A B1 magnetic field may be regulated during a magnetic resonance tomography (MRT) imaging sequence.

A MRI device includes: structure applying a main magnetic field on an axis Z over a sample zone; structure emitting a magnetic field gradient and structure emitting a radiofrequency pulse, and a controller. The controller performs on the sample zone, a sequence including: a radiofrequency pulse and/or phase at each repetition; and a spatial gradient of the component along the Z axis. The controller is programmed so that, in the course of repeated applications of the pulse and of the gradient of the sequence of one and the same set: the radio frequency pulse follows, between its repeated applications, a periodic series for its amplitude and for a series U+t=v+iv; and each repeated application of the gradient of magnetic field of the sequence a, according to a coding spatial direction, a non zero timing integral equal to A and identical for each application of gradient of this set.

A method of calibrating a RF power of a magnetic resonance imaging system is provided. With a fixed time-domain length of RF pulses, a RF pulse amplitude having a larger step size increment is selected to perform a traversal scanning to obtain FID signal values corresponding to different RF pulse amplitudes. In subsequent traversal scanning, the step size is continuously scaled down, and a start value and an end value are re-determined to continuously narrow a range for the subsequent traversal scanning, which may quickly and accurately determine a RF pulse amplitude corresponding to a 90 flip angle that can be obtained from a RF pulse amplitude corresponding to a maximum FID signal value in a last traversal scanning. A linear relationship between a flip angle and a RF pulse amplitude is obtained according to the 90 flip angle and its corresponding RF pulse amplitude for calibrating a RF power.

A method acquires RF magnetic field information (B1 magnetic field information) in response to generated radio frequency (RF) pulses in a magnetic resonance imaging (MRI) system. An RF excitation pulse sequence is generated, and the generated RF excitation pulse sequence includes a plurality of RF excitation pulses individually having different flip angles. The generated RF excitation pulse sequence is transmitted to a target object. RF echo response signals are received from the target object corresponding to the plurality of RF excitation pulses and B1 information is acquired by processing the received RF echo response signals.

A method can include obtaining a scaling factor for a location proximate a metallic object by optimizing a function of an acquired dataset and a simulated dataset. The simulated dataset can include a first signal from a first pulse having a first excitation flip angle and a first refocusing flip angle. The simulated dataset can include a second signal from a second pulse having a second excitation flip angle and a second refocusing flip angle.

A method of double-contrast magnetic resonance fingerprinting including: optimizing, using Cramr-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.

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.

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.

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.