Abstract: A medical imaging system (10) includes a nuclear imaging system (62), a timing optimization unit (40), a magnetic resonance (MR) scanner (12), an MR reconstruction unit (38), and an attenuation map unit (50). The nuclear imaging system (62) receives nuclear decay data and generates at least one nuclear image (64) of a first resolution based on the received nuclear decay data of an imaged subject (16) and an attenuation map (52). The timing optimization unit (40) which selects a first and a second echo time for a modified Dixon (mDixon) pulse sequence and a sufficient number of repetition times (TRs) to generate an image of the subject (16) of at least a first resolution, with the phase angle difference between water and fat at the first and the second echo time being unequal to 0° and 180°. The MR scanner (12) applies the sequence to the subject (16) and receives MR data (32) from the subject. The MR reconstruction unit (38) reconstructs at least one MR image (44) based on the MR data (32).

Abstract: MR imaging of at least two chemical species having different MR spectra provides a Dixon water/fat separation that avoids swaps of water and fat signals in the reconstructed MR images due to large gradients of the main magnetic field B0. The method includes the steps of: a) generating echo signals at different echo times by subjecting an object (10) positioned in a main magnetic field to a multi-echo imaging sequence of RF pulses and switched magnetic field gradients; b) acquiring the echo signals; c) correcting the acquired echo signals by virtual shimming.

Abstract: An improved method of MR imaging of at least two chemical species having different MR spectra, such as water and fat, enables a precise quantification of water and fat or derived measures, such as a fat fraction. The method includes the steps of: a) generating two or more echo signals at different echo times by subjecting a body (10) placed in the examination volume of a MR device (1) to an imaging sequence of RF pulses and switched magnetic field gradients; b) acquiring the two or more echo signals; c) separating signal contributions of the at least two chemical species to the acquired echo signals on the basis of a signal model including the MR spectrum of each of the chemical species, the spatial variation of the main magnetic field in the examination volume, the effective transverse relaxation rate, and eddy current-induced phase errors. The eddy current-induced phase errors are estimated by a fitting procedure from the two or more echo signals.

Abstract: The invention relates to a method of MR imaging of a body (10) of a patient. It is an object of the invention to provide a method that enables efficient compensation of flow artifacts, especially for MR angiography in combination with Dixon water/fat separation. The method of the invention comprises the steps of: a) generating MR echo signals at two or more echo times by subjecting the portion of the body (10) to a MR imaging sequence of RF pulses and switched magnetic field gradients, wherein the MR imaging sequence is a Dixon sequence; b) acquiring the MR echo signals; c) reconstructing one or more single-echo MR images from the MR echo signals; d) segmenting the blood vessels from the MR images; e) detecting and compensating for blood flow-induced variations of the amplitude or phase in the single-echo MR images within the blood vessel lumen, and f) separating signal contributions from water and fat spins to the compensated single-echo MR images.

Abstract: The invention provides for a Dixon method of controlling a magnetic resonance imaging (100) system. Acquiring (200) Dixon magnetic resonance data (142), first calibration magnetic resonance data (144), and second calibration magnetic resonance data (146) using pulse sequence commands (140). To cause the magnetic resonance imaging system to execute multiple pulse repetitions (310). The multiple pulse repetitions causes the magnetic resonance imaging system to generate a Dixon readout gradient (320) along a readout direction (402). The pulse sequence commands cause the processor to perform one or more first modified pulse repetitions (306) and one or more second modified pulse repetitions (308).

Abstract: The invention provides for a medical instrument (100, 500) comprising a magnetic resonance imaging system (102) for acquiring magnetic resonance data (142) from a subject (118) within an imaging zone (108). The magnetic resonance imaging system comprises: a main magnet (104) for generating a B0 magnetic field within the imaging zone; a memory (134, 136) containing machine executable instructions (160, 162, 164, 166) and pulse sequence commands (140); a processor (130) for controlling the medical instrument.

Abstract: A method and an apparatus for MR imaging of at least two chemical species having different MR spectra enables Dixon water/fat separation in cases in which a large field-of-view is required. The method includes the steps of: a) generating at least one echo signal by subjecting a body placed in the examination volume of a MR device to an imaging sequence of RF pulses and switched magnetic field gradients; b) acquiring the at least one echo signal; c) separating signal contributions of the at least two chemical species to the at least one acquired echo signal on the basis of a spectral model and prior knowledge about the spatial variation of the main magnetic field Bo in the examination volume; and d) reconstructing a MR image from the signal contributions of at least one of the chemical species.

Abstract: In an MR imaging method and apparatus, a portion of a body placed in an 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 (?) radiated toward the portion of the body during a preparation period (21), and ii) reading RF pulses (?) radiated toward the portion of the body during an acquisition period (22) temporally subsequent to the preparation period (21). FID signals (I1) and stimulated echo signals (I2) are acquired during the acquisition period (22) with equal T2*-weighting. A B1 map indicating a 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.

Abstract: The invention provides for a magnetic resonance imaging system (100, 300, 100) for acquiring magnetic resonance data (110, 1104) from a subject (118) within an imaging zone (108). The magnetic resonance imaging system comprises a memory (136) for storing machine executable instructions (160, 162, 164, 166, 316) and pulse sequence data (140, 1102). The pulse sequence data comprises instructions for controlling the magnetic resonance imaging system to acquire magnetic resonance data according to a magnetic resonance imaging method. The magnetic resonance imaging system further comprises a processor (130) for controlling the magnetic resonance imaging system.

Abstract: The invention relates to a method of MR imaging of a body (10) of a patient. It is an object of the invention to provide a method that enables efficient compensation of flow artifacts, especially for MR angiography in combination with Dixon water/fat separation. The method of the invention comprises the steps of: a) generating MR echo signals at two or more echo times by subjecting the portion of the body (10) to a MR imaging sequence of RF pulses and switched magnetic field gradients, wherein the MR imaging sequence is a Dixon sequence; b) acquiring the MR echo signals; c) reconstructing one or more single-echo MR images from the MR echo signals; d) segmenting the blood vessels from the MR images; e) detecting and compensating for blood flow-induced variations of the amplitude or phase in the single-echo MR images within the blood vessel lumen, and f) separating signal contributions from water and fat spins to the compensated single-echo MR images.

Abstract: The invention relates to a method of CEST or APT MR imaging of at least a portion of a body (10) placed in a main magnetic field B0 within the examination volume of a MR device. The method of the invention comprises the following steps: •a) subjecting the portion of the body (10) to a saturation RF pulse at a saturation frequency offset; •b) subjecting the portion of the body (10) to an imaging sequence comprising at least one excitation/refocusing RF pulse and switched magnetic field gradients, whereby MR signals are acquired from the portion of the body (10) as spin echo signals; •c) repeating steps a) and b) two or more times, wherein the saturation frequency offset and/or a echo time shift in the imaging sequence are varied, such that a different combination of saturation frequency offset and echo time shift is applied in two or more of the repetitions; •d) reconstructing a MR image and/or B0 field homogeneity corrected APT/CEST images from the acquired MR signals.

Abstract: At least two chemical species are imaged using magnetic resonance imaging with signal separation for two chemical species resulting in separate signal datasets for these two chemical species. First and second echo data are acquired at different echo times resulting in a first and second acquired complex dataset. The first and second acquired datasets are modelled by employing a spectral signal model of at least one of the chemical species. The modelling results in a first and second modelled complex dataset. The first and second modelled datasets include a first and second phase error and the separate signal datasets for the two chemical species. From the first and second acquired dataset and the first and second modelled dataset the separate signal datasets for the two chemical species are determined.

Abstract: At least two gradient echo signals are generated at two different echo times by subjecting a portion of a body (10) in an MR examination region (1) to an imaging sequence of RF pulses and switched magnetic field gradients. The 0th moment of the readout magnetic field gradient essentially vanishes at the time of a first gradient echo while the 1st moment of the readout gradient is non-zero. Both the 0th and 1st moments of the readout magnetic field gradient essentially vanish at a time of a second gradient echo. Gradient echo signals are acquired. Acquiring the gradient echo signals is repeated for a plurality of phase encoding steps. A first MR image is reconstructed from the gradient echo signals of the first gradient echo and a second MR image is reconstructed from the gradient echo signals of the second gradient echo. Ghosting artefacts in the first and/or second MR image are identified by comparing the first and second MR images.

Abstract: The invention relates to a method of performing contrast enhanced first pass magnetic resonance angiography, the method comprising: acquiring (302) magnetic resonance datasets of a region of interest using a single- or multi-echo data acquisition technique, wherein the echo times of the one or multiple echoes are flexible, wherein at the time of the data acquisition the region of interest comprises fat, water and a contrast agent, processing (304) the datasets using a generalized Dixon water-fat separation technique to eliminate the signal originating from the fat from the background for reconstruction of an image data set.

Abstract: A magnetic resonance (MR) imaging (MRI) system, the MRI system may include at least one controller which may be configured to: acquire MR information for at least first and second blades of a periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) imaging method; generate, for at least the first and second blades, main field inhomogeneity information based upon the acquired MR information, the main field inhomogeneity information indicating main field inhomogeneity; generate water and fat information individually for at least the first and second blades based upon the acquired MR information and the generated main field inhomogeneity information for the corresponding blade of the first and second blades; and correct at least one of the water and fat information for spatial distortions caused by the main field inhomogeneity or a predetermined chemical shift difference between water and fat.

Abstract: At least two chemical species are imaged using magnetic resonance imaging with signal separation for the two chemical species. The method includes acquiring first and second echo data at different echo times resulting in a first and second acquired complex dataset, —modelling the first and second acquired dataset, said modelling comprising a spectral signal model of at least one of the chemical species, —identifying in the first and second acquired dataset the voxels for which the modelling yields a single, unambiguous mathematical solution for the signal separation, and —resolving the ambiguity for the voxels for which the modelling yields more than one mathematical solution, if any such voxels remain.

Abstract: The invention relates to a method of MR imaging of at least two chemical species having different MR spectra. It is an object of the invention to provide a Dixon water/fat separation technique that avoids swaps of water and fat signals in the reconstructed MR images due to large gradients of the main magnetic field B0.

Abstract: A magnetic resonance image of a subject is generated by acquiring k-space samples by sampling an elliptical central area of k-space, k-space having a plurality of points. Each point is representative of a potential sample. An elliptical peripheral area of k-space which peripheral area surrounds the central area is partially sampled. Respiratory motion of the subject is detected and the magnetic resonance image of the subject is reconstructed using the k-space samples acquired before the detection of respiratory motion.

Abstract: The invention relates to a method of MR imaging of at least two chemical species having different MR spectra, such as water and fat. It is an object of the invention to provide an improved method that enables a precise quantification of water and fat or derived measures, such as a fat fraction.

Abstract: The invention provides for a magnetic resonance imaging system (300, 400) for acquiring magnetic resonance data (342) from an imaging zone (308). The magnetic resonance imaging system comprises a processor (330) for controlling the magnetic resonance imaging system.