the multi-parameter echo signal based on the image demand configuration information to obtain a required multi-parameter quantitative image. According to the invention, T2 preparation and a variable flip angle technology are combined, and a multi-parameter echo signal can be obtained through one-time scanning, so that a multi-parameter quantitative image is obtained, and the parameter imaging efficiency is improved.

This invention discloses a high signal-to-noise ratio (SNR) magnetic resonance (MRI) data acquisition method, signal processing method, and system, belonging to the field of MRI technology. The invention aims to maximize the image SNR while maintaining spatial resolution by simultaneously optimizing the radio frequency flip angle sequence of the echo train and the k-space filtering weights through a joint optimization framework. This invention can obtain high-quality MRI images, fundamentally improving the image quality of FSE sequences.

A method of acquiring magnetic resonance (MR) data from a subject using a magnetic resonance imaging (MRI) system includes generating, for each of at least one level in the subject, a first pre-saturated RF pulse having a first flip angle, generating, after each first pre-saturated RF pulse, a series of first gradient echo sequences, and calculating a B0 value for each of the at least one level. A second pre-saturated RF pulse having a second flip angle is generated for each of the at least one planes in the subject, then a series of second gradient echo sequences is generated, and B1 is calculated for each of the at least one planes based on the first gradient echo sequences and the second gradient echo sequences.

This application discloses a signal readout method and apparatus based on a Hall effect device array with lateral resistance, relating to the field of circuit technology. Each Hall effect device is provided with two power supply terminals and at least one Hall signal terminal. The method includes: changing the flip angle of the free magnetic layer of at least one Hall effect device using spin orbital moment, thereby setting the Hall resistance value of the corresponding Hall effect device to a desired target value; connecting the Hall signal terminals of several Hall effect devices in series to read the summed voltage; and connecting the Hall signal terminals of several Hall effect devices in parallel to read the summed current. The Hall effect device of this application can achieve current-induced out-of-plane magnetization reversal under shunt conditions; the flip angle can change the resistance value, thereby reducing the need for Hall effect devices with different resistance values; this application realizes that the Hall signal terminals of multiple Hall effect devices are connected in series to achieve voltage summation, or connected in parallel to achieve current summation.

The invention provides a magnetic resonance parameter determination method and device, electronic equipment and a computer program product, and the method comprises the steps: scanning a scanning object through employing a plurality of gradient echo sequences of different repetition times, and obtaining a magnetic resonance image corresponding to the gradient echo sequence of each repetition time; the radio frequency flip angles set by the plurality of gradient echo sequences are the same; performing nonlinear fitting according to a plurality of different repetition times, a radio frequency flip angle set by the gradient echo sequence, the signal intensity of each magnetic resonance image and a preset signal model to determine a longitudinal relaxation time constant, the independent variables of the signal model including the repetition time and the longitudinal relaxation time constant, the dependent variable of the signal model is the signal intensity of the magnetic resonance image. Therefore, the gradient echo sequences with the same flip angle and different repetition times are adopted for scanning, and nonlinear fitting is performed based on the steady-state signal model, so that the longitudinal relaxation time constant can be quickly and accurately determined without long waiting time.

A spectrum measurement method and apparatus in nuclear magnetic resonance, a device, and a storage medium. A target sample is arranged in a uniform magnetic field, a target direction of the target sample is consistent with the uniform magnetic field, a gradient coil is arranged on the target sample, and the method comprises: applying a linear gradient magnetic field in the target direction of the target sample; determining a uniform region of a radio frequency coil on the basis of a bandwidth of a radio frequency pulse signal; during reception of a nuclear magnetic resonance echo signal, adjusting the magnitude of the linear gradient magnetic field under the condition of a target flip angle until a region of the nuclear magnetic resonance echo signal is constrained within the uniform region of the radio frequency coil to obtain a target linear gradient magnetic field; obtaining a target nuclear magnetic resonance echo signal on the basis of the target linear gradient magnetic field; and performing inversion on the target nuclear magnetic resonance echo signal to obtain a T1-T2 spectrum. The problem of T1‑end tailing caused by conventional T1-T2 measurements is solved, thereby greatly improving the measurement accuracy.

The invention discloses a calibration radio frequency power acquisition method and system and a radio frequency power-flip angle mapping function establishment method and system thereof, and relates to the technical field of magnetic resonance, and the method comprises the steps: employing a DERA sequence to carry out the multiple scanning of a target object; wherein different radio frequency powers are applied in each scanning, so that the preset overturning angle range is 0-90 degrees; respectively acquiring the intensity of the echo signals of two different echo times in each scanning, and calculating the ratio of the double echo signals in each scanning according to the intensity of the echo signals; according to the ratio of the double echo signals of each scanning, inverting an actual flip angle under the radio frequency power of each scanning; and obtaining a radio frequency power-flip angle mapping function according to the actual flip angle under the radio frequency power scanned for multiple times. According to the method, the radio frequency power and flip angle mapping function can be quickly obtained on the premise that image acquisition and reconstruction are not carried out, so that quick, low-cost and full-power-range radio frequency response calibration is realized.

A magnetic resonance imaging apparatus according to one embodiment includes processing circuitry. The processing circuitry sets, in accordance with a preset repetition time (TR) or a duration for performing a suppression pulse train of suppression pulses to be applied for suppression of the same magnetic resonance signals, at least one or a combination of the number of the suppression pulses, flip angles of the suppression pulses, and pulse intervals between the suppression pulses. The processing circuitry acquires magnetic resonance data by performing a sequence including the suppression pulse train based on the number of the suppression pulses, the flip angles, and the pulse intervals.

A method for equilibrium phase contrast-enhanced magnetic resonance (MR) angiography using an extracellular MR contrast agent administered to a subject includes performing a balanced T1 relaxation enhanced steady-state (bT1RESS) pulse sequence to acquire MR data from a region of interest of the subject during an equilibrium phase of contrast enhancement after a first pass of the extracellular contrast agent through the region of interest. The bT1RESS pulse sequence includes a T1-weighted magnetization preparation including at least one contrast modifying (CM) radio frequency (RF) pulse, a single-shot balanced steady-state free precession (bSSFP) readout, and a time interval between the T1-weighted magnetization preparation and the acquisition of a center of k-space. The time interval is determined based on a T1 relaxation time of a contrast-enhanced blood pool and a flip angle of the at least one CM RF pulse. The method further includes generating an angiographic image of the region of interest.

A method for magnetic resonance imaging is provided herein. The method includes acquiring magnetic resonance data from a subject using a magnetic resonance imaging (MRI) system to sample a hybrid space along a zigzag trajectory. The hybrid space comprises a first axis along a temporal dimension and a second axis along a phase-encoding k-space dimension. The data acquisition involves, for each slice of a plurality of slices, consecutively acquiring all shots of a multi-shot acquisition for the slice before acquiring data for a next slice, with each shot using a radio frequency (RF) excitation pulse having a different flip angle. The method further includes reconstructing images from the acquired magnetic resonance data.

The application discloses an infant brain T2 weighted magnetic resonance imaging optimization method based on a fast spin echo sequence. First, T1, T2 and PD quantitative imaging of the infant brain from 0 to 24 months old is collected to obtain T1, T2 and PD values of the infant brain white matter and gray matter regions, and according to the relationship characteristics of the infant brain white matter T2 value and the gray matter T2 value, the infant is divided into different month groups. Then, based on the 3D T2 weighted imaging of the variable flip angle fast spin echo sequence, the signal intensity of the infant brain white matter and gray matter under different refocusing flip angle chains is calculated through an extended phase graph algorithm, and the best flip angle chain design scheme of each group is determined with the maximum white matter / gray matter contrast as the target. The application fills the blank of the infant brain T2 weighted imaging optimization, formulates the best flip angle chain optimization scheme of different month groups, and thus significantly improves the contrast of the infant brain T2 weighted imaging.

In a method for the improved recording of measurement data of an examination object, a desired imaging parameter and a desired flip angle are loaded for the recording of the measurement data by means of a recording method, the gradient to be switched for the position encoding of the measurement data having its total intensity during the incidence of an RF excitation pulse. A quantized value of an expected disturbance for the recording method is determined based on the desired imaging parameter, and a check of the performability of the correction of the disturbance is performed based on the quantized value and based on the desired flip angle.

Acquiring 3D MRI data using spiral-in-out encoding trajectories includes calculating a variable flip angle RF series for use as refocusing pulses, wherein the RF series includes a plurality of refocusing RF pulses. A spoiler gradient waveform is applied along the spoiler gradient direction, wherein the computer alternately adds and subtracts partition encoding waveforms to the spoiler gradient waveform. The method reads MRI data from each encoding step during an MRI sequence. The MRI sequence inserts a spiral-in gradient before a first refocusing RF pulse from the RF sequence, overlaps a pre-winder lobe for the encoding trajectory with the spoiler gradient waveform having the partition encoding waveforms added therein, and overlaps a rewinder lobe for the encoding trajectory with the spoiler gradient waveform having the partition encoding waveforms subtracted there from.

In a magnetic resonance imaging method, a first adjustment parameter is determined for presetting an initial contrast of a magnetic resonance image; a second adjustment parameter is determined for obtaining an optimized contrast of the magnetic resonance image and a specified data acquisition time of a blade artifact correction sequence; an optimized echo signal evolution curve is determined according to the first adjustment parameter and the second adjustment parameter; an actual variable flip angle train is calculated according to the optimized echo signal evolution curve; and the actual variable flip angle train is applied to a two-dimensional fast spin echo sequence, and the blade artifact correction sequence corresponding to the second adjustment parameter is used to acquire magnetic resonance signals and enable the magnetic resonance image to satisfy the optimized contrast.