42 results about "Flip angle" patented technology

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.

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 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.

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.

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 discloses a kind of calibration radio frequency power acquisition method and system and its radio frequency power-flip angle mapping function establishment method and system, it is related to magnetic resonance technical field, comprising: using DEAR sequence to scan target object multiple times;Wherein, different radio frequency power is applied in each scan, so that the pre-set flip angle range is 0 degrees to 90 degrees;The intensity of echo signal of two different echo times of each scan is collected respectively, and the double-echo signal ratio of each scan is calculated according to it;According to the double-echo signal ratio of each scan, the actual flip angle under the radio frequency power of each scan is inverted;According to the actual flip angle under the radio frequency power of multiple scans, radio frequency power-flip angle mapping function is obtained.The application can quickly obtain radio frequency power and flip angle mapping function without image acquisition and reconstruction, so as to realize fast, low-cost, full-power range radio frequency response calibration.

Disclosed herein is a medical system (100) comprising a magnetic resonance imaging system (102). Execution of the machine executable instructions (140) causes a computational system (132) to: repeatedly (200) acquire k-space data (144) in multiple shots (400) by controlling the magnetic resonance imaging system with pulse sequence commands (142) and reconstruct (202) at least one magnetic resonance image (146). The pulse sequence commands cause the magnetic resonance imaging system to perform an initial preparatory pulse (308). The initial preparatory pulse prepares magnetization for each of the multiple shots. The pulse sequence commands are configured to acquire the k-space data using a Turbo Field Echo readout (310) with T1 weighting, balanced or T2 weighting, and acquires the k-space data using a flip angle that decreases as a distance from a central k-space region increases. The flip angle has a starting flip angle of 10 degrees or less.

The application discloses a kind of 3D multi-parameter simultaneous quantification of magnetic resonance imaging method including myelin water, comprising: initialization includes two T2 preparation pulse and five readout section magnetic resonance quantification sequence;Using optimization model based on Cramer-Rao lower bound and self-supervised multilayer perception, flip angle, echo time and interval time of sequence are jointly optimized;Signal dictionary is constructed using optimized parameter and the base of subspace is extracted;Original k-space data is collected to reconstruct the timing of subspace and obtain timing reconstruction image;Finally, timing signal is matched with dictionary, and T1, T2 and MWF quantitative map of whole brain are generated.The application breaks the limitation of traditional experience parameter setting, significantly improves the quantification accuracy of short T2 myelin water and conventional tissue parameters, and realizes single whole brain high-resolution multi-parameter simultaneous quantification in 3 minutes 30 seconds, greatly shortens the scanning time, and greatly improves the clinical applicability.

The invention provides a multi-core MRI (Magnetic Resonance Imaging) method for rapid evaluation of living lung exchange dynamics, which is characterized in that a rapid qi-blood exchange dynamics imaging pulse sequence is designed and comprises a plurality of units, and each unit sequentially comprises a steady state establishment sub-module and a data acquisition sub-module; the repetition time of the steady-state establishment sub-modules in all the units is the same as the repetition time of the data acquisition sub-modules; in the same unit, the pulse flip angle of the steady-state establishment sub-module is the same as that of the data acquisition sub-module; different units have different pulse flip angles so as to correspond to different equivalent exchange time; original overall sampling data obtained by executing a fast gas-blood exchange dynamic imaging pulse sequence is split according to the number of pulse overturning angles and then image reconstruction is carried out respectively, and then a ratio is obtained point by point to obtain a gas-blood exchange proportion distribution diagram. The method can effectively shorten the scanning time, reduces the calculation burden, and facilitates the improvement of the image reconstruction speed.

The embodiment of the invention discloses a fat pressing parameter determination method, device and system applied to arterial spin labeling imaging. The method comprises the following steps: according to an acquisition parameter set adopted by the ASL imaging, determining the longitudinal magnetization intensity of fat when a first fat pressing pulse for the ASL imaging begins to be applied; according to the longitudinal magnetization intensity of the fat when the first fat suppression pulse begins to be applied, the overturning angle or overturning duration TI of the first fat suppression pulse is determined, so that the longitudinal magnetization intensity of the fat when the first excitation pulse of the ASL imaging begins to be applied is the expected longitudinal magnetization intensity. According to the embodiment of the invention, accurate acquisition of the overturning angle or the TI of the fat pressing pulse is realized, and the accurate overturning angle and the TI are selected for the fat pressing pulse applied to ASL imaging, so that the ASL imaging quality is finally improved, and fat ghosting in an ASL image is reduced.

The application relates to the technical field of flip timers, and discloses an inductive visual flip timer. A six-axis attitude sensor is used to acquire flip angle, flip angular velocity and attitude holding time length data, flip actions are classified and recognized, the flip angle is divided into fine adjustment angle intervals, switching angle intervals and reset angle intervals, and the flip speed is divided into first-level flip and second-level flip; according to the classification results, differentiated control functions such as timing time length fine adjustment, mode switching viewing, timing reset, fast switching of default custom time length, etc. are triggered; in the timing process, timing state snapshots are recorded, when a misflip operation is detected, the original display surface is returned within a preset recovery time window, and the timing progress before the misflip is automatically recovered from the state snapshot; high-frequency flip operation characteristics are recorded and attitude recognition parameters are adaptively optimized. The application significantly improves the functional richness and user experience fluency of flip interaction.