Abstract: The invention relates to a magnetic resonance imaging apparatus comprising an array of two or more RF antennas (9) for transmitting RF pulses to and receiving MR signals from a body (7) of a patient positioned in an examination volume (2), the RF antennas (9) having spatial transmit and receive sensitivity profiles. The apparatus is arranged to: control the temporal succession, the phase, and the amplitude of the RF feeding of each individual RF antenna (9), the phases and amplitudes being determined from the spatial transmit sensitivity profiles of the RF antennas (9), and reconstruct a MR image from a combination of the received MR signals received via the individual RF antennas (9) and from the spatial receive sensitivity profiles of the RF antennas (9).

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: MR imaging of a body (7) placed in an examination volume includes establishing a substantially homogeneous main magnetic field in the examination volume, generating switched magnetic field gradients superimposed upon the main magnetic field, radiating RF pulses towards the body (7), controlling the generation of the magnetic field gradients and the RF pulses, receiving and sampling MR signals, and forming MR images from the signal samples. A sequence of MR echo signals is generated by subjecting at least a portion of the body (7) to a single RF pulse and a plurality of switched magnetic field gradients. The switched magnetic field gradients are controlled to produce at least two sub-sequences of MR echo signals. Each sub-sequence traverses a different trajectory in k-space with subsampling in the phase encoding direction (ky) MR echo signals are acquired and sampled.

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 analogue 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 analogue-digital converter (118; 226) to convert the analogue 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 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 device performs MR imaging of a body (7) placed in a stationary and substantially homogeneous main magnetic field, with an RF transmit antenna (6) for radiating RF pulses towards the body (7), which RF transmit antenna (6) has different resonance modes. In order to improve image uniformity in high field MR imaging, the device (1) is arranged to determine the size and/or the aspect ratio of the body (7), and to acquire an MR image of the body (7) by an imaging sequence including RF pulses. The phases and amplitudes of the different resonance modes of the RF transmit antenna (6) excited during irradiation of the RF pulses are controlled on the basis of the size and/or aspect ratio of the body (7).

Abstract: The invention relates to a device for MR imaging of a moving structure of a body (7) of a patient placed in an examination volume. The device (1) comprises means (2) for establishing a substantially homogeneous main magnetic field in the examination volume, means (3, 4, 5) for generating switched magnetic field gradients superimposed upon the main magnetic field, means (6) for radiating RF pulses towards the body (7), control means (12) for controlling the generation of the magnetic field gradients and the RF pulses, means (10) for receiving and sampling MR signals, and reconstruction means (14) for forming MR images from the signal samples.

Abstract: The invention relates to a device (1) for magnetic resonance imaging of a body (7) placed in a stationary and substantially homogeneous main magnetic field. In order to provide an MR device (1) which is arranged to automatically select an optimum subsampling scheme for three-dimensional SENSE, the invention proposes to select the subsampling scheme such that the maximum number of folded-over image values is minimized and simultaneously distances between the positions of the folded-over image values within the predetermined field of view are maximized.

Abstract: The invention relates to a device for MR imaging of a body (7) placed in an examination volume, the device (1) comprising means (2) for establishing a substantially homogeneous main magnetic field in the examination volume, means (3, 4, 5) for generating switched magnetic field gradients superimposed upon the main magnetic field, means (6) for radiating RF pulses towards the body (7), control means (12) for controlling the generation of the magnetic field gradients and the RF pulses, means (10) for receiving and sampling MR signals, and reconstruction means (14) for forming MR images from the signal samples.

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: The present invention relates to a system and method magnetic resonance (MR) imaging. Furthermore the invention relates to the use of a material and to a computer program. In order to provide a technique which allows to prevent standing waves in an RF cage (3) of a MR imaging system (1) in a very cheap and simple way a MR imaging system (1) is suggested, which comprises a MR imaging apparatus (2) comprising an open magnet system (7), wherein operation of the MR imaging apparatus (2) creates a magnetic resonance field having a MR frequency, and which further comprises an RF cage (3), configured to enclose the MR imaging apparatus (2), wherein the walls (6) of the RF cage (3) are at least partly provided with a covering (5, 10), said covering (5, 10) is adapted in a way that the wavelength of the MR frequency within the covering (5, 10) is reduced.

Abstract: The invention relates to a device for MR imaging of a body (7) placed in a stationary and substantially homogeneous main magnetic field, with an RF transmit antenna (6) for radiating RF pulses towards the body (7), which RF transmit antenna (6) has different resonance modes. In order to improve image uniformity in high field MR imaging, the invention proposes the device (1) being arranged to determine the size and/or the aspect ratio of the body (7), and to acquire an MR image of the body (7) by means of an imaging sequence comprising RF pulses, wherein the phases and amplitudes of the different resonance modes of the RF transmit antenna (6) excited during irradiation of the RF pulses are controlled on the basis of the size and/or aspect ratio of the body (7).

Abstract: The invention relates to a MRI system and to a method for producing an image with such an system. In order to provide a MR imaging technique with a high efficient MR signal acquisition, which provides a high level of comfort to a patient, a MRI system and method are suggested, where image data from an object are acquired while the object is moving with variable speed relative to the MRI system, and where the image data are combined and an image of the object is reconstructed.

Abstract: A novel magnetic resonance imaging method is described, for forming an image of an object from a plurality of signals sampled in a restricted homogeneity region of a main magnet field of a magnetic resonance imaging apparatus. A patient disposed on a table is moved continuously through the bore of the main magnet and spins in a predetermined area of the patient are excited by an excitation pulse from a transmitter antenna, such that an image is formed over a region exceeding largely the restricted region. Data is undersampled in the restricted region by means off at least one receiver antenna in a plurality of receive situations being defined as a block of measurements contiguous in time having preserved magnetisation and presaturation conditions within the excited area of the patient. Fold-over artefacts due to said undersampling are unfolded by means of the known sensitivity pattern of the receiver antenna and/or the properties of selected factors determining said receive situations.

Abstract: The present invention relates to a system and method magnetic resonance (MR) imaging. Furthermore the invention relates to the use of a material and to a computer program. In order to provide a technique which allows to prevent standing waves in an RF cage (3) of a MR imaging system (1) in a very cheap and simple way a MR imaging system (1) is suggested, which comprises a MR imaging apparatus (2) comprising an open magnet system (7), wherein operation of the MR imaging apparatus (2) creates a magnetic resonance field having a MR frequency, and which further comprises an RF cage (3), configured to enclose the MR imaging apparatus (2), wherein the walls (6) of the RF cage (3) are at least partly provided with a covering (5, 10), said covering (5, 10) is adapted in a way that the wavelength of the MR frequency within the covering (5, 10) is reduced.

Abstract: A magnetic resonance imaging apparatus includes a plurality of radio frequency coils (34) that acquire variable density sensitivity encoded data that is undersampled at least away from the center of k-space. A reconstruction processor (52) for each coil reconstructs: a regularization image reconstructed from a higher density portion of the variable density sensitivity encoded data disposed at or near a center of k-space acquired by that coil; and a folded image reconstructed from the variable density sensitivity encoded data acquired by that coil. An unfolding processor (66) unfolds the folded images. The unfolding is regularized by the regularization images.

Abstract: A novel magnetic resonance imaging method and apparatus is described wherein an image is derived from sub-sampled magnetic resonance signals and on the basis of the spatial sensitivity profile of each receiving antenna. A sequence of RF-pulses and gradients is applied, which sequence corresponds to a set of trajectories containing at least one substantially non-linear trajectory in k-space, wherein the density of said trajectory set being substantially lower than the density corresponding to the object size. Each signal along said trajectory set is sampled at least at two different receiver antenna positions. The image is reconstructed by converting the data of said signals to a Cartesian grid by convolution with a gridding kernel, whereby the gridding kernel is specific for each antenna, differs between one region and another in k-space, and is a Fourier-transform of a pattern weighted for each antenna with respect to the Cartesian grid.

Abstract: The invention relates to a method for determination of spatial sensitivity profiles of RF transmit and/or receive coils (7, 8, 9) in an examination volume (17) of a magnetic resonance (MR) imaging device (1). In accordance with the method of the invention, nuclear magnetization is excited within the examination volume (17) by a sequence of RF pulses and switched magnetic field gradients, wherein the sequence comprises RF pulses with at least two different excitation flip angles. MR signals are acquired and processed so as to form at least two MR images, each corresponding to one of these flip angles. The spatial sensitivity profiles are then computed in the positions of the pixels or voxels of the MR images based upon the dependence of the pixel or voxel values on the respective flip angles.

Abstract: A novel magnetic resonance imaging method is presented for forming an image of an object from a plurality of signals acquired by an array of receiver antennae, whereas prior to imaging a sensitivity map of each of the receiver antennae is provided, at least two adjacent antennae record signals originating from the same imaging position and the image intensity is calculated from the signals measured by different antennae, wherein the number of phase encoding steps is reduced with respect to the full set thereof.

Abstract: The invention relates to a system for magnetic resonance imaging (MRI). Such systems face an additional contribution to the inhomogeneity of the radio frequency (RF) field when high magnetic fields are applied. The invention tries to improve the homogeneity of the RF field for high field strengths, particularly for field strengths at or above 3 tesla. To improve the homogeneity an electrically conducting material (4) is positioned within the cavity (2) of the system. The material has a conductivity and a thickness which ensure that the total radial conductance in an xy-plane perpendicular to the symmetry axis of the cavity becomes isotropic.