66 results about "Stimulated echo" patented technology

The invention provides a method for correcting fast spin echo sequence, aiming at solving the problem that the prior FSE images have the factors of an imaging system such as artifacts, magnetic field stability, eddy current, etc. which have impact on the quality of images. The method can be used to correct the parameter of the fast spin echo (FSE) sequence of a magnetic resonance diagnostic, in particular to correct the parameter of the fast spin echo (FSE) sequence of a magnetic resonance diagnostic which can switch frequence of a transmitter and a receiver. The method for correcting fast spin echo sequence of the invention eliminates the impact of the factors of the imaging system such as artifacts, magnetic field stability, eddy current, etc. on the quality of the images; and as the parameter which is obtained by the correcting method and used in the pre-scanning is the optimal parameter, thereby solving the problem of artifacts of the prior FSE images.

A method for RARE magnetic resonance imaging comprising slice selective excitation of two or more slices and of one or more nuclei, followed by refocusing of these slices and application of gradient pulses which cause a diversion of the signal into spin echoes and stimulated echoes, is characterized by application of refocusing slice selective RF pulses, which are placed to fulfill the echo-spacing CPMG condition for each slice and by arrangement of gradient pulses which cause the phase accumulated by spins in each slice between two consecutive refocusing RF pulses corresponding to that slice to be equal, thus fulfilling the CPMG phase accumulation condition. Thereby, the obtainable signal can be increased and stabilized.

An imaging technique is disclosed for multi-echo, magnetic resonance imaging that addresses amplitude modulations, such as those caused by T2 decay and stimulated echo refocusing, in acquired MR data. Acquired MR data is corrected by non-phase encoded data such that amplitude modulations in the echo signal are addressed. Reducing the effects of amplitude modulations in the echo signal reduces ghosting and thereby improves image quality.

The invention discloses a magnetic resonance system imaging method, which comprises the following steps: under a multichannel emission mode, according to spin echo signal intensity SSE and stimulated echo signal intensity SSTE, carrying out optimization on amplitude and phase parameters of a plurality of radio frequency emission channels to generate a target B1 field, wherein the target B1 field meets B1 field uniformity and radio frequency emission power optimization simultaneously; loading the optimized amplitude and phase parameters to a radio frequency pulse controller, and driving the plurality of radio frequency emission channels to generate the target B1 field; under the target B1 field, exciting a part to be scanned of a subject to obtain a magnetic resonance signal of the part to be scanned; and carrying out Fourier transform on the magnetic resonance signal to obtain a magnetic resonance image of the part to be scanned. The spin echo signal intensity and the stimulated echo signal intensity are collected to reflect distribution of the B1 field; and fast correction can be carried out to obtain a uniform B1 field, and radio frequency emission power can be corrected. The invention also provides a magnetic resonance system.

The invention relates to a method of MR imaging, wherein a portion of a body (10) placed in the examination volume of a MR device (1) is subjected to an imaging sequence (IMG) of RF pulses and switched magnetic field gradients. The imaging sequence (IMG) is a stimulated echo sequence including i) at least two preparation RF pulses (α) radiated toward the portion of the body (10) during a preparation period (21), and ii) one or more reading RF pulses (β) radiated toward the portion of the body (10) during an acquisition period (22) temporally subsequent to the preparation period (21). One or more FID signals (I₁) and one or more stimulated echo signals (I₂) are acquired during the acquisition period (22). A B₁ map indicating the spatial distribution of the RF field of the RF pulses within the portion of the body (10) is derived from the acquired FID (I₁) and stimulated echo (I₂) signals. It is an object of the invention to provide an improved B₁ mapping method which can be applied in magnetic resonance angiography (MRA) and, in particular, in cardiac imaging, where the acquisition of a complete B₁ map needs to be performed within the diastolic phase of the heartbeat. The invention proposes that the portion of the body (10) is subjected to a suppression sequence (BB) for suppression of MR signals emanating from blood prior to the imaging sequence (IMG). Moreover, the invention relates to a MR device (1) and to a computer program for a MR device (1).

The invention relates to a method of MR imaging, wherein a portion of a body is subjected to an imaging sequence of RF pulses and switched magnetic field gradients, which imaging sequence is a stimulated echo sequence including an off-resonant Bloch-Siegert RF pulse (BS) radiated during a preparation period (21) of the stimulated echo sequence. A B₁ map is derived from the acquired stimulated echo MR signals. Moreover, the invention relates to a method of MR imaging, wherein a portion of a body is subjected to a first imaging sequence, which comprises a first composite excitation RF pulse consisting of two RF pulse components having essentially equal flip angles and being out of phase by essentially 90°. Further, the portion of the body is subjected to a second imaging sequence, wherein a B₁ map is derived from signal data acquired by means of the first and second imaging sequences.

A system for magnetic resonance (MR) spectroscopy includes a plurality of gradient coils positioned about a bore of a magnet and an RF coil assembly coupled to a pulse generator to emit RF pulse sequences and arranged to receive resulting MR signals from a subject of interest. A system control is also included in the MR spectroscopy system and is coupled to the plurality of gradient coils and the RF coil assembly. The system control is programmed to cause the RF coil assembly to emit a first RF pulse and a second RF pulse, wherein at least one of the first and second RF pulses is spectrally selective and at least one of the first and second RF pulses is spatially selective. The system control is also programmed to cause the RF coil assembly to emit a third RF pulse after a pre-defined time delay to generate a stimulated echo and detect MR signals resulting from the stimulated echo.

The invention discloses a quasi one-time orthogonal complementary Golay (A,B) code ultrasonic phased array coded excitation method. The method comprises the following steps: coded excitation is carried out by Golay A code; Golay A to B code excitation transition of received echo is realized by software algorithm, and twice stimulated echoes of Golay A,B are obtained (orthogonal complementary Golay coded excitation condition is formed); pulse compression is carried out, decoding is realized by summarizing vectors, so that quasi one-time orthogonal complementary Golay coded excitation technology is realized, and replaces the traditional double-emission scheme with physical hardware. An effective noise inhibition-deconvolution algorithm is used, FPGA(Field Programmable Gate Array) is used for realizing excitation transition algorithm of sequence Golay A code excitation to Golay B code, in order to realize the purpose of quasi one-time excitation; the traditional Golay A,B code separated excitation scheme is improved, operation efficiency of the phased array system is increased by 50%, signal to noise ratio (related to coding length Lc) is greatly improved, the problem of decoding effect influenced by inconsistent received waveforms due to position changes of twice emissions in some dynamic scanning processes is avoided, and the method has an important application value in practical engineering.

Magnetic resonance (MR) data are acquired by applying magnetic fields to an examination region concurrent with stimulated echo signals, such that trajectories, which are not straight lines, are generated in k-space. For this purpose, sequence of RF pulses is applied to generate the stimulated echo signals in the examination object, undersampled MR measurement data are detected during reception of the stimulated echo signals in the at least two receiving coils, along the curved k-space trajectories, and fully sampled MR measurement are generated from the undersampled MR measurement data using sensitivity information of the at least two receiving coils. Alternatively, the MR measurement data are fully sampled in a central region of k-space, and a region outside the central region is not fully sampled, and a phase correction with a Partial Fourier technique is executed on the MR measurement data using fully sampled MR measurement data from the central region of k-space.

A method and a device are provided that improve quantification of the spin-spin relaxation (“T₂”) time of an image in nuclear magnetic resonance (“NMR”) applications using fast multi spin-echo sequences. The method employs time-efficient computer simulations for exact modeling of spurious stimulated echoes in multi-dimensional magnetic resonance imaging (“MRI”) runs. The method employs Bloch simulations and can use a plurality of parameters to produce echo modulation curves prior to correcting distorted experimental data based on pre-calculated simulation values.

Method, system and non-transitory computer-accessible medium can be provided for performing magnetic resonance spectroscopy for at least one structure. For example, with such method and/or computer-accessible medium, it is possible to receive information related to a substantially simultaneous acquisition of a stimulated echo pathway and a double spin echo associated with at least one portion of the at least one structure.

The invention relates to a method of MR imaging. A portion of a body placed in the examination volume of an MR device is subjected to an imaging sequence of RF pulses and switched magnetic field gradients. The imaging sequence is a stimulated echo sequence including i) two preparation RF pulses (alpha) radiated toward the portion of the body during a preparation period (21), and ii) reading RF pulses (beta) radiated toward the portion of the body during an acquisition period (22) temporally subsequent to the preparation period (21). FID signals (I1) and one or more stimulated echo signals I2) are acquired during the acquisition period (22) with equal T2*-weighting. A B1 map indicating the spatial distribution of the RF field of the preparation RF pulses within the portion of the body is derived from the acquired FID (I1) and stimulated echo (I2) signals.

In a method to acquire magnetic resonance (MR) data within a volume segment with a magnetic resonance system, the MR data are repeatedly acquired with a sequence that includes radiating a first resonant RF pulse, radiating a second resonant RF pulse, applying a dephasing first gradient after the first resonant RF pulse and before the second resonant RF pulse, radiating a third resonant RF pulse after the second resonant RF pulse, applying a second gradient after the third RF pulse in order to refocus a stimulated echo of a magnetization component prepared by the first gradient, and read out MR data. At least one of the first gradient and/or the second gradient is/are different in a respective repetition of the sequence and an additional repetition of the sequence that directly follows the respective repetition.

The invention discloses a brand-new nuclear magnetic resonance echo mechanism based magnetic resonance imaging method. The method includes: turning dispersion-phase spins to a longitudinal plane, andsubstituting transverse relaxation with longitudinal relaxation to reduce signal relaxation attenuation; combining with a brand-new echo generating mechanism to obtain completely gathered echo on a transverse plane to keep signals as far as possible, so that a signal-to-noise ratio of an imaging sequence is substantially increased. The method has advantages that the defect of respective signal loss of traditional echo sequences (spin echoes and stimulated echoes) is overcome, optimal echo signals are formed, sequence schemes comprehensively superior to the spin echoes and the stimulated echoesare provided for echo sequence applying diffusion imaging and flow imaging, the signal-to-noise ratio of images is increased to obtain high-quality images, and accordingly an accurate and reliable quantitative measurement method is provided for magnetic resonance in bulk diffusion and flow imaging, and a promising application prospect in biological medical research and clinical diagnosis is achieved.

The invention relates to a method of parallel MR imaging which comprises the steps of: —subjecting a portion of a body (10) to a first imaging sequence (21,22) of RF pulses and switched magnetic field gradients, wherein first MR signals (11,12) are acquired via at least two RF coils having different spatial sensitivity profiles within the examination volume, —deriving the spatial sensitivity profiles of the at least two RF coils from the acquired first MR signals, —subjecting the portion of the body to a second imaging sequence of RF pulses and switched magnetic field gradients, wherein second MR signals are acquired by parallel acquisition via the at least two RF coils with sub-sampling of k-space, and —reconstructing a MR image from the acquired second MR signals and from the spatial sensitivity profiles of the at least two RF coils. According to the invention, the type and/or parameters of the first imaging sequence are selected automatically depending on the presence of a metal implant in the body. The selection of the type of the first imaging sequence is made between a gradient echo sequence, if no metal implants are present, and a spin echo sequence or a stimulated echo sequence, if a metal implant is present.

In a method and magnetic resonance (MR) system to acquire MR data within a volume segment, the MR data are repeatedly acquired with a sequence that which includes the following steps. A first resonant RF pulse is radiated and a second resonant RF pulse is radiated. A dephasing first gradient is applied after the first resonant RF pulse and before the second resonant RF pulse. A third resonant RF pulse is radiated after the second resonant RF pulse. A second gradient is applied after the third RF pulse in order to refocus a stimulated echo of a magnetization component prepared by the first gradient. MR data are read out, and a fourth resonant RF pulse is radiated after the readout of the MR data, to reduce the longitudinal magnetization.

The invention relates to a method of parallel MR imaging, wherein a reference scan is performed by means of a stimulated echo sequence including i) at least two preparation RF pulses (a) radiated toward a portion of a body (10) during a preparation period (21), and ii) one or more reading RF pulses 03) radiated toward the portion of the body (10) during an acquisition period (22) temporally subsequent to the preparation period (21). One or more FID signals (I₁) and one or more stimulated echo signals (I₂) are acquired during the acquisition period (22). The spatial receive and/or—if applicable—transmit4 sensitivity profiles of at least two RF coils (11, 12, 13) are derived from the acquired FID signals (I₁) and/or from the acquired stimulated echo signals (I₂). The parameters of the stimulated echo sequence are selected such that it is robust against susceptibility-induced artefacts. Moreover, 10 the invention relates to a MR device (1) and to a computer program for a MR device (1).

In a diffusion tensor magnetic resonance imaging method for imaging a myocardial fiber structure, the diaphragm position of a subject is detected and a determination is made as to whether the diaphragm position of the subject falls into the acceptance region or not. If it does not, continue the diaphragm position of the examination subject is continued to be detected. If and when the diaphragm position is in the acceptance region, an echo planar imaging sequence with stimulated echo is executed with two electrocardiogram triggers, so as to acquire diffusion tensor image data of the myocardial fiber structure. The cardiac DTI image data thus can be obtained under free respiration of the subject, and the influence of respiratory movement is reduced and the scanning time is shortened.