41 results about "Repetition Time" patented technology

A method of double-contrast magnetic resonance fingerprinting including: optimizing, using Cramér-Rao lower bound (CRLB) via a computer system, radiofrequency (RF) pulse parameters in an MRF sequence; loading, via the computer system, the RF pulse parameters optimized into an MRI scanner; and capturing raw k-space data by selecting different signal contrast modules for dual-contrast encoding at varying repetition times (TR); reconstructing, via the computer system, at least one image including a plurality of pixels; defining, via the computer system, a dynamic range and step size for tissue parameters; and creating, via the computer system, a dictionary based on Bloch equations, the dynamic range, and the step size; and comparing, via the computer system, signal evolution for each of the plurality of pixels in the at least one image to the dictionary to determine quantitative parameters for each of the plurality of pixels, and generating a quantitative parameter map.

The invention relates to a magnetic resonance imaging electromagnetic parameter distribution scanning and calculation method, which comprises the following steps that a fast spin echo sequence I is adopted to scan a target body, parameters are (alpha1, TE0, TR0 and Bw1), alpha is a deflection angle, TE is echo time, TR repetition time and Bw receiving bandwidth; scanning a target body by adopting a fast spin echo sequence II, wherein parameters are (alpha2, TE0, TR0 and Bw1); scanning a target body by adopting a fast spin echo sequence III, wherein parameters are (alpha2, TE0, TR0 and Bw2); and scanning the homogeneous water model by adopting the fast spin echo sequences I, II and III. And under the condition that the magnetic vector precession meets the conditions that the amplitudes are comparable when the phases are the same and the phases are differentiable when the amplitudes are the same, each magnetic field and electric field parameter is calculated based on the homogeneous water model data. According to the invention, decoupling of the proton density and the sensitive field of the signal is realized, so that magnetic resonance weighted quantization imaging becomes possible.

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 a longitudinal relaxation time calculation method, nuclear magnetic resonance imaging equipment and a storage medium, and the method comprises the steps: executing a pulse sequence, and collecting a first multi-echo signal; the pulse sequence comprises a radio frequency pulse and a readout gradient, and the radio frequency pulse comprises a first excitation pulse and a plurality of second excitation pulses in a repetition time of the pulse sequence; the first multi-echo signal is a multi-echo signal acquired after executing a second excitation pulse; performing image reconstruction on the first multi-echo signal to obtain a multi-echo image; calculating target signal intensity according to a signal attenuation function and the information of the multi-echo image; and calculating the longitudinal relaxation time according to the target signal intensities of the plurality of repetition times. According to the invention, after a small number of first excitation pulses are applied, accurate longitudinal relaxation time distribution is obtained, and the problem of low calculation efficiency in the prior art is solved.

The embodiment of the invention provides a three-dimensional magnetic resonance imaging method and system and a storage medium, and the method comprises the steps: obtaining the k-space data of a target object, and the target object comprises a plurality of layers; and reconstructing a three-dimensional magnetic resonance image of the target object based on the k-space data. Wherein the k-space data comprises a spiral data line acquired in each of a plurality of repetition times, and the spiral data line is acquired by applying an imaging sequence to the target object by using the magnetic resonance equipment and acquiring the imaging sequence in a spiral sampling manner. The imaging sequence includes applying a random phase encoding gradient to the plurality of layers in a selected layer direction such that the spiral data line acquired within each repetition time corresponds to a random one of the plurality of layers.

Systems and methods are provided for a slice-ahead inversion sequence for jointly acquiring non-inverted and inverted contrast. In one example, a method for a magnetic resonance imaging (MRI) system includes acquiring k-space data with the MRI system according to a slice-ahead inversion sequence that jointly generates a contrast without inversion preparation and one or more inversion contrasts for a plurality of slices in a scan volume of a subject, wherein the k-space data comprises first k-space data of the contrast without inversion preparation acquired during one or more non-inversion repetitions and second k-space data of the one or more inversion contrasts acquired during one or more inversion repetitions, wherein a repetition time for each of the one or more non-inversion repetitions and one or more inversion repetitions is constant, and reconstructing one or more images from the k-space data.

The present invention discloses a magnetic resonance molecular imaging method and system for dynamically reading the accumulation of CEST signals. The method includes: applying N CEST saturation pulses for an object to be detected within each repetition time by a magnetic resonance imaging device; after each of the first N-1 CEST saturation pulses, a low-resolution, small-angle reading method is used to read the signal to obtain N-1 first-class signals; after the Nth CEST saturation pulse, a high-resolution, large-angle reading method is used to read the signal to obtain a second-class signal to compensate for the first-class signal, and N saturation-weighted magnetic resonance images of the object to be detected are obtained based on the compensated first and second-class signals. The method can improve the signal-to-noise ratio and robustness of CEST imaging, and can dynamically change according to the N readout signals, with better quantitativeness, such as reducing the influence of tissue longitudinal relaxation (T1) to obtain a proton exchange rate image.

An optimal pulse power measurement method for multinuclear simultaneous integrated magnetic resonance imaging includes the following steps: successively or simultaneously exciting multiple nuclides within a slice in a same repetition time (TR) of magnetic resonance imaging (MRI); applying, in a slice encoding gradient channel, a frequency encoding gradient in a direction opposite to a slice selection gradient, and acquiring free induction decay (FID) signals of all the nuclides; simultaneously changing shaped radiofrequency (RF) pulse power values of all the nuclides for multiple times, and acquiring multiple corresponding FID signals for each nuclide; and performing Fourier transform on the FID signals of each nuclide, selecting a spectral peak in an absolute spectrum, integrating the spectral peak for comparison, and taking a shaped RF pulse power value corresponding to a maximum signal intensity of each nuclide as an optimal shaped RF pulse power corresponding to a current TR.

The application relates to a multi-nucleus imaging sequence determination method, device and magnetic resonance system, wherein the multi-nucleus imaging sequence determination method comprises the following steps: acquiring an initial multi-nucleus imaging sequence, wherein the initial multi-nucleus imaging sequence comprises the pulse arrangement of several kinds of nuclei in a single repetition time; and adjusting the pulse arrangement of at least one kind of nucleus to optimize the initial multi-nucleus imaging sequence, thereby obtaining a target multi-nucleus imaging sequence. According to the application, the target multi-nucleus imaging sequence can be obtained, and the target multi-nucleus imaging sequence is a multi-nucleus imaging sequence obtained by combining and optimizing a plurality of single-nucleus imaging sequences. Therefore, the multi-nucleus imaging sequence can complete the scanning and imaging of multiple kinds of nuclei in one scanning and imaging process, and compared with sequentially imaging each kind of nucleus respectively, the scanning time of the sequence is shortened, and the imaging efficiency is improved. The application solves the problem that there is no imaging sequence determination method for multi-nuclear magnetic resonance imaging technology in the related art.

The invention relates to a method of MR imaging of an object (10) placed in an examination volume of an MR system (1). It is an object of the invention to provide a method that enables improved MR imaging using partial echo acquisition. The method of the invention comprises the steps of: subjecting the object (10) to an imaging sequence comprising a series of RF excitations, wherein an echo signal is generated in the presence of a readout magnetic field gradient in each repetition time interval between successive RF excitations, wherein phase-encoding magnetic field gradients (P, S) are switched in each repetition time interval to sample a pre-defined region of k-space; acquiring the echo signals from the object (10) as partial echoes with different readout polarities, each echo signal being associated with either a first direction of the readout magnetic field gradient or a second direction of the readout magnetic field gradient which is opposite to the first direction, wherein the echo signals associated with the first and / or the second direction sample k-space sparsely in at least one phase-encoding direction (P, S); and reconstructing an MR image from the acquired echo signals. Furthermore, the invention proposes to apply a shift in k-space in the readout direction to the acquired echo signal data and to reconstruct an intermediate MR image for each of a number of different shift values, wherein a final MR image is computed from these intermediate MR images by selecting, for each voxel of the final MR image, the voxel value with the maximum intensity from the set of intermediate MR images at the respective voxel position. Signal loss caused by phase variations of the acquired partial echo signals can be avoided in this way. Moreover, the invention relates to an MR system (1) and to a computer program to be run on an MR system (1).

A magnetic resonance imaging method and a magnetic resonance imaging system is provided. The method is used to acquire, in a plurality of consecutive time units, magnetic resonance signals representing one or more layers of an anatomical region of interest of a subject and generate a magnetic resonance image. The method includes: determining an effective repetition time of an (N−1)th time unit; determining the position of an inversion recovery pulse in an Nth time unit based on the effective repetition time of the (N−1)th time unit, wherein N is an integer greater than 1; transmitting, in the Nth time unit, a scan sequence generated based on the position of the inversion recovery pulse, and acquiring a magnetic resonance signal representing an anatomical region of interest of a subject; and reconstructing a magnetic resonance image at least based on the magnetic resonance signal.

Embodiments of the present application provide a magnetic resonance scanning and imaging method, and a magnetic resonance imaging system. The method includes: determining a pulse to be adjusted in a scan sequence, the pulse to be adjusted including a first radio-frequency pulse and a first gradient pulse applied along with the first radio-frequency pulse; determining an adjustment factor based on the first gradient pulse and a minimum repetition time related to a specific absorption rate of radio-frequency energy; adjusting the scan sequence based on the adjustment factor; and, using the adjusted scan sequence, performing a diagnostic scan on a site to be examined, to obtain a magnetic resonance image.

A method and a magnetic resonance imaging (MRI) system improve an MRI signal from a magnetization of interest. The method includes performing an MRI pulse sequence containing three consecutive radio frequency (RF) elements, namely, a first element that is an inversion-recovery pulse sequence characterized by a time of inversion, a second element that is an image-encoding pulse sequence starting at the time of inversion with an excitation RF pulse followed by an image-encoding gradient and a data sampling. The second element is followed by a third element. An MRI signal generated by the object and sampled by image readout blocks applied to the object by the MRI system during each repetition time, is acquired. From the MRI signal, an image of the object is reconstructed. The third element is a modified driven-equilibrium (mDE) pulse sequence configured for achieving a conversion of a transverse magnetization component.

Systems and methods are provided for a slice-ahead inversion sequence for jointly acquiring non-inverted and inverted contrast. In one example, a method for a magnetic resonance imaging (MRI) system includes acquiring k-space data with the MRI system according to a slice-ahead inversion sequence that jointly generates a contrast without inversion preparation and one or more inversion contrasts for a plurality of slices in a scan volume of a subject, wherein the k-space data comprises first k-space data of the contrast without inversion preparation acquired during one or more non-inversion repetitions and second k-space data of the one or more inversion contrasts acquired during one or more inversion repetitions, wherein a repetition time for each of the one or more non-inversion repetitions and one or more inversion repetitions is constant, and reconstructing one or more images from the k-space data.

The invention discloses a scanning method, system, equipment and product of a spatially selective nuclear magnetic two-dimensional spectrum, a plurality of constant gradients are generated, and nuclear magnetic scanning is carried out under each constant gradient, so that each overturning time and the number of repetitions are included in one constant gradient during each scanning, and therefore, the number of times of each overturning time and the number of times of repetitions are reduced. The influence caused by eddy current and residual magnetism under different gradients can be reduced; meanwhile, by taking the design principle of reducing the echo chain length without influencing the complete two-dimensional spectrum as the echo chain length, the echo chain time of each group of TI is gradually reduced; on the basis, the scanning time in a constant gradient can be reduced as much as possible, so that the overall scanning time can be shortened; besides, each overturning time and repetition times are included in one constant gradient, and the climbing times and interval times of the gradient can be reduced, so that the scanning time can be further shortened; therefore, the method not only reduces the influence caused by eddy current and residual magnetism under different gradients, but also shortens the scanning time.

Embodiments of the present application disclose a multi-echo data magnetic resonance imaging scanning method, device and magnetic resonance imaging system. The method comprises: in the process of multi-echo data magnetic resonance imaging scanning on an imaging target, if automatic calibration data needs to be collected in the current repetition time, and the position of the automatic calibration data in K space is inconsistent with the position of any imaging data in K space which needs to be collected in the current repetition time, then: when the plateau signal of the first readout gradient in the readout direction is applied, start to apply an offset gradient in the phase encoding direction, wherein the first readout gradient is any readout gradient in the readout direction except the last readout gradient; and during the application of the plateau signal of the dephasing gradient of the first readout gradient in the readout direction, the automatic calibration data is collected. Embodiments of the present application avoid TR oscillation in multi-echo data MR imaging scanning, and realize the continuity of the collected automatic calibration data and imaging data.

The application relates to a magnetic resonance signal acquisition method and device, computer equipment and a storage medium. The method comprises the following steps: acquiring the number of groups of multi-layer simultaneous excitation of radio frequency pulses for a target object; when the number of groups of multi-layer simultaneous excitation is even, adjusting a preset excitation timing for a target layer group to obtain a target excitation timing; the target layer group comprises a group of layers that are first or last excited in a repetition time of the radio frequency pulses; in the target excitation timing, spatially adjacent layers are not adjacent in the timing; controlling the radio frequency pulses based on the target excitation timing to perform multi-layer simultaneous excitation processing on the target object; acquiring multi-layer simultaneous excitation data of the target object; and the multi-layer simultaneous excitation data is used for magnetic resonance imaging of the target object. The method can improve the magnetic resonance imaging effect.

A 3D model of the AC conductivity (at a given frequency) of an anatomical volume can be created by obtaining two MRI images of the anatomical volume, where the two images have different repetition times. Then, for each voxel in the anatomical volume, the ratio IR of the intensities of the corresponding voxels in the two MRI images is calculated. Then, this calculated IR is mapped into the corresponding voxel of the 3D model of the AC conductivity at the given frequency. The given frequency is below 1 MHz (e.g., 200 kHz). In some embodiments, the 3D model of the AC conductivity at the given frequency is used to determine the position of the electrodes in TTField (Tumor Treating Fields) therapy.

The application relates to a magnetic resonance frequency calibration method and a magnetic resonance device. The method is applied to a magnetic resonance device, and the method comprises the following steps: applying an imaging sequence and a calibration sequence to an imaging object; the calibration sequence is located between two adjacent imaging sequences; the imaging sequence is a functional magnetic resonance elastography sequence; a first echo signal and a second echo signal corresponding to the current calibration sequence are acquired, and a frequency drift amount is determined according to the first echo signal and the second echo signal; the reference frequency of the magnetic resonance device is calibrated according to the frequency drift amount, and an imaging sequence adjacent to the current calibration sequence is applied to the imaging object based on the calibrated reference frequency. The magnetic resonance frequency calibration method provided by the application can realize calibration of the reference frequency of a magnetic resonance device with a short repetition time.

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.

The invention relates to a method of MR imaging of at least a part of a patient's body (10) placed in an examination volume of an MR system (1). It is an object of the invention to provide an improved rapid gradient echo imaging technique with the ability to obtain angiographic information. The method of the invention comprises the following steps: subjecting the body part to a magnetization preparation RF pulse (MP); after a preparation delay (TD), subjecting the body part to a gradient echo imaging sequence comprising a series of RF excitations (EP), wherein phase-encoding (PE) and refocusing gradients (RO) as well as at least one bipolar pair of velocity-encoding gradients (VE) are applied in a repetition time interval (TR) between successive RF excitations (EP) to sample a pre-defined region of k-space and to generate a gradient echo in each repetition time interval (TR); acquiring echo signals from the body part; reconstructing a morphological MR image of the body part from the acquired echo signals; and deriving phase-contrast angiographic information from the phase imposed on the echo signals by the velocity- encoding gradients (VE). Moreover, the invention relates to an MR system (1) and to a computer program.

Capturing MR image data of an examination object using an MR apparatus, including: performing a balanced steady-state free precession sequence with phase progress of 180 degrees per repetition time using the MR apparatus; in the balanced steady-state free precession sequence, providing a white-marker gradient in order at least partially to balance a dephasing caused by a magnetic-field-changing object in the examination object; capturing image data of the examination object using the MR apparatus at an echo time; and adjusting a phase development between phase magnetization of a first and second materials, which form an interface in the examination object, in the balanced steady-state free precession sequence using the MR apparatus, wherein due to the adjusting of the phase development before an effect of the white-marker gradient, a co-phasal alignment of a magnetization of the first material and of the second material at the interface is effected at the echo time.

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.

The application relates to the field of magnetic resonance, and discloses a magnetic resonance B0 eddy current compensation method, device and storage medium, which comprises the following steps: acquiring parameters of a scanning sequence; dividing each repetition time TR into p time segments to obtain a total of p+1 time points; calculating p sets of B0 eddy current compensation values by using the gradient waveform, multiple sets of B0 eddy current amplitude constants and multiple sets of B0 eddy current time constants; using the gradient waveform, multiple sets of B0 eddy current amplitude constants, multiple sets of B0 eddy current time constants and the B0 eddy current compensation value of a first specified time point, responding to the fact that the first specified time point is an echo signal receiving time point, using the B0 eddy current phase compensation value of the first specified time point to perform phase compensation on the echo signal of the first specified time point, and obtaining a compensated first magnetic resonance signal. The application accelerates B0 eddy current compensation through a modular partial preprocessing mode, and meets the requirements of real-time speed, low consumption and high precision.

The invention relates to a method of MR imaging of at least a part of a patient's body (10) placed in an examination volume of an MR system (1). It is an object of the invention to provide an improved rapid gradient echo imaging technique with the ability to obtain angiographic information. The method of the invention comprises the following steps: subjecting the body part to a magnetization preparation RF pulse (MP); after a preparation delay (TD), subjecting the body part to a gradient echo imaging sequence comprising a series of RF excitations (EP), wherein phase-encoding (PE) and refocusing gradients (RO) as well as at least one bipolar pair of velocity-encoding gradients (VE) are applied in a repetition time interval (TR) between successive RF excitations (EP) to sample a pre-defined region of k-space and to generate a gradient echo in each repetition time interval (TR); acquiring echo signals from the body part; reconstructing a morphological MR image of the body part from the acquired echo signals; and deriving phase-contrast angiographic information from the phase imposed on the echo signals by the velocity-encoding gradients (VE). Moreover, the invention relates to an MR system (1) and to a computer program.

The present invention relates to an active noise reduction method for magnetic resonance equipment based on sequential electromagnetic interference sampling, and belongs to the field of nuclear magnetic resonance technology. The method adopts an additional electromagnetic interference sampling imaging sequence, that is, after collecting magnetic resonance signals during sequence operation, the remaining repetition time is used to collect electromagnetic interference signals to simultaneously obtain two sets of k-space data, namely the magnetic resonance signal k-space and the electromagnetic interference k-space. The correlation coefficient matrix is ​​calculated using the least squares method or a neural network. For fixed frequency interference or residual electromagnetic interference signals due to insufficient correlation, a transform domain subtraction method is used to filter them out, that is, the difference between the magnetic resonance signal k-space and the electromagnetic interference k-space after active noise reduction is made in the transform domain to eliminate electromagnetic interference of specific modes. The present invention can achieve effective filtering of electromagnetic interference signals in the magnetic resonance radio frequency receiving coil.

Provided is a technique of minimizing an influence of TR extension due to a navigator echo for body motion detection without reducing a time resolution of body motion detection in imaging using the navigator echo.In a case in which imaging is performed in accordance with a predetermined pulse sequence by using an MRI apparatus, control of generating a navigator echo at a predetermined timing in the pulse sequence is performed, and control of making a timing at which the navigator echo is acquired different between a case in which a repetition time of the pulse sequence is equal to or greater than a preset threshold value and a case in which the repetition time is less than the threshold value is performed.

Systems and methods are provided for jointly acquiring non-inverted contrast and inverted contrast slice advance inversion sequences. In one example, a method for a magnetic resonance imaging (MRI) system includes acquiring (1102) k-space data with the MRI system according to a slice advance inversion sequence that jointly generates an inversion-free prepared contrast and one or more inversion contrasts for a plurality of slices in a scan volume of a subject, wherein the k-space data comprises first k-space data (1104) of the contrast acquired during one or more non-inversion repetitions without inversion preparation and second k-space data (1108) of the one or more inverted contrasts acquired during one or more inversion repetitions, wherein a repetition time of each of the one or more non-inversion repetitions and the one or more inversion repetitions is constant; and reconstructing (1112) one or more images from the k-space data.

An optimal pulse power measurement method for multinuclear simultaneous integrated magnetic resonance imaging includes the following steps: successively or simultaneously exciting multiple nuclides within a slice in a same repetition time (TR) of magnetic resonance imaging (MRI); applying, in a slice encoding gradient channel, a frequency encoding gradient in a direction opposite to a slice selection gradient, and acquiring free induction decay (FID) signals of all the nuclides; simultaneously changing shaped radiofrequency (RF) pulse power values of all the nuclides for multiple times, and acquiring multiple corresponding FID signals for each nuclide; and performing Fourier transform on the FID signals of each nuclide, selecting a spectral peak in an absolute spectrum, integrating the spectral peak for comparison, and taking a shaped RF pulse power value corresponding to a maximum signal intensity of each nuclide as an optimal shaped RF pulse power corresponding to a current TR.

The invention discloses a magnetic resonance imaging sequence trajectory rewinding compensation method and device, a medium and a product, and relates to the technical field of magnetic resonance imaging, and the method comprises the steps: collecting the actual gradient waveforms of three gradient axes in a set time period after an excitation radio frequency pulse is applied to a water model in a magnetic resonance scanner in the current repetition time; setting ideal gradient waveforms of three gradient axes in a set time period; any gradient axis is determined as a current axis; determining the residual gradient time moment of the current axis based on the actual gradient waveform and the ideal gradient waveform of the current axis in the set time period, and determining the waveform parameter of the current axis of the rewinding compensation gradient pulse; and applying a component of the rewinding compensation gradient pulse on the current axis to the current axis based on the residual gradient time moment of the current axis and the waveform parameter of the current axis of the rewinding compensation gradient pulse at the end moment of the phase disturbing gradient so as to realize the rewinding compensation of the magnetic resonance imaging sequence trajectory. According to the invention, the problems of quantitative deviation and image blurring of T2 weighted imaging are solved.