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: An apparatus for producing a corrected reconstructed image from magnetic resonance imaging data acquired by a magnetic resonance imaging scanner (10) includes a reconstruction processor (44) that reconstructs a corrected reconstructed image from acquired magnetic resonance imaging data. A parameters calculation processor (52) determines at least one characteristic of the imaging subject. A correction pattern adjustment processor (54) selects a correction pattern from a family of stored correction patterns based on the at least one characteristic. An image correction processor (56) corrects the uncorrected reconstructed image using the selected correction pattern to produce the corrected reconstructed image.

Abstract: A magnetic resonance imaging method is presented for forming an image of an object, wherein a stationary magnetic field and temporary magnetic fields having a position dependent field pattern are applied, magnetic resonance signals are acquired by at least one receiver antenna, spins are excitated in a part of the object, MR signals are acquired during application of the position-dependent field patterns (G1, G2, . . . ) and a magnetic resonance image is derived from the sampled magnetic resonance signals. The field patterns are substantially non-linear, the number N of total field patterns is larger than 3, and at least N?1 field patterns are independently controllable in field strength. The magnetic resonance signals are acquired in a sub-sampling fashion.

Abstract: A novel magnetic resonance imaging method is described for forming a sequence of images from a plurality of signals acquired by at least one receiver antenna. Each receiver antenna has a spatial sensitivity profile. An activity map is calculated as a standard deviation over a series of images acquired by a reference scan. Thereupon, the object is sampled in an actual scan in an interleaved manner in k-space with a reduction factor. The resulting data is Fourier transformed to the spatial domain to form a sequence of folded preliminary images, and the fold-over artefacts or the ambiguity in the preliminary images resulting from the undersampled data in k-space is resolved in forming the actual images on the basis of the activity map.

Abstract: An apparatus for producing a corrected reconstructed image from magnetic resonance imaging data acquired by a magnetic resonance imaging scanner (10) includes a reconstruction processor (44) that reconstructs a corrected reconstructed image from acquired magnetic resonance imaging data. A parameters calculation processor (52) determines at least one characteristic of the imaging subject. A correction pattern adjustment processor (54) selects a correction pattern from a family of stored correction patterns based on the at least one characteristic. An image correction processor (56) corrects the uncorrected reconstructed image using the selected correction pattern to produce the corrected reconstructed image.

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: The invention relates to an MRI system (1) for nuclear magnetic resonance imaging which comprises a plurality of transmit coils (11, 12). Each coil receives a coil drive signal (SD1, SD2). The respective coil drive signals have the same shape, but may have a different amplitude and phase, controlled by a controller (103) on the basis of characteristic information in a memory (104) as well as user input information. The controller is designed to set the respective amplitudes and phases in such a way that the resultant overall B1 field is as homogeneous as possible in a volume of interest.

Abstract: A system is described for the acquisition of a magnetic resonance scan of a subject. The system is particularly useful when the subject which contains a volume of interest which is larger than the field of view of the system and when the scan includes a time dependent signal. The system also comprising a subject support capable of movement relative to the field of view. The system presented is arranged to perform at least a first scan and a second scan, the first scan being arranged so that signal is acquired from the central region of k-space as the subject support is moved through the field of view in a first direction and the second scan being arranged so that signal is acquired from the periphery of k-space as the subject support is moved through the field of view in a second direction.

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: An interventional magnetic resonance method and apparatus utilizing a microcoil which enable localization of an interventional instrument by detecting magnetic resonance signals from the surroundings of the microcoil under the influence of magnetic field gradients. The outstanding reliability and the high speed of the method are due to the application of spatially non-selective RF pulses in conjunction with a sequence of gradient pulses in non-colinear directions. The localization method can be used inter alia for angiography wherein the signal intensity is used to determine the amount of blood present in the blood vessel.

Abstract: A magnetic resonance imaging method is presented for forming an image of an object, wherein a stationary magnetic field and temporary magnetic fields having a position dependent field pattern are applied, magnetic resonance signals are acquired by at least one receiver antenna, spins are excitated in a part of the object, MR signals are acquired during application of the position-dependent field patterns (G1, G2, . . . ) and a magnetic resonance image is derived from the sampled magnetic resonance signals. The field patterns are substantially non-linear, the number N of total field patterns is larger than 3, and at least N?1 field patterns are independently controllable in field strength. The magnetic resonance signals are acquired in a sub-sampling fashion.

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: In a magnetic resonance imaging method flow quantities and diffusion quantities are measured in the presence of temporary magnetic gradient fields (gradient pulses). Signal amplitudes of the magnetic resonance signals and/or flow and diffusion quantities calculated from the magnetic resonance signals are corrected for non-linearities in the magnetic gradient fields.

Abstract: A magnetic resonance imaging method for forming an image of an object from a plurality of signals acquired by an array of multiple receiver antennae, wherein spins are excitated in a part of the object. MR signals are measured along a predetermined trajectory containing a plurality of lines in k-space by application of a read gradient and other gradients. Further, a navigator gradient is applied for the measurement of navigator MR signals and an additional gradient is applied in order to achieve diffusion sensitivity of the MR signal, wherein phase corrections are determined from phases and moduli of the navigator MR signals so as to correct the measured MR signals. An image of the part of the object is determined from the corrected MR signals. The corrected phase is determined from the weighted phase difference between a reference navigator signal for each antenna and the actual navigator MR signal of said antenna.

Abstract: A novel magnetic resonance imaging method is described, wherein the object to be imaged is segmented into a region of slow variation and into a region of fast variation which defines a restrictive dynamic FOV. The object in the overall FOV is sampled in k-space with a reduction factor. The k-space sampling positions in the region of fast variation are transformed by Fourier Transformation to the spatial domain and are transformed additionally to the temporal-frequency domain. Further the positions in the temporal-frequency domain derived from the sub-sampled positions in k-space are unfolded on the basis of the spatial coil sensitivity profiles of the set of receiving coils, whereas the parts of the temporal-frequency domain related to the region of slow variation are set to zero, and the resulting data in the temporal-frequency domain is Fourier transformed to the temporal domain.

Abstract: A magnetic resonance method is described for fast dynamic imaging from a plurality of signals acquired by an array of multiple sensors. The k-space will be segmented into regions of different acquisition. In the region of a first acquisition type a first partial image will be reconstructed by data of normal magnetic resonance imaging with a full set of phase encoding steps or by data of fast dynamic imaging with a number of phase encoding steps being with a low reduction factor with respect to the full set thereof and in the region of a second acquisition type a second partial image will be reconstructed by data of fast dynamic imaging with a full reduction factor. Thereafter the first and the second partial images will be formed to the full image of the scanned object.

Abstract: A magnetic resonance method is described for fast dynamic imaging from a plurality of signals acquired by an array of multiple sensors. The k-space will be segmented into regions of different acquisition. In the region of a first acquisition type a first partial image will be reconstructed by data of normal magnetic resonance imaging with a full set of phase encoding steps or by data of fast dynamic imaging with a number of phase encoding steps being with a low reduction factor with respect to the fall set thereof and in the region of a second acquisition type a second partial image will be reconstructed by data of fast dynamic imaging with a full reduction factor. Thereafter the first and the second partial images will be formed to the full image of the scanned object.

Abstract: Magnetic resonance imaging method and apparatus which employ multiple magnetic resonance signals from an array of multiple sensors or coils for the reconstruction of images. The method is used in fast dynamic MR imaging. Prior to formation of fast dynamic images, a normal magnetic resonance image with a full set of phase encoding steps is acquired for each sensor or coil. A subset of phase encoding trajectories is extracted commensurate with the phase encoding trajectories obtained by the fast dynamic imaging and an image is reconstructed from the subset. Subsequently, the signals of the fast dynamic image are compared with the signals of the reconstructed image, thus yielding an estimate of the fold-over artefacts of the fast dynamic image. The signals of the fold-over artefacts thus compensate the signals obtained by the fast dynamic imaging and deliver a corrected image without artefact parts.

Abstract: A magnetic resonance imaging method employs sub-sampled signal acquisition from a number of receiver coils such as surface coils. A full field-of-view magnetic resonance image is reconstructed on the basis of the sensitivity profiles of the receiver coils, for example on the basis of the SENSE technique. The reconstruction is carried out mathematically as an optimization, for example, requiring a minimum noise level in the magnetic resonance image. According to the invention, a priori information is also involved in the reconstruction and the a priori information is taken into account especially as a constraint in optimization.

Abstract: The invention relates to an interventional magnetic resonance method utilizing a microcoil. The method enables localization of an interventional instrument by detection of magnetic resonance signals from the surroundings of the microcoil under the influence of magnetic field gradients. The outstanding reliability and the high speed of the method are due to the application of spatially non-selective RF pulses in conjunction with a sequence of gradient pulses in non-colinear directions. The localization method can be used inter alia for angiography wherein the signal intensity is used to determine the amount of blood present in the blood vessel. The invention also relates to a magnetic resonance apparatus for carrying out the method.