11 results about "Repetition Time" patented technology

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.

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.

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 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 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.

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

The disclosed systems and methods use the developed Flexible Relaxation and Saturation Time (FIRST) approach to provide customization of parameters for a Magnetization Transfer (MT) sequences to maximize sensitivity and efficiency. The methods may include generating one or more customized parameters for one or more iterations of a Magnetization Transfer Magnetic Resonance (MR) sequence that is executed on a Magnetic Resonance Imaging (MRI) System. The generating may include receiving input parameters for each iteration of the sequence. The one or more input parameters may include radiofrequency (RF) offset and / or saturation power. The generating may further include determining a set of one or more customized parameters for each iteration using the input parameters for each RF offset and / or saturation power. The one or more customized parameters may include repetition time (TR).