Abstract: The invention relates to a nuclear magnetic resonance imaging radio frequency-receiver (112; 216; 308; 404), the receiver (112; 216; 308; 404) being adapted to receive analog signals from at least one radio frequency receiver coil unit (106; 200; 202; 300; 400; 402), the radio frequency receiver (112; 216; 308; 404) comprising: an analog-digital converter (118; 226) to convert the analog pre-amplified magnetic resonance signal into a digital signal, means (120; 230) for digital down converting the digital signal and a first communication interface (130; 252) adapted for transmitting the down converted digital signal via a communication link (e.g. wireless, optical or wire-bound).

Abstract: The present invention relates to a method for side-band suppression in a Magnetic Resonance imaging, MRI, system (100), the method comprising providing a first multiband RF pulse for simultaneously exciting at least two slices in a subject (118) at a first and a second frequency band (301,303) and to acquire using the MRI system (100) signals (307, 308) from the excited two slices and at least one additional signal (309) at a third frequency band (305), the additional signal (309) resulting from a sideband excitation of a slice different from the two slices; using the first multiband RF pulse for determining the additional signal (309); deriving a pre-compensating term from the first multiband RF pulse and the additional signal (309), adding the pre-compensating term to the first multiband RF pulse to obtain a second multiband RF pulse, thereby replacing the first multiband RF pulse by the second multiband RF pulse for suppressing at least part of the additional signal (309).

Abstract: Coil elements (18) generate a B1 excitation field in an examination region (14), which B1 excitation field is distorted by patient loading (e.g., wavelength effects). Passive shimming elements (22, 24) are disposed between the coil elements and the subject in order to improve the B1 field uniformity. In one embodiment, passive shimming elements include one or more dielectric rods (55) disposed below the subject which generate no substantial MR proton signal and which have a permittivity of at least 100 and preferably greater than 500. In another embodiment, tubes (24) adjacent each coil element are supplied with a dielectric liquid, a thickness of the dielectric liquid between the coil element and the subject adjusting a phase of the B1 field generated by the coil element. Active B1 shimming may be combined with passive shimming elements (22, 24) to effect an improved RF field homogeneity result.

Abstract: In an EPI acquisition sequence for magnetic resonance signals k-space is scanned along sets of lines in k-space along opposite propagation directions, e.g. odd and even lines in k-space. Phase errors that occur due to the opposite propagation directions are corrected for in a SENSE-type parallel imaging reconstruction. The phase error distribution in image space may be initially estimated, calculated form the phase difference between images reconstructed from magnetic resonance signals acquired from the respective sets of k-space lines, or from an earlier dynamic.

Abstract: A magnetic resonance elastography method includes application of mechanical oscillations with an oscillation period (T) to an object to be examined to generate mechanical waves in the object. A motion sensitive magnetic resonance acquisition sequence with repetition time TR issued to acquire magnetic resonance signals from the object. This acquisition sequence including application of one or more phase encoding steps within an individual repetition time. The repetition time times the number of phase encodings within one repetition time is not equal to an integer multiple of the oscillation period. Thus a magnetic resonance image of the wave pattern is reconstructed from the magnetic resonance signals assembled in a sample space spanned by the phase of the mechanical oscillation and the phase encoding.

Abstract: The invention relates to a method of MR imaging of an object positioned in an examination volume of a MR device (1), the method comprises the steps of:—subjecting the object (10) to an imaging sequence of RF pulses (20) and switched magnetic field gradients(G), which imaging sequence is a zero echo time sequence comprising: i) setting a readout magnetic field gradient (G) having a readout direction and a readout strength; ii) radiating a RF pulse (20) in the presence of the readout magnetic field gradient (G); iii) acquiring a FID signal in the presence of the readout magnetic field gradient (G), wherein the FID signal represents a radial k-space sample; iv) gradually varying the readout direction; v) sampling a spherical volume in k-space by repeating steps i) through iv) a number of times, with the readout strength being varied between repetitions;—reconstructing a MR image from the acquired FID signals, wherein signal contributions of two or more chemical species to the acquired FID signals are separated.

Abstract: The invention relates to a method of MR imaging of an object (10) placed in an examination volume of a MR device (1). The method comprises the steps of: subjecting the object (10) to an imaging sequence for acquiring MR signal data, wherein the MR signal data are acquired as a function of k-space position and time by using an irregular k-space sampling pattern with sub-sampling of k-space; reconstructing MR image data from the MR signal data, which MR image data comprise spatial dimensions and a frequency dimension, sparsity of the MR image data in a transform domain being exploited for suppressing sub-sampling artefacts in the MR image data. Moreover, the invention relates to a MR device (1) and to a computer program.

Abstract: An imaging method comprises acquiring an undersampled magnetic resonance partially parallel imaging (MR-PPI) dataset using a plurality of radio frequency receive coils and reconstructing the undersampled MR-PPI dataset to generate a reconstructed magnetic resonance (MR) image. The reconstructing includes: (i) using a generalized auto-calibrating partially parallel acquisition (GRAPPA) operator or direct convolution to fill in at least some missing data of the undersampled MR-PPI dataset so as to generate an enhanced dataset; and (ii) using an algorithm other than a GRAPPA operator and other than direct convolution to reconstruct the enhanced dataset or to reconstruct the undersampled MR-PPI dataset using the enhanced dataset as an initialization dataset for an iterative reconstruction algorithm. In some embodiments the MR-PPI dataset is a non-Cartesian dataset and a GRAPPA operator for wider radial bands (GROWL) is used in the operation (i).

Abstract: The invention relates to a method of MR imaging of an object (10) placed in the examination volume of a MR device (1). It is an object of the invention to provide a method of MR imaging with improved susceptibility weighted contrast. The method of the invention comprises the steps of: a) generating at least two echo signals at different echo times by subjecting the object (10) to an imaging sequence of RF pulses and switched magnetic field gradients; b) acquiring the echo signals; c) repeating steps a) and b) for a plurality of phase encoding steps; d) reconstructing an intermediate MR image for each echo time from the acquired echo signals; and e) generating a susceptibility weighted MR image by computing, for each voxel of the susceptibility weighted MR image, a non-linear combination of the voxel values of the intermediate MR images at the respective image position, wherein the non-linear combination emphasizes lower voxel magnitude values more than higher voxel magnitude values.

Abstract: A magnetic resonance imaging system (1) includes a denoising unit (24), and a reconstruction unit (20). The denoising unit (24) denoises a partial image and provides a spatially localized measure of a denoising effectivity. The reconstruction unit (20) iteratively reconstructs an output image from the received MR data processed with a Fast Fourier Transform (FFT), and in subsequent iterations includes the denoised partial image and the spatially localized measure of the denoising effectivity.

Abstract: The invention relates to a magnetic resonance imaging apparatus including an array of two or more RF antennas for transmitting RF pulses to and receiving MR signals from a subject positioned in an examination volume, and where the RF antennas have spatial transmit and receive sensitivity profiles. The apparatus is configured to control the temporal succession, the phase, and the amplitude of the RF feeding of each individual RF antenna. The apparatus is also configured to determine the phases and amplitudes from the spatial transmit sensitivity profiles of the RF antennas, and reconstruct a MR image from a combination of the received MR signals received via the individual RF antennas and from the spatial receive sensitivity profiles of the RF antennas. Further, the apparatus is configured to determine the spatial transmit sensitivity profiles of the RF antennas from the spatial receive sensitivity profiles of the RF antennas, or vice versa.

Abstract: A magnetic resonance imaging system (1), comprising a plurality of receiving units (4.1-4.4) for receiving magnetic resonance signals from an object (2), and an image reconstruction device (8), said image reconstruction device being adapted to receive magnetic resonance signals of said object (2) from said plurality of receiving units (4.1-4.4) and to perform image reconstruction by combining magnetic resonance signals received by said plurality of receiving units using an image reconstruction algorithm (11), characterized in that said image reconstruction device (8) comprises means (12a) for combining magnetic resonance signal contributions from respective receiving units (4.1-4.4) in such a way that a combined sensitivity of the plurality of receiving units (4.1-4.4) to a predetermined spatial region of the object (2) is reduced.

Abstract: 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 device (1). The object of the invention is to provide an improved, i.e. faster, parallel imaging technique. The invention proposes to acquire a survey signal data set (21, 22) at a low image resolution, which survey signal data set (21, 22) includes MR signals received in parallel or successively via a volume RF coil (9) and via a set of array RF coils (11, 12, 13). Spatial sensitivity profiles (23) of the array RF coils (11, 12, 13) are determined from the low resolution data. As a next step, a reference scan is performed in which a reference signal data set (25) is acquired at intermediate resolution solely via the array RF coils (11, 12, 13). The spatial sensitivity profiles (27) of the array RF coils (11, 12, 13) are determined from the data acquired at intermediate resolution and from the spatial sensitivity profiles (23) determined before at low resolution.

Abstract: A method of measuring a magnetic field within a magnetic resonance imaging system (300) comprising a magnet (304) with an imaging zone (308) and a radio-frequency transceiver (316). The magnetic resonance imaging system further comprises a magnetic field probe (322) located within the imaging zone. The magnetic field probe comprises a fluorine sample (404) comprising any one of the following: a fluoroelastomer (700), a fluorine containing ionic liquid (600), and a solution of a fluorine containing compound. The field probe further comprises an antenna (406) for manipulating the magnetic spins of the fluorine sample and for receiving fluorine magnetic resonance data from the fluorine sample. The antenna is connected to the radio-frequency transceiver. The method comprises the steps of acquiring (100, 200) the fluorine magnetic resonance data using the magnetic resonance imaging system; and calculating (102, 206) a magnetic field strength (344) using the fluorine magnetic resonance data.

Abstract: Coil elements (18) generate a B1 excitation field in an examination region (14), which B1 excitation field is distorted by patient loading (e.g., wavelength effects). Passive shimming elements (22, 24) are disposed between the coil elements and the subject in order to improve the B1 field uniformity. In one embodiment, passive shimming elements include one or more dielectric rods (55) disposed below the subject which generate no substantial MR proton signal and which have a permittivity of at least 100 and preferably greater than 500. In another embodiment, tubes (24) adjacent each coil element are supplied with a dielectric liquid, a thickness of the dielectric liquid between the coil element and the subject adjusting a phase of the B1 field generated by the coil element. Active B1 shimming may be combined with passive shimming elements (22, 24) to effect an improved RF field homogeneity result.

Abstract: An imaging method comprises acquiring an undersampled magnetic resonance partially parallel imaging (MR-PPI) dataset using a plurality of radio frequency receive coils and reconstructing the under-sampled MR-PPI dataset to generate a reconstructed magnetic resonance (MR) image. The reconstructing includes: (i) using a generalized auto-calibrating partially parallel acquisition (GRAPPA) operator or direct convolution to fill in at least some missing data of the undersampled MR-PPI data-set so as to generate an enhanced dataset; and (ii) using an algorithm other than a GRAPPA operator and other than direct convolution to reconstruct the enhanced dataset or to reconstruct the undersampled MR-PPI dataset using the enhanced dataset as an initialization dataset for an iterative reconstruction algorithm. In some embodiments the MR-PPI dataset is a non-Cartesian dataset and a GRAPPA operator for wider radial bands (GROWL) is used in the operation (i).

Abstract: A magnetic resonance imaging system (1), comprising a plurality of receiving units (4.1-4.4) for receiving magnetic resonance signals from an object (2), and an image reconstruction device (8), said image reconstruction device being adapted to receive magnetic resonance signals of said object (2) from said plurality of receiving units (4.1-4.4) and to perform image reconstruction by combining magnetic resonance signals received by said plurality of receiving units using an image reconstruction algorithm (11), characterised in that said image reconstruction device (8) comprises means (12a) for combining magnetic resonance signal contributions from respective receiving units (4.1-4.4) in such a way that a combined sensitivity of the plurality of receiving units (4.1-4.4) to a predetermined spatial region of the object (2) is reduced.

Abstract: A magnetic resonance elastography method includes application of mechanical oscillations with an oscillation period (T) to an object to be examined to generate mechanical waves in the object. A motion sensitive magnetic resonance acquisition sequence with repetition time TR issued to acquire magnetic resonance signals from the object. This acquisition sequence including application of one or more phase encoding steps within an individual repetition time. The repetition time times the number of phase encodings within one repetition time is not equal to an integer multiple of the oscillation period. Thus a magnetic resonance image of the wave pattern is reconstructed from the magnetic resonance signals assembled in a sample space spanned by the phase of the mechanical oscillation and the phase encoding.

Abstract: The invention relates to a method of performing a magnetic resonance imaging (MRI) reference scan of an examination volume comprising a plurality of image points, the method being performed using a set of detector elements (142), the method comprising: phase sensitive acquisition of a first and a second complex echo signal originating from a first (214; 306; 310) and second (216; 308; 312) echo for each image point, wherein the acquisition is performed by each of the detector elements of the set of detector elements (142), determining for a detector element of the set of detector elements (142) a phase difference between the first and the second echo signal for each image point, —calculating from the phase difference a local magnetic field inhomogeneity value for each image point, deriving for each image point a coil sensitivity matrix, wherein the coil sensitivity matrix is derived by calculating complex ratios of the first or the second complex echo signals acquired by the set of elements.

Abstract: A magnetic resonance imaging system (1), comprising a plurality of receiving units (4.1-4.4) for receiving magnetic resonance signals from an object (2), and an image reconstruction device (8), said image reconstruction device being adapted to receive magnetic resonance signals of said object (2) from said plurality of receiving units (4.1-4.4) and to perform image reconstruction by combining magnetic resonance signals received by said plurality of receiving units using an image reconstruction algorithm (11), characterized in that said image reconstruction device (8) comprises means (12a) for combining magnetic resonance signal contributions from respective receiving units (4.1-4.4) in such a way that a combined sensitivity of the plurality of receiving units (4.1-4.4) to a predetermined spatial region of the object (2) is reduced.