8 results about "Stimulated echo" 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.

This invention discloses an echo signal processing method, apparatus, electronic device, and storage medium. The method includes: acquiring a first echo signal from a CPMG pulse sequence of a full-diameter core sample; wherein the first echo signal is the first wave signal in the CPMG pulse sequence; when it is determined that the first echo signal is affected by a stimulated echo, acquiring a stimulated echo correction factor; wherein the stimulated echo correction factor is a correction factor determined based on the simulated nuclear magnetic resonance signal response corresponding to the MAPS scan image of the full-diameter core sample; and correcting the first echo signal based on the stimulated echo correction factor. The technical solution of this invention corrects the first echo signal using a correction factor determined by the simulated nuclear magnetic resonance signal response corresponding to the MAPS scan image of the full-diameter core sample, reducing the influence of stimulated echoes on the first echo signal and significantly improving the quality of the first echo signal.

Systems and methods are provided for producing diffusion-weighted images of a subject using a magnetic resonance imaging (MRI) system. The method includes performing a stimulated echo preparation module using non-selective radio-frequency (RF) pulses designed to induce a stimulated echo, performing an acquisition module that includes a multi-slice acquisition of MR data in the presence of diffusion gradients, and reconstructing the diffusion-weighted images of the subject from the MR data.

A method for applying a diffusion-weighting gradient during acquisition of diffusion-weighted imaging signals from a selected portion of a nervous system of a subject. Planar diffusion-weighted spin-echo (DWSE) imaging signals and planar diffusion-weighted stimulated-echo (DWSTE) imaging signals can be obtained to provide a plurality of sets of imaging signals. At least one set of imaging signals includes DWSTE signals that are associated with a high-b-value. A signal difference between DWSE imaging signals and DWSTE imaging signals can be corrected based on respective sets of DWSE imaging signals and DWSTE imaging signals having b-values at or near zero.

Systems and methods are provided for producing diffusion-weighted images of a subject using a magnetic resonance imaging (MRI) system. The method includes performing a stimulated echo preparation module using non-selective radio-frequency (RF) pulses designed to induce a stimulated echo, performing an acquisition module that includes a multi-slice acquisition of MR data in the presence of diffusion gradients, and reconstructing the diffusion-weighted images of the subject from the MR data.

The invention relates to a method of MR imaging. It is an object of the invention to provide an improved B1 mapping method that is less affected by T1 relaxation. The invention proposes that a first stimulated echo imaging sequence (25) is generated comprising at least two preparation RF pulses (α) radiated during a first preparation period (21) and a sequence of reading RF pulses (β) radiated during a first acquisition period (22) temporally subsequent to the first preparation period (21). A first set of FID signals (IFID) and a first set of stimulated echo signals (ISTE) are acquired during the first acquisition period (22). A second stimulated echo imaging sequence (27) is generated comprising again at least two preparation RF pulses (α) radiated during a second preparation period (21) and a sequence of reading RF pulses (β) radiated during a second acquisition period (22) temporally subsequent to the second preparation period (21). A second set of FID signals (IFID) and a second set of stimulated echo signals (ISTE) are acquired during the second acquisition period (22). The first and second sets of FID signals (IFID) have different T1-weightings and / or the first and second sets of stimulated echo signals (ISTE) have different T1-weightings. A B1 map indicating the spatial distribution of the RF field of the RF pulses is derived from the acquired first and second sets of FID (IFID) and stimulated echo (ISTE) signals, wherein the different T1-weightings are made use of to compensate for influences on the B1 map caused by T1 relaxation. Preferably, either the first or the second preparation period (21) is preceded by an RF inversion pulse to obtain the different T1-weightings. Moreover, the invention relates to an MR device (1) and to a computer program for an MR device (1).

Method for operating a magnetic resonance tomograph for spatially resolved spin resonance measurement of an object, in particular a living object, which is arranged in a static magnetic field B0, whereby an alignment of the object's spins and a longitudinal net magnetization Mz along the direction Z of the static magnetic field results, and wherein a transverse magnetization component Mxy is generated or changed, in particular by generating a spin flip from the Z direction by a desired flip angle, in particular by 90 degrees, by means of at least one high-frequency excitation pulse (1) in spin resonance, wherein spin echo signals from at least one desired volume element of the object are measured using a sequence of high-frequency pulses (4, 5, 7) and switched gradient magnetic fields (2, 3, 6).wherein the at least one volume element is determined by several gradient magnetic fields superimposed at least temporarily on the homogeneous magnetic field B0, wherein the sequence of high-frequency pulses comprises a first (4) and a second high-frequency rephasing pulse (5), in particular a first (4) and second high-frequency rephasing pulse (5) directly after the generation of a transverse magnetization component by means of a high-frequency excitation pulse (1), wherein from the second high-frequency rephasing pulse (5) onwards both a spin echo and a stimulated echo are generated, wherein in addition to a gradient magnetic field (6) in the frequency coding direction, which is switched on during the measurement acquisition to acquire a line of the raw data space, an additional gradient magnetic field (8) in the frequency coding direction is switched on, which generates echo signals or echo signal components newly generated by the high-frequency rephasing pulses (5, 7),in particular, those not attributable to a refocusing of the original spin echo after the first radio frequency rephasing pulse (4) and / or of the original stimulated echo after the second radio frequency rephasing pulse (5), are shifted out of the raw data space or raw data line acquired in a subsequent measurement, characterized in that, during an evolution time (Tau) between the first (4) and second radio frequency rephasing pulse (5), T2*-induced relaxation processes act on a transverse magnetization component present after the first radio frequency rephasing pulse (4), and a magnetization component present in the longitudinal direction after the first radio frequency rephasing pulse (4) remains unaffected, wherein the absolute time between the first (4) and second radio frequency rephasing pulse (5) is extended by the evolution time beyond the duration of an echo interval,which is present between subsequent equidistant high-frequency rephasing pulses (5, 7).

An apparatus and method for improved S / N measurements useful for electron paramagnetic resonance imaging in situ and in vivo, using high-isolation transmit / receive surface coils and temporally spaced pulses of RF energy (e.g., in some embodiments, a RF pi pulse) having an amplitude sufficient to rotate the magnetization by 180 degrees followed after varied delays, by a second RF pulse having an amplitude half that of the initial pulse to rotate the magnetization by, e.g., 90 degrees (a pi / 2 pulse), to the plane orthogonal to the static field where it evolves for a short time. Then a third RF pi pulse sufficient to rotate the magnetization by, e.g., 180 degrees, forms an echo (in some embodiments, the second and third pulses are from the same signal as the first pulse but are phase shifted by 0, 90, 180, or 270 degrees to reduce signal artifact), to image human body.